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      02-19-2009, 02:33 AM   #1
J Tyler
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Post Driving questions? Setup questions?

Hi everyone,

I've been reading and posting here on 1addicts for a few months now, mainly in this Track/Autocross/Dragstrip/Performance Driving section. And I hate to say it, but I see a ton of bad information, misinformation, and people with little or no experience spouting off as if they know everything when in reality they don't have a clue. Sorry to be blunt, but that's what I see. I also see several people new to Autocross/Track/Performance driving posting here, and them being given all sorts of bad info. Not good!

So, I decided to make a thread to introduce myself, and to give you guys a place where you know you'll get reliable information about performance driving and car setup. If people want this, post up! I'd like to help make this forum a better place. I'll do my best to answer your questions when I have time. If you guys don't want this, then let the thread die and that'll be that I think for the people who want it, this could be a really good thing. Also, it won't result in people getting into senseless arguments with keyboard warriors in somebody else's thread. I want this to be a place where you can post a question and get a truthful, reliable answer; not 25 different answers from lord knows where.

Here's some backround info about me, just so you know who I am and who you're getting information from:

Name: Jeff Tyler
Home: Orange County, CA
Experience: Started racing Karts, then Skip Barber formula cars, Spec Miata, lots of modified street cars, a few purpose-built Time Attack cars, did Formula SAE with school, development testing with MazdaSpeed NA, I do private instruction, and instructed at Skip Barber. I currently drive for Berk Technology and occasionally other companies in TimeAttacks, do private instruction whenever I can, and am in school working on a Mech E degree at CSUF. I also have worked in GrandAm Cup and on the FactorX TimeAttack cars as a chassis setup consultant/engineer. My dad is a race engineer professionally, and this has given me the chance to work on a few Atlantic and IndyLights race teams as well. He has done IMSA, GrandAm Prototypes, IndyLights, Atlantics, ChampCar, Indycar, NASCAR, I forget what else... and has won many races and championships as an engineer in those series. I'm somewhat unique in that I've been able to drive as well as learn about the engineering side of things.

Here are some videos of the Berk cars:




2009 CSUN FSAE car:
http://www.youtube.com/watch?v=J65r2w_tyeg

And some pictures:












I would like to have a few guidelines to keep things organized:

- If I don't know the answer, I'll be honest and say "I don't know!" And I'll do my best to find the answer for you from a reliable source.
- I'd like to keep this a place where reliable information can be found. If you have a mechanical engineering degree or professional racing experience, please share your thoughts. If you don't, please PM me and ask if it's OK to answer a question!



Ok, that should be enough to get the ball rolling. Ask away!

Last edited by J Tyler; 12-14-2009 at 10:41 PM..
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      02-19-2009, 03:47 AM   #2
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OK I'll start:

If a 135 owner was interested in taking their stock vehicle to a track day, in order, what would be the top five modifications or preparations you would advise them to make to their car?

Assume the goal here is to have a safe, enjoyable time without thrashing the car too badly. Fastest lap time is not necessarily the goal - especially for a track novice. Assume also that one has a helmet and appropriate clothing already.

Thanks,
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      02-19-2009, 10:30 AM   #3
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Let me stick in a quick question also.

I have been going to the track for over 25 years. Have been an instructor with the Porsche club for 20 years. I have probably wasted a ton of money turning perfectly nice street cars into piece of crap track cars......

I now have a 135. I want to improve handling without making the car unpleasant on the street.....

I don't want to spend a fortune doing it......

Thoughts???
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      02-19-2009, 11:24 AM   #4
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Hi, I am recently a new member but have been reading for awhile. you seem like a guy who can help. I have a 128i, which is more than enough power for me. But what could I do to make it a little faster without spending alot of money?
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      02-19-2009, 02:51 PM   #5
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Quote:
Originally Posted by Caduceus View Post
OK I'll start:

If a 135 owner was interested in taking their stock vehicle to a track day, in order, what would be the top five modifications or preparations you would advise them to make to their car?

Assume the goal here is to have a safe, enjoyable time without thrashing the car too badly. Fastest lap time is not necessarily the goal - especially for a track novice. Assume also that one has a helmet and appropriate clothing already.

Thanks,
For a novice, I'd recommend:

1) Upgrade the brake fluid. Motul Racing or ATE Super Blue. This is a performance upgrade as well as a safey upgrade: If, for whatever reason you end up in a bad situation on track, you want to be able to get yourself out of it! Brake fade is cheap and easy to eliminate.
2) Upgrade the brake pads. I would recommend a combination "Street & Track" pad, like the Hawk HPS or something similar. Again, it's both a performance upgrade and a safety upgrade.
3) The 'nut behind the wheel' upgrade. Honestly, it's the best thing you can do to get started. It will greatly increase your personal safety, as well as how much fun you have. Do be careful with who you get instruction from, however. I often see bad/misinformation being doled out at HPDE/autocross days... but on the other hand, good instruction is expensive. I'd also suggest reading some before getting instruction; it's much easier to absorb the info at the track day when you've already read a lot about it. Going Faster, the Skip Barber book, is the best one to start with IMO.

For the question you posed, those are the big 3 things I'd suggest! You asked for 5 things, so the remaining 2 would depend on what your goals are. If your goal is lap time, then upgrading your 135i's suspension & tires is the next step. If your goal is safety, then I would honestly suggest a good racing school course (or two!). Skip Barber, Bondurant, and Jim Russell are the best. I believe that your personal car control ability and understandindg of vehicle dynamics will do more to keep you safe than a racing seat and harness.

Good luck man, thanks for posting! Have fun out there

Quote:
Originally Posted by Hairy View Post
Let me stick in a quick question also.

I have been going to the track for over 25 years. Have been an instructor with the Porsche club for 20 years. I have probably wasted a ton of money turning perfectly nice street cars into piece of crap track cars......

I now have a 135. I want to improve handling without making the car unpleasant on the street.....

I don't want to spend a fortune doing it......

Thoughts???
KW V2 (single-adjustable) or V3 (double-adjustable) + camber plates. Lack of negative front camber is the biggest cause of understeer in these cars! That's just how BMW designs in understeer to their cars: They design the rear to gain negative camber in roll, and the front to go into positive camber in roll. I don't recommend going to a stiffer rear bar to try to cure the understeer because of the open diff. A stiffer rear bar will unload the inside rear tire even more; when we had the Berk 135i like that, it was impossible to add any meaningful amount of throttle until the car was pointed straight! The inside rear would go up in smoke.

The KW V-series kits are only moderately stiffer than stock. They are too soft for a full-on track car, but IMO a perfect compromise for a car that is usually a street car and occasionally a track car. The ride quality is very good (not 'bouncy' like other similar-priced kits).

The Porsche Club guys are great. I instructed with them once and had a blast... they definitely put on great track days.

Quote:
Originally Posted by Jay's128i View Post
Hi, I am recently a new member but have been reading for awhile. you seem like a guy who can help. I have a 128i, which is more than enough power for me. But what could I do to make it a little faster without spending alot of money?
I assume you mean 'faster' as in lap-time?

Like I said above, for track driving I'd start with the brakes (pads & fluid).

The next thing would be to increase negative camber in the front via camber plates. I'm not sure if you can do that with the stock suspension, but if you can that would be a cheap way to improve the balance of the car. But you may have to go ahead and do a coilover kit at the same time (not sure if the stock top hats will fit with any camber plates? Or if they would mess up the stock ride height? - Maybe someone can answer that for him). If you can use aftermarket camber plates with the stock suspension, without messing up ride height, then I think that would be a good cheap thing to do. Another cheap thing to add after the camber plates would be a stiffer front sway bar. This will decrease body roll and (to make it simple) improve the way the front suspension behaves.

Tires are also a good way to improve lap time, but that can get expensive (especially when you have a staggered wheel setup like our cars). I really liked the Dunlop Direzza Star Specs we ran at SuperLap. The Yokohama Advan Neova is also a good street tire, but will not last as long and is more expensive.

Also, to add to what I said above: When you're starting out with this stuff, upgrading the driver is going to yeild the biggest improvement in handling & lap time, hands-down!




Hope that helps guys, thanks for posting. Have fun out there
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      02-19-2009, 05:40 PM   #6
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Caduceus - davemohan sent me a PM this morning and he asked a good question: Why not recommend a 5 or 6pt harness?

Now, I'm definitely not an expert on this topic, but I do know a little bit. Basically, the reason why I did not recommend a harness to you is that the vast majority of the ones I see at the track are done wrong, and I just don't know if they provide a net benefit or a net loss safety-wise in a hard crash. That's why for you, with a modern BMW with all it's airbags and designed-in crumple zones, I'm hesitant to recommend anything short of a race seat + racing harness + cage/harness bar. I honestly am not sure if just adding a harness to a stock seat is going to be safer. See my conversation with Dave:



Quote:
Originally Posted by J Tyler
Quote:
Originally Posted by davemohan
Following your rules ..... I would say that #4 would be a 5 or 6 point harness. Not only for safety, but for me anyway it allowed me to concentrate on steering the car, working the pedals, etc. instead of holding myself in position in the seat. It also greatly increased my level of confidence.
Thanks Dave, I really appreciate the PM.

To do a 5 or 6pt racing harness safely, you need a properly-designed harness bar in conjunction with a properly-positioned (and mounted) racing seat. All of that basically turns the car into a track-only car, which I didn't think was what the guy was looking for.

I'm not an expert, but from the accidents I've seen, just adding a 5pt harness to a stock seat is usually not the best thing in an bad crash. You want to let the modern stock safety systems do their thing (the airbags & belt tensioners are all designed to distrubute acceleration over time to minimize the force applied to your head/neck/back).

The only thing I've seen that works OK is the Schroth 4pt ASM system:


But, aside from all that, you have to keep in mind that the stock BMW safety systems (belts, seats, chassis structure, airbags, etc etc) are all designed to work together to protect you in an accident. Passenger safety is not as simple as just keeping the body from hitting anything; you are also worried about acceleration loads on the head/neck/back. The stock BMW systems all work together to minimize those loads (the belts absorb some energy, the airbags absorb some energy, etc). When you go and add stiffer/stronger belts, you increase the acceleration load on the head/neck/back in an impact. So, it's really tough for non-professionals like us to determine what is the safest (or safer) setup in a "street/track car" situation like this. And I am very hesitant to recommend anything that I have doubts about safety-wise, short of a full chassis-integrated cage or harness bar and racing seat.

This is an interesting topic. You're right, a good seat + belts does help keep your arms & legs free and able to focus solely on the wheel & pedals.

If it's OK with you, can I post up your PM and my reply? And we can just talk publicly from there? This is something I need to do more research on before I can give a confident answer, but it's definitely something that should be talked about. I appreciate you bringing it up!

I admit, this is something I should know more about. Hopefully I/we can find more detailed info to post.
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      02-19-2009, 06:42 PM   #7
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Jeff,Thank you so much for starting this thread.I have a 2008 Steptronic 135i which I bought as a second car for driving enjoyment on the mostly winding hillside roads(and a few highways) in Hong Kong.I have installed the JB3 1.22 piggyback on the car and have found that gives the car more than enough power and torque for my needs, even though I have ordered the RR intake and catless DPs which are(still) on their way.I have since turned my attention to giving the car better stopping power and handling. As you've suggested, I've installed Carbotech Bobcat street pads with Motul racing brake fluid. Wheels have been changed to Volk RE30s, 18x8 ET40 front and 18x8.5 ET42 rear with Bridgestone RE01-R 225/40/18 front and 255/35/18 rear. The wheel/tire combination has shaved 30 lbs of unsprung weight, and I feel that the car does accelerate and brake better.Next mod on the way is the BMW performance suspension which has a larger front sway bar and springs that lower the car by 3/4 inch front and 1/2 inch rear, among other things. I will have the front alignment pins removed during the installation which will allow me to get up to -1.0 front camber, which together with the lowering hopefully will give enough front camber adjustment without camber plates. What would you recommend for front/rear static camber settings for spirited street driving?To fight engine heat, I have also ordered an aftermarket IC, and would consider an oil cooler upgrade if you think the car needs one. We have warm summers in the 80-90 degree range.Finally, what are your thoughts on a Quaife LSD for this car?Thanks for your time.DDTUNG
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      02-19-2009, 07:37 PM   #8
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ZOMFG that Deuce is pure sex.
I knew Berk had good taste working on the 135 but I didnt realize they were that hardcore classy. God that makes me want to go back to my GRW20 (Mk2 + 2GR + 2 GT28rs = win) project, which is never going to happen now that I have a 135i to pay for =P
Where can I find info on the two? I tried poking around the berk website to no avail =*(

Anywho, awesome thread.
Good luck
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      02-20-2009, 08:26 AM   #9
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Jeff, you are a brave man to volunteer your service like this! Be prepared for tons of questions! Anyway while I am at it, I note with interest your comment that the rear goes into neg camber in a roll. Given that, how many degrees is the set up on your car? Mine is at -2.1 and I feel that I am not getting the optimum grip in the rear. Haven't had the chance to play around as I have been busy and the track session is just starting up again for the year. Would be interesting to hear your experience on this. Btw, I completely agree with your comment on the rear bar which is against what many have said around here!
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      02-20-2009, 11:18 AM   #10
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Quote:
Originally Posted by J Tyler View Post
I don't recommend going to a stiffer rear bar to try to cure the understeer because of the open diff. A stiffer rear bar will unload the inside rear tire even more; when we had the Berk 135i like that, it was impossible to add any meaningful amount of throttle until the car was pointed straight! The inside rear would go up in smoke.
thank god someone agrees with me on this one! great thread idea, by the way!!! i'm going to try NO rear swaybar as soon as i get my camber and square tire setup.
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      02-20-2009, 01:16 PM   #11
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Jeff, if you haven't already, you will soon regret your open invitation. You will be inundated with questions. Therefore I would like to ask a couple before your head explodes.

I have a 135i and here is my current setup for the track and street. I want to limit what I spend, yet get the best bang for my buck. I think I have done that so far.

1) Vorshlag camber plates and M3 lower wishbone. I can dial in up to -3.2 neg camber for the track, and run about -2 on the street.
2) A square wheel/tire setup for the track with 8.5 x 18 lightweight wheels and 245 R compound tires on all four corners. Same offset so I can rotate for maximum tire wear. Stock wheels/tires for the street
3) Motul brake fluid and Hawk HT-10 pads for the track. Stock pads for the street.
4) Good helmet
5) Open mind

I have participated in dozens of track days over the last 7 years and would consider myself an advanced track day driver, but no where near an expert. And I agree with you assessment of some HPDE instructors. I have been fortunate, however, to have been paired up with instructors with similar resumes as yours. It is a world of difference between someone who knows a particular track vs someone who knows how to drive on any track.

My questions are
A) Besides more professional instruction, would a stiffer front roll bar be my next investment to improve handling and lower lap times, while maintaining streetability? My last track car was an Audi S4 which is very different than this car.

B) Are my R compound tires too much for a soft stock 135i suspension? Meaning, am I getting any measureable improvement with R compounds over a good street tire? I have no baseline. This is more of a "on average" type question.

I appreciate your time.
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      02-20-2009, 02:03 PM   #12
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Quote:
Originally Posted by ddtung View Post
Jeff,Thank you so much for starting this thread.I have a 2008 Steptronic 135i which I bought as a second car for driving enjoyment on the mostly winding hillside roads(and a few highways) in Hong Kong.I have installed the JB3 1.22 piggyback on the car and have found that gives the car more than enough power and torque for my needs, even though I have ordered the RR intake and catless DPs which are(still) on their way.I have since turned my attention to giving the car better stopping power and handling. As you've suggested, I've installed Carbotech Bobcat street pads with Motul racing brake fluid. Wheels have been changed to Volk RE30s, 18x8 ET40 front and 18x8.5 ET42 rear with Bridgestone RE01-R 225/40/18 front and 255/35/18 rear. The wheel/tire combination has shaved 30 lbs of unsprung weight, and I feel that the car does accelerate and brake better.Next mod on the way is the BMW performance suspension which has a larger front sway bar and springs that lower the car by 3/4 inch front and 1/2 inch rear, among other things. I will have the front alignment pins removed during the installation which will allow me to get up to -1.0 front camber, which together with the lowering hopefully will give enough front camber adjustment without camber plates. What would you recommend for front/rear static camber settings for spirited street driving?To fight engine heat, I have also ordered an aftermarket IC, and would consider an oil cooler upgrade if you think the car needs one. We have warm summers in the 80-90 degree range.Finally, what are your thoughts on a Quaife LSD for this car?Thanks for your time.DDTUNG
Wow, that sounds like an awesome setup you've got

Without changing the geometry of the suspension on these cars (i.e. no things like camber plates, custom control arms, M3 arms, etc), you can't get very much camber front or rear (as you know). But, since your car is a street car, that's probably OK because I bet you're somewhat interested in your tires lasting more than a couple months. Also, IMO on public streets safety should be #1 so I'm hesitant to tell you to dump -2.5* of camber in so you can terrorize the local highways at max velocity........ not cool
But, I will give you a few tips that I would give someone looking to set their car up for HPDE days. And please please please, be safe on the public streets! If at all possible, take the car to the track. You will learn so much more, and have so much more fun.

On the rear suspension, when aligning the car, you want to set the toe first and then the camber: I would suggest going with a slight amount of toe-in (2/16" total or so) and then setting the camber to around -1.7*. That should give you good tire wear while being reasonably performance-oriented.

For the front, I'd suggest just a tiny amount of toe-out (1/16" total) with as much camber as you can get. Once you go beyond -1.7* or so, you're going to wear the inside of the tire a lot during street driving so keep that in mind. That little bit of toe-out in the front will give the steering a very nice, sharp response and really "point" the nose into corners well. For castor, I'd stay within factory spec. You could take a little out if you lower the car, to reduce the 'jacking' affect on the inside rear.

One general thought: All of the things on you car add up to = understeer. The 225F/255R, the lack of negative front camber, and the stiffer front sway bar, all tell me this car is going to understeer.


Based on my experience with the 135i/335i, I think you will be more than fine with the aftermarket IC. Just to be safe, as always, keep an eye on that oil temp guage; but I'm sure you'll be fine. It takes me 2-3 laps of 10/10ths driving to get the Berk 135i too hot, and we have a JB3 + IC (no aftermarket oil cooler).

Our HP Autowerks/Quaife LSD works great, especially for a street car. For a full-on track car, a clutch-pack Salisbury-type diff would be ideal; but those are miserable on the street (they cause the car to "hop" when making U-turns or tight turns). The 3.46 diff ratio we run also seems to really suit this 135i. You lose a little gas mileage, but the car really scoots off of corners! So yea, highly recommended!
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      02-20-2009, 02:04 PM   #13
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Quote:
Originally Posted by SpeedballTrix View Post
ZOMFG that Deuce is pure sex.
I knew Berk had good taste working on the 135 but I didnt realize they were that hardcore classy. God that makes me want to go back to my GRW20 (Mk2 + 2GR + 2 GT28rs = win) project, which is never going to happen now that I have a 135i to pay for =P
Where can I find info on the two? I tried poking around the berk website to no avail =*(

Anywho, awesome thread.
Good luck
PM BerkTechnology and ask them. I believe it's going into production soon...?
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      02-20-2009, 04:05 PM   #14
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Jeff,

Thanks for the quick and helpful advice.

After the BMW Performance Suspension is installed and the alignment pins removed, I'll see what kind of camber is possible in the front. Since the M3 front lower control arms can give 0.5 to 0.75 more camber, I'll probably get them as well. Would you recommend any other M3 suspension parts while I am at it?

As far as understeer is concerned, I realize that 225/255 tires don't help, but at the moment high performance tire/lightweight(but strong) wheel choices for the 135i are rather limited for the street and I had to settle for what I have. As for the front bar, my understanding is that the thicker one that comes with the BMW P/S is supposed to reduce understeer, is it not?

Looks like HP Autowerks will be shipping out another Quaife LSD in the near future.

Thanks again.

DDTUNG
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      02-20-2009, 10:28 PM   #15
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I'll bite first of all, Jeff, thanks for your time answering our questions.

My track car is not the 1er, but a 2004 VW R32. My question is regarding tires, so it may (i hope) apply regardless of what car you drive, and it is so important for those of us who do this as a hobby since consumables get expensive really quickly.

What methods do you recommend to take care of your track tires in terms of using them with the appropiate camber and air pressure? I want to get the most out of my tire: both longevity and grip.

For air pressure, I was told a good method was to use chalk to mark the inner and outside edge of the tire, near the sidewall. After a session, you can see if your tire rolled too much (or too little) by looking at whether the chalk was erased or not and thus, adjust air pressure accordingly.

For camber, I was told to use a pyrometer soon after a session, and measure the temperature of the inner (towards the center of the car) thread of the tire vs the outer (towards the outside of the car) thread. If the temperatures are within 15 degress, you are doing well. If the outside is 15 degress or hotter than the inside, you need more negative camber. If the opposite is present, you have too much negative camber. Supposedly, the value is specific to the tire manufacturer/model and not necessarily the car.

Are these good methods or do you recommend others? Does it matter if you have street competition tires (like Falken Azenis) vs. R-compounds?

Looking forward to your reply.
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      02-21-2009, 04:47 AM   #16
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Quote:
Originally Posted by WAY View Post
Jeff, you are a brave man to volunteer your service like this! Be prepared for tons of questions! Anyway while I am at it, I note with interest your comment that the rear goes into neg camber in a roll. Given that, how many degrees is the set up on your car? Mine is at -2.1 and I feel that I am not getting the optimum grip in the rear. Haven't had the chance to play around as I have been busy and the track session is just starting up again for the year. Would be interesting to hear your experience on this. Btw, I completely agree with your comment on the rear bar which is against what many have said around here!
Well, I should clarify. The rear goes into negative camber geometrically (if you put the car on a lift and compress the rear, it's plain to see that), but in the real world of bushing flex, subframe bushing flex, deflection of various supports/bushings/bearings, roll center movement, etc, it's tough to say. From looking at pictures, it looks like the suspension goes into negative camber geometrically like I said, but the whole car rolling negates that affect and can sometimes end up with the rear in positive camber during roll (especially if your rear springs are soft like our V3's are). Also, we're going to start playing with rear ride height (we've been running it too high) which will change our dynamic roll center movement and what camber the rear ends up at in roll; so all of my/Berk's assessments on this may get thrown out the window! But here's what I see so far:

Ex of what the inside suspension does in roll (somewhat high rear ride height):



Outside suspension in roll:



^That's running about -1.8* static in the rear. We lowered the rear recently which should give us some more (which is what I want). Haven't re-aligned the car yet. Your -2.1* sounds about right... it may put power down better with a little less camber, though. It's tough to say without driving it on a track and then looking at the tires, but I know we've been at -1.8* and I want more.

For a street car, you're probably worried about tire wear. But for a track car, you do want quite a bit of camber, especially with radial tires. Ideally, with these cars, I think you'd want to end up with a little more negative camber in the front than in the rear, because the front really loses camber geometrically and the rear doesn't.


Quote:
Originally Posted by pkcormier View Post
Jeff, if you haven't already, you will soon regret your open invitation. You will be inundated with questions. Therefore I would like to ask a couple before your head explodes.

I have a 135i and here is my current setup for the track and street. I want to limit what I spend, yet get the best bang for my buck. I think I have done that so far.

1) Vorshlag camber plates and M3 lower wishbone. I can dial in up to -3.2 neg camber for the track, and run about -2 on the street.
2) A square wheel/tire setup for the track with 8.5 x 18 lightweight wheels and 245 R compound tires on all four corners. Same offset so I can rotate for maximum tire wear. Stock wheels/tires for the street
3) Motul brake fluid and Hawk HT-10 pads for the track. Stock pads for the street.
4) Good helmet
5) Open mind

I have participated in dozens of track days over the last 7 years and would consider myself an advanced track day driver, but no where near an expert. And I agree with you assessment of some HPDE instructors. I have been fortunate, however, to have been paired up with instructors with similar resumes as yours. It is a world of difference between someone who knows a particular track vs someone who knows how to drive on any track.

My questions are
A) Besides more professional instruction, would a stiffer front roll bar be my next investment to improve handling and lower lap times, while maintaining streetability? My last track car was an Audi S4 which is very different than this car.

B) Are my R compound tires too much for a soft stock 135i suspension? Meaning, am I getting any measureable improvement with R compounds over a good street tire? I have no baseline. This is more of a "on average" type question.

I appreciate your time.
A) I don't see how it would be a bad thing! - Especially for your non-staggered R-comp setup. Even if you end up going with coilovers someday, I'd bet you'll still want that front bar on there.

The stiffer bar will increase the front roll resistance, which will increase the load transfer across the front tires during cornering. This will tend the overall balance of the car towards more understeer; BUT, the stiffer bar will also decrease how much the front rolls, which will decrease the amount of negative camber the front loses during cornering, which may (or may not) overcome the bad affects of the increased load transfer by increasing the overall grip ability of the car. A stiffer front bar will also add some more load to the inside rear tire during corner exit, which will help you put power down sooner with that open diff. Overall I'm confident it would be a net gain in performance.

A coilover kit like the KW V2/V3 would net you more lap time, though. And (IMO) keep the car perfectly streetable. The KW spring rates are only moderately stiffer than stock, but the ability to tune the dampers is huge for track driving.

Sounds like you've tuned out a lot of understeer (and maybe tuned in some oversteer?)... I bet your car is fun to drive!

B) Ideally, yes, they are too much. Well, the proper way to think of it would be to say "the stock springs are not stiff enough for R-comp grip". Adding stickier tires will never make a car slower Yes, there is a measurable improvement of R-comp vs Good Street Tire (usually about 1.5-2s per lap over a 2:00 lap), even on stock suspension rates. The stock dampers are wayyy too soft for any kind of track driving; there is a huge compromise between street comfort and track performance when it comes to damper rates.

Quote:
Originally Posted by ddtung View Post
Jeff,

Thanks for the quick and helpful advice.

After the BMW Performance Suspension is installed and the alignment pins removed, I'll see what kind of camber is possible in the front. Since the M3 front lower control arms can give 0.5 to 0.75 more camber, I'll probably get them as well. Would you recommend any other M3 suspension parts while I am at it?

As far as understeer is concerned, I realize that 225/255 tires don't help, but at the moment high performance tire/lightweight(but strong) wheel choices for the 135i are rather limited for the street and I had to settle for what I have. As for the front bar, my understanding is that the thicker one that comes with the BMW P/S is supposed to reduce understeer, is it not?

Looks like HP Autowerks will be shipping out another Quaife LSD in the near future.

Thanks again.

DDTUNG
I actually haven't tracked a 135i/335i with any M3 parts yet, so I can't say what I would recommend. I drove the HP Autowerks 335i for a few minutes on the street, and it had several M3 parts (front and rear). It felt great, but I'll have to report back once I drive it on track to really give a decent assessment.

Like I said above, the stiffer front bar will probably tend the car towards understeer; but, the car may grip better overall due to the lessening of front camber loss. In general, a stiffer front bar will send the balance towards understeer due to increased load transfer across the front tires.

On the Berk 135i, adding a stiffer front bar added understeer.

Quote:
Originally Posted by Alow View Post
I'll bite first of all, Jeff, thanks for your time answering our questions.

My track car is not the 1er, but a 2004 VW R32. My question is regarding tires, so it may (i hope) apply regardless of what car you drive, and it is so important for those of us who do this as a hobby since consumables get expensive really quickly.

What methods do you recommend to take care of your track tires in terms of using them with the appropiate camber and air pressure? I want to get the most out of my tire: both longevity and grip.

For air pressure, I was told a good method was to use chalk to mark the inner and outside edge of the tire, near the sidewall. After a session, you can see if your tire rolled too much (or too little) by looking at whether the chalk was erased or not and thus, adjust air pressure accordingly.

For camber, I was told to use a pyrometer soon after a session, and measure the temperature of the inner (towards the center of the car) thread of the tire vs the outer (towards the outside of the car) thread. If the temperatures are within 15 degress, you are doing well. If the outside is 15 degress or hotter than the inside, you need more negative camber. If the opposite is present, you have too much negative camber. Supposedly, the value is specific to the tire manufacturer/model and not necessarily the car.

Are these good methods or do you recommend others? Does it matter if you have street competition tires (like Falken Azenis) vs. R-compounds?

Looking forward to your reply.
The worst thing you can do to shorten the "grippy" lifespan of a tire is to overheat it to the point where it becomes very greasy. That is such a severe heat cycle that it literally changes the make-up of the rubber compound; after a bad overheat, it will never grip very well again. That applies to any tire.

So, how do you keep from doing that to your tires? Well, to make a very long story short, and assuming we are talking about Street tires: A tire will get overheated from either A) too little pressure + hard track driving or B) hard track driving for several laps in a row. So what does this mean for you? This means that when you're experimenting with tire pressure, you should start high and bleed it down; not the other way around. Bleed it down until you feel the tires getting greasy after a few (3 or so) laps, and then add a few pounds. Also, give your tires a cool-down lap every few (4-5 or so) laps. In general with street tires, heat cycling is bad and will slowly reduce their ability to grip over time; but when you're tracking your car, there's just nothing you can do about that! What you can do is reduce the severity of the heat cycles by giving the tires a cool-down every 5 laps or so and making sure they don't get greasy (very overheated) from too little pressure.

Camber-wise... well, like I've said, the ideal camber for track performance will result in pretty even wear on the track, because you're cornering a lot, but will wear the inside of the tire like crazy on the street because you're driving straight all the time. Same goes for toe: ideally for the track, you'd tend to run more toe-in in the rear than what is ideal for the street. This results in bad tire wear during street driving. (You could try F1-style 'tire warming esses' all the time, but that gets tricky in rush hour traffic )

Air pressure.... Don't use chalk to determine air pressure. Go by what I described about heat cycling. If you're curious, a pyrometer can tell you which part of your tire is overheating; but the important thing to be aware of is when/if it overheats (gets greasy). Chalk tells you nothing about that. Also, looking at the tire can tell you alot about camber: Look at where the rubber is starting to shed/ball up (does it do this more on the inside or outside?); look at where the rubber is graining (does it do this more on the inside or outside?) - etc.

Pyrometer.... They're great for testing an easily-adjustable racecar, but for a street car where it's a pain to adjust camber on the fly, I just don't find them to be all that useful. If you do have access to one, great! Play around with it and write down what you learn. Ideally you want a temp spread of about 20*F from inside to outside, with the inside being the hottest. Measure temps roughly like this, where the periods are:
\ . . . / - Imagine looking longitudinally at the tire
- I.e., don't measure really close to the inside/outside edges of the tire.


Yes, street tires vs R-comps does matter. Street tires are designed to give max grip at a pretty cold temp, whereas R-comps have an "operating temp" that must be acheived for them to grip at their best. R-comps are also designed to take the inherent heat cycling of track driving, and will retain more of their original level of grip than a street tire after several heat cycles. It's much easier to overheat a street tire than it is an R-comp. As far as temp spreads go, street tire vs R-comp doesn't matter too much IMO.... I still look for about a 20*F spread on R-comps. They are both radial tires and behave fairly similarly that way. But, I am not a tire engineer and it is somewhat of a black art even to those guys! So I'm sure there is a ton I don't know here.



Hope that helps guys, I'm really glad to be getting positive feedback from everyone. Thanks for the nice words, I'm glad to be of help.

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      02-21-2009, 11:37 AM   #17
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I wouldn't be worried with anything below -2 to -2.5 degrees of camber. Generally, i've seen excessive inside tire wear an issue with more than -2.5 to -3 degrees of camber.

Tire wear depends on driving conditions and suspension geometry. I would say you're fine with anything less than -2.5*

A stiffer front bar does improve turn-in for the strut-type front suspension of BMWs, but as Jeff said, it will result in steady-state mid-corner and exit understeer.
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      02-21-2009, 12:06 PM   #18
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Thanks Jeff for your advice. And yes my setup is now neutral to a bit of oversteer. And yes I could use more grip on corner exit. Sound like a front bar might be just the trick.
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      02-21-2009, 04:25 PM   #19
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Quote:
Originally Posted by pkcormier View Post
Thanks Jeff for your advice. And yes my setup is now neutral to a bit of oversteer. And yes I could use more grip on corner exit. Sound like a front bar might be just the trick.
You're welcome, feel free to post your thoughts/analysis of the bar when you get it
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      02-21-2009, 04:43 PM   #20
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Thanks for sharing your knowledge about tire care Jeff. I'll definitely keep it in my book of tricks
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      02-21-2009, 04:48 PM   #21
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Stock suspension + R compounds = bury the tire in the fender.
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      02-21-2009, 10:46 PM   #22
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Wow, this thread is great.
Props to J_Tyler. I'm eating this up and loving it

Quote:
Originally Posted by pkcormier View Post
Stock suspension + R compounds = bury the tire in the fender.
Wow those tires are STUFFED in there.
Looks sexy though.

God I wish LI had a racetrack =*(
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