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[11135i]

Absolute tire newbie, browsed around and after looking through various threads, I was wondering why this isn't feasible/done. It seems like the people running on the 17s are running off of 225/45, so why isn't this combination done?

[rogm]

why would you go from 245 to a 215? is this snow tires?

[BrokenVert]

The cars torque makes it unfeasible

[11135i]

I'd prefer more neutral handling + the added benefit of being able to rotate the tires all around. Ah, the torque would be an issue?

[Lefthandblack]

Originally Posted by 11135i

I'd prefer more neutral handling + the added benefit of being able to rotate the tires all around. Ah, the torque would be an issue?

Have you ever put the accelerator pedal to the floor in your car? These cars make good torque, even factory stock, and are plagued with traction issues. I couldn't even imagine running a 215 in the back! My car spins them in 3rd gear with the factory run flats!!

[VMRWheels]

215's are quite a narrow tire for a 135i to be running in the rear. Like everyone has said, the stock sizes already deem to be difficult to have the rear end stick under acceleration.

-Charles@VMRWheels

[11135i]

Something must be wrong with my car (or me) then as I've never really seem to have traction issues. It's just so... fluid. It doesn't feel like a forced induction car as power delivery is just so incredibly linear, perhaps even boringly so. But I've never really gunned it below 2nd and I've done quite a few spirited runs before and haven't had traction break besides on bumpy roads.

[RaihaX]

Originally Posted by ianf2002

maybe it has a the N52 engine with a 135i badge

[11135i]

I was thinking that it might actually be a 128i in disguise

So what's my best option for going 4 equal sizes then without rubbing/speedometer issues?

[fboutlaw]

I'm very concerned for you. With the 135i... you should be burning through 245 rears, no problem.

If you are contemplating a square setup for tire rotation, it's not really going to save you a lot on the wear. Your fronts will wear off the edges (due to a lack of negative camber) and the rears will wear evenly. It's actually easier to just wear out the fronts and replace 2 tires at a time in my experience.

The other problem is that you're going the wrong way. Wider tires = more ability to grip in corners and general higher stability. Skinnier tires will decrease lateral grip and the car will feel more "wobbly" under normal driving circumstances.

In my experience, I tried to fix the understeer issue with going slightly wider in the front to 225 / 245 setup. Unfortunately for me I picked the wrong tires (continental DW) and it felt mushy and the understeer was just as bad as with 215/245 run flats. When I realized that the correct way to fix the problem and even out tire wear was to add negative camber in the front and go with wider tires all around, everything became much much better.

So my advice (and why 215 square isn't done):
- If you're looking to increase tire life, add negative camber
- If you're looking to fix understeer, add negative camber
- If it's time for performance, add negative camber + add the widest tires possible
- Stock fenders: 255/275
- Wide body kit: 275 square (maybe wider in front depending on kit)
- Widest square with a stock suspension: 235/40-18s

[sparkyblue]

Originally Posted by Lefthandblack

Have you ever put the accelerator pedal to the floor in your car? These cars make good torque, even factory stock, and are plagued with traction issues. I couldn't even imagine running a 215 in the back! My car spins them in 3rd gear with the factory run flats!!

When you say spins them, do you mean with traction control on? (Not DTC or Fully off).

Even in second gear, it feels like car with the stock run flats cant break traction. No blinking light if its dry out.

[GaryS]

Originally Posted by 11135i

I'd prefer more neutral handling + the added benefit of being able to rotate the tires all around. Ah, the torque would be an issue?

A square setup might make sense with track tires on track wheels for track or autocross. But not for street.

Do you track or autocross your car? When are you experiencing non-neutral handling?

...adding: Oh, I see.

Originally Posted by 11135i

Something must be wrong with my car (or me) then as I've never really seem to have traction issues. It's just so... fluid. It doesn't feel like a forced induction car as power delivery is just so incredibly linear, perhaps even boringly so. But I've never really gunned it below 2nd and I've done quite a few spirited runs before and haven't had traction break besides on bumpy roads.

My advice is to leave your tires alone except maybe replace the runflats for a better ride on bumpy roads. In my opinion, you're thinking about it too much.

[BrokenVert]

I currently run a 245 square setup and for the most parts its perfect.

Tires last longer because when you rotate you change the forces applied to the tires. This realigns the rubber molecules so that when you rotate again the rubber is more resistant to the striations that cause the tire to wear.

For example, my sister and I both have SVT H/O 302 2000 Mountaineers. I rotate and she doesn't. We have a similar driving style.

Her tires lasted 35,000 miles. My tires lasted 80,000. I front back rotated every 3K miles.

It's as simple as that.

[GaryS]

^^ As simple as that? I'm pretty sure you omitted to mention either new wheels or camber plates or fender rolling to fit 245s in front. I'd be surprised if spending money like that to extend tire life would actually add up to a significant savings for the OP.

[BrokenVert]

I said as simple as that to the extended life of the tires through rotation


And no I shelled out 2 grand for a set of OZ wheels and star specs, no fender rolling no plates. It made sense to me as i cracked and bent my stockers and needed new wheels and tires anyway.

[Tom K.]

Originally Posted by 11135i

I was thinking that it might actually be a 128i in disguise

So what's my best option for going 4 equal sizes then without rubbing/speedometer issues?

The optional "square" BMW tire/wheel combo for the 135i is 205/50R17 all-season tires mounted on 17" wheels. I assume you are aware your 18" wheels are not the same size.

Tom

[and 1]

Originally Posted by BrokenVert

I currently run a 245 square setup and for the most parts its perfect.

Tires last longer because when you rotate you change the forces applied to the tires. This realigns the rubber molecules so that when you rotate again the rubber is more resistant to the striations that cause the tire to wear.

For example, my sister and I both have SVT H/O 302 2000 Mountaineers. I rotate and she doesn't. We have a similar driving style.

Her tires lasted 35,000 miles. My tires lasted 80,000. I front back rotated every 3K miles.

It's as simple as that.

you more than doubled your tire mileage by just rotation? i dunno man, that's kinda hard to believe. there's gotta be more to it than that

is that molecular alignment thing for real? i know the whole directional thing makes a difference in sharpening skis, tho not at such a minute level

[BrokenVert]

It makes sense when you see it in pictures...Its hard to paint a good picture with words.

Pretend these are the wear patterns of tires

--
-- <- Thats a front tire (main forces left right)
--
--


|
| <- thats a rear one (main forces front rear)
|
|


By doing a front back rotate the forces that caused the above wear patterns are no longer acting in conjunction with way the tires have worn (ie the direction of the weakened molecular bonds between rubber molecules)

So the tires are more resistant to wearing. Over some time the molecules realign themselves to their new wear pattern as surface rubber wears off, thats when you rotate again.

Its a whole big thing that has to do with molecular geometry and force vectors, but it is real.

Thats the simple explanation, make anymore sense?

[fourtailpipes]

with symmetrical directional tires, they can be flipped as well, which even further increases tire life. this makes a HUGE difference, especially in camber-impaired cars.

[sparkyblue]

Originally Posted by ianf2002

without turning any DTC or DSC off you should be easily able to get the RFT's to lose grip and for the DTC warning light to flash. I get it daily even with Michelin PSS, although I do have the PROcede on.... bring on the Quaife LSD

Seriously, maybe you have a 128i, or your boost is off

Mine is bone stock, except for a DCI. And like I said, if its dry out on my stock run flats even in 2nd I dont have traction issues. Smooth up until 6k.

Is something wrong with my car? I want to dyno now...

[11135i]

Thanks for the responses guys, appreciate all the feedback

235/40-18s are the ones to go I'm reading if I REALLY want to go square, however,

Originally Posted by BrokenVert

I currently run a 245 square setup and for the most parts its perfect.

What exactly are you running on? 17s? Or 18s?

[BrokenVert]

I'm on a set of 17x8 et 40 OZ Ultraleggeras with 245/40 star specs all around