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      08-02-2017, 04:58 PM   #1
Chaslieb
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My Ohlins Saga

I love my M2 but was not in love with the way its suspension was set up. On the stock car the springs are stiff but the dampers are not up to the task. What this means on a broken or bumpy road is that the back end would bounce up and lose traction on the road. The roads in NYC where I live are third-world bad. Add the odd cobblestone street and frequent speed bumps as well as bridge seams, and you can see that using this car as a daily driver would lead you to look for modifications.

After a varied search, with little good information, I took it on faith that the best damper I would find were the Ohlins road and track. These are adjustable dampers meaning that the spring rate, although suggested by Ohlins, could be changed.

As to other owner's complaints about too stiff spring rates, I chose to look at other suspension providers and noticed that TC Kline specs a 350lb in front and 650lb in rear street setup. Using this as a baseline I ordered springs in the metric 60n front and 110n rear rates. This is significantly softer than the 90/190n rates suggested by Ohlins.

After installation, I found the car sitting too low.

https://www.flickr.com/photos/604550...posted-public/

In addition to being so low I could only get a finger between the fender and tire, the car was constantly on its bump stops requiring I dial in a slower or stiffer shock setting to slow the travel of the wheel so it would not always hit the bump stop.

The installation instructions show a 21 mm preload using a 45mm gap on the rear spring perch. Using the numbers given to equate to a preload of 3990n on a 190n spring I divided this by the rate I was actually using, 110n to get a 36 mm preload for this spring. As the gap of 45mm on the spring perch was represented as leading to a 21mm preload, I subtracted the 21 from 45 and saw that 24 mm should be added to whatever preload figure I require. For my purposes the spring perch should show a 60mm gap.

I cut a piece of wood to 6 cm by 2 cm to use as a gauge and gapped the spring perch, which is an arduous task given the minimal room to work, even while the wheel is off.

Once I could insert the wood between the top of the spring perch and the nut I tightened up the two nuts, put back the wheel and lowered the car. Now I had two fingers worth of thickness between the tire and fender and a decidedly different presence to the car.

In the front, the preload was recommended to be 5mm on the 90n spring. This is easily seen from the instructions that show the 200mm spring to measure 195mm after install. Given the difference in spring rates, I would require my spring have a 7.5 mm preload after install to measure 192.5 mm.

After looking underneath, I understood this to be problematic as even if one were to loosen the spring compressing nut to its maximum, there is a welded flange that blocks the bolt from going lower than 190mm

https://www.flickr.com/photos/604550...posted-public/

As the preload was basically correct, I left things as they are but note that a lesser preload, given the design of this strut, is impossible.

As to the ride, after readjusting the heights I took a 100 mi drive on winding and bumpy roads and immediately felt the improvements. The car did not bottom and the back did not lift off the road. It was still a bit bumpy and the rear still rose in reaction and softening or quickening the rear dampers made the difference to bring the rear reaction to bumps in parity to the front. Now the car is stable and comfortable and is able to confront streets that a stock M2 would suffer over. Bumps that would previously upset the car now glide past as a vibration. Hard bumps are dealt with. It greatly improved the ride and handling characteristics as the car gives you confidence to deal with road conditions instead of constantly braking and swerving to avoid what was a punishing ride.

Right now front is 16 from full stiff and rear is 15. So far so good.
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      08-03-2017, 03:09 AM   #2
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I rum 3 clicks front and 10 clicks rear on stock Öhlins springs :-D

Last edited by MagnusT; 08-05-2017 at 04:34 AM..
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      08-04-2017, 05:26 PM   #3
Chaslieb
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Lucky for you that you have decent roads. Does the back come up over bumps?
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      08-05-2017, 04:32 AM   #4
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Quote:
Originally Posted by Chaslieb View Post
Lucky for you that you have decent roads. Does the back come up over bumps?
Don't have that decent roads but more that it's my track setting and I'm too lazy to crawl under the car and change it between track meets

IMHO the oem chassi had a bit of a bouncy rear when on track and hard braking on bumpy sections. That is much much better with the Öhlins with the settings I've tried it.
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      09-12-2017, 07:00 PM   #5
Chaslieb
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Ohlins updated their installation instructions

Ohlins updated their instructions for both the front and back coilover install here:

https://www.ohlins.com/app/uploads/w...MI_BMSMR40.pdf

There is a change in spring preload and height adjustment for front and back. For avoidance of doubt, the rear preload is now a straight 40mm with a 190n recommended spring. To get an equivalent preload for my 110n springs I would need to dial in a 69mm preload.

Right now the ride is better than stock but still could be better and the car is noticeably lower than stock, so it would not hurt to raise it a bit. As I am running out of threads on the rear spring perch I may need to add a helper spring or go to a longer 228 mm Swift spring in place of the 200 mm ohlin spring to get the right spacing. Anyone have thoughts on whether one would have benefits over the other?
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      09-13-2017, 12:03 AM   #6
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I would contact Ohlins and see what they say. They generally know what they are talking about...
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      09-13-2017, 10:51 AM   #7
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Lower spring rates will require more preload to achieve the same ride height.

If you are running out of adjustments, longer springs should be installed. Helpers can work as well since helpers are merely spacers with the weight of the vehicle on them. Helpers can also serve to keep a shorter main spring in tension and allow height adjustments a little easier.
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      09-14-2017, 10:54 AM   #8
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The stock suspension after 5000 miles is lower I think is perfect !






Last edited by AGM2; 09-15-2017 at 10:12 AM..
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      09-18-2017, 12:08 PM   #9
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Quote:
Originally Posted by Chaslieb View Post
Ohlins updated their instructions for both the front and back coilover install here:

https://www.ohlins.com/app/uploads/w...MI_BMSMR40.pdf

There is a change in spring preload and height adjustment for front and back. For avoidance of doubt, the rear preload is now a straight 40mm with a 190n recommended spring. To get an equivalent preload for my 110n springs I would need to dial in a 69mm preload.

Right now the ride is better than stock but still could be better and the car is noticeably lower than stock, so it would not hurt to raise it a bit. As I am running out of threads on the rear spring perch I may need to add a helper spring or go to a longer 228 mm Swift spring in place of the 200 mm ohlin spring to get the right spacing. Anyone have thoughts on whether one would have benefits over the other?
But that's not all. Also added is the number 4 and 6 in the front suspension
https://www.ohlins.com/app/uploads/w...BMS-MR40_2.pdf
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      09-18-2017, 12:16 PM   #10
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Quote:
Originally Posted by Leonidm2 View Post
But that's not all. Also added is the number 4 and 6 in the front suspension
https://www.ohlins.com/app/uploads/w...BMS-MR40_2.pdf
....and number 8 in rear suspension
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      09-23-2017, 09:06 PM   #11
Chaslieb
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Yes, spring spacers now added by Ohlins

I was actually planning to get the swift spring spacers, at least for the front due to the constant spring binding and popping as the springs compress and rotate on their seats. The swift setup is a plastic and metal washer on both spring ends to allow them to rotate on their seats as they compress and release. It now seems Ohlins is offering this with their new sets. I wonder if they will offer this to prior purchasers through their dealer network?
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      02-18-2018, 07:22 PM   #12
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An update on my updated R&T Installation

Turned out the knocking I heard from the front shocks was caused not by spring bind but by an installer who overtorqued the bolts and stripping the threads causing the shocks to get loose and bang against the top hats.
I fortunately found another shop not too far away who was an official dealer and who got me replacement front shocks at a decent price due to the mercy Ohlins USA gave to an unfortunate customer. They not only replaced and properly fitted the front shocks but let me know that the 8" springs I had in back were too short for the lower compression rating of 110n. They were able to order 10" Swift springs at the rear in 100n rating, which Swift said would be fine since the springs were going to be compressed over 2" to get to the same preload as the 190n 8" springs in the stock Ohlins kit. What this gets me is a softer back end for the horrific bumps and potholes in the northeast.

Right now my suspension is just where I wanted it from the time I bought the car. The Ohlins suspension glides over bumps where the stock suspension would rattle my teeth. If you bought the M2 to be a track day car then this is probably not for you. If you use your car as a daily driver, the Ohlins setup with 60n 8" Ohlins springs in front and 100n 10" Swift springs out back is just perfect. Bumps that would have caused the back end to lift off or walk sideways just come and go. With the other mods I have made, including a Wagner intercooler, a Pure inlet and a Fabspeed Sport Cat, as well as the sound deadening from adding the 2 series door foam inserts, has made this car into the ultimate touring car. It is comfortable, responsive and the problems of heat soak which I could feel by my feet when the engine was pressed, are a thing of the past. This car is a keeper.
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