Ohlins Road & Track Suspension Deep Dive!

[FaRKle!]

Let's take a deeper look at the Ohlins Road & Track coilover kit for the BMW M2/M3/M4. In addition to going over the design, hardware, and spring rates, we have a real treat (courtesy of Fat Cat Motorsports) of being able to look at various damper dynos across the adjustment range. This will let us see just what those "clicks" are doing, and whether they're useful or not.

Originally Posted by Index

-0:00 Intro
-0:29 Kit's small hardware
-4:48 Front strut
-9:44 Front spring
-10:42 Rear damper
-13:24 Rear spring
-14:49 Front damper dynos
-20:26 Rear damper dynos
-25:56 Summary and closing remarks

[clutchdj]

Thanks very much for putting this together.

Have you dynoed bilstien yellows or KW dampers before, or even a stock ///M (Sachs?) damper. Really interested in seeing how they may compare as far as where their damping limitations begin.

[FaRKle!]

Originally Posted by clutchdj

Thanks very much for putting this together.

Have you dynoed bilstien yellows or KW dampers before, or even a stock ///M (Sachs?) damper. Really interested in seeing how they may compare as far as where their damping limitations begin.

I have dynos for F8x Bilstein B6 passive dampers (also courtesy of Fat Cat Motorsports). Maybe I'll make a video on them and how various stock/aftermarket springs will be appropriately/over damped.

I also dyno'd my stock M2 dampers which you can see the info about in the below video:

Originally Posted by Index

-0:00 Intro
-0:26 Motion ratios
-2:10 Bump stops
-6:24 Springs
-8:03 Ride frequencies
-8:40 Damper dynos
-10:38 Sway bars

[dvq]

Originally Posted by FaRKle!

I have dynos for F8x Bilstein B6 passive dampers (also courtesy of Fat Cat Motorsports). Maybe I'll make a video on them and how various stock/aftermarket springs will be appropriately/over damped.

Maybe you know this, but I've always wondered — how does one figure out how much damping you need to match a specific spring rate? Everyone always covers range of adjustment damper curve shape and force per shaft velocities for a damper but I've yet to really find anything that talks about guidelines for matching the appropriate amount of damping to a specific spring rate. You alluded to some of that by saying you'd try a specific click setting which you presumably have a dyno graph for, just wondering how you came to that conclusion.

[FaRKle!]

Originally Posted by dvq

Maybe you know this, but I've always wondered — how does one figure out how much damping you need to match a specific spring rate? Everyone always covers range of adjustment damper curve shape and force per shaft velocities for a damper but I've yet to really find anything that talks about guidelines for matching the appropriate amount of damping to a specific spring rate. You alluded to some of that by saying you'd try a specific click setting which you presumably have a dyno graph for, just wondering how you came to that conclusion.

From what I've seen in academic literature, they say a factor around 60-65% is "ideal" from a damping perspective, or how fast settling is achieved, but that doesn't necessarily take into account other things like ride quality. What you can get from that though, is factors above that are greater than they need to be/overdamped. There are models out there where you can see what the damping factors are with the various inputs (weights, spring rates, motion ratios, ect.)

There are also other factors to consider like how much force on compression would make the car launch. You don't want to exceed that in any case, so the damping factor doesn't need to be the same across all shock velocities. I'd be looking more for those textbook damping factors around the shock velocities that control typical body motions, and lower damping factors at high shock velocities.

With a lot of these aftermarket dampers I've seen damping factors well into the >90% range (and even over 100%). Much more than needed, and it just makes the ride quality and grip worse.

[m4forum]

Very interesting material and discussion. Tks for sharing the damping curves on Ohlins. I have them on my car which I used for the first time last year. Definitely felt the rear was a little bit happy but also had old tires which didn't help.
I decided to lower the spring rate on rear (before watching your video) and looks like this was a good call. I am going from 200N to 180N. More interesting will to try your recommendation to run few clicks on rear in comparison with front.
Did you have the opportunity to track those dampers. What has been your experience?
Even with 90N front and 200N rear running dampers 20 clicks from full riding is pretty good.

[FaRKle!]

Originally Posted by m4forum

Very interesting material and discussion. Tks for sharing the damping curves on Ohlins. I have them on my car which I used for the first time last year. Definitely felt the rear was a little bit happy but also had old tires which didn't help.
I decided to lower the spring rate on rear (before watching your video) and looks like this was a good call. I am going from 200N to 180N. More interesting will to try your recommendation to run few clicks on rear in comparison with front.
Did you have the opportunity to track those dampers. What has been your experience?
Even with 90N front and 200N rear running dampers 20 clicks from full riding is pretty good.

I haven't had a chance to put these on my car and track them yet. Still working through the 3100mi break in (about 900mi to go)! Haha. Need to track with the stock suspension first to baseline, then I can start rotating the various suspensions I already have for this car on...

[m4forum]

I understand. Let us stay in touch. I was not patient enough and tracked the car already with the Ohlins so I dont have a bottom line. Anyway I will track the car end of May and will follow your suggestions specially on the rear. I will post here.

[jim1013yyf]

saw your video earlier today! Great stuff - please do more of them!

BTW I'm in bay area, and have a F82 with B16 Damptronic - if you ever want to drive and test em out, let me know!

[M 4 FUN]

Interesting! Like many others i found the car too stiff and decided to change the springs. I went for 80 160 lb/in which works very good for me.

[FaRKle!]

Originally Posted by jim1013yyf

saw your video earlier today! Great stuff - please do more of them!

BTW I'm in bay area, and have a F82 with B16 Damptronic - if you ever want to drive and test em out, let me know!

Thanks, that would be cool! Once more folks are vaccinated I'd love to organize another suspension demo day where enthusiasts can all try each other's setups to see how the various aftermarket options feel back to back.

[dvq]

Originally Posted by FaRKle!

Thanks, that would be cool! Once more folks are vaccinated I'd love to organize another suspension demo day where enthusiasts can all try each other's setups to see how the various aftermarket options feel back to back.

I'm down for that in line at Levi stadium for mine.

[m4forum]

FaRKle this is great stuff. Thanks for sharing. For front you showed the curves for 10 clicks and 2 clicks but as indicated there is a huge change in rebound between those 2 positions. I see on the graph there is also 7 clicks but I dont believe is was presented. Would you mind sharing he curve for 7 clicks? tks
By the way do you know if there is difference on curves between the previous and current generation besides the lower rear spring rate?

[MTB656]

Great review. Keep this in mind:

The spring recipe from Ohlins specifically for the M2 has always been 90 N/mm front, 190 N/mm rear so you should really consider changing the rear spring to the 190 N/mm before testing as Ohlins never tested or intended the 230 N/mm rear spring on that model.

The springs included with the M2 specific kit at 200mm length front and rear. This is the same as the current kit spec'd for M2/M3/M4. Your front spring is 20mm short and will nearly coil bind at full compression. ...nearly...

Just a side note - spring preload is what dictates how much of one's travel is divided between bump and droop travel. Once that's set, the "height adjusting" gold cup at the base of the strut determines the static ride height. It does not determine the percentage of droop travel available from the total amount of travel.

Also, for the rear, great note on the shock length. Great clarification here that the shock length in a divorced arrangement does not dictate ride height, but does dictate bump and droop travel. You did a great job of clarifying that here!

I hope this helps. well done!

***Change rear springs to 190 N/mm before testing as this has always been Ohlins spec for M2***

[m4forum]

I would like to follow up on the topic after my first track event after reviewing the curves shared by FaRKle!.

I went to Mid Ohio which is a very technical track which combines a lot of different elements like high speed turns, elevation changes, off camber, low mechanical grip, low speed corners, ... in summary need a very well balanced car to around specially on back side as car will be always business with transfer weight side to side and front and rear.

This is a track I know very well with extensive experience on my previous E46 M3. Overall I would say a nimble car would be a preferred choice here but still a M4 can still do a pretty good job.

I was at Mid Ohio last year with the same car but with 3 clicks from full what based on video would be very stiff on compression / rebound. This weekend I was able to run the setup softer (Front 10 clicks from full , Rear 5 clicks from full). The car felt very compliant and very stable much better than my original setup. Based on this I can confirm what has been discussed here and again appreciate for sharing such information.

[adc]

Great info, thank you so much. Made me realize I was setting it up too stiffly, so I’ll adjust accordingly.

Mine is the older 40 kit, with the higher rear spring rate. After seeing the damper curves, I think I’ll install the other, lower spring rate going forward to see if I can get back a bit more compliance in daily driving.

Even so, I was running in the 5-7 clicks from stiff on both front and rear. I think I’ll start with Stiff-10 F, Stiff-15 R and go from there.

I’m heading over to VIR for a 2 day event this week, and I’ll report back.

[theweebabySeamus]

How comfortable are these in comparison to stock? How far in comparison?

[adc]

Originally Posted by theweebabySeamus

How comfortable are these in comparison to stock? How far in comparison?

Street comfort is mainly dependent on your spring rates. In my personal experience, the kits with the higher spring rates are just marginally acceptable for street use (with the damper adjustments set as close to the full 20 clicks as possible).

Comfort is a relative term and very variable between individuals.

[theweebabySeamus]

Definitely. I meant to put "how firm...." Oops