Ohlins Road & Track setup discussion

[FaRKle!]

Originally Posted by Mrfurious214

FaRKle! hoping you see this

I don't like setting low ride heights. My ride height is around 0.25-0.5" lower than stock. For the out of the box R&T springs, you really need forward rake too, to get the car to handle better (the kit understeers in general).

Anytime you have a single spring setup with stiff main spring you're not going to have very much droop unless running a lot of pre-load (which you can only really do in the front for R&T). Honestly, I don't think Ohlins thinks about pre-load and where their damper is in its stroke at all because no matter what spring rates they put in their kit, they always say "5mm pre-load." This is particularly more important for those softer 3DM kits because if people installing those use the same 5mm pre-load they'll end up with even less compression stroke before hitting the bump stops.

Also, like M3SQRD said, check your damper settings so you're not running grossly overdamped and over constraining the suspension's ability to follow the ground.

[Mrfurious214]

I put it at stock height. I wish it looked better in the front lol...so much wheel gap.

I might try going a little lower but I need to understand the suspension better. I measured my jack pads and my rake is currently about 7/8" forward which I thought was weird based on what you guys are saying. I would assume the standard ride height would have less rake than 3/8"? That being said....any less than 3/8" and the car would be flat lol.

Do you guys know what the rake should be when at default? I want to make sure my mechanic didn't set the incorrect height.

[Mrfurious214]

Originally Posted by M3SQRD

Do you have significant forward rake? Bimmerworld recommends 3/8-1/2” of rack measured at the center of the rectangular jack pads. This will get you close to a corner balanced car but cross weight adjustments are still needed.

Are you adjusting ride height per the R&T manual? Did you set the ride heights based on the manual? How much lower are you now vs. R&T recommended ride heights? If your tire is lifting off the ground then you’re exceeding droop travel at one or more corners which I find odd on a R&T damper. I’d recommend the max lowering to be ~1/2” F and 3/4” R relative to the R&T ride heights (or set the rear and then set the front using the 3/8” rake measured from the F and R jack pads).

3/8" seems like such little rake for a front engine car struggling with understeer. I as said above, after my mechanic put the default heights on the springs I was around 7/8".

[M3SQRD]

Originally Posted by Mrfurious214

3/8" seems like such little rake for a front engine car struggling with understeer. I as said above, after my mechanic put the default heights on the springs I was around 7/8".

The actual rake from wheel to wheel will be higher than the jack pad-to-jack pad measurement. 7/8” from jack pad to jack pad is going to result in a significant amount of forward rake from rear tire to front tire. Did this produce the same fender gap on the front and rear? The delta I listed is to get you close to relative ride heights when corner balancing a car. Cross weights still need to be dialed in but no large changes in corner ride heights are needed. This is to get the four tires to work together and produce similar left and right cornering characteristics/feeling unlike an unbalanced car which is rocking back and forth on two opposite corners just like a four legged chair that always has only three legs in contact with the ground at any point in time. Understeer should be addressed with spring rates, sway bar stiffness, square tire setup, tire width, track width, rake, damper adjustment (only if there’s relative piston velocity between the chassis and the tires), etc. However, I don’t think there’s enough available forward rake to resolve understeer issues on the f8x. I have played with many different front 600-800 lbf/in springs and rear 800-1200 lbf/in springs. Settled on F/R 700/1100 lbf/in spring rates with 285/305 tires or 295/295 tires. 285/305 tires still maintain a neutral balance with a slight bias towards understeer in certain situations but the 305s advantage is its ability to put more power down.