Ohlin RT guys: front wheel/tire sizes/offsets

[LSB4Me]

18s especially 40 series shouldn’t struggle to be comfortable on street - stock top hats? That’s disconcerting if the case with this chassis. Ohlins from all I hear is comfort plush soft riding joy.

@giz - is that setting because of upped spring rate?


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Agreed. Pretty sure I’m in a very small minority of unhappy Ohlins users, so something must be amiss. The setup on my e92 felt like a dream. Compliant, stiff and capable … all at once. I am chasing that same feel that I remember well.

I think my setup is underperforming due to installer error. After much driving and more adjustments than I can count, I have traced the issue to the rear shocks feeling overly compressed at rest or simply not having enough travel to dampen properly. Doesn’t matter what the rears are set to, the back end is jittery, unsettled and just plain busy. We will be adjusting/lengthening the rear shock next week and checking to ensure the bump stops were cut.

Currently running 12/18 (clicks from full stiff/closed). Oddly enough, it is the most balanced the car has felt and rotates beautifully. It’s just moving about too much in the rear.

Edit: Yes, stock top hats and OE rubber bushings everywhere. I wanted a comfortable daily driver …

[LSB4Me]

Per my testing with Shaikh on his shock dyno (years ago at this point), I run them on close to full soft (~20-22 clicks from full stiff), due to high amount of gas pressure and the curves we saw. No, I don't touch the knobs when I autox or track.

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Very interesting. Thanks for the info. Tough to argue with shock dyno data.

Do you the same turns in the front and rear? If not, do you recall the offset?

[Exclusivs]

FWIW, I’m running an 18x8.5 et 32 on 245/40 PS4S without issues.

Off Topic: What setting are you guys running on Ohlins RT on the street? Still struggling to get the same comfortable feel I had when I ran Ohlins on my e92.

18s especially 40 series shouldn’t struggle to be comfortable on street - stock top hats? That’s disconcerting if the case with this chassis. Ohlins from all I hear is comfort plush soft riding joy.

@giz - is that setting because of upped spring rate?


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[mrgizmo04]

Off Topic: What setting are you guys running on Ohlins RT on the street? Still struggling to get the same comfortable feel I had when I ran Ohlins on my e92.

Per my testing with Shaikh on his shock dyno (years ago at this point), I run them on close to full soft (~20-22 clicks from full stiff), due to high amount of gas pressure and the curves we saw. No, I don't touch the knobs when I autox or track.

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[LSB4Me]

FWIW, I’m running an 18x8.5 et 32 on 245/40 PS4S without issues.

Off Topic: What setting are you guys running on Ohlins RT on the street? Still struggling to get the same comfortable feel I had when I ran Ohlins on my e92.

[mrgizmo04]

Thanks Giz for summing this up, and noting that. Makes total sense. What have you finalized on? (Not that matters- plan to run out of box as stated)

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I bought a few springs initially (Swift/Hyperco) in 7" to try, running on 350 7" now (I never ran stock Ohlins springs front or rear). Recently got the car corner balanced and was a bit nervous with the amount of threads engaged on the collar, it's way up there.

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[repoman89]

Far as I see - not many "beehive" style rear springs available in high rates like 700-750? Only linear. Could be wrong - interesting Ohlin,KW,Tck all use a rated rear spring that's not linear.

Both front and rear springs in the Ohlins kit are linear despite their shape. To replace the rear you’d be looking at something like the Eibach XT in the same length and ID (I think it’s 6” / 2.5” ID but worth measuring to confirm)

https://eibach.com/us/c-9-ers.html

[Exclusivs]

You might consider a 700-750 lb rear spring to get a slightly higher rear ride frequency vs the front. That’s an easy one since it just sits between the adjuster and chassis with no camper plate spring perch BS. May end up riding better at speed and certainly will handle better than the stock rates.

Far as I see - not many "beehive" style rear springs available in high rates like 700-750? Only linear. Could be wrong - interesting Ohlin,KW,Tck all use a rated rear spring that's not linear.

[repoman89]

You might consider a 700-750 lb rear spring to get a slightly higher rear ride frequency vs the front. That’s an easy one since it just sits between the adjuster and chassis with no camper plate spring perch BS. May end up riding better at speed and certainly will handle better than the stock rates.

[Exclusivs]

Nah, 7.5” is close to the minimum. Usable travel on these before bind is only like 4.5”, close to the 4” stroke of the Ohlins strut. The included beehive spring is 8”.

Got it, thanks for clarifying this. Didn’t realize front stock spring was 8”

Note that he uses a 325 rate. I tried a 7" 336 rate and I couldn't get the car to 13.5 and was rubbing fender liner on bumps. The softer the rate the taller the spring you need.

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Thanks Giz for summing this up, and noting that. Makes total sense. What have you finalized on? (Not that matters- plan to run out of box as stated)


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[mrgizmo04]

Thanks Repo - 7.5" seems long for a front spring no?

Note that he uses a 325 rate. I tried a 7" 336 rate and I couldn't get the car to 13.5 and was rubbing fender liner on bumps. The softer the rate the taller the spring you need.

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[repoman89]

Nah, 7.5” is close to the minimum. Usable travel on these before bind is only like 4.5”, close to the 4” stroke of the Ohlins strut. The included beehive spring is 8”.

[Exclusivs]

Spring perch location vs the tire also depends on your ride height and top hat choice, in addition to spacer vs no spacer. The spacers are almost a requirement to get a high enough ride height with the right amount of bump travel by the way.

I run 9.5 ET35 with a 265 Hankook RS4 on track and had no issues with the following setups, both at 13.5" hub to fender ride height and with the 3dm spacers:

- TMS Street camber plates, 400 lb Ohlins beehive spring
- (current) TMS Street camber plates with 2.5" spring perch, 325 lb 2.5" / 7.5" length springs

Thanks Repo - 7.5" seems long for a front spring no? No plan to convert to a linear, would run out of box first


robgill
Thanks Rob, are you running CSL Squared? Didn't realize that, nice! Dont anticipate a OEM CSL front wheel rubbing stock Ohlin on a 265/35 PS4S'...

[LSBNick]

I have TE37s 18x9.5 et 22 with 265/35/18
And CSL 19x9.5 et 27 with 265/30/19

Both have no clearance issues with the R&T spring. A 275 on the TE37s would be tight.

Do you have the 3DM spacer?

[robgill]

I have TE37s 18x9.5 et 22 with 265/35/18
And CSL 19x9.5 et 27 with 265/30/19

Both have no clearance issues with the R&T spring. A 275 on the TE37s would be tight.