Ohlins R&T DFV spring rates for more aero

[cliffordm4]

Howdy!

I have Ohlins R&T on my F82 M4 at the moment, and am planning on upgrading to more track oriented coilers next year. In the interim, however, I'm looking to adapt these to this year's track setup.

I have a GT4 wing on order, as well as a GTS chassis mount splitter, and GT4 canards.

I have the stock Ohlins springs on the coils. 513 lb/in front (90n/mm) and 1313 lb/in (230 n/mm).

What spring rates would you recommend given the additional aero? I think the rear may be plenty stiff, but the front may need some slightly stiffer springs. In that case, is a re-valve necessary?

[RugbyBro]

If you're in the Bay you can get in touch with Performance Shock - they're based out of Sonoma (Raceway). I'd imagine they could get you sorted with the right springs and any necessary revalving.

[M3SQRD]

The GTS comes with F/R 400/700 lbf/in spring rates. The GTS front splitter is trying to reduce front lift more than it is trying to generate measurable downforce. Your R&T stock spring rates are fine. However, the R&T can achieve critically damped levels at 10 or so clicks from fully open so you can run higher rate front springs without revalving. You could go up 100-150 lbf/in, likely higher, without revalving. However, as suggested above, contacting PSI or 3DM or any other authorized Ohlins damper service shops to discuss your specific needs/goals is a good idea.

[cliffordm4]

Originally Posted by M3SQRD

The GTS comes with F/R 400/700 lbf/in spring rates. The GTS front splitter is trying to reduce front lift more than it is trying to generate measurable downforce. Your R&T stock spring rates are fine. However, the R&T can achieve critically damped levels at 10 or so clicks from fully open so you can run higher rate front springs without revalving. You could go up 100-150 lbf/in, likely higher, without revalving. However, as suggested above, contacting PSI or 3DM or any other authorized Ohlins damper service shops to discuss your specific needs/goals is a good idea.

I really wanted to go with 3DM, but I've been having a hard time getting ahold of Barry via email/phone. PSI is another great choice but their prices are harder to swallow than 3DM

But good to know on the stock GT4 spring rates - I agree that given that, the stock Ohlins rates look fine for now. I'll wait till I upgrade to some nicer multiway adjustable before messing with the spring rates/valves any more.

Cheers!

[M3SQRD]

Originally Posted by cliffordm4

I really wanted to go with 3DM, but I've been having a hard time getting ahold of Barry via email/phone. PSI is another great choice but their prices are harder to swallow than 3DM

But good to know on the stock GT4 spring rates - I agree that given that, the stock Ohlins rates look fine for now. I'll wait till I upgrade to some nicer multiway adjustable before messing with the spring rates/valves any more.

Cheers!

lol…you’re probably talking about their Ohlins TTX kits which are $8k-12k but they’re dedicated track and true race setups and are twin tube dampers , not monotube like the R&T dampers. TTX are phenomenal dampers but they’re limited in the range of spring rates you can run before they need to be revalved.

[cliffordm4]

Originally Posted by M3SQRD

lol…you’re probably talking about their Ohlins TTX kits which are $8k-12k but they’re dedicated track and true race setups and are twin tube dampers , not monotube like the R&T dampers. TTX are phenomenal dampers but they’re limited in the range of spring rates you can run before they need to be revalved.

I had called PSI, and they still quoted me somewhere in the $1500 ballpark to rebuild all four.

The good news, I did get a callback from Barry and he is able to help me out. Super knowledgeable and helpful guy, just has been busy with many projects.

[M1500Z]

Originally Posted by cliffordm4

I had called PSI, and they still quoted me somewhere in the $1500 ballpark to rebuild all four.

The good news, I did get a callback from Barry and he is able to help me out. Super knowledgeable and helpful guy, just has been busy with many projects.

Your situation sounds very similar to my story of Öhlins R&T -> Öhlins TTX and is part of the reason I went to 3DM in the first place. Glad to hear Barry is able to help—like you said, he's very knowledgeable and helpful but also busy. As far as I am aware it's a one-man show at 3DM.

[jbalabas]

Originally Posted by M1500Z

Your situation sounds very similar to my story of Öhlins R&T -> Öhlins TTX and is part of the reason I went to 3DM in the first place. Glad to hear Barry is able to help—like you said, he's very knowledgeable and helpful but also busy. As far as I am aware it's a one-man show at 3DM.

curious how wide of a tire you fit on the front with the R&T? That's my urrent set up. wondering if I can run 1 295 18
Cheers
Jay

[cliffordm4]

Originally Posted by jbalabas

curious how wide of a tire you fit on the front with the R&T? That's my urrent set up. wondering if I can run 1 295 18
Cheers
Jay

Gooooooood luck. I have very very tight clearance with 19x10 ET25, plus a 15mm spacer and 275/35/19 PS4S. And lots of front camber. Ohlins is known to be tight up front.

[M 4 FUN]

You can use a 7 inch front spring instead of 8 inch and gain a little clearance.

[M1500Z]

Originally Posted by jbalabas

curious how wide of a tire you fit on the front with the R&T? That's my urrent set up. wondering if I can run 1 295 18
Cheers
Jay

I have an M2 which is much tighter on clearance—currently I run an 18x10 with an effective offset of +20 and a 275/35-18 RE-71RS.

Originally Posted by M 4 FUN

You can use a 7 inch front spring instead of 8 inch and gain a little clearance.

Yes, I ran a 7" swift spring that was slightly stiffer with 0 issues. Pics are in this FS listing that I forgot about—still have the springs if someone is interested.

[jbalabas]

Originally Posted by M1500Z

I have an M2 which is much tighter on clearance—currently I run an 18x10 with an effective offset of +20 and a 275/35-18 RE-71RS.



Yes, I ran a 7" swift spring that was slightly stiffer with 0 issues. Pics are in this FS listing that I forgot about—still have the springs if someone is interested.

Thanks,
I want to pullthe trigger on some 18x10.5 et36 bimmrworld wheels this summer but want to make sure they'll fit before I do. I'm a year or so away from switching to MCS.

[M3SQRD]

Originally Posted by jbalabas

Thanks,
I want to pullthe trigger on some 18x10.5 et36 bimmrworld wheels this summer but want to make sure they'll fit before I do. I'm a year or so away from switching to MCS.

If this post is correct

https://f80.bimmerpost.com/forums/sh...&postcount=191

then you’d need a 10.5” wide wheel with an effective offset of +5 (10.5et5) to clear the R&T strut. This is too aggressive of an offset for the outer fender even with 4 deg of negative camber.

[jbalabas]

Originally Posted by M3SQRD

If this post is correct

https://f80.bimmerpost.com/forums/sh...&postcount=191

then you’d need a 10.5” wide wheel with an effective offset of +5 (10.5et5) to clear the R&T strut. This is too aggressive of an offset for the outer fender even with 4 deg of negative camber.

Thanks!!

[M3SQRD]

Originally Posted by jbalabas

Thanks!!

You’re welcome.

If you’re fine with 3 mm of clearance (a lot of track guys run with 3 mm of clearance between the tire/wheel and strut/spring) then you’d probably be able to run a 10.5et10 with a 275, maybe a 285 if it doesn’t run wide or doesn’t have a large bead protector, without hitting the strut/spring. Must track guys run a 10.5et20 with 285 or 295 but’s 10.5et10 would stick out (frontspacing) ~0.4” more. Unfortunately, it’s still too aggressive for the front fender.

[jbalabas]

Originally Posted by M3SQRD

If this post is correct

https://f80.bimmerpost.com/forums/sh...&postcount=191

then you’d need a 10.5” wide wheel with an effective offset of +5 (10.5et5) to clear the R&T strut. This is too aggressive of an offset for the outer fender even with 4 deg of negative camber.

Originally Posted by M3SQRD

You’re welcome.

If you’re fine with 3 mm of clearance (a lot of track guys run with 3 mm of clearance between the tire/wheel and strut/spring) then you’d probably be able to run a 10.5et10 with a 275, maybe a 285 if it doesn’t run wide or doesn’t have a large bead protector, without hitting the strut/spring. Must track guys run a 10.5et20 with 285 or 295 but’s 10.5et10 would stick out (frontspacing) ~0.4” more. Unfortunately, it’s still too aggressive for the front fender.

I was hoping to make the bimmerworld 18x10.5 et36 fit with these until I can upgrade to MCS, if not I'll just wait on rims until i can do shocks. The increaed tire wear of rotating is attractive.

[M3SQRD]

Originally Posted by jbalabas

I was hoping to make the bimmerworld 18x10.5 et36 fit with these until I can upgrade to MCS, if not I'll just wait on rims until i can do shocks. The increaed tire wear of rotating is attractive.

10.5et20 is a close fit with MCS setups (I currently have three MCS 2WR setups). Depending on the width of a 295 tire, you may have to run a 5” long main spring but it requires a higher front spring rate. I think 700-750 lbf/in is too soft to run a 5” main spring so you’ll have to run at least an 800 lbf/in front spring rate.

A poster above said he’s able to run a 10et20 wheel with clearance. That would mean you’d be able to get away with a 10.5et13, maybe et14, but that’s still too aggressive for the front fender. It looks like you’ll have to hold off on getting the BW 10.5et36 wheels.

[jbalabas]

Originally Posted by M3SQRD

10.5et20 is a close fit with MCS setups (I currently have three MCS 2WR setups). Depending on the width of a 295 tire, you may have to run a 5” long main spring but it requires a higher front spring rate. I think 700-750 lbf/in is too soft to run a 5” main spring so you’ll have to run at least an 800 lbf/in front spring rate.

A poster above said he’s able to run a 10et20 wheel with clearance. That would mean you’d be able to get away with a 10.5et13, maybe et14, but that’s still too aggressive for the front fender. It looks like you’ll have to hold off on getting the BW 10.5et36 wheels.

Thanks for the clarification.
J