Ohlins R&T Spring/Sway Choice

[OldRanger]

Good dampers are exponentially more important for ride quality than “flat ride”.

Now that you mention that...I don't think I've seen any comments on Ohlins damper settings in this thread. Granted, Road and Track is a single adjuster, with a dual flow valve...so it's pretty simple...but it does work to alter the ride.

Based on what I understand: if you are increasing spring rates on your car (and changing "frequencies") you'll probably need to increase damping on an Ohlins R&T setup to handle higher rebound forces the spring generates. Unless for some reason you added weight to your car in the equation. On the other hand, controlling compression events with a combination of tire psi, damper settings, spring rates, swaybar stiffness, etc. with an approach that optimal for the track and available traction is a bit more complicated. So, it likely just boils down to "did that feel better?" or "was that faster?"

I'm still curious to learn what folks are setting the dampers at using the original Ohlins springs for track use - focusing on how you want the car to handle low (shaft) speed compression events.

[Bry5on]

Obioban mentioned it earlier in this thread but 350 front 700 rear (or 6kg/338lbs & 13kg/728lb) will give you flat ride. And then a CSL front sway bar with stock rear will get you to around 69% FRC. I don't understand FRC enough to ELI5, but that spring and sway combo is what I'll be running when I order ohlins for myself.

This is a good target if you run OEM ride height. If you’re lowering the car (really, the front) then you’ll want to bring the FRC up because of how much the roll center drops in front when you lower the car. Geometrically, a ~66% FRC is neutral at OEM ride height. Neutral is hard for us humans, so a few percent higher will keep traction on corner exits. These numbers come from my own measurements and CAD models of the suspension geometry, everyone should feel free to recreate and verify! The math never lies

As much compliance as you can get away with will be fastest and most grip. Also, the net least disruption to the driver is likely to also be fastest, that’s the nature of pitch balanced ride frequencies. Flat ride is just a term coined by one dude to make this easier for people to understand, which is why it looks like its origin comes from fat cat motorsports.

[T.J.]

I don't have any bounce or modulation with mine, and like I mentioned, mine feels WAY better than my old Dinan springs and Konis which are said to be "flat ride".

But, I'm also probably a tad lower than your average bear, which requires higher spring rates.

Also FWIW I have the Ohlins camber plates, 3DM spacers, and Hotchkis swaybars.

Good dampers are exponentially more important for ride quality than “flat ride”.

[9kracing]

I don't have any bounce or modulation with mine, and like I mentioned, mine feels WAY better than my old Dinan springs and Konis which are said to be "flat ride".

But, I'm also probably a tad lower than your average bear, which requires higher spring rates.

Also FWIW I have the Ohlins camber plates, 3DM spacers, and Hotchkis swaybars.

[cobra]

I think the 400lb front for Ohlins is too much for their 628 rear. I have that 628, but went with 343lb up front. Looks like they fixed it for E9x though - they went with 343/685lb. I think they should have come with 336/628lb by default for e46.

Why do you think the 400 in front is too high?

[Tbonem3]

I think the 400lb front for Ohlins is too much for their 628 rear. I have that 628, but went with 343lb up front. Looks like they fixed it for E9x though - they went with 343/685lb. I think they should have come with 336/628lb by default for e46.

[Obioban]

Obioban mentioned it earlier in this thread but 350 front 700 rear (or 6kg/338lbs & 13kg/728lb) will give you flat ride. And then a CSL front sway bar with stock rear will get you to around 69% FRC. I don't understand FRC enough to ELI5, but that spring and sway combo is what I'll be running when I order ohlins for myself.

That’ll be a bit oversteer biased at the limit, assuming you retain the rear sway.

[gaiakai]

Soooo... is there a consensus on an optimal spring/sway bar combo to achieve flat ride w Ohlins R&T?

Cliff notes appreciated

Obioban mentioned it earlier in this thread but 350 front 700 rear (or 6kg/338lbs & 13kg/728lb) will give you flat ride. And then a CSL front sway bar with stock rear will get you to around 69% FRC. I don't understand FRC enough to ELI5, but that spring and sway combo is what I'll be running when I order ohlins for myself.

[freshprince2421]

Soooo... is there a consensus on an optimal spring/sway bar combo to achieve flat ride w Ohlins R&T?

Cliff notes appreciated

[Obioban]

Sorry what I meant was your rear spring rate hz, not overall spring rate. IE 1.8 front, 2.0 rear

Everything I can find posted on the web traces back to this guy Shaikh, who owns Fat Cat Motorsports. Everything, on every single forum. BMW, Porsche, Miata. Every single one.

I'm not saying he doesn't know what he's talking about, because I've watched his videos, and he seems pretty knowledgeable.

But there's a ton of factors that go into your suspension besides spring rate, I'm not sold on generic "flat ride" spring rates for every E46 M3.

Flat ride was THE biggest suspension upgrade I've ever done, when I moved my Ohlins to flat ride. I've since moved all my cars to it. IMO there's a reason the OE's all use it-- I find it makes the car more predicable, faster, easier, and better riding at overall frequencies.

But you do need to change you mindset to make it work-- with softer front springs, you need to be higher (also beneficial for geometery) and have a beefier front sway.

Good to do, since it's very much dependent on corner weights, etc.

I'm not sure if the term "Flat ride" is fat cats specific, but agreed that term doesn't come up much-- but I think that's why all search results come back to Fat Cats.

But, as a concept-- seems to be almost universally adopted by those who know most (the OEs).

[Obioban]

What I meant is who came up with the recommended spring rates for our cars RE flat ride.

You only need your rear spring rate 10-20% higher than your fronts, and Ohlins are higher than that. So why is Ohlins not considered flat ride.

You need frequencies that are higher in the rear than the front for flat ride-- not spring rates.

If you want to figure out your own flat ride spring rates, you can do so here:
https://www.fatcatmotorsports.com/FC..._M3_Online.htm

[9kracing]

Sorry what I meant was your rear spring rate hz, not overall spring rate. IE 1.8 front, 2.0 rear

Everything I can find posted on the web traces back to this guy Shaikh, who owns Fat Cat Motorsports. Everything, on every single forum. BMW, Porsche, Miata. Every single one.

I'm not saying he doesn't know what he's talking about, because I've watched his videos, and he seems pretty knowledgeable.

But there's a ton of factors that go into your suspension besides spring rate, I'm not sold on generic "flat ride" spring rates for every E46 M3.

[Tbonem3]

You only need your rear spring rate 10-20% higher than your fronts

Where'd you get that from?

Stock is 143lb/in front to 345-685 (progressive) so rear is a good 200%+ greater, not 10-20%

You have to remember that the location of the rear spring diminishes its net rate (something like 60% of original rate) nevermind that you want the rear stiffer in order to "catch up" to the front which is the core tenet of "flat ride" I believe - bounce ratios.

[cobra]

What I meant is who came up with the recommended spring rates for our cars RE flat ride.

You only need your rear spring rate 10-20% higher than your fronts, and Ohlins are higher than that. So why is Ohlins not considered flat ride.

You don't want spring rate 10-20% higher you want wheel rate 10-20% higher. Because the rear springs are inboard there's more leverage on them, the effective spring rate at the wheel is quite a bit softer.

therefore with ohlins 400/630 rates it's actually stiffer at the front than the rear

[oceansize]

What I meant is who came up with the recommended spring rates for our cars RE flat ride.

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/5660-fcm-e46-m3-ride-harmonizer-suspension-spreadsheet-aka-flatride