Ohlins R&T Spring/Sway Choice

[Obioban]

I don't remember what the stock spring length is, but it doesn't get the perch above the tire-- so if you want a wide front tire, stock length won't cut it.

[repoman89]

Aren’t the stock Ohlins springs 8 inches? Thought that’s what I measured before I put mine in. Based on the spreadsheet I also have a 325lb and 350lb 7.5” spring I want to install in the front right and left side of my car respectively along with stock 630lb rears for now.

[Obioban]

Whether your change your springs out or not, you should absolutely corner balance and dial out preload. That kind of of wonkiness just makes the car worse, with no benefit in exchange.

350 lb front springs would get you into flat ride, just. Better to go 350 up front, 700 in the rear. Either way, you want to beef up the front sway and leave the rear sway stock to get a reasonable FRC.

How long of a spring you can use depends if you're trying to get the perch above the front tire. If you want to run wide tires (track) with a reasonable alignment, you'll need a shorter spring. If it's just a street car, get a longer spring as it's much easier to get everything to work right.

The R&Ts are very limited on travel, so I'd set front ride height entirely based on bump/droop (60% bump, IMO), then set a 1/2" stagger (rear 1/2" lower, fender to wheel lip, which isn't a real measure of stagger, but is super easy to measure and sets the car up correctly), then set the rear to be 60% bump using their adjustable shock length feature, then corner balance and eliminate preload :P

Flat ride was the most dramatic change for the better (in all ways-- comfort, civility, drivability) of any suspension change I've ever made. But, you can't really do it as a half measure. And, not corner balancing and/or eliminating preload just makes the car worse than stock, with or without flat ride.

TCK makes nice 700 lb rear springs, Eibach makes front springs with abnormally much travel (their "extreme travel" line) if you're trying to get the perch above the front tire.

[Slideways]

One thing that did not come up much in the flat ride thread is how the added stress from the larger front bar and grippier tires can cause the chassis mounts of the sway bar to tear away. Reinforcement plates would add cost to the setup.

[Thoglan]

You generally set your springs for a desired ride frequency and don't need to mess with it. If you're within a normal range and feel like its uncomfortable it's very likely the damper itself. That DFV is not known as being the most comfortable.

What are your spring rates and how would you describe the ride in terms of ride quality and handling?

I am running the stock ohlins rates, which IIRC are 400F/630R. Would be nice to try out a flat ride set up, but ideally I'd like to do so without jumping in straight away and corner weighting/buying 4 new springs and a new front and rear sway. In essence my question is whether just going with a lower rate front spring and removing the rear sway is a worthwhile exercise in determining whether I want to go down the rabbit hole or not. Obviously this would not be a permanent solution.

My current setup is fairly compliant I would say. Firm, but not uncomfortable unless on really bad roads where it can feel quite 'busy'. Like I said, I don't really have any complaints but given how highly others on here speak about flat ride I wonder if it's worth toying with. If so am I right in thinking 350lb/in 7" springs are a good starting point?

[cobra]

You generally set your springs for a desired ride frequency and don't need to mess with it. If you're within a normal range and feel like its uncomfortable it's very likely the damper itself. That DFV is not known as being the most comfortable.

What are your spring rates and how would you describe the ride in terms of ride quality and handling?

[Thoglan]

I am by no means well versed in suspension but I try my best. My current setup is ohlins r&t with stock ohlins springs, stock sways, GC street camber plates, 3DM ohlins strut spacers. Personally, I think they ohlins are beautiful and I don't really have any complaints, but my fear is that I might unknowingly be forgoing additional comfort and performance by not trying out some different spring options.

Without access to corner weighting my car, I can only really guess for what the weight would be. But to be honest, from what I can see from others it seems most people end up at around the 325-375lb/in range anyway. Seems a safe bet to aim for 350 front and run the stock ohlins spring in the rear. If anyone does want to guess weights, my M3 is close to no options with the exceptions being xenon headlights and power seats (which have been replaced with recaro PP ABE's on manual sliders). With regards to spring length, is the stock ohlins spring length of 7" optimal? If I understand correctly, simply slapping in a lower rate spring in the front will throw the front roll couple off and require a stiffer front sway. For the purpose of seeing if the exercise is worth while, is it sufficient that I just remove the rear sway (I recall Ian saying something to this sentiment)?. That way if I'm unimpressed I can quit while I'm ahead only having bought a couple springs, and if I am I can go down the rabbit hole of getting different sways/rear springs etc.