What to do? JRZ-RS1 suspension set up

[VictorH]

Background: My car is 09 E90 M3 which I purchased from new. Car has now almost 70,000 miles and is my daily driver. This my most favorite car I have ever owned and I plan to keep it for a while yet. 99% of my driving is freeway and some city, track use varies from 3 to 10 events per year. This year hoping for 5-6 events. Home track Road Atlanta and VIR close second.

Suspension: In the fall of 2012 I had a JRZ suspension installed, RS-1 model single adjustable, with all the proper mounts, sleeves, torrington bearing, ground control adjustable camber mounts, helper springs, etc installed by a very reputable dealer who also runs a race program. Springs are hyperco 425 pound front and 700 pound rears. Anti-roll bars are stock. Suspension height is approximately 1/2" lower than stock and the front struts are maxed out as high as they go (i.e. I can only go lower), rears have plenty of adjustment both up and down available. I have the mono-ball bearing on the front lower tension arm struts as well. Yes, it's been corner balanced and aligned by a good shop a couple of times since the install ( I had strut failure in front with my first set when they started leaking).

Wheels: I have 19x9 and 19x10 RAC forged wheels (anyone remember those?) for track use. Current tires are 255/35/19 and 275/35/19 F&R AD-08R with no spacers (wouldn't work, no room).

The situation: Only manifests at Road Atlanta, not VIR and it's only Turn 1 and 6. For those of you not familiar, turn 1 at RA is a slightly banked uphill right turn that you enter depending on your confidence and set up at between 80-90 mph (90 if your line is perfect) and you come out going up hill well over 100. Turn six is similar in that the entry is fast also around 80 mph, with more banking but it's a bit shorter turn. Both turns generate some pretty impressive cornering forces.

The problem: My suspension and I think probably most coil over set ups don't have a bump stop or suspension stop, they just keep compressing until something hits. That's my situation on turns 1 and 6, my tires both left front and rear bottom out on the inner upper fender about 1/3 of the way onto the tread (from the outside). I burned through both front and back fender liners and the tires have rubbed the paint to bare metal in back and plastic in front. This happens every lap at Road Atlanta. No one has said they see smoke but , there's certainly a lot of friction when this happens.

Solutions: This is where I need help/advice. What I see as options
1) Drive slower. Right, it's a DE and what fun would that be?
2) Install stiffer springs- This is the most obvious solution, but most of my driving is street and I want to preserve ride comfort for 99% of my driving, which is currently pretty good. If I am stuck with this solution, what's the next step up?
3) Install stiffer anti-roll bars - This might help, but I don't have that much body roll and would it reduce it enough that I don't rub? This seems more of something that would be an experiment to see if it helps or not.
4) Raise the ride height- This would give me more suspension travel, but as I noted above I can't increase my ride height in front as I'm at max unless there's some other trick.
5) Other ideas? If I'm having this trouble on street tires, what happens if I ever go to R-comp or slicks? Cornering forces would be even higher, leading to more suspension compression (well not really) but certainly more rubbing as the suspension can only go so far before something hits, even harder.

one other issue, just specific to the JRZ-RS-1. When I adjust the shocks from 3-8 clicks the difference for each 2 clicks is pretty noticeable, i.e it gets stiffer. However on the track last weekend, I went from 14, 16, 18 to 21 clicks which is max setting and I could not feel any difference whatsoever between any of those settings. I would think 21 clicks which is max adjustment would be like driving on rocks, but it didn't feel any different than 14. Anyone else with this set up notice that?

Thanks for your input.

[MasterP]

Helper springs. It can give you the extra height you need without changing any of your hardware. I had this issue in the rear of mine and I put a Helper in the back.

Or you could get longer springs too if you are also considering changing spring rates. My rates are 450/850 for now. But will move to 700/1100 once I get aero. I'm on full slicks though. On street tires this may be too much.

I also had to have my rear shock shaft replaced with a longer one.

[STALKER]

I had helper springs in the front I believe and my spring rates were a bit higher then yours, and I don't recall rubbing the front or rear fenders. I was actually a bit lower as well.

[M3SQRD]

Just as STALKER stated, with my RS1 setup, I'm running higher spring rates, a much lower ride height as well as wider tires F and R on 9.5"/10" wide wheels. I have zero F or R rubbing under any condition.

What are the offsets of your RAC 9" and 10" wide wheels?

[STALKER]

Originally Posted by M3SQRD

Just as STALKER stated, with my RS1 setup, I'm running higher spring rates, a much lower ride height as well as wider tires F and R on 9.5"/10" wide wheels. I have zero F or R rubbing under any condition.

What are the offsets of your RAC 9" and 10" wide wheels?

I think they are ET22 front and rear.

[JAJ]

You didn't say what offset rims you're running, but from my experience you have two things that need attention:

- First, it's entirely possible that your problem is just a combination of a tires that are a little too big for the wheel wells on rims that don't have quite enough offset. They're only 10mm wider than stock, but the wheel wells are not very forgiving if the tires are pushed out by not having enough offset. You didn't say what offset you have but if it's not negative enough, it'll make a modestly bad situation worse.

- Second, you may need different bump stops; there must be a stop of some kind installed already or the damper valve assembly would be damaged by the shock bottoming out.

There is nothing you can do to solve this by changing the damper settings or the springs. Nothing. The suspension will always find a way to move from one limit to the other regardless of the settings. Helper springs remove travel, but if they cause a "hard coil bind" event when you take a curb, it's like hitting the suspension with a 4000 pound sledgehammer and it can do a lot of damage, so it's best avoided. Proper bump stops cushion the impact, and that's possibly what you need.

If you really want to know what's going on, put the car on a lift, disconnect the swaybars and remove the springs and reassemble the suspension with no springs. Then you can move the wheels through the full range of travel and steering arc and see where the problem is and what you can do about it. It's expensive if you don't have a lift and do your own work, but it's also definitive.

[STALKER]

I also ran RAC rims with same size tires, but with PS2s and PSS. Did not have the same issue. These were my street set up, ran 18" Volks TE37 for track with RS3 in 265/35 and 275/35.

[VictorH]

It's not an offset problem. The fender lip is fine, I'm contacting the fender liner well inside the fender well both front and back. If you were to draw a chalk line around the tire where it's rubbing it's about 1/3 of the way in from the outside tire shoulder to where the contact is. This is a problem of too much suspension compression.

In regard to the idea of helper springs, I have those but they don't do anything except prevent the main spring from flopping around if you go into full rebound or when you lift the car.

Also, there's no provision for a suspension stop on this type of system.

[STALKER]

Did you purchase the kit from Bimmerworld?
If so, have you sent James an email yet?

[kitw]

Originally Posted by VictorH

Wheels: I have 19x9 and 19x10 RAC forged wheels (anyone remember those?) for track use. Current tires are 255/35/19 and 275/35/19 F&R AD-08R with no spacers (wouldn't work, no room).

You're running taller (slightly!) than stock tires. Plus, the AD08R is way oversized, in width.

I could not get the 255/35r19 / 275/35r19 to stop rubbing on my car. I ended up going to 18" wheels with 265/30r18 and 285/30r18 (smaller than stock) which solved the issue, but I suspect that 275/30r18 and 295/30r18 would be fine too. (IIRC the AD08R doesn't come in one of those sizes)

You can try a stiffer front roll bar, but that will only delay the problem - at the end of the day, the RS1's additional compression travel is going to give you fits. The RD Sport bars may limit compression travel enough, though you'd want to run stiffer rear springs or spend the $$$ on the rear bar install as well.

[VictorH]

I agree, I didn't realize that the AD-08R runs so wide. It's even wider than the RE-11s in 285/35 that I was running before and those fit with only the slightest rubbing on the sidewall on the same turns (basically a non-issue). Now the sidewall is fine, but the tread is rubbing.

I agree I might (probably) stuck with stiffer springs.

[RickyBobby]

Are there really no bumpstops on this setup? I ran into this with my moton street sports because the supplied bumpstops were too short. Stiffer springs won't help as much as you think. I still rubbed with 600/900. Longer bump stops solved my problem.