Hey guys, thanks to
Expert@ApexRaceParts this year we had the opportunity to run JRZ'S RS PRO suspension on our race-winning F87.
I just wanted to take the time to briefly review my experience with this set up from a perspective of dedicated track use, backed by previous knowledge and experience with tracking BMW platforms, and also with the full technical support of a larger organization behind the effort, which was really helpful in extracting the best set up on this car.
To paint a better picture this car also has :
-Full race suspension including either spherical or hard poly bushings
-Dinan Sway bars (to be swapped over the winter)
-Ground Control height-jackers in the back and Ground Control Race front camber plates
-The car is 3180 LBS with driver.
-The car runs on Apex Race FL5 wheels (m2 specific rear fitment) with 285/30R18 Hoosier R7's
(We've experimented with many different tires and sizes this year...more on that another time)
At the beginning of the 2018 Race season after we began to work out the various cooling issues at the car we spent a test day at our local track, New Jersey Motorsports Park, trying various settings on the suspension.
In my opinion, in order to optimize your suspension settings you must have a good point of reference. For me, this was my Crew chief Drew. We work together both over the radio on track, and by reviewing notes after a session to optimize the set up. He is intrumental in helping us make the best decision on which way to go with the changes, based on many factors on any given weekend...
While there were many various trial and tribulations dialing in what I felt made (our) car have confident handling on track, we ultimately learned that these cars have such stiff chassis, especially with a full cage, that any changes to the suspension , even small ones, had big effect on handling . That being said my first piece of advice is to take that into consideration when starting to dial in your JRZ suspension (or any performance suspension) on your M2 .
We ended up eventually landing on 1000LB front Springs and 1200LB rear.
What we found with this car is that it experiences a lot of roll- probably due to both the weight of the car and the speeds its capable of, and that the roll center has been changed significantly by lowering it to "race height". Our splitter is only about 2" off the ground in the front, with a slight rake to the ride height. This , in combination with trying to balance out our aero provided for a car that has a slight push on entry, neutral corner behavior, and on power over-steer. This is how I prefer mine, everyone drives differently...
Anyways, I will post up some corner balance #s and weights, as well as base settings , hopefully as a **POINT OF REFERENCE*** should you install JRZ RS Pro suspension on your car, and track it
Installation of the suspension was very straightforward. Everything fit with better than factory fit, the directions are clear , and we had no trouble with hardware or mounting.
I'd recommend at minimum when installing adjustable coil overs on your M2 to get adjustable end links for your sways, even if you intend to leave stock.
This will allow you to dial in suspension corner weights easily because you won't be binding on the sway bar with small variances in ride height.
We chose to mount our rear reservoirs in the back corner pockets of the trunk, which -on the left rear is ok, but on the factory car in the right- is the battery compartment. The braided hose that connects the actual shock to the reservoir is quite long, so it affords you significant range of placement(if not too much) depending on where you're trying to put it.
In the front we routed accordingly up through the front fender liners into the engine bay, and affixed to the stock front strut bar on either side.
In some instances you may have to disconnect the reservior from the hose to route it into the body (not necessary in the front) which will require de-pressurizing and then re-pressurizing after installation. This is an easy task with an appropriate shrader style shock valve tool, and a small bottle of N2.
Speaking of pressures, we upped ours from 300psi to 350psi, which seemed to help take away some of the initial under-steer we were experiencing on the tighter tracks like T1 At summit point, and through the esses around Pittsburgh International Raceway.
That being said during initial on track testing we found the following settings to be effective for the JRZ RS PRO on the M2 chassis:
-4.5* Camber, front
-2.8* Camber Rear (Fall Line shim stack*
--0--- to 1/16" total toe out up front
1/8" total toe in , rear
Front Bump is set at 11/15 Clicks
Front Rebound is set at 14-15/22
Rear Bump is set at 13/15 clicks
Rear Rebound is set at 13/22
While I can't promise you this will be 100% effective for a street-driven-track car, we have worked all year to dial in the suspension to my liking, which yields a pretty quick lap around the glen. :
https://www.facebook.com/tyspeedauto...3440048126709/
Overall, I think its an excellent set up for this car- the dampers respond immediately to changes and have been holding up to crazy abuse all year long in full race conditions. What more could you want from a damper?
I will take some opportunity over the weekend in the garage at Watkins Glen for our championship race to grab some pics of the suspension on the car, including our chosen mounting locations. IOU
Oh and PS if you want to buy these for your car , Apex is running a group buy with some steep discounts :
https://www.gangup.com/apex/jrz-rs-f...2-q3-2018.html