First things first…
This is my first M car. It's also my first foray into lowering a car and fiddling with the suspension.
It's an M4 on passive suspension. It is my year round daily driver and it only sees 1 or 2 track days per year. It is my baby, which means I labor over any decision to modify it in any way. Until now, the only changes I’ve made were to the exhaust and diffuser. Not very adventurous, I know. But that should give some perspective on how big of a decision it was for me to modify something as important as the suspension.
So, I am decidedly not an expert in all things suspension, but did want to share just in case someone else found it helpful.
My goals/requirements:
1) Reduce the wheel gap, but do it in a way that doesn’t compromise performance.
2) Reduce the little bit of body roll that (I think) can be felt on hard cornering.
3) Reduce the “wobble” that (I think) can be felt going over very rough roads.
4) Need a wide range of height adjustability—I wasn’t sure how low I can safely go given the general crappy-ness of the roads I drive on and the fact that there are many speed bumps and steep parking garage ramps between home and work.
5) Maintain a reasonably civilized ride. Generally speaking, I don’t find the OEM passive system to be a rough or stiff ride at all.
Decisions, decisions, decisions:
After getting schooled on the various pro’s and con’s of lowering springs, height-adjustable kits and coilovers, I decided that the best way for me to hit most if not all of my goals/requirements was to go with coilovers.
As I was doing research on the numerous kits available for the F8x, I narrowed down my choices looking for what I thought gave me the best intersection of performance, adjustability (both for height and for damper settings), daily comfort, service life and price.
And the winner (for me) is:
JRZ RS ONE Touring.
The JRZ RS TWO Touring get a lot more visibility/press than the RS ONE, but the TWOs are a bit more expensive and frankly, a bit more sophisticated than a rookie like me needed.
Notes on the RS ONE Touring:
- considered more of a street setup than a track setup
- single adjustable dampers (24 clicks from soft to stiff)
- height adjustable on the F80/F82 from ZERO inches (OEM) to 1.5” front and rear
- uses OEM top mounts
- fully rebuildable
- kit includes springs, dampers, bump stops, dust boots, etc. (i.e., no additional components required)
Obligatory parts porn:
Showed up carefully packed in swiss cheese looking cardboard tidbits.
Some very pretty Eibach springs for the front (left) and rear (right)
Rear dampers
Rear springs and height adjuster
Front dampers
Front adjusters
Full kit
Purchase and Install:
I bought the kit from Supremepower. We’re very fortunate to have many excellent forum sponsors and I’ve always found the crew at Supreme to be knowledgeable and patient with questions while offering competitive prices and excellent customer support.
It was important to me to bring the car to someone I COMPLETELY trust for the install. Fortunately, I live pretty close to Turner Motorsport. Turner is so motorsport oriented, even their lobby seats are Recaro. Seriously.
Install took about 6 hours plus alignment. All came up green post align.
Initial impressions (first couple days):
Looks: I had the car lowered 1” in front and 0.75” in the rear. To my eye, the drop looks perfect and I’m very happy to report that I have experienced NO scraping or bottoming out on my daily commute (whew).
JRZ adjustment specs from installation manual
Front BEFORE
[url=https://flic.kr/p/NjM1U1]
Front AFTER
Rear BEFORE
Rear AFTER
Side view AFTER
Noise: No clicks, creaks, pops or groans. None noises whatsoever. Indistinguishable from stock.
Ease to make adjustments: Front damper settings are extremely easy to access and adjust. Just peel back the soft rubber covers and twist the knob. Rears, not so much. Adjuster wheel is on the top of the damper, so it’s not very accessible. It's difficult, maybe impossible to access the rear adjusters with the wheels on and the car on the ground. I assume it will be much easier to adjust up on jack stands with wheels off. Also, just as an FYI, height needs to be adjusted with the wheels in full droop.
Steering feel: I drive with steering set to Sport. I never thought the stock steering feel was bad or “disconnected”, but now, there’s much more weight and connectedness in the steering. Feels much more like my memory of hydraulic steering. Not sure how much of that comes from getting a proper alignment and how much comes from the JRZ’s, but either way…I LOVE it.
Stability/grip: The car feels MUCH more planted and stuck to the road. Even with my completely trashed PSS’s, tires feel stickier and the chassis feels completely flat when taking corners at “spirited” speeds. No sense of body roll at all even though I’m going into corners at higher speeds and with more confidence. Granted, this is still at street speeds and track will be another test entirely. I’m guessing this too is a combined result from the JRZ’s and having a proper alignment.
Bumps: Car absolutely soaks up bumps both big and small at slow and highway speeds. The roads on my commute SUCK. The unavoidable craters that used to upset the suspension and make the car feel a bit like a bucking bronco are much more civilized now. Seams in the highway that used to make me cringe are now GONE.
My only complaint:
This is kind of hard for me to explain, but maybe those more coilover savvy than I will make sense of this. With the recommended settings of 5 clicks from soft, the car feels somewhat “springy” or “jiggly”. Bouncy or floaty don’t feel like the right terms. Bouncy and floaty make me think of BIG and SLOW oscillations. This is not that. This is more like small and fast oscillations. Feels a bit like the chassis is just riding on springs w/o dampers if that makes any sense. The weird thing is that the car feels grippy and stable, does not roll and soaks up bumps, but still has a bit of that jiggly feel. Maybe part of that is the springs just needing some time to settle in? I’m spending some time today fiddling with damper settings, but haven’t found a setting that feels “just right” yet. Any thoughts or wisdom on this would be greatly appreciated…
Wrap up:
All in all, the JRZ’s really hit all of my key requirements. The car looks, handles and rides great. I’m optimistic that time and a bit of fiddling will get rid of the “jiggly” feel, which really isn’t THAT noticeable, but it’s definitely there. The only other thing that I’m a little worried about is service life. JRZ lists a recommended service interval of 6 track races or ~12,500 street miles (20,000 km). I asked the guys at Supremepower about this and they were kind enough to reach out to JRZ on my behalf. Not surprisingly, JRZ indicated that their spec is a guideline for maintaining PEAK performance and, literally, your mileage my vary. So, I’ll be curious to see how well they hold up over time as getting them off, having them rebuilt and getting them put back on is not an inexpensive proposition.
Many thanks to all the kind and knowledgeable forum members that answered my numerous annoying posts and PMs and to the forum sponsors, most notably, Neema @ TAG and Eric @ Supremepower.