E9X Every mod still have Wheel hop

Brule

Specialist
Feb 20, 2017
65
#1
Hi all,

I have an issue with wheel hop while warming up the tyres and launching.

The issue is mass shutter that will not resolve by adjusting suspension bump snd rebound. Its a problem doing a warm up burnout or launching. I have to reduce my launch to low rpm to not spin the tyres which will resolves in heavy wheel hop.

Things i have tried:
Tyre pressure 25 20 18 14
14 psi had plenty of grip but lost 3mph

Front suspension is set pretty soft with 5 bump 7 rebound.

Rear i changed each run with no success.
Initially 15 bump 17 rebound
17 bump 17 rebound
20 bump 20 rebound quick sharp shutter even in 3rd gear had 20psi tyre pressure
10 bump 10 rebound 18psi
1 bump 10 rebound 14 psi softer compression sloeed the shutter speed on wet burnouts at start line but was still violent on every run.
1 bump 1 rebound
1 bump 20 rebound


I have the following suspension parts:
Kwv3
Megan toe arms
Ecs trailing arms
M3 guide rods
M3 control arms
Stiff sway bar

Tyres hoosier slicks 17 40 275

Ade diff and axles driveshaft - this has aluminium bushings but it feels lime it shakes a shit load.
Power approx 400kw



Previous set up was oem diff axles an driveshaft with a $100 diff brace and it was super smooth on street tyres but never tried slicks. With ade diff on street tyres 19s it has wheel hop on 17 bump 10 rebounnd but its not to bad.

Considering i have all upgraded suspension could it be the driveshaft angle to the diff? I have vibrations from the diff and driveshaft that i have not been able to rectify.
 
Dec 1, 2016
212
New York
#2
Stiffen the rebound in the rear and soften the compression.

Lowering tire pressure is not going to help wheel hop. I don't see how driveshaft alignment would result in wheel hop either.

The rear-end is bouncing around. Sounds like you already have solid subframe and diff bushings and stiffened control arms. You need to get the kwv3 dialed in right, or, run a different damper because it doesn't sound like youre having any success with them. And, you've shifted pretty much all the load handling to the damper already...

Did you stiffen the upper and lower shock mounts?

Also, check your diff mount bolts. I've snapped my diff bolt 2x already since putting in an M3 diff with an n55 on street tires. Im pretty sure an n54 is even more likely to shear the diff bolts with more power and Hoosiers.
 
Last edited:
Nov 5, 2016
268
San Antonio, Texas
#3
My guess is your spring rates are all wrong for drag racing. I would start with softer rates but it could take some changing to get it correct so find out what size spring the KWV3's use. I think Swift makes a spring upgrade for the 335i KW's, might want to see what the specs are.
 

Brule

Specialist
Feb 20, 2017
65
#4
Cheers guys.
Current setup is softest compression and stiffest rebound.

I had no grip in 3rd so i kept lowering pressure. I think the sweet spot for grip and mph and drivability squirming down the track was between 18-16 psi.

No i didnt put stiffer bump stops in just new oem ones. I dont think the spring rate and dampener would be an issue as alot of people have stock and other coilovers with no issues and its been nice and smooth with thr last diff and axles.

I gotta get under and see what I can find.
 
Dec 1, 2016
212
New York
#5
No i didnt put stiffer bump stops in just new oem ones. I dont think the spring rate and dampener would be an issue as alot of people have stock and other coilovers with no issues and its been nice and smooth with thr last diff and axles.
I meant this:

Also, plenty of people have had issues with insufficient rear rebound with aftermarket coilovers. Due to the motion ratio of the rear suspension we run pretty high rear rates that most generic coilovers like KW aren't specd to handle off the shelf. No idea what your spring setup is though...
 
May 4, 2017
1,759
Plano TX
#6
It doesn’t matter what you do to your suspension if the foundation it is bolted to is moving causing the hop. You need to look at your subframe and diff bushings.
 
Oct 28, 2017
830
Monroe CT
#7
I would think having solid diff mounts and stock subframe bushings deff the prob I never had consistent wheel hop but my suspension was pretty tight but when I did rsfbs It made huge difference I have never had any hop since then.
 

Brule

Specialist
Feb 20, 2017
65
#10
With slicks it makes everything minor large.

After That drag night I was able to tighten up the subframe bolts a full turn or more on all 4.

That and one of the diff bushing bolts were loose. One bushing from ad diff has a bushing and bolt that fits snug and the other has a few mm slop on the bushing.
The one that has slop came loose.

I wont know if tightening them will fix the issue as the car will be off the track for a while.
 
May 4, 2017
1,759
Plano TX
#11
With slicks it makes everything minor large.

After That drag night I was able to tighten up the subframe bolts a full turn or more on all 4.

That and one of the diff bushing bolts were loose. One bushing from ad diff has a bushing and bolt that fits snug and the other has a few mm slop on the bushing.
The one that has slop came loose.

I wont know if tightening them will fix the issue as the car will be off the track for a while.
Not likely to help. My guess is they were vibrated loose due to the wheel hop. They are a symptom of the problem, not the cause of the problem. You have spent thousands of dollars on rear suspension and drivetrain...I'm confused as to the hesitancy to spend a couple hundred more to solidify the foundation all that runs on.
 
Dec 1, 2016
212
New York
#12
With slicks it makes everything minor large.
Have you taken a look at your suspension travel? You might be banging off the rear bump stops...

I have 16k rear springs and I am practically riding the bump stops. I put a camera under there and recorded the struts bottoming out. Car feels a bit better after cutting th bump stop 1/4", but seems like I could benefit from moving to a stiffer rear spring like 20k. Or, using a spring helper type bump stop that engages at pretty much all travel (like stock suspension).
 

Brule

Specialist
Feb 20, 2017
65
#13
If I knew what to buy I would buy it.
What would cost a couple of hundred to fix it?
It has kwv3 not sure what the spring rate is.
 
Aug 21, 2017
56
#14
I suspect that wheel hop has a lot to do with the harmonics of the rear suspension, which will not be addressed by Springs, shocks, bushings, et cetera. Maybe a little but not enough, obviously.

I recommend getting just one upgraded rear axle that is a larger diameter then factory, and trying that. Changing the actual diameter size was a common solution for will hop in the newer GTO community. It took years of trying different things before they figured that out. Also I believe the different diameter axle set up is used by OEMs on some newer cars for the same reason.
 
#15
Hi all,

I have an issue with wheel hop while warming up the tyres and launching.

The issue is mass shutter that will not resolve by adjusting suspension bump snd rebound. Its a problem doing a warm up burnout or launching. I have to reduce my launch to low rpm to not spin the tyres which will resolves in heavy wheel hop.

Things i have tried:
Tyre pressure 25 20 18 14
14 psi had plenty of grip but lost 3mph

Front suspension is set pretty soft with 5 bump 7 rebound.

Rear i changed each run with no success.
Initially 15 bump 17 rebound
17 bump 17 rebound
20 bump 20 rebound quick sharp shutter even in 3rd gear had 20psi tyre pressure
10 bump 10 rebound 18psi
1 bump 10 rebound 14 psi softer compression sloeed the shutter speed on wet burnouts at start line but was still violent on every run.
1 bump 1 rebound
1 bump 20 rebound


I have the following suspension parts:
Kwv3
Megan toe arms
Ecs trailing arms
M3 guide rods
M3 control arms
Stiff sway bar

Tyres hoosier slicks 17 40 275

Ade diff and axles driveshaft - this has aluminium bushings but it feels lime it shakes a shit load.
Power approx 400kw



Previous set up was oem diff axles an driveshaft with a $100 diff brace and it was super smooth on street tyres but never tried slicks. With ade diff on street tyres 19s it has wheel hop on 17 bump 10 rebounnd but its not to bad.

Considering i have all upgraded suspension could it be the driveshaft angle to the diff? I have vibrations from the diff and driveshaft that i have not been able to rectify.
Like someone else said earlier, Rear subframe bushings... I did inserts instead of full bushings and toe arms at the same time and that was when I first felt the rear be very very stable. So stable I slid into a curb the next day while playing around lol. Completely different feeling after adding those components. Just giving my 2 cents.
 

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