+400WHP Wheel Hop / Axle Tramp

[Panici]

Has anyone used the black poly 80A differential bushings from Revshift?

Since the solid rubber Z3M diff bushings are so expensive, I was hoping the revshift 80A do a good job without NVH added.

[HertE30]

Decide on anything? I'm considering trying a vibratechnics with my new Z3M diff cover

[Panici]

Decide on anything? I'm considering trying a vibratechnics with my new Z3M diff cover

I updated one of my previous posts.
Here is the plan unless people have further ideas.

Looks like the 80A revshift bushings are OEM+. I spoke to the Revshift guys and they assured no additional NVH.

• Garagistic Weld-in Reinforcements
  • Rear Sway Bar
  • Differential Mount Point
  • Rear Shocks
  • Trailing Arm (Wing & Tube)
• Garagistic Secondary Diff Mount (Two new 80A Revshift diff bushings from RaceGerman)
• RaceGerman HD Differential Stud Kit
• Revshift 80A Subframe Bushings (from RaceGerman)
• Uprated Swaybars Front & Rear (22mm/19mm ST from RaceGerman?)

[Panici]

Here's a thought I had while looking at my rear subframe today.
Would alignment affect or contribute to wheel hop?

My car is within factory specs and rear alignment is not adjustable as stock. It is mildly lowered in the rear, but it's not "slammed".
I have not considered adjusters as I've heard of them losing position over time, in addition to finding a shop willing to play with aftermarket alignment bits.


I will think about welding in adjusters if you guys think wheel hop can be reduced via alignment changes.

[moatilliatta]

Factory alignment specs are super loose tolerance because nothing is adjustable. So actually getting better toe in and better camber for contact patch would add grip, assuming making wheel hop worse.

I think just stiff springs and shock package is about the only way. I run a pretty stiff setup and still get wheel hop. I don't thin there is a way out, just a way to make it less.

Usually loose hardware is poor craftmanship of doing the eccentrics with poor choice of sleeve materials bushings.

What shocks and springs are you running?

[Panici]

Factory alignment specs are super loose tolerance because nothing is adjustable. So actually getting better toe in and better camber for contact patch would add grip, assuming making wheel hop worse.

I think just stiff springs and shock package is about the only way. I run a pretty stiff setup and still get wheel hop. I don't thin there is a way out, just a way to make it less.

Usually loose hardware is poor craftmanship of doing the eccentrics with poor choice of sleeve materials bushings.

What shocks and springs are you running?

H&R Sport Springs w/Bilstein Sport Dampers.
The springs are pretty soft, which is what I want for ride comfort.

I will be switching to a 19mm rear swaybar, which should add some effective spring rate.
Also am going to reinforce both sides of the rear swaybar mounts. (trailing arm and chassis)

[moatilliatta]

Probably to much play in all the rubber bushings with soft progressive springs. I think sport shocks have to much compression and not enough rebound.

I also think mid sprung GC coil over kit with matched valve Konis rides better than any spring with Bilstein sports. Bilstein sports actually IMO ride better with the Spec e30 coil overs spring rates.

I would look at Group-N subframe bushings and do a dual Z3 diff bushings. Adding the bigger rear bar will give you less traction which I know a turbo E30 is already fighting.

[Panici]

I think sport shocks have to much compression and not enough rebound.

I also think mid sprung GC coil over kit with matched valve Konis rides better than any spring with Bilstein sports. Bilstein sports actually IMO ride better with the Spec e30 coil overs spring rates.

I always felt that the Billy Sports weren't valved right for the H&R Sports, even though they sold them together for quite a while.
They've been "good enough" for my needs up to this point.
Although come to think of it, I'm coming up on 9 years since I installed the set. Even though I haven't put that many miles on them, might be worth changing them out based on age alone.

I seem to recall the Konis are an upgrade over Billy Sports for soft springrates, but haven't looked into it in detail.


Thinking long-term, I'd like to go with a set of $$$ custom coilovers.
I have no experience with coilovers, but I bet something with 2/3/4 way valving could be set up to ride more comfortably then stock on the street, while being able to be adjusted for sporty/track performance.
Have my cake and eat it too? I'll have to find some suspension experts when the time is right.

[moatilliatta]

Not really sure what Bilstein sports are valved for other than good enough kits. They last for years, but I'm starting to think since they retooled and newer units are crimped, they wont last as long.

Konis wont last as long, but have a better side of shops being able to valve them to match the spring package.

I think even the entry level Ground Control setup were able to valve Bilstein's (Which would last longer) with no adjustability. Would ride better and last longer than most higher dollar kits. Most cars don't need adjustment once the shock is tuned other than track use.

Konis leaking so much, Bilstein poor rebuild / revalve support has me even looking at BCs... KW's ok, but herd horror stories about the service side, I guess no worse than Bilstein side..