+400WHP Wheel Hop / Axle Tramp

[Panici]

Hey Team,


Getting some decent wheel hop in 1st and 2nd gear with the new turbo setup. I'm only at 4PSI (300whp?) and I'm assuming it will get worse as I turn up the power.
It shakes bad enough that it popped my side view mirror glass out and caused slight turbo drain to hood contact making a dent in my fresh paint. :/
It seems to only hop in a straight line. When getting on it in a corner the back end steps out smoothly.


I'm going to drop the rear subframe over the winter to install Garagistic Reinforcements [Rear Sway Bar, Differential Mount Point, Rear Shock, Trailing Arm (Wing & Tube)].

What else should I be doing to make the rear tires break free smoothly & keep the rear end together at 400+WHP?
I've heard a stiffer rear swaybar can make the rear act more like a solid axle (resistant to wheel hop.)
How about a second rear diff ear mount?
Will this LSD stay together at these power levels, or should I be looking at aftermarket LSD clutches?

As an aside, i'm not really interested in stiffer suspension/bushings or sticker tires at this time. Setting the car up as a sporty & comfortable cruiser.
Obviously i'm not expecting the car to hook in 1st and 2nd at WOT with a 450+ treadwear tire, but I would like tire spin without wheel hop.

-


Current setup for reference:
H&R Sport Springs, Bilstein Sport Dampers in 2014. I've only put 27k kilometers (17k miles) on it since then.

New rubber trans bushings in 2015.

Refreshed rear subframe in 2016. 20k kilometers (12k miles) on it since.

• Outer subframe trailing arm mounts reinforced/welded.
• Replaced rear wheel bearings
• Lemförder rubber bushings (subframe, trailing arm, rear swaybar & endlinks)

New E28 rubber motor mounts in 2020.

2.91 LSD (medium case) with new rubber bushing in 2022.
15x7 Euroweaves w/ Dunlop Direzza dz102 (205/55r15)

[Northern]

Wheel balance, wheel out of round, dampers (dead or just bilsteins not up to the task?)
maybe worth doing stiffer diff/subframe bushings - like 95a poly or something (I think delta park carries RevShift)?

[Panici]

Wheel balance, wheel out of round, dampers (dead or just bilsteins not up to the task?)
maybe worth doing stiffer diff/subframe bushings - like 95a poly or something (I think delta park carries RevShift)?

I doubt it's wheel balance or out of round. I would feel vibration when driving down the road in that case.

REALLY don't want stiffer/aftermarket bushings for the NVH. I'm a big fan of OEM rubber bushings.

[ForcedFirebird]

Sub frame bushes can't handle the power, so you get an oscillation between the diff mount and outer bushings. If you don't want to go solid, you can rubber fill the voids on the bushings, but you most likely will want to get something more solid.

[Panici]

Sub frame bushes can't handle the power, so you get an oscillation between the diff mount and outer bushings. If you don't want to go solid, you can rubber fill the voids on the bushings, but you most likely will want to get something more solid.

Hmm might be beneficial to stick a gopro under there and see if I can catch the parts in motion at 60FPS. I wouldn't have guessed the subframe bushings to have so much flex. Although I'm hesitant to make it hop on purpose, it has to be awful for the drivetrain.

Is there a solid rubber bushing available for the rear subframe?
For example, I put in OEM rubber solid offset (E30 M3) front CABs as a good compromise.

[moatilliatta]

Stiffer rubber options. Group N subframe, vibratechnics / z3m diff. Over 300 hp and I’d add a second ear to the diff.

But the wheel hop is a tough one to completely get rid of.

Check your motor mount and trans mounts.

Engine and trans mount materials should
match. Diff Ana subframe materials should
match.

[ForcedFirebird]

Don't even need to video. Just jack the rear up, and put a lever and move the sub frame. Even with fresh OE bushings there's a ton pf play. I notice it all the time when a car is on the lift and working back there. Unbloting one sway link, shocks, and diff mount the weight of the assembly tweaks them horribly.

When I bought my first e30, took it to the mid-west on a road trip. Camped in Bowling Green and they had test and tune drag racing next door. Jumped on the track and instantly learned the wheel hop issue lol. When I got back, the bushings were so bad, the frame could actually slide 1/2" up and down on the bolts - the rubber had torn all the way around..

I've done up to 500whp e30 projects and have never upgraded the diff mount (probably would if it was intended for drag racing). The ti and z3's cross members are much thinner than e30, I've used the Randy Forbes kit several times on those, though. I have videos on my youtube of launching e30's with power, there's no wheel hop (drag racing vid was on 10" drag radial). Some people don't like the noise, but UHMW/Delrin has always worked from me. Condor Speed Shop is literally a bike ride away, so I tend to use them since I can just go pick stuff up on a will call.

[It's Soda Not Pop]

Don't even need to video. Just jack the rear up, and put a lever and move the sub frame. Even with fresh OE bushings there's a ton pf play. I notice it all the time when a car is on the lift and working back there. Unbloting one sway link, shocks, and diff mount the weight of the assembly tweaks them horribly.

When I bought my first e30, took it to the mid-west on a road trip. Camped in Bowling Green and they had test and tune drag racing next door. Jumped on the track and instantly learned the wheel hop issue lol. When I got back, the bushings were so bad, the frame could actually slide 1/2" up and down on the bolts - the rubber had torn all the way around..

I've done up to 500whp e30 projects and have never upgraded the diff mount (probably would if it was intended for drag racing). The ti and z3's cross members are much thinner than e30, I've used the Randy Forbes kit several times on those, though. I have videos on my youtube of launching e30's with power, there's no wheel hop (drag racing vid was on 10" drag radial). Some people don't like the noise, but UHMW/Delrin has always worked from me. Condor Speed Shop is literally a bike ride away, so I tend to use them since I can just go pick stuff up on a will call.

Now I'm no where near the power level in this discussion. But I have had several makes and models of cars that I've thrashed. The one thing that is constant is bushings and suspension components. If always stiffened up my vehicles and it has served me well. I totally agree with you.

[Panici]

Stiffer rubber options. Group N subframe, vibratechnics / z3m diff. Over 300 hp and I’d add a second ear to the diff.

But the wheel hop is a tough one to completely get rid of.

Check your motor mount and trans mounts.

Engine and trans mount materials should
match. Diff and subframe materials should
match.

I wonder if those Group N subframe bushings are still available from BMW? All the online sites don't have stock. Those look perfect though.

Vibratechnics diff bushing is pricey, but also a good piece of kit. Think I will try the dual-ears first and then go to vibratechnics mounts if needed.

All mounts are currently OEM rubber and fresh.

Don't even need to video. Just jack the rear up, and put a lever and move the sub frame. Even with fresh OE bushings there's a ton of play.

Some people don't like the noise, but UHMW/Delrin has always worked from me. Condor Speed Shop is literally a bike ride away, so I tend to use them since I can just go pick stuff up on a will call.

Now that you mention it, I do recall visible subframe movement when jacking from the differential.

Yeah I really don't like the noise of UHMW/Delrin bushings. It's not a good trade-off for a street car IMO.

[varg]

FWIW I still get some wheel hop if I spin the tires from a stop, I don't get wheel hop if I spin them in 1st or 2nd gear while already rolling. I have condor's bushings, poly engine mounts and transmission mounts. I think it's more to do with how stiff my suspension and tires are though, 650lb/in springs with koni single adjustable shocks and 200TW tires. I don't exactly make it a habit of doing burnouts since 200TW tires aren't cheap and wheel hop can contribute to breakage of parts your engine has no business breaking. I'm interested in the above mitigation steps since I'm very concerned that my E34 might wheelhop and actually break things since I think it's nearly 1,000lbs heavier and will make considerably more torque than my E30. I to do not want stiff or squeaky bushings in that car since it is meant to be comfortable and quiet. OE style subframe bushes (Meyle HD), powerflex diff bushings. Not gonna be doing any burnouts with those expensive rear tires though

[hasa]

If you have lowered your car a lot and so gained lot of squat tendency, you need to control it by shock absorber settings.

[Panici]

I posted on r3v facebook looking for opinions on subframe bushings.
Revshift 80A or AKG 85A bushings seemed to be well-liked.
The revshift are specifically marketed as OEM+, and folks said there wasn't an NVH increase.


So far the best combo seems to be Revshift 80A bushings with E30M3 subframe washers.

There was also a suggestion to use Vibra-technics differential bushings.
I'm going to go with the (garagistic?) dual-ear setup first with OEM bushings, then see if I need to upgrade to the spendy vibra-technics

[Panici]

For reference here is my planned list of modifications (thus far):

• Garagistic Weld-in Reinforcements
  • Rear Sway Bar
  • Differential Mount Point
  • Rear Shocks
  • Trailing Arm (Wing & Tube)
• Garagistic Secondary Diff Mount (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?)

[HertE30]

33332225797 - E30 M3 subframe washer
I believe those only work with OE style rubber bushings, all poly bushings seem to be designed around a flat washer

[Panici]

33332225797 - E30 M3 subframe washer
I believe those only work with OE style rubber bushings, all poly bushings seem to be designed around a flat washer

Looks like you are correct.

I referenced the pictures here:
https://www.r3vlimited.com/board/for...7#post10022087

I emailed Revshift and they said:

If you don't already have them then I don't see them as a necessity. No need to spend the extra money. The washers just act as a seat for the top part of the bushings. We include large thick washers that serve the purpose very well.