Wheel Hop - Annoying

[Philo]

Not sure if the E28 rear trailing arm setup is prone to wheel hop or if it's my setup. With all the rain it's hard to keep the right rear on the ground. This is in a straight line taking off from a light. It's even worse around corners.

[Ju@n]

+1, although I haven't refreshed everything back there... so might be some old bushing in my case

[Philo]

It's not bushings, I think it's a - traction - no traction - issue. I have Fortune Auto sport coilovers, 17" wheels and some fat Continental Extreme Contact tires. Maybe it's too much grip for the suspension.

[Ju@n]

It's not bushings, I think it's a - traction - no traction - issue. I have Fortune Auto sport coilovers, 17" wheels and some fat Continental Extreme Contact tires. Maybe it's too much grip for the suspension.

Hmm, stock suspension, normalish tires, old, probably worn bushings in my case

[Dimm6]

For me it was blown right rear shock. Replaced all shocks with B8s and it all went away.

[Freight]

Not sure if the E28 rear trailing arm setup is prone to wheel hop or if it's my setup. With all the rain it's hard to keep the right rear on the ground. This is in a straight line taking off from a light. It's even worse around corners.

Sorry to revive a deadish post, but did you ever get this sorted?

I just replaced my diff mount and it started to rain. Figured perfect time for a test drive. Did a couple slow roll launches(I have an lsd) and the right rear sounded like it wanted to launch out of the car as soon as traction was lost. I did it 3 times, two of which the right rear made itself known. But once, the rear happily stepped out and we slid on down the road sideways as tidy and precise as one would expect from a bmw. No clue what was different on that one. All my suspension+bushings are healthy and almost entirely replaced within the last 8 years(15kish miles).

thankfully I don’t have this happen when driving normally in the rain, and it only happened to me one other time, when I decided to do a launch in the rain. I had chalked that up to the diff mount, which is why I gave it a try tonight. Keen to hear if you ever tracked it down, given I see some folks here saying it’s a bit of an e28 quirk.

[turbodan]

I have a bit of experience with wheel hop.  More than I would like.

One thing that helps is a lower profile tire.  Too much sidewall seems to exacerbate the inherent tendency of the e28 rear suspension to hop.  Stiffer suspension helps as well.

A properly functioning LSD will prevent the inner rear wheel from breaking free to such an extent while accelerating in a turn.  These old diffs were 25% from the factory and are probably doing only a fraction of that now. 

It's been many years since I wheel hopped an e28, but I don't drive like I used to either.  I don't remember the last time I got off the line with a 4000 RPM clutch drop.  I often have people riding my ass coming off of red lights because I am so inconsiderate as to accelerate gradually and short shift my way through the gears.  If you go slow enough, the stock e28 suspension handles it just fine.

[Freight]

How can one evaluate and refresh the performance of their LSD? This isn’t a problem I’m going to run into, I don’t do much in a car beyond get a little fast on the backroads. I’m more concerned about ensuring it’s not symptomatic of something needing replacement. If it’s just an e28 quirk, I’m happy with that cause I don’t intend to ever run into it intentionally again. To me it does seem like a peculiar quirk tho, and probably one that shouldn’t exist and presumably didn’t from the factory. Granted, these cars are all on tires they were not designed to be on these days, and to my understanding, the TRX sidewall was much stiffer on top of the tires overall construction being significantly different from traditional tires. If someone told me this isn’t a thing on TRXs, I see no reason to doubt that.

[turbodan]

You can jack up one rear corner, leave the other wheel on the ground.  Chock the wheels on the opposite side, just to be diligent.  E30 guys have a nice axle nut they can put a socket on and apply torque, I think our best bet with the e28 is to apply torque to a wheel lug bolt.  Unfortunately, you probably won't need more than 40-50 ft-lbs to overpower the clutch pack in the diff.  A relatively healthy LSD clutch pack might be good for 60+ ft-lbs.

The radius from the axis of rotation to the lug bolt gives you a little more leverage than a standard foot pound but it's not going to throw your reading off too much.  If you're slipping at 30 ft-lbs that clutch pack isn't doing a whole lot. 

[Freight]

I’ll do that the next time I have the car jacked up. Is replacing the clutch packs a DIY job or does it need to go to a tranny shop?

[turbodan]

Never messed with them myself. Diffs are simple but the process of putting them back together must be done with care and precision. 

Might be something in the BMW TIS about it. I don't know if the clutch pack can be serviced without fully dismantling the diff.