Wheel Hop?

Aragorn30d · 11-07-2015, 02:05 PM

Had an interesting encounter earlier.

I'm used to driving 4wd cars, and have driven 4wd cars for years. The E90 is my first RWD car, and i find it catches me out from time to time when i try to do certain things that 4wd cars just do without any drama.

Applying power on the exit of wet roundabouts was something that would catch me out quite a lot, but i'm getting used to it now.

Anyway today i'm driving to the shops in the lashing rain. Waiting at a roundabout, and it was one of those situations where traffic flows meant a constant stream of cars coming. I'd already waited for a while behind a bus, and now i was at the front. Saw a small gap and decided i'm having that and gave it a boot full. Not full throttle, perhaps half throttle but a good strong launch.

What i expected was it to launch forwards with perhaps a small amount of slip which the ESP usually does a fine job of controlling. What actually happened was it spun the rear wheels, but then it all went rather odd. I've become used to the fact that you can just keep the throttle down and let the ESP sort out the available grip, except today it didnt seem to. It spun the wheels up, then you could feel the rear end almost bouncing across the road surface. It felt like wheel hop you get in a FWD car when you floor it and it transfers all the weight off the front end. The ESP didnt seem to sort it out and the car somewhat slowly crawled out onto the roundabout. I lifted a bit and it seemed to sort itself out and regain traction and off i went.

I tried a similar launch at the next roundabout and it just did what it usually does with no drama.

Is this perhaps a sign of worn suspension bushings in the rear end?

IanS100 · 11-08-2015, 03:47 AM

It sounds more like something specific to the road at that point, maybe there was a patch of diesel etc

Aragorn30d · 11-08-2015, 06:43 AM

Yeh perhaps, but i'd have expected it would just have spun the wheels in that case, not started hopping around. It was also noisey, bang bang bang as it lost and regained traction.

If you've ever driven an old leaf sprung RWD car and experienced axle tramp, it was similar to that.

Fundguy1 · 11-08-2015, 07:03 AM

Wheel hop happens with large amounts of power. If you're stock it's more likely the road surface. It's not good to do as it's how drag racers snap axles.

Aragorn30d · 11-08-2015, 08:57 AM

Yeh its stock. Must have just been a weird quirk of the road surface i guess.

I can sure imagine it snapping axles, it felt and sounded bloody awful in the wet on road tyres. Must be horiffic to get that happening on drag radials and a prepped track with lots of power!

I really just wondered if it was a sign that the rear suspension needs attention. The cars on 145k and the control arms on the front seem to be needing replaced, so i can imagine that bits out back also need looked at.

Fundguy1 · 11-08-2015, 09:52 AM

Coilover time. Front control arms. Trw m3 ones. Subframe bushings.

OGM2LCI · 11-09-2015, 03:54 AM

I got this when doing a hard start in my 320d, never happened again until a couple months later it started doing it if I put my foot down round a corner on a dodgy surface and it turned out my rear shock had gone..

Aragorn30d · 11-09-2015, 04:08 AM

hmm! The shocks look like they've been replaced (they look new/rust-free and say "Sachs Pro-Touring" on them) but they may well be crap.

Will defo need to have a good look over the rear suspension i guess. Swapping winter wheels on soon, so i'll have a poke around then.

OGM2LCI · 11-09-2015, 04:36 AM

Quote:

Originally Posted by Aragorn30d

hmm! The shocks look like they've been replaced (they look new/rust-free and say "Sachs Pro-Touring" on them) but they may well be crap.

Will defo need to have a good look over the rear suspension i guess. Swapping winter wheels on soon, so i'll have a poke around then.

I do remember you saying the other day actually, worth a punt whilst you're changing wheels though

Since I've replaced mine they've been ok, although I'm starting to get a similar feel to before and I'm unsure whether this is the shocks gone straight away or the new shocks have caused something else to go

Either way if you find anything keep us updated as I may look at it on mine soon!

AWSAWS · 11-09-2015, 05:57 AM

The bushings in the rear subframe are quite soft and can be upgraded to help but the best option is to secure the diff to the subframe. That'll directly reduce the wheel hop and reduce the chances of you snapping components like suspension and drive shafts.

I can supply kits for £160 to people in the UK. I just need to know if it's for a small or large diff. E9x (3 series) and E8x (1 series). Right now turn around would be a few weeks for machining.

You were on the limit of grip on your tyres where they will either slip (wheel spin) or hop over the surface to relieve the pressure. By adding stiffer bushes and securing the diff to the subframe, less energy will be wasted in subframe flex or wheel hop.

The large plate attaches to the diff and the arm connects to the bushing which mounts in the subframe reducing independent movement.

Similar to

mob17 · 11-09-2015, 01:34 PM

AWSAWS, you can supply a diff lockdown kit? What manufacturer?

AWSAWS · 11-09-2015, 05:45 PM

Quote:

Originally Posted by mob17

AWSAWS, you can supply a diff lockdown kit? What manufacturer?

No brand name. I get them made by a machinist who is an expert in aluminum.

11-07-2015, 02:05 PM	#1
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	Wheel Hop? Had an interesting encounter earlier. I'm used to driving 4wd cars, and have driven 4wd cars for years. The E90 is my first RWD car, and i find it catches me out from time to time when i try to do certain things that 4wd cars just do without any drama. Applying power on the exit of wet roundabouts was something that would catch me out quite a lot, but i'm getting used to it now. Anyway today i'm driving to the shops in the lashing rain. Waiting at a roundabout, and it was one of those situations where traffic flows meant a constant stream of cars coming. I'd already waited for a while behind a bus, and now i was at the front. Saw a small gap and decided i'm having that and gave it a boot full. Not full throttle, perhaps half throttle but a good strong launch. What i expected was it to launch forwards with perhaps a small amount of slip which the ESP usually does a fine job of controlling. What actually happened was it spun the rear wheels, but then it all went rather odd. I've become used to the fact that you can just keep the throttle down and let the ESP sort out the available grip, except today it didnt seem to. It spun the wheels up, then you could feel the rear end almost bouncing across the road surface. It felt like wheel hop you get in a FWD car when you floor it and it transfers all the weight off the front end. The ESP didnt seem to sort it out and the car somewhat slowly crawled out onto the roundabout. I lifted a bit and it seemed to sort itself out and regain traction and off i went. I tried a similar launch at the next roundabout and it just did what it usually does with no drama. Is this perhaps a sign of worn suspension bushings in the rear end?
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11-08-2015, 03:47 AM	#2
IanS100 Major General 136 Rep 5,050 Posts Drives: 520d F10 LCI M Sport Join Date: Nov 2011 Location: Southport UK iTrader: (0)	It sounds more like something specific to the road at that point, maybe there was a patch of diesel etc
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11-08-2015, 06:43 AM	#3
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	Yeh perhaps, but i'd have expected it would just have spun the wheels in that case, not started hopping around. It was also noisey, bang bang bang as it lost and regained traction. If you've ever driven an old leaf sprung RWD car and experienced axle tramp, it was similar to that.
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11-08-2015, 07:03 AM	#4
Fundguy1 Major General 2036 Rep 8,339 Posts Drives: 335 e93 Join Date: Aug 2014 Location: Orlando, fl iTrader: (0)	Wheel hop happens with large amounts of power. If you're stock it's more likely the road surface. It's not good to do as it's how drag racers snap axles.
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11-08-2015, 08:57 AM	#5
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	Yeh its stock. Must have just been a weird quirk of the road surface i guess. I can sure imagine it snapping axles, it felt and sounded bloody awful in the wet on road tyres. Must be horiffic to get that happening on drag radials and a prepped track with lots of power! I really just wondered if it was a sign that the rear suspension needs attention. The cars on 145k and the control arms on the front seem to be needing replaced, so i can imagine that bits out back also need looked at.
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11-08-2015, 09:52 AM	#6
Fundguy1 Major General 2036 Rep 8,339 Posts Drives: 335 e93 Join Date: Aug 2014 Location: Orlando, fl iTrader: (0)	Coilover time. Front control arms. Trw m3 ones. Subframe bushings.
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11-09-2015, 03:54 AM	#7
OGM2LCI Lieutenant 45 Rep 444 Posts Drives: E87 M2 LCI Join Date: Oct 2014 Location: UK iTrader: (0)	I got this when doing a hard start in my 320d, never happened again until a couple months later it started doing it if I put my foot down round a corner on a dodgy surface and it turned out my rear shock had gone..
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11-09-2015, 04:08 AM	#8
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	hmm! The shocks look like they've been replaced (they look new/rust-free and say "Sachs Pro-Touring" on them) but they may well be crap. Will defo need to have a good look over the rear suspension i guess. Swapping winter wheels on soon, so i'll have a poke around then.
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11-09-2015, 05:57 AM	#10
AWSAWS Colonel 283 Rep 2,343 Posts Drives: E92 GC Turbos, FBO, 335i DCT Join Date: Nov 2012 Location: Valhalla iTrader: (0)	The bushings in the rear subframe are quite soft and can be upgraded to help but the best option is to secure the diff to the subframe. That'll directly reduce the wheel hop and reduce the chances of you snapping components like suspension and drive shafts. I can supply kits for £160 to people in the UK. I just need to know if it's for a small or large diff. E9x (3 series) and E8x (1 series). Right now turn around would be a few weeks for machining. You were on the limit of grip on your tyres where they will either slip (wheel spin) or hop over the surface to relieve the pressure. By adding stiffer bushes and securing the diff to the subframe, less energy will be wasted in subframe flex or wheel hop. The large plate attaches to the diff and the arm connects to the bushing which mounts in the subframe reducing independent movement. Similar to __________________ GC Turbos, FBO, JB4, DCT, Port Meth injection, BMS Charge Pipe, NGK plugs. EBC brakes and pads, LED Angel lights, LED foglights, LCI rears OCC, Braided brake lines. Custom Diff Lockdown Kit, VTT inlets, TMAP, stage 2+ fuel pump 11.79@119mph (stock turbos) 11.74@129mph (GC Turbos)
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11-09-2015, 01:34 PM	#11
mob17 Major General 400 Rep 5,623 Posts Drives: E92 335D Join Date: Mar 2012 Location: East Midlands, UK iTrader: (5)	AWSAWS, you can supply a diff lockdown kit? What manufacturer?
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