Rear end fishtailing

[S3 Hilife]

I was having a play yesterday when the rear end started fishtailing on a 4th gear pull at full boost from around 70mph ish. I was accelerating out of a very slight bend when it happened so the haldex may have been engaged. It probably wasn’t a massive amount of movement but felt very unstable. I’ve also occasionally had the back end step out a little in lower gears on full boost when traction is lost and the haldex kicks in but never fishtailed like this. I was hoping someone may be able to advise what the most likely cause might be so I know where to start looking to fix the problem.

Rear suspension setup:
Koni STR.t struts & H&R springs
Standard ARB with polybushed mounts
New ARB links
Traililg arm front polybushed
Silver project lower control arms
(Probably a bit too much neg camber)

Wheels/tyres:
8.75” et10 (inc spacer)
225/40/18 Goodyear eagle F1 (with slight stretch) 33psi rear (& 35psi front)

I suspected it’s probably caused by the slight stretch in the tyres but just looking for other opinions in case it could be something completely different

A few pics for reference

Thanks,

Steve

 

[S3 Hilife]

It’s it possible for a faulty haldex to cause the back end to fishtail on full load or is it more likely a result of poorly sized tyres?

Any ideas

Steve

 

[Alex C]

what deg negative camber are you running? How much power are you running?

 

[S3 Hilife]

I honestly don’t know what degree neg camber it’s set to tbh but it’s probably a bit too much. Power wise it was 501bhp/382lbft at Badger5

 

[desertstorm]

That looks like way too much negative camber on the rear along with the stretched tyres and they are only 225 section. Get some wider rubber on the car , you could run 245/35 tyres on those rims and lose some of that rear camber. Aim for something around 1.5 degrees .

 

[S3 Hilife]

That looks like way too much negative camber on the rear along with the stretched tyres and they are only 225 section. Get some wider rubber on the car , you could run 245/35 tyres on those rims and lose some of that rear camber. Aim for something around 1.5 degrees .

I knew I was pushing it with this size tyre and suspected it to be the issue lol but it had never caused any problem until now. I’ll sort the camber and get some wider rubber on if I can squeeze it inside the arch

Thanks

 

[Alex C]

I would guess the negative camber has reduced the contact patch too much. I used to have 225 on my 8.5" rims but sized up to 235; I could probably go 245. I wasn't sure from that photo how much neg camber you've got because i know the profile of the bumper/wheel arch cuts back in which can exaggerate how the camber looks - it does look quite extreme though

 

[Gazwould]

Way too much negative camber reducing contact patch .

Camber on the road for drainage you go to overtake and it's even less contact , just the insides .

 

[badger5]

get the tyre flat to the road.. and check what camber you actually have and toe importantly.. rear wheel steering.. makes thing well lively

 

[S3 Hilife]

Thanks guys, I’ll get that sorted and aligned properly