TRANC3

Hi Guys,

My car has 24k miles on it and has recently been lowered on Swift springs including rear adjustable camber arms, plus new 20" wheels. I've recently noticed that under hard acceleration there seems to be a slight vibration coming through the chassis. If I had to guess I'd say it was coming from the rear. My question is, has anyone had something similar happen after lowering, and what was the cause?

I don't believe it to be a wheel balance or alignment issue as the vibration is only apparent under acceleration - it goes away as soon as you come off the throttle. The internet suggests something along the lines of CV joints (is still what they are called on a rear drive car?) or bent driveshaft. Any ideas appreciated.

For clarity, the rear is now running about 3° neg camber, and about 1° neg up front. The car is also TVD equipped.

Mingofish

JT2MA71

iTrader: (7)

It could be wheel hop. Does the trac light come on while it's vibrating? Mine does slip but no vibration, but that depends on alot of things, titres, suspension setup including alignment, tire pressures, etc.

yooniverse

Negative 3 camber will not cause that vibration.
You might wanna look at the axle or the drive shaft that could of been damaged while raising the car up for the services you got done.

lobuxracer

iTrader: (2)

Maybe yes and maybe no. -3.0 degrees of camber is enough to induce genuine camber wear on many tires. If you are on summer tires and it is cold outside, you could be getting tire shake, and -3.0 turns even more negative on launch when the rear squats which reduces your contact patch even more. Why did you choose this setting? I would never choose this for a street driven vehicle, and would only choose it for a road course where I needed a lot of cornering traction AND the tires I am running will benefit from this much camber. No street tire likes this much negative camber.

TRANC3

Thanks for the responses guys.

- the issue is not occurring in a launch scenario, rather a WOT roll on in 2nd 3rd gear - higher rpm range.
- trac light not coming on and def doesn't feel like wheel hop - its a harmonic vibration through the chassis.
- will check the axles if below doesn't fix issue.
- tyre shake from aggressive camber? - hmmm, haven't heard of this but will investigate.

Spoke to my wheel guy today and took him for a drive so he could feel it, and have decided to dial back the -3° to it's original -2° (I can't remember feeling this when this was the setup - mind you it was on OEM wheels). I'll also check to see how the guys are jacking the car up to see if contact with the axle may have bent them. This will get done next week, so I'll update then.....god I hope it's not the axles!!

Oh, and as to why the -3° in the first place, I can't really answer that....I guess they chose that as a safety net for close fitment, but I'm sure we have room to move it back out.

1BAD4DR

TRANC3

That's actually a reasonable approach....might try this first. Cheers

jonmonkey

TRANC3

Just a quick update...we dialed out about 1/2 a degree of camber from the back and it seems to have solved the problem. Issue seemed to stem from reduced tolerance in the driveshaft as a result of running aggressive camber, i.e. it was too tight, exacerbated when WOT as this naturally causes the car to squat, further increasing camber. The adjustable control arm fitted to the rear (SPC in this case) essentially pulls the top of the wheel in towards the car, effectively reducing any play the driveshafts need to operate smoothly.

Still somewhat baffled as I've never seen this occur on another lowered car, and I know a lot of RC-F's run lower than me.

Anyway, happy the problem is solved

Mingofish

lobuxracer

iTrader: (2)

Glad you're fixed, but you're looking through the wrong end of the telescope. Reducing contact patch increases stress on the rubber blocks and causes tire shake, especially with street treaded tires. It's not the geometry, it's the tires. It wouldn't do this with slicks.

TRANC3

Appreciate the comment, and if that was the cause of the issue then we've done exactly what you said and have increased the contact patch of the tyre by reducing camber. Either way it's sorted, and the car is once more capable of breaking laws smoothly!

TRANC3

So I wanted to give a further update to this as the fix that we thought had fixed it, actually didn't. I finally had some time to send it in to the shop to try and diagnose....

First thing we did was reinstall the factory rear springs as a way of eliminating possible suspects. Suddenly the problem was gone....literally like someone had flicked a switch. Acceleration was now smooth as silk (I'd almost forgotten how it's suppose to feel). So at least now we knew the problem is focused around the rear drive shafts/axles area and it's components. Of course raising the car means that the camber of the rears was reduced. So once again, we installed the lowered springs but this time removed the SPC adjustable control arms to bring the camber back to something very neutral. At this stage we are all a bit nervous as I've opted for a 295 tyre which is already a squeeze to fit in with 2.5 degrees of camber. Fortunately they still fit....just.

So the upshot is that the amount of rear camber was definitely the issue. We just hadn't dialed enough out when trying to remedy the issue. I'm not sure if it is to do with the tyres (as mentioned above) or if its the angle of the CV's, or if the shaft was getting compressed to a point it wasn't happy. Either way, my question to the forum now is, what's the most amount of rear camber you have run at the rear (at rest), because I could not find this problem replicated on the RCF in any of my google searches....and I know some of you run crazy low.

Lammyyy

My drive height runs -2.5 camber and I can launch with no vibrations. Our drive club does 150-165mph pulls from a dig pretty often and I have no issues. Hope this helps!