MiniTorque.com banner

1 - 3 of 3 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter #1
Hi,

I recently had a set of ST XTA coilovers fitted along with adjustable rear control arms and some powerflex bushes (rear trailing arm and rear top mount). The car already has other powerlex bushes on the rear engine mount and front wishbones (non-caster adjustable). After the coilover install I had a full re-alignment. I'm not sure exactly how much lower the car is now but I'd guess maybe 2 inches max.
I'm currently running 215/45/17 tyres front and rear with 13mm spacers front and 6mm spacers rear. I can't go any lower at the moment as I already get some tyre rubbing at this height on bigger bumps. I'll eventually swap to lower profile tyres.

The car has about 40k on the clock and was on stock suspension up to this point. As far as I know it still has the original driveshafts, although I had to get one CV joint refurbished last year due to a cracked boot.

The car now handles much better than it did on the worn out stock suspension but the problem I have is I'm now getting a fairly bad vibration when accelerating. This mostly happens between about 2k rpm and 4k rpm and is worse going up hill. From doing some research it seems that this is a fairly common problem with lowered Minis but unfortunately I didn't realise that until now. The general consensus seems to be that the vibration comes from the driveshafts and this could be due to the CV joints now being at a sub-optimal angle, or at an angle that puts the CV joint bearings near the edge of the old wear area, causing them to kinda tramline in the bearing race. Or possibly both.

As far as I can tell from looking under the car, it looks like my driveshafts are now angled slightly up towards the wheels while the car is sat on the ground. I'm assuming that with the stock suspension height the driveshafts were angled slightly down towards the wheels. So as far as I can see, even under hard acceleration the driveshafts should be quite flat rather than at an extreme angle. If anything, during acceleration I think they will be flatter now due to the front end lifting. If that true, then with the stock suspension the angle would have got greater under acceleration.

I've read that some driveshafts (or CV axles to be more accurate) can vibrate if they're run too flat. They need some angle to work smoothly. I don't know if that's true but it could help explain what myself and others are experiencing.

So my questions are, does anyone know if the driveshafts are likely to vibrate due to being too flat during acceleration and if so, can this be dialled out by introducing more "anti-lift" to the suspension geometry and potentially lowering the car more to prevent the car lifting enough to make the driveshafts flat? I've read that caster adjustable front wishbone bushes can help.

One reason I'm wondering if the driveshafts are too flat is that I've seen some people with very low Minis say they don't experience any vibration. So I'm wondering if actually their driveshafts are closer to the correct angle during acceleration, just in the opposite direction if that makes sense. The other thing I realised is that the rpm range that the vibration occurs over is right around peak torque, which I'm assuming is when the most front end lift is going to occur during acceleration.

I should mention I have a 2010 Cooper S (N18B16A) with stage 2 Manic tune (250HP @ 5165rpm, 400Nm @ 3171rpm).

So if there are any suspension geometry or CV joint experts out there, I'd really appreciate some input on this. Thanks.
 

·
Registered
Joined
·
1,564 Posts
I had the same vibrations on my Meister's

Basically car was too low.

Raised it up and tested each turn until the vibrating stopped. Easy enough

Sent from my EML-L09 using Tapatalk
 
1 - 3 of 3 Posts
Top