TVR Tasmin, Broken Brakes

With the KJet Cologne firing on all cylinders, the next step toward a WOF was to look into the brakes and why they shudder horribly.

I had noticed the shudder on the first drive when I got the car, but hoped that it was just rust on the rotors from sitting and some heavy braking might scrape it off and make it go away. Sadly not, having done some heavy braking in the car now, it still shudders and shakes its self to bits when braking. It can be felt in the pedal and the whole car sort of pulsates as it slows down.

I had originally planned to get the front rotors skimmed and see if that improved it much, but it was bad enough that I thought I should prepare for the worst, and check the runout. I like my WOF guy, so I try to pre-empt as much as possible so I don’t send him rubbish that’s guaranteed to fail.

To check rotor runout (rotor warping basically, the difference between flat, and the high and low points) you use a dial indicator. A dial indicator is a gauge that moves when the little pin slides in and out of the gauge body, as the item its measuring gets closer or further away from the gauge body.

A rotor should have very little runout, somewhere in the vicinity of less than 0.10mm is a good guide.

I started with my rear rotors, as these are the ones I was most worried about, as they will be an arse to replace, and cannot be skimmed on the car.

Even after some hard stops, the rotor wasn’t looking great.

Mounting the dial indicator was proving to be an issue initially. It’s on a magnetic base, but it’s heavy and bulky. I tried mounting it to the exhaust and suspension, but it just made the dial hard to read

And then I engaged brain and mounted it to my jack as a solid base on the floor. Duh, much easier.

Zeroed the dial at the lowest point

And turned the rotor until I found the highest point. Uh. Crap.

So yes, that’s that rotor completely stuffed. 0.35mm runout. I didn’t even bother checking the other side, if one is bad, that’s a pair ruined. I checked in a couple of spots on the disc and came back with similar results.

Hows the front then? I mounted the dial to the caliper and zeroed it

Well, it’s not great. 0.19mm runout.

That’s the sort of runout that could be skimmed out, except I also measured the front rotors, and found they’re below minimum thickness (11.4mm) already, so cannot be skimmed.

Well damn, that sets me back a bit, both financially and time wise.

I have ordered a set of new rotors, with the fronts coming from the UK in the form of some lovely slotted and dimpled rotors, and the standard rears from Aus. I will be reusing the existing pads as they are all near new, but will give them a scuff up first.

Not what I wanted, especially with the holidays getting in the way, so looks like we will be off the road over Christmas now too.

Oh well, at least it should stop as well as it goes now. Someone will get a damn good car when I inevitably move it on.