Brake disc run-out

[stevie_b]

Someone has told me I may need to get the run-out checked when I change the brake discs (we were talking about my Ford Cmax runabout, but it applies equally to the supra). Is this something that needs to be checked/adjusted?

 

I can't remember exactly how the discs attach on to the hub on the supra. On my Cmax, they simply go on the wheel studs. In which case, any run-out setting would be lost when you undo the wheel nuts.

[bignum]

Discs go on the same, runout can`t be adjusted, its either warped discs(most common) or warped hub flange, you need to get them seriously hot to warp the hubs though as did i, fix is either new discs or get the discs refaced on the car which takes all the runout out, http://www.spsimnett.co.uk/#!pro-cut-brake-discs/c1opc , that garage has nothing to do with me just 1 i found local which i may use in the future.

[Scooter]

What I've found is that you need to give the hub face a really good look and then clean. The temptation is, old disc off new one on, but the old disk can leave a bit of its rusty self in various spots and cause poor run out.

 

I have a dial gauge and bolt on the new discs without the wheel and spin/test it to ensure it's not far out.

[bignum]

What I've found is that you need to give the hub face a really good look and then clean. The temptation is, old disc off new one on, but the old disk can leave a bit of its rusty self in various spots and cause poor run out.

 

I have a dial gauge and bolt on the new discs without the wheel and spin/test it to ensure it's not far out.

 

Good call scooter on cleaning hub faces.

[stevie_b]

Arse, I didn't do that (I changed the discs on the CMax at the weekend). Oh well, something to remember for next time. Thanks gents.

[Scooter]

You might be ok, but I've been there before, and it only takes a very small piece of incompressible crud to remain to cause an issue.

 

Jack the wheel up give the brake a press and then rotate and feel/listen for a dragging spot. Some pad drag is to be expected but you may feel a particularly bad/worse section. If you do go and take the wheels off you can do the same with just the disk still bolted on. You can also rig up a basic dial gauge, a sort of stiff wire from a heavy base so it's sprung to just touch the outer part of the disc, then as you rotate it may scrape/stop scraping audibly on rotation (if you do this I'd pry the pads away so the disc is completely free from external forces). Clean and repeat, sometimes taking the disc off and rotating it one bolt hole can just make for a truer position (NB also fit all the 4 or 5 bolts each time)

Edited May 24, 2016 by Scooter (see edit history)

[stevie_b]

I hesitate to raise this question (it gave rise to some debate last time), but do you put any copper grease on the disc/hub surface so the disc doesn't seize on? last time I asked about copper grease, I was talking about the alloy/disc interface, so the question's a bit different this time.

 

Thanks for your help.

[Scooter]

I've personally never had a disc badly stuck on a hub and also there is usually a bolt hole you can screw into to pop off a stubborn disk so I wouldn't/don't