Brake disc skimming

[Stedman8]

Just wondering if its possible to get the discs skimmed and if so how much would it cost approx, and what the minimum thickness for a disc is ,cheers Steve

[darrsi]

Normal wear limit is 4.5mm, they're not thick enough to skim.

[packie]

....plus they'd cost a bit to get done. Every engineering works will have different rates, so you will need to shop around.

[darrsi]

Why would you want it skimmed, what is the problem?

[Dead Eye]

Well with a question like this I assume the discs have become warped and the open was hoping they could be skimmed to restore them

[darrsi]

Well with a question like this I assume the discs have become warped and the open was hoping they could be skimmed to restore them

People presume their discs are warped, but it's not always the case.
This is one subject i have a lot of experience at, believe me!

[Stedman8]

What it is, I was thinking of buying some second hand discs and just thought that maybe if there was a little damage on them or they were warped slightly if it would be possible to get them cleaned up or sorted somehow,  I haven't bought them yet and there's probably nothing wrong with them at all - it just got me thinking about whether it was possible to take a mil off a disc,cheers for the replies anyway so I take it that its probably too expensive,and a waste of time and its probably better to wait for a lottery win and buy new ones if they get damaged 

[darrsi]

Believe it or not new discs are only about 1mm to 1.5mm extra than the wear limit.

[Stedman8]

Has anyone any idea on how long a new disc would last before it needed replacing - I know they'll be variations like how hard you are on your brakes, conditions they are used in ,summer or winter use  etc but what parameters are we talking given normal road riding in decent conditions and say 10,000 miles a year or is it the case that when it needs changing it needs changing 

[darrsi]

Fronts last way longer than rear because they're "floating".
The outer disc that stops you gets hot, but doesn't transfer the heat to the inner part, whereas the the rear is one plate and receives all the braking heat, hence the reason people have so much grief undoing the bolts.
All depends on the grade of pads used really.
Organic pads are soft and will wear out quicker and create more dust, sintered are harder and will bite more but are more abrasive.
I just wore out an EBC Pro-Lite rear disc with sintered Galfer pads in 11 months, but i had a front brake issue so compensated by over using the rear brake.

[Stedman8]

Cheers for that darrsi- great explanation made it clearer about what floating meant and the difference between the pads used - all these bits of info come in really handy , especially when you bugger around with things as much as I do 

[darrsi]

Not bad considering i'm mullered texting from the pub on an unusual weekend off work 

[packie]

Has anyone any idea on how long a new disc would last before it needed replacing - I know they'll be variations like how hard you are on your brakes, conditions they are used in ,summer or winter use  etc but what parameters are we talking given normal road riding in decent conditions and say 10,000 miles a year or is it the case that when it needs changing it needs changing 

Well if its a Cop that I know, his discs would last about 100,000 miles. This guy is an excellent pilot and uses about 95% engine braking. I could be up behind him for 2-3 hours of hard riding, and you'd only see his brake light come on only a handful of times. 

[Lumpy]

Fronts last way longer than rear because they're "floating".

The outer disc that stops you gets hot, but doesn't transfer the heat to the inner part

please would you clarifiy what you mean on both of these points. The temptation was to dispute both but I'd best find out what you mean before I discredit it. See, I'm being diplomatic
 
My rear caliper is a 2 piston affair, opposed, and I think the standard is too, so the fact the disc is not floating shouldn't make any difference because the caliper is.