Brake Disc Skimming

[Bradley1500]

I will be changing the front brake pads on my Supra soon and as the discs are lipped, I have been looking into having the discs skimmed.

There is some judder from heavy application of the brakes from high speeds, otherwise they feel fine on the road. The discs are in good condition minus the lip and haven’t done many miles. The discs are also £223 a pair to replace, so not cheap!

A garage local to me offer a disc skimming service while the discs are still fitted to the car for £40 per axle. I believe they use the same machine as seen on Wheeler Dealers during the Porsche Boxster episode.

Are there any major downsides to skimming, and has anyone had their brake discs skimmed?

Most of the information I have found online is from biased companies trying to sell their service, so it would be good to hear other opinions. I have seen mentioned that disc skimming can be better than replacing, as the discs have already been heat cycled meaning after skimming they should be less susceptible to warping again – is there any truth behind this?

[stevensdrs]

Had it done once and it was fine. You should only consider it though if your discs are still well above the minimum thickness.

[mgv8]

Ask more people who have owned an Evo 5, they needed doing almost every time the car was serviced. As long as they know what they are doing and don't take to much off then all fine.

[M-SportMatt]

I had an issue with a mondeo years back where for some reason the disc wasn't quite square on the hub and it wasnt financially viable sorting it properly, it vibrated under braking, car was just a cheap hack so I had the discs skimmed on the car, solved my issue and gave me another year or so of service before i flipped it on.

I subsequently had some discs skimmed on the car on a track prepped fiesta I ran at trackdays after overheating the brakes and warping the discs slightly, again no issues afterwards and a cheap fix with no downsides as far as i was concerned

[Charlie Croker mk2]

New discs ( Front pair ) start from £32 on a well known auction site , possibly less from a local motor factors if you are in the trade ? Still think its worth trying to get the old ones skimmed ??

[sim16v]

I wish I could find a reputable company near me to do it for a sensible price.

My Jeep destroys front discs so it might help if I could skim them every now and again.

[RobXjcoupe]

The only advantage of skimming the disc still attached to the hub is getting it running true. But, any good machine shop should clock up the mounting face first before removing any material.
All discs have a minimum thickness. If the lips on the disc are quite large and you have warped discs, chances are they are at minimum thickness already hence they have warped.
Regular discs are made from cast iron and as such isn't a heat treatable material. Cast iron is used as it's soft and will wear in conjunction with the pad material. Most regular modern cars will need a disc change with every pad change as both components wear at the same rate now

[sparkythecat]

This is how to do it.

https://www.youtube.com/watch?v=SLR9AlI8qe0

[M-SportMatt]

Charlie Croker mk2 said:

New discs ( Front pair ) start from £32 on a well known auction site , possibly less from a local motor factors if you are in the trade ? Still think its worth trying to get the old ones skimmed ??

Depends what discs they are and what the issue is............as above. So yes its massively worth it in some circumstances

[The Wookie]

As said, no downside to having them skimmed as long as they are done properly and are above the minimum thickness when finished.

It can in fact be an advantage if your hubs have runout and are causing problems as you're truing the disc on the vehicle.

In terms of being skimmed off the vehicle, unless it's a precision machine shop or an incredibly careful one who is used to working with brake discs then they should only really be twin turned (i.e. both sides machined at once). The opportunity for causing disc thickness variation and ruining them is very high

[The Wookie]

Charlie Croker mk2 said:

New discs ( Front pair ) start from £32 on a well known auction site , possibly less from a local motor factors if you are in the trade ? Still think its worth trying to get the old ones skimmed ??

I'd rather have a set of skimmed OEM discs above the minimum thickness than a new set of chinese crap any day.

[Bradley1500]

Thanks for all the replies.

I am not sure what the minimum thickness is for the discs I have. I will try ringing the manufacture and asking them. If not, how could I find out a minimum thickness?

I assume the garage offering the skimming service will know how much material to take off the discs, although maybe I am being naïve here.

Charlie Croker mk2 said:

New discs ( Front pair ) start from £32 on a well known auction site , possibly less from a local motor factors if you are in the trade ? Still think its worth trying to get the old ones skimmed ??

I can’t find any discs for the price you mentioned. The cheapest I have found online are EBC at £105 a pair. Genuine Toyota discs are slightly more expensive, but as I mentioned in my original post, the discs I have fitted were £223 new.

Even if discs could be bought as cheaply as you say, I wouldn’t want to fit the cheapest possible part to my car – I can’t imagine the quality to be good!

[mwstewart]

Cheap discs are awful. Low carbon content.

[f1nn]

The Wookie said:

I'd rather have a set of skimmed OEM discs above the minimum thickness than a new set of chinese crap any day.

Absolutely this.

[buzzer]

One thing I would say is that with skimming the discs on the car they are turning the metal off, rather than grinding. ( I THINK this is the case....) New discs come with a ground surface.

Over the years I have turned down the circumference and mounting face of dozens of Ford Escort Discs. Depending on the manufacturer, some turn really nicely, and others leave a terrible finish that I would not be happy with as a braking surface. So it depends on the material of the discs. From memory Eicher discs turned with a really rough finish. Lockheed turned with a finish I would have been happy with as a braking surface.

I would add that the reason I was turning them down was to fit them as a brake on a cement mixer drum that a mate used to manufacture he used Escort discs as they were cheap!

[Sheepshanks]

Bradley1500 said:

A garage local to me offer a disc skimming service while the discs are still fitted to the car for £40 per axle.

Presumably they need to remove the caliper to do the skimming and you're supposed to fit new pads when it's done, so if they're including that in the £40 then it seems remarkably cheap. Even just for skimming, when you think of the time and kit involved, it's still cheap.

I asked a couple of places about doing the rusty fronts on my Merc C Class and they were both talking around £100.

[Ruffy94]

Ive never been a fan of this, but never had any experience of it. If they skim the discs with them on the car, the inner face is normally forgotten and can still be in poor condition. Just not worth in imo

I watched a wheeler dealers repeat the other day (the boxster, where they skimmed the discs) and checked the MOT history for a laugh. It passed with no advisories in 2013 (when the program was filmed) every year since then its had advisories for 'brake discs worn pitted or scored' a couple of tests have mentioned the 'inner face' being in poor condition

[Zoobeef]

Last time I had it done it was £50 a corner.

[KungFuPanda]

Charlie Croker mk2 said:

New discs ( Front pair ) start from £32 on a well known auction site , possibly less from a local motor factors if you are in the trade ? Still think its worth trying to get the old ones skimmed ??

£32 for a pair of front discs for a Supra?

[CoolHands]

Back when I was an apprentice (at a main dealer) we used to have it done. But never on the car, that sounds a bit weird. You would take em off, give to bloke to skim on a lathe and a tenner later jobs done.