Disc skimming - comments ?

[timlit]

Having seen Wheeler Dealer last night with Ed doing his stuff on an opd Boxster,

was interested to see the disc skimming technique on the car.

Due to wheel shimmy at high speed ( track days ) am keen to get it done on my

3.2 Carrera, without the cost / hassle of changing all the discs.

Assume that new pads would be needed also, any advice on type to fit,

Only do 2 half track days a year.

Any helpfull comments please,

Thanks

[Pickled Piper]

Yes, I've had mine done at my local Porsche Indy. This is the process where the disc is not removed from the car. The calliper is unbolted and swung away from the disc. The machine locates on the hub and then grinds the disc. There are a couple of videos on youtube showing the machine in action. The benefit is that the disc is very true to the hub with minimal runout. The cost of having it done is about the same as sourcing the discs yourself and changing them (DIY). My Indy advised it worked well on the aircooled cars as the discs just had more "meat" on them. I didn't have to change the pads. The Indy just degalzed them and refitted.

From memory it was about £70 per corner.

pp

[dry664]

I saw that last night. Couldnt help but think of the response he would get if he'd gone into an OPC and asked for those discs skimmed.

Slightly off topic but a grand for that Boxster? Really?

[Koln-RS]

Rear disc corrosion is quite common - especially on 'garage queens' that are washed then garaged without a good drive.

If the discs are thick enough, then OPCs can skim them. I've had it done.

[granpappy]

had mine done at indie last month £30 a corner massive improvement

[Slippydiff]

timlit said:

Having seen Wheeler Dealer last night with Ed doing his stuff on an opd Boxster,

was interested to see the disc skimming technique on the car.

Due to wheel shimmy at high speed ( track days ) am keen to get it done on my

3.2 Carrera, without the cost / hassle of changing all the discs.

Assume that new pads would be needed also, any advice on type to fit,

Only do 2 half track days a year.

Any helpfull comments please,

Thanks

If you've got wheel shimmy at high speed, I doubt skimming your discs will make a lot of difference, the clue being in your description of the issue, that being wheel shimmy.

Which begs the question, is it wheel shimmy ? as opposed to a pad transfer issue or warped discs ? I suspect it's most likely a pad transfer issue that goes away a few days after you've done a track day ?

If however it is warped disc/s, skimming them probably won't solve the problem either, what runs true when it's cold and being rotated at 100rpm by the disc facing machine, won't be true at 400 degrees and 80 + mph.

If you haven't already done so, check your wheel balance, also get your wheels checked to make sure they're true and not buckled/flatspotted. Then get a runout check done on the discs. If all is fine with regards to these items, I suspect you're experiencing inconsistent pad transfer issues when hot.

Hope that helps. Good luck !

[mollytherocker]

A 3.2 Carrera, honestly, I would just put new discs on. They are pretty cheap anyway.

I wouldnt piss about skimming discs.

[996ttalot]

mollytherocker said:

A 3.2 Carrera, honestly, I would just put new discs on. They are pretty cheap anyway.

I wouldnt piss about skimming discs.

Tend to agree with you on this one.

The guy who sold that Boxster must have been gutted after watching how much it sold for.

K.

[BliarOut]

I'd go and do a few hard high speed stops in quick succession then let the discs cool while the car is still rolling. Chances are it's pad transfer from hard stops then putting the handbrake on or similar.

Wait till it's a bit more grippy out there though.

[X-UFO]

Surely skimming is something from 20 years ago when the metal was almost forged from an anvil.

Nowadays if you skim modern discs it will thin them and make warping at higher temps more likely?

[sportsandclassic]

X-UFO said:

Surely skimming is something from 20 years ago when the metal was almost forged from an anvil.

Nowadays if you skim modern discs it will thin them and make warping at higher temps more likely?

Hi,

As long as the skimmed disc is still above the minimum thickness stamped onto the bell it will be ok.

You only take small amounts off to true the disc face back up.

Mike

[Pickled Piper]

X-UFO said:

Surely skimming is something from 20 years ago when the metal was almost forged from an anvil.

Nowadays if you skim modern discs it will thin them and make warping at higher temps more likely?

See the comments in my post above from my local Indy. Works well on the aircooled cars. Discs were thicker. He said you could do it a couple of times. Not so with modern Porsches.

pp

[VonSenger]

Ive had this done on every car Ive owned including my turbo which I tracked regularly. Absolutely no difference, makes me laugh when people throw a set of discs away due to "lipping".

[Chrisp5782]

I've had it done at Autofarm, much cheaper than replacement, why spend extra money when you don't have to?

Provided the disc, once skimmed, is within wear limits it's a good option.

[anonymous-user]

Two things:

As already said, 'wheel shimmy' is not likely the result of a disc issue.

You won't find many people who believe in skimming discs other than those who have been persuaded to 'invest' in the equipment to do it.

[clockworks]

Watched the Wheeler Dealers episode last night. I was slightly worried by the way the whole machine rocked gently back and forth as the cutters moved across the disc.
Since the machine is locked to the car by the hub adaptor, I reckon the whole thing was running out of true.

Far better to remove the disc and skim it on a decent lathe, having centred it properly.

[MadMark911]

mollytherocker said:

A 3.2 Carrera, honestly, I would just put new discs on. They are pretty cheap anyway.

I wouldnt piss about skimming discs.

Yup - just replace them!

Snake Oil anyone??

[Chrisp5782]

REALIST123 said:

Two things:

As already said, 'wheel shimmy' is not likely the result of a disc issue.

You won't find many people who believe in skimming discs other than those who have been persuaded to 'invest' in the equipment to do it.

OPC's and a number of very highly recommended specialists then? I think you'll probably find a fair few that believe in it and why wouldn't they - legal, safe and a money saver, whats not to believe in?

I trust the likes of Autofarm to do work like that, mine were skimmed due to corrosion on the back of the disc due, in part, to the shield on the back that tends to trap moisture and debris.

Don't knock it till you've tried it.

Edited by Chrisp5782 on Thursday 14th March 13:19

[anonymous-user]

Chrisp5782 said:

REALIST123 said:

Two things:

As already said, 'wheel shimmy' is not likely the result of a disc issue.

You won't find many people who believe in skimming discs other than those who have been persuaded to 'invest' in the equipment to do it.

OPC's and a number of very highly recommended specialists then? I think you'll probably find a fair few that believe in it and why wouldn't they - legal, safe and a money saver, whats not to believe in?

I trust the likes of Autofarm to do work like that, mine were skimmed due to corrosion on the back of the disc due in part to the sheild on the back thatvtends to trap moisture and debris.

Don't knock it till you've tried it.

As I said, once you've been persuaded to invest in it, you are going to need to recoup the investment. Just like the shock absorber testers that were once the thing to have, the wheel washers etc.

None of them necessary and any money saved machining modern discs is inconsequential. And they don't corrode on the back if they're maintained and used properly.

[Chrisp5782]

REALIST123 said:

Chrisp5782 said:

REALIST123 said:

Two things:

As already said, 'wheel shimmy' is not likely the result of a disc issue.

You won't find many people who believe in skimming discs other than those who have been persuaded to 'invest' in the equipment to do it.

OPC's and a number of very highly recommended specialists then? I think you'll probably find a fair few that believe in it and why wouldn't they - legal, safe and a money saver, whats not to believe in?

I trust the likes of Autofarm to do work like that, mine were skimmed due to corrosion on the back of the disc due in part to the sheild on the back thatvtends to trap moisture and debris.

Don't knock it till you've tried it.

As I said, once you've been persuaded to invest in it, you are going to need to recoup the investment. Just like the shock absorber testers that were once the thing to have, the wheel washers etc.

None of them necessary and any money saved machining modern discs is inconsequential. And they don't corrode on the back if they're maintained and used properly.

They do corrode on the back (common on those Boxsters) and my cars are maintained perfectly well so you can drop your cheap shots.

Machining modern discs isn't inconsequential or it simply wouldn't be offered and it works, I know I've had it done, as have plenty of others.

I assume you run or own a Porsche specialist and therefore fully qualified to de-bunk the working practices of Autofarm who have been running since 1973? Nope, thought not.

Edited by Chrisp5782 on Thursday 14th March 14:08