Minimum disc thickness specification for front discs?

[robotnik]

Hi
 Does anybody here know what the minimum disc thickness specification is for the 298 x 7mm type discs?
I've got a couple of front discs that have a good ammount of surface rust, I got them included on a wheel I bought a while back.
I'm thinking of sending them to an engineering shop and having  them re-surfaced.
Thanks
 Neil

[annie]

Hi,and welcome to the forum....Bit quite at the moment, but quite a few look in and should be able to answer your query s
Re discs  the manual I have states 6.5 min
Rusty discs in the past I have cleaned up with abrasive paper on a block to ascertain if pitted. If not pitted,  fit and used them.
Sending them off to be dressed would, in my mind take to much off,

[Tom]

Its stamped on the discs, I can't remember what it is but its bollox anyway, I machined mine down to waaaaaay thinner than the minimum and my MOTer commented on how he liked old school discs coz they are loads thicker than modern discs. 

[Tom]

The first thing I'd do is fit them to a wheel and spin with and 100 grade wet and dry to clean them up, then use them, see if the pads clean them up more. Maybe they will look ok, and you've lost nowt but a bit of elbow grease, and lets face it - that beats paying gym membership

[AlanB]

Hi Neil,

I have also run heavily machines discs without any issues, although not on an XS11.

My SG came from the States with a set of slotted discs which looked identical to the originals, but were a factory 5mm thick.  I believe these may be what was originally supplied on some of the Virago 1100s.

I left them on there until I eventually moved to a more modern front end.  Back in those days the bike was not only used, but used pretty hard; all of my mates had much more modern bikes, so the old XS got pushed as hard as I could manage and the discs survived fine.  They are now on the front of one of the Chops in the back of the shed.

I would guess that a machine shop will want more to cut a new surface onto your discs than a pristine set would cost you?  I certainly have a stack of stockers in the corner of the garage, and I guess I am not alone....

Back in the day, we used to deliberately rough-up the surface of the Stainless discs to try to get better (some!) braking in the wet... less of an issue with modern pads, but I wouldn't worry about a bit of pitting unless it is going to be purely a showpiece.

AlanB

[robotnik]

Hi all, thanks very much for all your replies.
I'll get some elbow grease directed at them this coming weekend, I'll see if I can get some before and after pics too.
 Neil

[robotnik]

I didn't get a chance to do anything with the discs yet but I did buy one of these..

http://www.sealey.co.uk/PLPageBuilder.asp?id=20&method=mViewProduct&productid=17820



Priced at £114 on Sealey website, you can buy the set around £60 on ebay though.

The Scotchbrite type pads will hopefully bring the discs up nicely.
  Neil

[Tom]

So not going with.....

a bit of elbow grease, and lets face it - that beats paying gym membership

 

[robotnik]

So not going with.....

a bit of elbow grease, and lets face it - that beats paying gym membership

 

Ha ha , my idea of a good workout is getting from the car to the chip shop door. 

[Tom]

Be careful using power tools with abrasive discs/wheels on your brake discs, they can be very aggressive and take significant metal off, thinking a few thou here. This will cause serious pulsing on the brake lever which an MOTer will fail. For this reason hand cleaning up of the discs is advisable, or going with your original idea of machining. (£££££) Hand cleaning will take little off and so not be an issue for disc minimal thickness, machining will.

[fortj3]

Vinegar will remove rust. As will phosphoric acid, both without removing metal.
They should also etch the surface of the disc, for a little better grip.