brake drums

Post by **les** » Thu Sep 04, 2003 9:48 pm

I've just bought some new brake drums, but before I make the change I'd like to know what the limit for skimming is, so that I can see if the originals have been done. I need the total diameters (front & rear ) including the allowable skim. Also one of the rears show half a thou out of round what is considered an acceptable amount of oval? Any help would be gratefully received.

Post by **Willie** » Thu Sep 04, 2003 10:02 pm

I don't think that you will notice half a thou" ovality on
the rear brakes Les. I think the acceptable amount is
one which does not produce any noticeable grabbing
when you brake. I know from experience that you can't
miss it,especially on the fronts,when it is too oval.
If you can feel it it is not acceptable.

Post by **les** » Thu Sep 04, 2003 10:19 pm

Cheers Willie, I haven't experienced any problems with grabbing so will happily accept the small variation. Can you help on the diameters?

Post by **Kevin** » Fri Sep 05, 2003 9:27 am

Les as have measured the rear drums for ovality it proves your mechanical know how and equipment (dial guage ?) just measure your new ones and compare to the old ones this will show if they have been skimmed I assume you have access to a vernier caliper, or more unlikely an internal micrometer.
These days would not the cost of skimming be the same as buying new drums, or do you do your own ?

Post by **rayofleamington** » Fri Sep 05, 2003 4:09 pm

I would not recommend skimming - if the drum is old enough to have developed problems, then it is also likely to have corroded a bit.
The corrosion (and skimming) and normal wear makes the drum wall section thinner and much more prone to brake fade.
New drums will have thicker walls...
I tend to measure that by eye, though I'm sure there's a more accurate method.

Post by **Kevin** » Fri Sep 05, 2003 4:16 pm

I tend to measure that by eye,

Does it measure in mm or thou`s

Post by **rayofleamington** » Fri Sep 05, 2003 6:51 pm

in 16ths ;-)

Post by **les** » Fri Sep 05, 2003 9:48 pm

Thanks for the replies, Yes Kevin I can compare them with the new ones, an obvious solution that I missed completely! I will still need to find the maximum safe diameter though. It's not my intention to skim them, it's just that if they had already been skimmed but were still within the allowable diameters I would not use the new ones yet. I was lucky enough to buy an internal micrometer set from a shop that sold secondhand tools etc, its not used that much, but when it's needed it's very handy.
Just out of interest I have bought and fitted a stainless exhaust and apart from the usual huffing and puffing it fits really well, there is actually some clearance where the pipe passes through the bulkhead! Unlike most I've tried. I bought it from east sussex minors. I also fitted a new clutch relay assembly bush.