Grooves in brake disk?

Hello:

I'm the owner of a 2003 Kawasaki Voyager with 12,500 kms (7,800 miles)
on the clock.

I noticed recently that there are several quite deep grooves in the
front brake disks. I guess this happens when a small piece of gravel
gets caught between the pad and the disk. The bike only has 12,500 km
on it, and has hardly ever been driven on actual gravel roads, and
then, only for very short distances. Would you think that this would be
normal? Anything to worry about? It certainly isn't affecting braking
power at this point, but it seems a bit early in the bike's life for
this kind of wear to be appearing.

Any ideas for preventing more of the same would be good, as well as
ideas as to how this happened.

Thanks for any comments.

Paul Harris
Victoria, BC

 

I'm new at this, but... I'd recommend pulling the pads, at the
least. You may have caught a small piece of stuff laying on the
pavement, and embedded it into the pad surface.

Hope the disk hasn't been take to below minimum -- you might
need to have it turned down.

--

 

Thanks Kaybear. Are you saying that this is normal, and I shouldn't
worry about it?

I failed to add that the low mileage on my Voyager is almost entirely
highway miles, and therefore not that much use of braking, compared
with city riding.

Paul Harris

 

I'm going to take off the calipers this weekend, and take a look. I can
hardly imagine that my disks are actually worn much thinner than when
new, aside from the grooving, as most of my mileage, quite low, has
been highway miles, and therefore not a lot of braking, all in all.

PH

 

You can try getting the disc skimmed, if it doesn't take it below the
recommended service limit thickness.

Try different pads, and avoid gravel roads.....

 

<1geeys0.1h0mow51rvb78hN%>, The

Thanks for your suggestions. I figure that out of the 7,800 miles,
approximately, on this bike, maybe 5 miles total have been on gravel
roads. No, make that 3 miles.

PH

 

The disks on this bike can not be "skimmed".
All disks get grooves to some extent. If there are particularly nasty ones
you should check the pad surface for an imbedded particle.
Regardless, don't worry about the disk, it's fine.
B

 

Thanks. I'm starting to get the idea that this is nothing to worry
about.

Best . . .

PH

 

Thanks for your further comments KB, Your input to this newsgroup is
great, your knowledge of things mechanical/electrical is phenomenal,
and I always enjoy reading your responses to almost any question posted
here. I've learned a lot just reading your postings.

Isn't the internet great?

Keep it coming.

Paul Harris

 

Why not, out of interest?

I'd have thought all dics can be skimmed, as long as they don't get
reduced below the wear limit.

After all, what's the difference between a disc wearing thinner and
being machined thinner? Or is it a metallurgical thing?

 

You are right, there is no reason a motorcycle brake disk can't be
skimmed. But in my admittedly limited experience, it is hard to find
anyone who will actually touch one. Most of the brake lathes for
automobile rotors won't work on such thin disks, and thus your only
option is a machine shop with a surface grinder, and a machinist who
isn't afraid to try it. Bike disks start out so thin (saves weight)
that by the time they have developed warp or grooving bad enough to
warrant skimming, they are likely to be worn below the minimum.

 

Why not, out of interest?

me too
you should not cut bike discs on a lathe or car disc machine, they need to
be ground on a particular grinding machine...but apart from that???
do tell?

 

That's true enough. The last disc I had skimmed was off an old 1979 Z400
twin, and (like all discs of the period) was about half an inch thick.