front brake rotors

[bigbore2]

Need to clean up my right front brake rotor [stock] when I rebuild the caliper. Has anyone found a way to resurface/turn like for a car.  My local car place said if he can mount the rotor, he can do it. 

[Arnie]

Its very doubtful.  If the rotor is grooved/worn/pitted enough to need resurfacing, there's not likely enough meat left to do it and stay within minimum thickness spec.
Just out of curiosity, do you have the early ventilated disks or the later (89+) solid ones?

Arnie

Need to clean up my right front brake rotor [stock] when I rebuild the caliper. Has anyone found a way to resurface/turn like for a car.  My local car place said if he can mount the rotor, he can do it. 

[bigbore2]

84 1100.  The disc is solid, I am pretty sure, but will confirm that.

[1tinindian]

84 1100.  The disc is solid, I am pretty sure, but will confirm that.

They were internally vented, not solid, the same as the later model rears.

Leon

[FJmonkey]

84 1100.  The disc is solid, I am pretty sure, but will confirm that.

Measure how thick they are. You might be at the limit already and cleaning them up will just thin them out even closer to the danger point. I have a set off an 86 that are still with in spec.

[JCainFJ]

 Try glass beads. I glass bead blast my front discs whenever I change pad material. It removes any contamination and restores the surface tention of the metal. Galfer and Ferodo recommend this.

[bigbore2]

Yes internally vented [venting located between inner and outer disc surface] which limits my possible turning options. I will have to measure. Glass beading-will have to check on the cost of that, sounds like a good idea.  FJmonkey- I will keep that in mind if I can't sort it out.

[Pat Conlon]

I have a Makita random orbital sander, on which I use a scotch bright pad....with a squirt or two of brake cleaner it scrubs well...

You just need to remove the old transfer layer.....Pat

[bigbore2]

Pat- I have used that idea before and that will work for 3 of the front 4 surfaces, but one surface, right outer is grooved and will need a little turning or replacing.  I should rebuild calipers also, esp. the right one.

[tmkaos]

If you do end up turning, grinding or otherwise machining that grooved rotor, if you only do the one side of it, removing the surface layer by machining will tend to make the rotor bend either towards or away from the machined surface.  The surface layer (more than the inside) of the rotor is stressed because of the heating/cooling cycles of braking, removing this layer one side only makes the stresses uneven. If it gets machined get them to check it before you take it back, it would probably pay to do both sides.

Sanding etc doesn't remove enough thickness to remove the entire surface layer so the problem doesnt occur.

I skimmed my mildly grooved rotors ('92, so not the same as yours), found that they had bent to shit, threw them out in disgust at bought Chinese Galfer knock offs. Massive improvement.

Good luck with yours. 

James

[SlowOldGuy]

Don't worry about the grooves in the rotor, just surface them like Pat says and slap some new pads in.  They'll bed in and you won't waste and rotor by needlessly grinding it away.

DavidR.

[Mark Olson]

If you know a good machinist with a flywheel grinder they can be resurfaced.

I have done this myself when I had access to one. it is a bit tricky for a novice , that is why I say a GOOD machinist.

any thing more than .oo1 runout will cause a pulse when braking.

I remember seeing a guy on the interweb who was resurfacing rotors .

[SlowOldGuy]

A question: What performance will grooves in the rotors affect?  It's been 30+ years since I turned a brake rotor or drum on an auto (never on a bike).  I used to turn rotors and drums all the time, because that's what "they" tell you to do.  Know what?  Half the time the person doing the turning screwed it up and I had to have it re-done or buy a new rotor/drum.

Unless your rotor is badly damaged or warped and turning/surfacing it is the ONLY way to recover (within thickness limits) then leave it alone!

Some may say grooves will cause premature wear on the brake pads.  Who cares!  Get 95% of the life out of a set of pads because the grooves wore them out a bit sooner then buy another set for $30, or go spend $300 on a new rotor when you don't really have to.

I've changed probably 100 set of pads on bikes and cars without turning anything and have had no problems.  Lightly sand the surface contamination and go with it.

Sorry that turned into a mini rant.

DavidR.

[AustinFJ]

A question: What performance will grooves in the rotors affect?  It's been 30+ years since I turned a brake rotor or drum on an auto (never on a bike).  I used to turn rotors and drums all the time, because that's what "they" tell you to do.  Know what?  Half the time the person doing the turning screwed it up and I had to have it re-done or buy a new rotor/drum.

Unless your rotor is badly damaged or warped and turning/surfacing it is the ONLY way to recover (within thickness limits) then leave it alone!

Some may say grooves will cause premature wear on the brake pads.  Who cares!  Get 95% of the life out of a set of pads because the grooves wore them out a bit sooner then buy another set for $30, or go spend $300 on a new rotor when you don't really have to.

I've changed probably 100 set of pads on bikes and cars without turning anything and have had no problems.  Lightly sand the surface contamination and go with it.

Sorry that turned into a mini rant.

DavidR.

+1

I'm with you on this one, David.   I actually had a boss many, many moons ago that raced cars in club racing and he always said (I think with a little tongue-in-cheek) that the grooves gave him more surface area for braking!  As long as they are not pulsing or giving you any other issues, leave 'em alone.