Brake Pad Recommendations for '82 GS850GL

[Nessism]

Thickness variation is rarely an issue with GS rotors. Scuffing in the rotors never hurts with new pads, but I wouldn't waste time with 400 grit. I'd use something rough like 150 and scuff them down good.

[TooManyToys]

Ed,

Then why the variation in deceleration?

[joejeweler]

Well, today i recieved 2 sets of EBC FA51 front brake pads to see if they would end the slight bobbing of the front end when using the front brakes.
I also recieved a set of EBC FA36 pads for the rear, soon to be installed when i rebuild that caliper next week.

I had already rebuilt both front calipers with the K&N kits, and that alone helped a lot. But there was still some up/down motion with front brake application.

Anyway, today i removed the old (probably original 30 year old) pads from each front caliper, even though they still had plenty of thickness left. (only 14.2K miles on the bike now)

Then i lightly sanded the rotors on all sides with 150 grit sandpaper to remove any glasing that might be there but not apparant, followed by a damp paper towl rinsing with a drop of dish detergent followed by a clear water rinse and pat down with some dry paper towels.

The metal shims were transfered from the old to the new piston side pads, and a small dab of hi-temp silicone grease was applied to the lip of each piston. Besides helping with any squeel, i think it's good there to seal out moisture.

One of the pistons previously had a bit of rust in the hollow that i was able to clean out, but the working outer edges of each piston was perfect ofter an application of brake cleaner and a paper towel rub down. (when i originally rebuilt the calipers a few weeks ago)

Back together the calipers went, and i bled a small amount of brake fluid out only because the new pads were a bit thicker than the ones removed, and i wanted to create a little reserve space in the master cylinder to offset fluid being sent back by pushing in the pistons a bit on the new pad install.

Crossed my fingers on the first test ride,......and i'm happy to report the problem has GONE AWAY!

The new pads still need to completely mate against the rotors for maximum stopping power,.....but that's a quick 100 to 200 mile city mileage ordeal,....probably a week or less.

For now,....no more bobbing of the front end when braking! It does show that even when everything "looks" ok,......there can be something wrong that only a part change will confirm.

I've concluded that although the front brake pads "looked" OK,.....somewhere over their life they picked up some fluid contamination that rendered them inconsistant and causing the grab/release sensation!

Over the 6 years i've owned the bike (last 3 of which the bike was stored), this has always been a problem that i was going to eventually find the cause of. I didn't put a lot of miles on the bike originally,....old tires one other reason besides the braking question.

So far this season i've put on 1500 miles or thereabouts,....with many more to follow! And now with new tires and great brakes (soon to be upgraded with SS HEL lines), my GS850L has become my (most) everyday ride.

[TooManyToys]

Joe,

I really hope this did take care of the issue. But if you were having a cyclic issue then it would be from the rotors not the pads. One thing not discussed was having an area of heavy friction transfer onto the rotor at one spot. This can also cause variation in deceleration just like thickness variation. Sorry for not mentioning it.

If it was a thick transfer the sanding would have taken care of the issue permanently along with a change in brake pad composition. If there still is an issue with thickness variation or hardness, you may meet up again with Bobby. A rough sanded surface just does not behave like a burnished in, smooth rotor and friction surface that has trace friction material transfer.

But again, I hope you have no more issues.

[joejeweler]

Joe,

I really hope this did take care of the issue. But if you were having a cyclic issue then it would be from the rotors not the pads. One thing not discussed was having an area of heavy friction transfer onto the rotor at one spot. This can also cause variation in deceleration just like thickness variation. Sorry for not mentioning it.

If it was a thick transfer the sanding would have taken care of the issue permanently along with a change in brake pad composition. If there still is an issue with thickness variation or hardness, you may meet up again with Bobby. A rough sanded surface just does not behave like a burnished in, smooth rotor and friction surface that has trace friction material transfer.

But again, I hope you have no more issues.

I'm keeping an eye on it,.....hope to permenentally ban "Bobby" from the invitation list! If it begins to rear it's ugly head again, i guess new rotors will be my only choice left.

......or possibly have these turned down as there really isn't much wear showing save for the typical shallow record groove look.

Not sure if that is often done on bike rotors today or not

(funny,.....i initially typed in "bile" rotors above as a typo! Kinda fitting when your rotors are acting like crap!)

I don't expect the same performance you'd get today with the modern brake caliper advances. But as i'm not planning on pushing the bike to it's limits,.....i can "live" with less.

[joejeweler]

Joe,

I really hope this did take care of the issue. But if you were having a cyclic issue then it would be from the rotors not the pads. One thing not discussed was having an area of heavy friction transfer onto the rotor at one spot. This can also cause variation in deceleration just like thickness variation. Sorry for not mentioning it.

If it was a thick transfer the sanding would have taken care of the issue permanently along with a change in brake pad composition. If there still is an issue with thickness variation or hardness, you may meet up again with Bobby. A rough sanded surface just does not behave like a burnished in, smooth rotor and friction surface that has trace friction material transfer.

But again, I hope you have no more issues.

I just came across this interesting article on brake pads and rotors, talks about car brakes but i'm thinking a lot of this applies to motorcycles also.

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

I had never heard of "cementite" formation on the rotors, or of the proper break-in proceedure on new disc brakes, thickness variation, etc.....

Also about what happens when brake fluid overheats. The article was too long to include here in 1 post. Plenty to think about........