djb

Despite me doing this, as seeker mentions, there are potential hazards to this, and possible oversanding or uneven sanding making the rotors too thin could be bad--I can only broadly describe what I did, and certainly dont have a thickness "before and after" number, and now that Ive done it, I cant even show a before and after photo.
Also, one persons "light gentle sanding" may be a really hard pressured sanding to a mechanic who has done this before, I really dont have the reference, so I did what I thought was very little--but maybe Im all wrong on this.
All I know is that the screeching stopped.

do read up on how to properly bed in new pads, or pads that have been sanded, and or rotors that have been cleaned etc. My understanding is that this is very important to getting everything to work properly.

re asbestos, this is referring to the pads, and the sanding is very minimal, but as the fellow states, use common sense and dont blow the stuff around and breath it in.

Bike Jedi

I thought about this off and on all day...something doesn't seem correct about this or like sound advice that someone might stumble upon this and think this is a sure fire remedy, and I don't think it such a good idea. I don't think that I would do that to mine.

But what I did want to point out is that a LBS a while ago showed me this trick and said it's the best way to get contaminated pads clean. He makes money off this all the time for this little simple trick.

He had one of these: https://www.amazon.com/3M-99436-Dryw...i&sr=1-1-fkmr0

I think if I remember, he had something DIY'd so that the ends were wrapped, locked in place, and elevated as if it was hung like a hammock. Then he would just simply take the brake brads and rub them on top of it with the pads being face down. He claims it works like a charm and solves most of the squeaky brakes problems. However, I don't see how this would apply to changed pads or new rotors unless you are cross contaminating in some way. My brakes are squeaking on the rear, changed pads, always clean rotors with rubbing alcohol, lines have been blead multiple times, but still squeaks. The only thing constant has been the rotors have never been changed and have a lot of miles on them. If that has somehow been contaminated, I guess when I put the new pads on each time, I am cross contaminating again, although I clean them with alcohol, and it's metal, so I am not sure the logic there.

I am putting this up in the event other's don't know about this trick. I haven't tried it yet, but I will soon. But I might need to change my rotors too.

edthesped

My Hy/Rd's came with spacers installed in them. It's one of the few things I was smart enough to keep. If you have a 3d printer or access to one you can print your own spacers, Disc brake spacers on Thingiverse...

djb

I have used those drywall sanding things once, and they are made for "sanding" a very soft material, so let us know if it works for you.

djb

thanks, if new bikes come with these, I'll ask at a store I know to put some aside if they do see them regularly with new bikes and toss them along with all the other packing stuff.

edthesped

I'm sure the bike shop would have some laying around... I replaced my BB7's with the Hy/Rd's so the Hy/Rd's were shipped with the spacers in them. The Ultegra calipers I purchased for another build last spring also shipped with spacers installed for shipping so I'm assuming the spacers are pretty common and that bike shops either bin or toolbox the spacers rather than pass them on to the customer.

TimothyH

Not sure if anyone mentioned using a machinists surface block or other reasonably flat surface to sand the pads and rotor.

The sandpaper is placed on the surface block or flat surface and the pads are moved across the sandpaper in a figure-eight motion. The same might be done for both sides of a six-bolt rotor and one side of a centerlock rotor.

The idea is to back the sandpaper with something flat and move the part against it. Using a surface block or other flat surface and rubbing the part on the block allows more control for an even surface with minimal material removal.

I've scuffed automotive rotors and pads this way many times.


-Tim-

edthesped

Okay, a quickie search through the parts bin showed the spacers are the same for the Hy/Rd's and the Ultregra, though I would have bet that wasn't the case. At this point I'll assume they're pretty much universal.

djb

well, I guess Ed that I could get my grubby fingers on these also, but on a trip, it might be nice when you often end up rushing to prep the bike before a flight, to have one of these in a nook in a pannier, or in my repair kit bag, kept clean, and be able to just slap it in the front brake as soon as you take the front wheel off. Put some tape on it to stop it falling out and good to go.

edthesped

I can easily drop one in the mail if you'd like...

djb

thanks, dont know if it would fit into a BB7 properly. How about I take a rain cheque? I'll try to swing by a store sometime and get my rotor thickness checked, and at the same time Ill ask about these. The store in question sells a bunch of bikes with BB7s, surly stuff, and I know the mechanics, so theres a good chance they have them.
If not, I'll get back to you, but thanks a lot for the kindly offer.

edthesped

I'll save you the trouble... I forgot about the BB7 requirement. I happen to have those in the parts bin as well, yes I'm a packrat, and there's no pin in the BB7's, just a flat spring that's about 4mm off center and the pin clip is centered on the spacer. Maybe I'll try to model something up and put it on Thingiverse if you can't find anything that works. Sorry for the blurry pic

Trevtassie

Hmmmm, this is why I have mechanicals, so I don't have to worry about spacers, hoses or anything. The pad springs should keep the pads in place and if the piston(s) were in any danger of popping out if a lever was depressed it'd only be because the brakes needed a massive amount of adjustment anyway. The only thing I care about are the discs, I always take them off any wheel I have to remove and tape them to the inside of the box.. Otherwise, it's ZFG.

djb

Trev, first of all, I agree with your view of mechanical and the no worry of this and that.
Second I laughed when I had to look up zfg
But thirdly, I still think it's worth putting in some spacer when boxing a bike for a flight, especially with drop bars and like the situation I described, where the bars probably shifted in transit and the front brake lever got pushed vey hard, pushing the front piston out on my bb7.

Trevtassie

The only thing I can think of is that the steel retaining C ring on the moving shoe of your caliper is worn/lost tension out so the shoe can drop out of the piston. It can't be pushed out by the operation of the brakes. It can be pushed out if you use maximum adjustment on the outboard adjuster. I just tried mine and I needed to lever it out with a screw driver, there was no way it could pop out under it's own steam.. The retaining ring is a little C ring on the shoe shaft. Because the shoe on the BB7 needs to pivot to compensate for the off centre pressure the BB7 creates it has a lot of slop and it's retained by the C ring. Technically the pad separating spring should also hold the pad and shoe in place. With the pads in place and adjusted to fit a disc there isn't enough room for the shoe come out. Potentially with a missing inboard pad and the outboard pads adjusted to the max it could come loose.
Anyway, it's a good chance to service your caliper while you have a look. It'd be worth trying to spread the C ring to add a little tension. They come with bugger all grease from the factory anyway, so a touch of high temperature brake grease wouldn't hurt to extend it's life.. The SRAM site has a service manual.

edthesped

I guess we're all different, I ran the BB7's for a few months and they squealed and I had a tough time adjusting them, TBH maybe I never gave them a chance as I was already used to hydraulics when I got the bike with BB7's. Having run BB7's, now in the parts bin, and hydraulics, Hy/Rd (hybrid) and Ultegra, (full) I prefer the hydraulics. For long touring I'd probably stick with the hybrid setup, Hy/Rd's, but would be comfortable with either. Adjustment for the hydros is stupid easy. Loosen the caliper mounting bolts, squeeze the brake, hold pressure on the brake, and retighten the mounting bolts slowly by alternating between the two bolts. Once tight release the brake and check for rubbing. 9 times out of 10 you'll be fine but occasionally will have to repeat. That being said my tourer with Hy/Rd's has a few thousand miles on it without any adjustments being done. I used to have to adjust every time I pulled the wheel but since switching to the DT Swiss skewers I can easily come close to previous skewer tightness so that caliper alignment doesn't need to be fiddled with. As an aside, I'm a little OC so I shine a flashlight on the back side of the caliper while the wheel is spinning so I can verify the spacing between the pads and rotor is pretty much equal on both sides.

Trevtassie

Pretty well the same deal with mechanical Spyre/Spykes, You use the cable adjustment on the bars until you start to run out of travel. Back it off, then use a 3mm allen key to adjust the pad gaps. Over 2500km tour didn't need to touch the pad adjustment .Chalk and cheese to the BB7s which are a very poor design.

edthesped

I've read good things about the Spyre's and almost got those when I started down this path but decided on the Hy/Rd's instead...

Brett A

It's standard practice to do this with hydraulic disc brakes. Because if the brake leaver gets pulled while in transit, the pads don't pull back on their own and it's difficult to get them to.

djb

thanks, will look into that at some point. I would need to look at a diagram of them to really understand properly what you describe, I admit I dont properly visualize the C ring right now.
I will check out the service manual to get a better understanding.
Lots of house projects and work and family stuff going on right now, so I'm realistic that I wont look into this for a while--but thanks again.

Igotdibs

Thank you @djb ... I sanded the front disc today before my ride and viola! It's fixed!

djb

glad it worked out, but as the others with more disc experience have stated, its probably always better to do stuff to the pads first, to see if thats the issue, rather than reducing thickness of rotors if you are a bull in a chinashop with sanding, and or doing uneven sanding.
My take on the article mentioned, is that my disc looked like the one in the photo, and I did really really minimal sanding, and was super conservative in how much I pressed etc.

but glad it worked out.

Still prudent to get a proper evaluation of rotor thickness though by anyone doing this, as I defer to those with lots of experience who brought it up.

DropBarFan

I doubted that but did a quick search & indeed, the consensus seems to be that organic pads give less rotor wear. While some folks have horror stories about organic pads wearing out very quickly, my SwissStop pads lasted about a year though mileage was not esp high.

Bike Jedi

No it didn't work. I think I sanded them uneven or did something to them, and it ended up cutting into my new rotor some because I must of cut an uneven line or something. I went and got new pads. Brakes work awesome now...except for the squek on the back brake. New rotor, new pad, bled several times, and I am clueless at this point other than just having a bad caliper of some type.

I wouldn't recommend the dry wall sanding thing to someone, especially someone who hasn't done it before.

They are old entry level shimano's anyway. Not terrible worried about it. Just wish I kind of knew, so I know.

TimothyH

Lay the sandpaper on a hard, flat, very smooth surface and run the parts across the sandpaper in a figure-8 motion.

You don't want to remove significant material. All you want to do is break through the glaze.


-Tim-