Mountain Bike Reviews Forum banner
1 - 20 of 21 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter · #1 ·
:madman: if i spin my front wheel it hits on the disc brakes a little. i also noticed it does it in the back to. do i just need to keep trying or what?

it is a 2011 GF mamba
 

·
Thread Killer
Joined
·
131 Posts
With the bike upside down, unlatch the quick release, spin the wheel, apply brake hard and latch the quick release, let go of the brake lever. Check again.
 

·
Registered
Joined
·
1,330 Posts
You need to center the calipers. What you do is loosen up the caliper so that you can wiggle it with your hands. Next thing you will do is grab the brake and hold it on as you are holding on the brake tighten the caliper back up and it should be good. If not try a few times till you get it. I think you can google it and find a how to vid on youtube or something.
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #4 ·
thanks i got it to work on the front one. is it the same thing on the back or is it more complicated because of the gears
 

·
Registered
Joined
·
136 Posts
First, make sure that the axle is all the way into the dropout on both sides of the wheel. If it is and the rotor is still rubbing, then the disc brake caliper or pads just need to be adjusted. This is fairly simple to do and you can do it yourself. (If your bike is new and you bought it from an LBS then they will usually do minor adjustments like this free for the first year or more.)

Park Tool Company has repair guides for every part of a bike. Here is the link for Avid Mechanical Disc Adjustment:
http://www.parktool.com/blog/repair-help/avid-reg-mechanical-disc-adjustment
 

·
Picture Unrelated
Joined
·
5,123 Posts
Fatboy209 said:
thanks i got it to work on the front one. is it the same thing on the back or is it more complicated because of the gears
Exactly the same thing. If you don't center your wheel in the dropouts, you can never center the brake rotor in the caliper. Think of it as the gears being on the other side of the wheel and having nothing to do with the brakes. Though both the brakes and the gears will not work if the wheel is not properly seated in the dropouts.
 

·
Registered
Joined
·
2,310 Posts
Most rotors are not perfectly true. It's harder to get the brakes dialed in when they are more "untrue" so that they work well and don't rub. Some people use crescent wrenches to true them. It's not hard to do, but takes some patience the first time. Search the topic for more info.
 

·
Class Clown
Joined
·
3,446 Posts
this happens sometimes, usually the pads just need a slight adjustment. if you look at them from the right angle in the light you can see where they are off and make the appropriate adjustment. then spin the wheel and listen if there is any rubbing noise.
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #9 ·
Ok well I got the front one figured out last night then went for a ride today. And I noticed the front tire is rubbing again. Do I just need to tighten it more?
 

·
Registered
Joined
·
1,330 Posts
dont over tighten it you will mess up the fork. Put the bike upright and undo the qr let it settle and re tighten If the wheel is still rubbing you need to adjust the brake also make sure the wheel is true. Just get a stick and tie it to the frame and put it to the rim and make sure the gap stays the same as you spin it. My rotors hit all of the time on the pads and make noise just a little its from flex in the wheel and its ok. If non of that works sometimes the caliper is not retracting all of the way in that case you need to bleed and lube the caliper (NOTE no matter what dont get oil on the pads )
 

·
Registered
Joined
·
3,739 Posts
Is it the tire rubbing or the brake rubbing? Two different things, If the tire is rubbing you most likely need to tighten the the quick release/bolts that secure the wheel. If it's the brake then the other comments address this. One thing to add is that there are videos on you tube that will show how to do repairs.
 

·
Trail Ninja
Joined
·
6,196 Posts
I totally gave up on eliminating brake rub with disc brakes and rotors... if it's only rubbing a little at maybe 1 point of revolution, I'm fine with it. If it's constant rub or noticeable drag, that's when I fiddle.

Since I have avid brakes, I simply just use the CPS method (loosen caliper bolts, apply brake, tighten while holding brake, release and test) and from there fiddle by hand. I also always make sure the wheel is installed in a consistent manner/position.

It makes a little noise sometimes, but I'm tolerant, despite being fairly mechanically inclined. I'd prefer a little tolerance and savings over headaches from obsessing about it and money "lost" from buying other brakes.

Some guys that work at JensonUSA have XX brakes (who were prior haters of Avid) and say their contact adjust actually affects pad spacing, which I find hard to believe. I only thought it did something to the plunger within the reservoir. Anyone able to confirm/deny? I've only seen schematics of Elixir CR, so I can't really say there's 0% possibility of it being true.
 

·
Registered
Joined
·
923 Posts
I had this same issue with my front wheel. It only rubs in one place and when you look down into the caliper while the wheel is spinning you can actually see the rotor wobbling back and forth from one pad to the other. I did everything to make sure the wheel was on straight, still rubbed. I had the disc trued, still rubbed. I re-positioned the caliper and adjusted the pads, still rubbed. I knew someone who had the same bike who's front brake never rubbed so I put his wheel on my bike, including the "skoor" (in case my skewer was bent) and it still rubbed. At this point I've eliminated everything but mis-aligned dropouts. I'll probably wear through pads a bit faster but it's still braking just fine, so why bother fiddling with that or replacing the fork? I've just adjusted the caliper and pads to minimize the rub and let it be.
 

·
Registered
Joined
·
2,310 Posts
skullcap said:
I had this same issue with my front wheel. It only rubs in one place and when you look down into the caliper while the wheel is spinning you can actually see the rotor wobbling back and forth from one pad to the other. I did everything to make sure the wheel was on straight, still rubbed. I had the disc trued, still rubbed. I re-positioned the caliper and adjusted the pads, still rubbed. I knew someone who had the same bike who's front brake never rubbed so I put his wheel on my bike, including the "skoor" (in case my skewer was bent) and it still rubbed. At this point I've eliminated everything but mis-aligned dropouts. I'll probably wear through pads a bit faster but it's still braking just fine, so why bother fiddling with that or replacing the fork? I've just adjusted the caliper and pads to minimize the rub and let it be.
It's not surprising that a different wheel would rub on your bike, even the same brand and model. You often have to tweak one (or both) of the rotors a little to run two different wheels.

The rotor wobble you mention is common. In my experience, you will never be able to adjust your brake to get optimum performance from it until you true the rotor.

This site shows how to true one using professional tools. It's just as easy to do this using crescent wrenches and using the caliper as a guide.

http://www.utahmountainbiking.com/fix/diskrotortrue.htm
 

·
Registered
Joined
·
923 Posts
rlouder said:
It's not surprising that a different wheel would rub on your bike, even the same brand and model. You often have to tweak one (or both) of the rotors a little to run two different wheels.
Actually no, I just had to re-position the caliper. And I had the rotor professionally trued.

Unless the problem is with the hub, and that would involve some magic for the other hub since it wasn't rubbing on the other bike, then at this point it's really a non-issue. If it's only rubbing in one spot and then not by much, then why obsess?
 

·
Registered
Joined
·
2,310 Posts
skullcap said:
Actually no, I just had to re-position the caliper. And I had the rotor professionally trued.

Unless the problem is with the hub, and that would involve some magic for the other hub since it wasn't rubbing on the other bike, then at this point it's really a non-issue. If it's only rubbing in one spot and then not by much, then why obsess?
So, if a person runs two sets of wheels - one with mtb tires and one with slicks, they should adjust their calipers each time they change wheels? It's easier to tune the rotors and be done with it.

Why obsess about true rotors? I like one-finger braking.
 

·
Registered
Joined
·
923 Posts
rlouder said:
I like one-finger braking.
Cool. So do I :) . Please help me convince other people that this is a much better way to brake.

I'm not talking about swapping two completely different wheel sets like in your situation. These were identical. Same model bike, with identical components, bought on the same day and ridden together so same mileage in the same conditions. And if one is true on one bike, it should be true on the other. I don't see any way that would have changed just by switching it onto another bike without magic or superstition entering into the equation somewhere. But if you know of one please enlighten me. I mean that, if there's something missing here I want to know about it.

And that was really the point -- to eliminate all other variables. I wanted to know if the dropouts were misaligned and that was the quickest, simplest way to find out as I don't have a dropout alignment tool nor any desire to own one or make one. (It can be done, I looked into it.)

If the rotor really is out of true then repositioning the caliper won't help, you'll just have to re-true the rotor. I'd just rather check caliper position first, it's a much quicker and simpler fix.
 

·
Class Clown
Joined
·
3,446 Posts
are you guys talking about hydro's? i use mechanical brakes and never had a real hard time getting them perfect even when they were used and abused.
 

·
Trail Ninja
Joined
·
6,196 Posts
Why did this thread include 1-finger braking in the discussion? :confused:

I see this as simply can't figuring how to eliminate brake rub which seems to be incorrect wheel installation. I'd be more likely to point out that the issue has way more to do with various tolerances, which out take great obsession to go through to check.

- Disc rotor trueness (it can get warped through normal use)
- Caliper alignment
- Hardware tolerances (hub mount, post mount, adapter, drop outs, axle)
- Caliper tune (how evenly the pistons/pads extend and retract each time)

You can scrape the paint/finish off the fork, hubs, and frame in the dropouts and mounts in sort of a "facing" fashion. You can true your rotors often. You can buy new rotors, calipers, and pads. You can bleed it. You can get it to stop rubbing for a while and pat yourself on the back, but it'll come back eventually. :crazy:

I've been through a lot of that and, honestly, I find it's not worth the fuss. The drag isn't a big deal--roll the bike 1 foot and lift the wheel off the ground and if it spins more than 3 times, it's fine, since your weight and inertia easily makes it insignificant (there's more drag in your drivetrain). The noise, I can deal with since there's all sorts of noise going on from the drivetrain to the fork, tires, wind, and whatever other creaks you have (seat, cables, linkages, etc.). While some have pet peeves for that stuff, in the end it's all about the ride and not about what your riding on. :cool:
 

·
Registered
Joined
·
2,310 Posts
I mentioned one finger braking to answer the question about why people "obsess" over true rotors. On mechanical brakes, I can't adjust a the stationary pad close enough to rotor to get good performance if there is too much wobble. On hydros, I just don't like brake drag.

Some other people have also mentioned that they don't mind a little brake drag, so perhaps I'm in the minority. I've never had a rotor become warped from normal use, as you mention. Once trued, mine have stayed that way until I crash or bump them on something. If I had to true them every few rides, I might have a different outlook.

Skullcap, in theory, you are absolutely correct - the same parts should be interchangeable. In practical application, even though a rotor may be true in the sense that it has no wobble, the braking surface may be offset a little from center. The offset will vary from bike to bike. It won't be a huge amount but can be enough to cause you to have to reset the caliper.

Sorry if I got off topic.
 
1 - 20 of 21 Posts
Top