Rear Brakes Slipping

[wiredued]

My mountain bike rear brakes don't seem to grab as good as the front brake I've made adjustments and I still can't stop by using the rear brake by itself. What would you suspect the problem is? My wife's MTB has the same problem front brake works great rear brake barely does any thing.

 

[riverfever]

My mountain bike rear brakes don't seem to grab as good as the front brake I've made adjustments and I still can't stop by using the rear brake by itself. What would you suspect the problem is? My wife's MTB has the same problem front brake works great rear brake barely does any thing.

What kind of brakes are these?

Sometimes it helps to clean the braking surface really good on the rim and use some sand paper to scuff up the surface a bit. It's also not uncommon for debris to get lodged in the pad itself. Sometimes I've taken a flat file and roughed up the pad a little as well. Make sure the cables lubed. Are these older cantilevers b/c I can't imagine a V brake not grabbing enough. Hope this helps.

 

[hd reynolds]

as in a motor vehicle, rear brakes by themselves do not stop a bicycle if moving forward. it is the front brake that does most of the stopping. In cany case if the rear brake does not grab enuf to stop the tire then that is a prob - what kind of brakes are they?

 

[wiredued]

Mine are V levers hers are old cantelevers thanks for the ideas I can't figure out why it hasn't happened to the front.

What kind of brakes are these?

Sometimes it helps to clean the braking surface really good on the rim and use some sand paper to scuff up the surface a bit. It's also not uncommon for debris to get lodged in the pad itself. Sometimes I've taken a flat file and roughed up the pad a little as well. Make sure the cables lubed. Are these older cantilevers b/c I can't imagine a V brake not grabbing enough. Hope this helps.

 

[riverfever]

Mine are V levers hers are old cantelevers thanks for the ideas I can't figure out why it hasn't happened to the front.

Do you use it more? I try to do most of the breaking with the front just to keep the rear end from sliding around. Also make sure with hers that the pads are adjusted properly. Again, it's been a bit since I worked in a shop and I'm just now starting to ride again after some time off but....I believe that with the older style cantis, when they are engaged and the pads strike the rim, you want the allen bolts to sit right on top of each other. One allen bolt is used to hold the brake to the frame and the top one is really not a bolt but there is a place for an allen head to hold while your 10mm goes on the back and does the tightening. Pretty sure that was straight from Shimano. It'll take some futzing but slide the pad in or out as needed. Also wouldn't hurt to make sure that the boss where the breaks mount to the frame has a film of Teflon grease on it so they rotate with as little friction as possible. Hope this helps.

-river

 

[Jemsquash]

Front brakes are always sharper than rear brakes. On a hard surface most of your stopping power will come from your front brakes. If you can lock up the rear breaks then nothing is wrong with them, you can't expect them to do anything more.

The way I view it is that when you apply your front breaks a lot of you weight will push onto the front wheel thus pushing the wheel onto the ground and hence it will have more friction to stop you with. With the rear wheel the opposite happens since your weight is in front of the wheel. If you apply your front breaks really heavily you will lift your rear wheel right of the ground and it will have no effect at all!

I used to play as a kid pretending I could not stop by leaning right forward up against the handle bar and then applying the rear breaks. I would skid for ages and ages, if I sat on the saddle and did the same thing I could not skid far at all.

If you are on loose gravel it is difficult to keep control when breaking heavily with front breaks. You will need to compensate for this and mainly use rear brakes.

 

[riverfever]

If you can lock up the rear breaks then nothing is wrong with them

I think his issue/concern is that he CAN"T stop with just the back break. He should be able to lock up the back break...even with cantis.

 

[gclark8]

Blessed is the man who replaces inner and outer brake cables regularly and keeps them lubricated.

 

[wiredued]

Correct I can not even stop using the rear brakes and don't even come close to locking them up. Cables move freely and are adjusted the brakes just slip.

I think his issue/concern is that he CAN"T stop with just the back break. He should be able to lock up the back break...even with cantis.

 

[dabac]

My mountain bike rear brakes don't seem to grab as good as the front brake

(assuming that your brakes are wire-operated...) Rear brakes have a longer wire between handle and brake. All other things being equal (pads, rims, alignment..) the extra stretch in the longer wire will reduce the "feel" of the brake and can sometimes cause the handle to bottom out before the brake begins to work properly. A good quality brake wire will make this problem less noticeable. Bigger (eg thicker) isn't always better, because they might actually stretch more than a thinner wire depending on how it's spun.
I've toyed with the idea of using a single-strand gear wire from an old Shimano positron RD as a brake wire, but so far I haven't tested it so I can't recommend it.

In some cases it might also be the rear stays that flexes and robs you of braking power. In that case you might want to try one of those horseshoe-shaped brake boosters to stiffen it up.

 

[dabac]

Mine are V levers hers are old cantelevers

Cantis levers have shorter stroke than v-brake levers. Made it fairly easy to lose brake performance on the rear due to wire stretch and poor wire routing. Sheldon Brown has some pointers on wire routing for best performance.

V-brake levers also comes with different strokes. Maybe your bike simply has poorly matched levers and brakes?

 

[wiredued]

My brakes worked great when I bought it new for about 6 months and then began to slip in rear. My wifes brakes worked great also when she first got her bike at a yard sale. I'm going to try cleaning and sanding the rims and cleaning the pads to see what happens.

Cantis levers have shorter stroke than v-brake levers. Made it fairly easy to lose brake performance on the rear due to wire stretch and poor wire routing. Sheldon Brown has some pointers on wire routing for best performance.

V-brake levers also comes with different strokes. Maybe your bike simply has poorly matched levers and brakes?

 

[reelbf]

My brakes worked great when I bought it new for about 6 months and then began to slip in rear. My wifes brakes worked great also when she first got her bike at a yard sale. I'm going to try cleaning and sanding the rims and cleaning the pads to see what happens.

Do your brake pads have oil on them? I dont know whether the brake pads are interchangable if they are you could switch them with the front to see if its the pads that are the cause.

 

[wiredued]

I am suspecting that but haven't taken them off yet the rim does feel slightly waxy compared to the front the T9 I use to lube the chain may have got over sprayed. I think I might try washing the rim with orange hand cleaner.

Do your brake pads have oil on them? I dont know whether the brake pads are interchangable if they are you could switch them with the front to see if its the pads that are the cause.

 

[wiredued]

Update: I cleaned the pads sand papered the rims and noticed a slight difference then I noticed the metal cable housing going to the rear break was hitting the rear rack supports so I bent it to make a more gradual sweep to the v brakes and that made a big difference. It was a problem that got worse as the brakes wear I still havent solved my wife's rear brake trouble yet. Thanks for the ideas.

 

[dabac]

..I noticed the metal cable housing going to the rear break was hitting the rear rack supports so I bent it to make a more gradual sweep to the v brakes and that made a big difference.

I've got a little gadget called a "smooth operator", a pulley that replaces the noodle on my v-brakes. That can work wonders if you have cabling issues.