Rear v-brake has no power!
- Thread starter Hulk_slogan
- Start date
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shouldbeinbed
Rollin' along
- Location
- Manchester way
Have you tried switching the rear pads with the front ones to see if that makes a difference at either end? Rear brakes suddenly become good and fronts bad = your pads are the problem
No difference at either end = pads are fine look for something else.
I'd be very surprised if the frame parts of the bike were flexing enough naturally to cause this problem. I'd have a seriously hard look for cracks or failed joints & let an experienced bike mechanic do too. If the frame is broken in some way, it could be a weld repair to a crucial safety part or a new bike at that price.
Discounting frame failure
If I understand this bit right, you pull on the lever and once its at half way you can't pull it any further even though there would be freedom and range to do so if the rear wheel wasn't in place?
i.e. The brake pads are pressed to the rim before the travel of the brake lever is exhausted?
If so then you have a problem with your pads or rims having some sort of contaminant that is basically lubricating the contact surfaces and destroying your braking efficiency.
Have you spray oiled/lubed the chain or sprayed oil anywhere near the bike recently?
Job 1: have the rear pads and rim off and thoroughly scrub them clean with degreaser.
Job 2: put it back together and 'toe in' the brakes : from above the brake pads should look like this: / \ :front end of the pads angled in by 1-2 mm more than the rear so as the wheel rotates, the front of the pad contacts the rim first and the momentum of the wheel helps pull the rest of the pad hard onto the surface.
Pads flat fitted: I I will cause the pads to judder & squeal, making a bit of a drop off in braking
Worst of all: \ / :badly fitted or unevenly worn front to back will be actively pushed off the rim as the wheel rotates and seriously reduce braking performance.
Assuming not a faulty frame and if correctly fitting &/or the pads off the front fail to improve braking at the rear, off the top of my head you could consider
Contaminated rims.
Solid fitted mudguards catching the top of the V arms & stopping them moving freely?
Cracked V brake arm only shown when pulled on?
Incorrectly fitted/badly kinked/trapped cable & /or outer - you've not cable tied something to one of the tubes that has trapped the cable (A decathlon mechanic setting up daughters new bike trapped the rear derailleur cable under the kickstand he tightened up).
Faulty brake lever or the flappy cable end holder not having been aligned properly?
Although if the front pads do work well on the back, most of the above will have had to work properly too and you're stuck with contaminated rims.
No difference at either end = pads are fine look for something else.
I'd be very surprised if the frame parts of the bike were flexing enough naturally to cause this problem. I'd have a seriously hard look for cracks or failed joints & let an experienced bike mechanic do too. If the frame is broken in some way, it could be a weld repair to a crucial safety part or a new bike at that price.
Discounting frame failure
If I understand this bit right, you pull on the lever and once its at half way you can't pull it any further even though there would be freedom and range to do so if the rear wheel wasn't in place?
i.e. The brake pads are pressed to the rim before the travel of the brake lever is exhausted?
If so then you have a problem with your pads or rims having some sort of contaminant that is basically lubricating the contact surfaces and destroying your braking efficiency.
Have you spray oiled/lubed the chain or sprayed oil anywhere near the bike recently?
Job 1: have the rear pads and rim off and thoroughly scrub them clean with degreaser.
Job 2: put it back together and 'toe in' the brakes : from above the brake pads should look like this: / \ :front end of the pads angled in by 1-2 mm more than the rear so as the wheel rotates, the front of the pad contacts the rim first and the momentum of the wheel helps pull the rest of the pad hard onto the surface.
Pads flat fitted: I I will cause the pads to judder & squeal, making a bit of a drop off in braking
Worst of all: \ / :badly fitted or unevenly worn front to back will be actively pushed off the rim as the wheel rotates and seriously reduce braking performance.
Assuming not a faulty frame and if correctly fitting &/or the pads off the front fail to improve braking at the rear, off the top of my head you could consider
Contaminated rims.
Solid fitted mudguards catching the top of the V arms & stopping them moving freely?
Cracked V brake arm only shown when pulled on?
Incorrectly fitted/badly kinked/trapped cable & /or outer - you've not cable tied something to one of the tubes that has trapped the cable (A decathlon mechanic setting up daughters new bike trapped the rear derailleur cable under the kickstand he tightened up).
Faulty brake lever or the flappy cable end holder not having been aligned properly?
Although if the front pads do work well on the back, most of the above will have had to work properly too and you're stuck with contaminated rims.
Last edited:
OP
OP
Hulk_slogan
Active Member
Thanks for all the in depth replies. You guys have been real helpful!
I am based on the borders or East London/Essex.
Yep there is loads more range available to pull the brake lever if the rear wheel wasn't there.
Havn't had a chance to take the bike apart again to clean and swap pads yet.
Currently awaiting a reply from Decathlon so we shall see what they say as well!
I am based on the borders or East London/Essex.
Yep there is loads more range available to pull the brake lever if the rear wheel wasn't there.
Havn't had a chance to take the bike apart again to clean and swap pads yet.
Currently awaiting a reply from Decathlon so we shall see what they say as well!
OP
OP
Hulk_slogan
Active Member
Did it the lazy route and drove with the bike in the back 
Came away today with a rockrider 500 for no extra cost so I'm pretty chuffed with that. Downsized to a medium frame too as I felt a little more comfortable on it.
Came away today with a rockrider 500 for no extra cost so I'm pretty chuffed with that. Downsized to a medium frame too as I felt a little more comfortable on it.
