Bicycle Mechanics - V-Brakes issues
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10-28-12, 02:08 PM
I bought, not even 2 months ago, a Trek FX 7.2 bike.
Rode ~1000 km on it.
At some point, the rear braking started to sound a bit "metallic" and lost around half of its efficiency: even if I press very hard on the lever at low speed I cannot block the wheel (not that blocking the wheel is any useful but a functioning brake would do it).
I looked at the shoes and they look pretty used and "unevenly" : the bottom of the shoe is almost brand-new whereas the top looks more used (but it does not feel completely dead: it "feels" soft when touching it so it is still rubber and not the metal behind ... so I don't think it explains the metallic sound).
Nonetheless, I believe the shoe should have been used evenly and that it had not been properly set-up to begin with right?
Nevertheless, my re-seller told me when I bought the bike to come in with it after 2 months for a 2-months revision so I will do this in any case and talk to him about this: a bike with 1000 km is still basically new compared to its lifetime... so it should have functioning brakes...
Still I am trying to get better in the whole cycling mechanics thing, so just from an educational point of view, let us forget about the revision: what would my options be?
From another point of view, I intend to keep this bike for a while and intend to maintain it and possibly improve some of it (next step: a Brooks saddle and SPD pedals :):):) ) so I was considering (not directly related to my very current braking issues) change the whole brakes and upgrade them by better ones...: assuming I stick to V-Brakes, can I keep the same levers and cables?
10-28-12, 02:33 PM
Welcome to the fourms
From what you are describing, the brake pads aren't set up so they have full contact with the rims, this really should have been set up when the bike was sold / pre deliver inspection. For the metallic sound, this is probably bits of metal getting engrained in the pads, this happens, though some pads seem to be more susceptible to this than others.
What you haven't mentioned is what conditions you ride in; if wet, you can go through pads real quick, if dry, they can last a very long time, but the distance you are putting on it is probably more than most bikes will see over may years.
For the lever pull issues, have you tried adjusting the cable, there should be an adjuster bolt a the end of the lever that can be dialled to reduce the pull.
For replacing the brakes, initially would look at the pads, the brakes as fitted aren't bad, but Tektro pads are never the best, Koolstop Salmons are normally the pad of choice on BF, but Swissstop, Shimano and others also make good pads. Changing them (the pads) initially will be cheaper than replacing the complete brake system. If you did choose to replace them, your brake levers are compatible with other v-brakes.
10-28-12, 02:35 PM
Your best bet would to be just upgrade the pads like Kool-Stop salmons. The metallic sound could be from something that got lodged in your brake pad or quite simply because the pads are excessively worn. It does sound like the brakes were never set up correctly if your pads are not wearing evenly so hopefully your shop will take some responsibility by giving you a deal on a new set. It is possible that in 1000 km that the pads could just simply be worn out though. If you ride in a lot of rain/dirt along with having some bigger hills it is possible to go through them. On my mountain bike I have even went through a set of pads in a single day but it was pouring raining, along with big hills and an all day ride.
10-28-12, 02:43 PM
Thank you guys!
I am mostly commuting on this bike (~20 km a day in Paris).
A few long rides, but mostly roads, although most of the long rides (which represent ~400 of the 1000 km ridden with the bike) were in a rainy weather.
I have tried adjusting the cable, it was actually my first attempt to improve things; I even tightened the cable directly on the brake which helped but still not to the point to fully functionnal brakes.
I am going to my reseller the day after tomorrow.
Thanks for the advice.
10-28-12, 03:55 PM
lots of futzing over Brakes ,like, pads not coming away from the rim equally
is something to have the mechanics at the Bike shop show you some adjustments .
there is just so much text is not up to showing as fast as being there ..
10-28-12, 04:08 PM
It's a routine adjustment problem - your dealer will no doubt take care of it - not to worry.
10-29-12, 09:42 AM
Yep definately a case of the pads not being aligned correctly as others have pointed out. Fix is a set of Koolstops and a correct setup. The Sheldon site has instructions if you want to do it yourself. And recommend a close examination of the rims to ensure they have not been damaged by some bits of crap that might have gotten picked up on the OEM pads... look for any kind of scratch or streak running around the rim sidewall. If it is damaged, you may need to replace the rims. Err on hte side of caution.
10-29-12, 02:12 PM
Actually, I might have exagerrated a bit for the uneven use (it was dark when I looked for the first time)... at second look, it is not ideal, but does not looks *that* bad...
Anyway... it does not really matter: it does not brake as it should and the dealer will fix it...
10-29-12, 02:31 PM
You are over due for new brake pads.
as the pad wears, it's contact surface moves towards the Pivot.
so midway thru the wear-use cycle, a prudent person, adjusts the pads,
and relocates their brake shoes, again, to fully meet the rim surface.
10-29-12, 02:41 PM
Fair enough... thanks!
10-29-12, 03:39 PM
That's a lot of wear for 2 months.
10-29-12, 04:05 PM
That's a lot of wear for 2 months.
So? does it mean the set-up was bad to begin with? that the shoes quality was too poor? some other reason?
10-29-12, 04:23 PM
The pad was not properly aligned to the rim & therefore it has worn unevenly causing a lip to form on the edge of the pad. Change of pads with proper alignment and you are good to go.
10-29-12, 04:25 PM
+1, I'd recommend Kool Stop replacement brake shoes..
the OEM stock ones wore.
but better the pad wear down than the rim..
Now you have the opportunity to get brake pads that are nicer,
more costly.. ,$15~20 a pair
they chose the 1st ones on Price..
that was passed along as the final price of the bike,
that you found affordable enough to take home.
Now, you know.. mind the pad wear and re adjust
Or have the LBS, do so, how they contact the rim , occasionally..
as I said, the Wear alters the contact with the rim,
so correcting that is part of an aware cyclist maintaining their bike.
Perhaps the new setup the pad was Fine, but it changed with use..
FWIW U brakes and Center-pulls had to be adjusted downward,
they too acted like they went off the edge over time,
some seen were wearing rubber off the tire,.. sidewall
do safety checks on your bike regularly. :innocent:
10-30-12, 09:11 AM
The photos provide seem to me to show that the pads are thicker (vertically) than the sidewalls of the rims are and thus there would be no way to avoid what happened given those pads (otherwise than the alignment issue). When replacing the pads, make sure the thickness of the pad surface is less than the rim sidewalls. Different pads have difference thicknesses. Have to wonder where FatBottomGirl is riding as those brakes and rims seem to be taking a real beating in only 2 months... Would have to offer her a heartfelt "you go girl" because she is clearly working it hard and probably enjoying the hell out of it! Yeah, Do It!
10-30-12, 03:52 PM
1,000 km is only 621.37 miles. Consequently, it is difficult to fathom how the rear brake pads could display the degree of accelerated wear in so relatively few miles unless you are essentially only using your rear brake. If this is the case, you should be applying both front and rear braking forces equally for slow to moderate slowing/stops, with greater emphasis on the front brake when emergency stops are required. The front brake provides primary emergency stopping power due to the applicable physics and geometry associated with a bicycle and the orientation of its rider.
I recently discovered that my cousin’s teenage daughter was genuinely afraid to apply the front brake for fear of being thrown over the handlebars (as though the front brake was in reality a “catapult the rider” feature - :D). I took a moment to educate her on the bicycle’s brakes and though her long harbored fear still had her initially somewhat leery, she also knew that I’d never mislead her and being that I always arrive via one of my mountain bikes, she knows I’m well attuned concerning bicycling. Now she uses the front and rear brakes and is enjoying bicycling all the more.
Thanks for the advice!
I used to be like your cousin's daughter at the beginning (note: not on this bike, so the wear is not the consequence of 100% use of rear brake). And then I discovered how much more efficient the front brake so learnt to use them both in conjunction (is that a word in english? well... you got my point...).
And currently I am using mostly the front one since it does not yet have the problems the rear one has...
Maybe the explanation of the rapid wear is that the pads were not that good to begin with, that the set-up was not that great and also I have been doing quite a lot of climbing which also means quite a lot of downhills and I must admit I am not that secure yet going very fast down especially on pavement so have been using the rear brake a lot (which is right on downhill-pavement roads, since there is even more wight than usual on the front, the risk of falling over the bars is higher and the uneven road causes a micro "jumps" of the bike and a wheel in the air blocks more easily than on the road so once again => higher risk... so I think I'm right with the rear brake in these situations... although it might accelerate the wear...)....
Still, thanks. I will have it fixed!
10-31-12, 01:27 AM
The pads are toast; the primary cause seems to be the pads were set too low along with some abrasive material grinding on the pads. The tendency of the pads as they wear is to cause the pads to cant top first into the rim brake surface; that lip will magnify the affect. If you look around the brake arm you can see the brake particles that have been ground off. Most brakes pads and rims brake track height are designed to work together so doubt that the pads are/were wider than the rim brake surface (they may be now, but that is because they brake pads taper at the end, so they get wider as they wear. Regardless I'm pretty sure Bontrager rims and Diacomp brake pads are made to play together. The other issue is the grinding you've been hearing. Whether it's aluminum bits from the rim or something else, if you hear grinding there is some foreign material between the pads and rim surface that needs to be removed. In the future don't allow the grinding to continue and keep an eye on the on the pad surface; once the wear indicators line start to disappear the pads need to be replaced.
10-31-12, 05:22 AM
I've never seen pad and rim wear that much ever. Look at all the brake "dust" on the mounts and the "grooves" on the rim. Something abrasive got into that brake. It does need looking after and it appears the OP is going to do that. It does sound like the OP is having fun riding. Good job on actually noticing there might be a problem. Most people just ride until something major breaks.
You should be cleaning your rims and brakes pads regularly. I find dish soap and water with a toothbrush works good. After riding in the rain, the leftover residue of rim, grit and sand needs to be removed.
I think you might need to revise your style of riding. By that I mean try to be more aware of what is ahead and avoid harsh stopping. Instead just slow down gradually. The amount of wear on those pads and rims looks to be the result of aggressive riding. The seller won't be able to perform miracles. Is there a lot of grit in the air where you are?
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