[Robert1]

So I bought my son (who really loves biking) a 20" Specialized Hotrock about 2 months ago. He loves the bike except for one thing. The rear brake knocks really bad and loud when he's braking. It's easy to reproduce when the bike is on a stand though not as pronounced.

I tried making all kind of adjustments to the brake and pads but nothing helps. Finally I just broke down and took it back to the LBS where we purchased it from. They looked at it and said it's most likely because those bikes have a seem in the rim that's causing the brake to bounce when it hits the seem. They tried a few adjustments to no avail and pretty much said I'd have to live with it. I said I found that unacceptable for a $350 plus bike. I could understand if it was a $100 Walmart bike. After getting a little pushy with them they reluctantly agreed to try to swap out the rim with an after market one to see if it would help but he said it would have a seem too and probably wouldn't elminate the issue. I said well let's check the seem compared to the one on the bike to see if it was any better so they didn't waste their time if it was the same.

After comparing closely, I could feel that both sides of where the seem meet were not flush. The rear portion was slightly raised so I could see how this could cause the brake bad to get hung up. Does this seem like the likely culprit here? After inspecting the aftermarket rim, it too had a seem but it seemed flush. I had to leave the bike in order for them to do this and should be ready in a week. I commented that I expected this to resolve the issue and that the problem seemed obvious to me.

I kind of got a vibe from the LBS like they really didn't want to do this for me. Am I expecting too much? I don't see what the big deal is. Can't they just charge back the time and material to Specialized? I assume Specialized stands behind their products. They also kind of implied they've seen this before but not to that extent, yet they said they've never discussed it with Specialized. Has anyone experienced anything similar? What would you do if the issue does not get fixed?

 

[wim]

Pretty common for a rim to have a seam or seams not exactly flush. Almost always, toeing the brake pad(s) eliminates the noise made when the edge of the pad strikes the raised edge of the seam. If that doesn't help much, grinding or sanding the seam(s) flush will fix the problem. Either way, you're talking 15 minutes of work. Not sure why this wasn't done.

Often, the issue goes away by itself. This is especially true if the bike gets ridden in wet conditions and doesn't receive much care. The road grime embedded in the the pads together with water acts as a very efficient grinding paste which smoothes out the rim seam(s) in short order if there's a reasonable amount of braking.

 

[frdfandc]

Yes, the raised edge on the seam is the cause of the knocking. Common on inexpensive wheels, especially kids bikes. Doesn't matter if it's a $100 K-mart Schwinn or a $350 Specialized kids bike.

Working for a LBS, there isn't too much difference between a brand name kids bike or a dept. store kids bike, except for the frames and the care during assembly. That is where the money is. Components are pretty similar. I made my sons Next bike (K-mart) ride smoother than a brand name bike, just by lubing and adjusting everything.

Best bet would be to smooth the seam with a file followed by some fine grit sand paper.

 

[wim]

Best bet would be to smooth the seam with a file followed by some fine grit sand paper.

Agree, and to the OP: just do it yourself. The issue is so insignificant that involving the LBS in this is just wasting time and, possibly, money.

 

[Cyclo-phile]

If you don't get the results you want by filing down the rim seam or toeing the brake pads, it is possible to get welded and machined rims in the correct size. That will run $40-50 for the rim plus having the LBS re-lace the wheel, possibly with new spokes.

 

[wim]

If you don't get the results you want by filing down the rim seam or toeing the brake pads, it is possible to get welded and machined rims in the correct size. That will run $40-50 for the rim plus having the LBS re-lace the wheel, possibly with new spokes.

I'm reminded of the old saying from back in the days when people were still smoking: "Crap, the ashtray is full. I need a new car."

 

[Cyclo-phile]

I'm reminded of the old saying from back in the days when people were still smoking: "Crap, the ashtray is full. I need a new car."

Yeah, I never said it would be a practical solution, just an option. My son is also on a Hotrock 20 and they're great bikes for what they are.

 

[Robert1]

Guys, thanks for all the comments. When I was discussing the issue with the LBS, filing/sanding down the seem is exactly what I suggested. They told me they didn't want to do that because it might compromise the integrity of the rim. I have no idea whether he was just blowing smoke up my azz or there's a real concern. Anyway, if they can't get it fixed that's what I'll try.

As far as asking the LBS to resolve this issue, why not? This is a brand new bike that I expect to be defect free with reasonable expectations of quality. If I wanted to tinker with a brand new bike then I would have ordered it from bikes direct or some place else rather than a full service LBS.

 

[Cyclo-phile]

Concerns about a little bit of sanding on the seam "compromising the integrity" are overblown. I used to take a grinder to the entire brake track of my rims when I was doing trials competitions and never had a rim failure.

 

[wim]

They told me they didn't want to do that because it might compromise the integrity of the rim.

As said above, that's not a realistic assessment. I'm sure they know this, so what they're basically saying is "we don't know how to do this properly." It seems to me that you would actually do a better job of fixing this little issue than they could.