Bicycle Mechanics - Trek Aluminum Frame Issue?
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07-10-10, 08:06 PM
Hey everyone, I have a 2008 Trek 1.5 road bike. It's one of their intro road bikes with an aluminum frame. I have about 1700 miles on it to this point.
Here's my concern. I was cleaning it today and I found a dent in the bottom of the seat tube. It's a few inches below the front derailleur clamp and a few inches above the bottom bracket and it's on the crank side. I never noticed it before so I have no idea if it was there before or not. I did go from a standard crank to a compact months ago but the work was completed by my LBS which is where I bought it new. And the old clamp location was further above the clamp now and the dent is below that. There is no scratches and no paint chips.
It's not that big of a dent, but you can definiately feel it by hand and you can see it in direct light (kinda like a ding on your car fender). Should I be concerned about this? Do you think it's a defect in the frame? I never crashed the bike and the position that it is in seems inpossible for it to be something I did. It's protected by the derailleur and the crank.
Anybody heard of this before or am I worrying over nothing?
07-10-10, 08:13 PM
Weird spot for a dent. I suspect your shop did it when they installed your new crank.
I'd talk to the shop owner and ask for a replacement frame. Whether Trek or the shop takes care of it doesn't matter - I just think you deserve an undamaged frame.
07-10-10, 08:24 PM
the dent is for the front derailleur
07-10-10, 08:33 PM
It's inches below the derailleur but I never thought about the movement to the smaller chainring. It was on the largest chainring when I found it. I may have to check tomorrow and switch the chain over just to see if it's there for clearance to the derailleur. I just never noticed it before and I cleaned my bike several times before.
07-10-10, 08:49 PM
I don't know new Treks very well. reptilezs is probably right.
07-10-10, 09:08 PM
Nothing that the shop or a chain would do would produce a dent in that sort of protected area without chipping or scratching the paint. Since it sounds like the paint is fine it was like that when it went to the paint shop during manufacturing. And being so small that you need to really look for it there is certainly no issue about any sort of frame compromise. And it may well be a recess for clearance of some part of the derrailleur that swings by that spot if the seat tube is an odd size and a particular style of derrailleur is being used. But either way if the paint is fine then it's been like that all along.
07-10-10, 09:08 PM
The only a things I can think of that would cause that are: careless handling during assembly or maintenance of the bike - the crank and chainrings are generally in a place where they protect the frame in that area; or possibly from a front derailleur snapping back into the small ring and, instead of being stopped by the low limit screw it hits the frame and puts a little ding - although I do not know if a derailleur can snap back hard enough for this.
Yep the dent is supposed to be there
You may have a serious dent on the right chainstay also! That falls into the same category of this dent.
(maybe it has a recess to fit a clamp, or braze-on/welded thingy for odd FD's like many dura-ace FD's)
07-11-10, 11:18 AM
From the description of the dent (esp. the small size and location) I seriously doubt there will ever be any chance of this 'dent' causing a problem, if in fact it is damage and not there intentionally.
Forget it and ride the bike.
Nobody 'owes him a new frame' or anything.
07-11-10, 11:27 AM
Well, I think everyone is right that it's for the derailleur cage. I e-mailed Trek and they said the same thing. I feel kinda stupid because I never noticed it before but I wanted to make sure the frame wasn't collapsing. But the more I think about it, aluminum is really strong and if there was an issue there, there would be other issues in the frame.
Thanks for the help guys! I'm still a noobie at this but I'm having a lot of fun!
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