Gtowngolfer

I was careless today and put a dent on the seat tube next to the front Derailleur. It's a dent right beside it about the size of a quarter. I'm just wondering if it is a cause for concern and will it effect the integrity and safety of the frame. I don't want to end up crashing from frame failure due to the dent. Any thoughts and comments would be greatly appreciated. I'm going to take it to the shop or an opinion as well

Its a 2011 Specialized Allez Comp. I'm 5'10 and about 220lbs.

10 Wheels

Good Photo might help much...The Mechanics on here are very skilled people.

They need something to work with.

What bike? How much do you weight?

JohnDThompson 

Steel frame? No worries. Aluminum or carbon fiber might be a different matter.

FBinNY 

Not great, but not a disaster. If you have to dent any tube on the frame, the seat tube may be the best choice, and where you dented it the best place.

Put it out of your mind. It may fail eventually, if you ride it enough, then again it might not. If it does fail, it's very unlikely to cause a crash, though it may strand you. Over the years I've seen a number of seat tube failures, including one I experienced 1st hand. What happens is the bike stays together, but you cannot put any weight in to the pedals.

oldbobcat

I've seen some new aluminum frames with this dent. Unless it's carbon or very lightweight aluminum (like a Cannondale CAAD10), I would tend not to worry.

Gtowngolfer

Info updated with pictures.

FBinNY 

Ignore it. For better o worse, it's done, and there's no fix. It may or may not ever lead to a crack or tube fracture, but that's a long tome away, and won't cause a crash.

Andrew R Stewart 

Are you sure the dent was not there from the factory? Looks to be a der inward travel clearance dent. That's a hard location to impact, how did you dent it? Andy.

koolerb

That's what I thought when I looked at it too.

bradtx

Gtowngolfer, I don't think there's any cause for alarm. If the frame is aluminum you want to watch for a sharp crease(s) developing. Dents with rounded edges are rarely a bother.

Brad

bobotech

How the heck could you have put a dent in that particular location? It looks factory to me, like a clearance dent put there to allow the front derailleur to operate properly.

Are you sure you didn't do something like just bump the front derailleur and then panicked and looked at the seat tube and thought you did that? If the bike is shifting fine, then I don't think you put that dent there.

Gtowngolfer

I was pushing the derailleur from the back side to adjust it and using a back end of a screwdriver to hold it in place. That's how I dented it.

Kimmo

Nope - I'd swear blind you haven't done a thing to it.

That dent is there from the factory for FD clearance. If you'd made it the paint would be damaged. And it wouldn't be so smooth.

cyccommute 

Yup. It's not damage but design. Aluminum isn't delicate enough to be bent by a screw driver. The 'dent' is also very conveniently located.

fietsbob

that looks like a clearance dent (there before being painted) , but it means the height of the FD stays there,
no smaller chainrings..

techsensei

I agree with everyone else; that dent is there by design, to allow the front derailleur to swing without interference.

epiking

+1 Factory clearance relief...

Gtowngolfer

Thanks for all the quick replies. I called Speialized today and they confirmed it was designed that way. It just does not seem normal for such a large dent to be there. It's almost 2mm deep and width of a quarter.

I braced the the screwdriver handle against the frame and pull the derailleur towards the large chain ring. So I assumed I caused the dent as the chain stay is fairly strong.

FBinNY 

Point of information.

You keep referring to the chain stay, but I assume you're talking about the seat tube.(where the FD mounts)

techsensei

He wrote seat tube in the original post.

Gtowngolfer

Sorry guys. New to this so I'm not familiar with all the part names yet. But it's the seat post. I meant the front derailleur is quite strong so I held it in place but putting a screwdriver handle behind it while trying to tighten the cable.

FBinNY 

Here's a trick that many experienced mechanics use when setting FD cables. Flex the FD to outward, or shift to large chainring if the chain is on and stick a pen or pencil into the pantograph so it can't retract. That allows you to pull up the cable very effectively. Then tighten the pinch bolt just enough to hold the cable very gently yet let it slip. Now, Push the lever to retrieve your pen, and let the FD shift inward, with the cable slipping. Finally tighten it, and you'll have a zero slack cable trim.

Sometimes you actually want a bit of slack, so a gentil pull away from the frame at the downtube before tightening the pinch bolt does the trick.

Most of the pople I know who use this method, and hit perfect FD trim 1st time about 95% or the time.

Metaluna

I'm trying to visualize this method...either I'm missing something, or maybe you missed a step? I think you want to ensure that the FD is shifted back down to the smallest chainring before the you tension the cable and gently tighten the pinch bolt? Otherwise you end up with the shift lever set in the highest gear, but the FD cage in the lowest gear, i.e. a huge amount of cable slack. Still, it sounds way better than pulling the cable tight with pliers.

FBinNY 

You initially only tighten the cable to a light touch, so it'll slip as the FD shifts in on the spring after you remove the pencil.

Others' do a variation, where they tighten more at first, remove the pencil, then ease off the tension so the cable slips trough and the FD shifts inward. Either way you need a loose hold that allows the cable to slip, but not so loose that it goes slack.

Gtowngolfer

Thanks for all the replies but I was able to see te same bike and the dent in the seat post is by design. So relieved that I wasn't the one that dented it.