Mondo734

Hi all,

So the title pretty much says it all. The bike is a Columbia Trailhead from 2010 or so. The bike rides fine and is basically new except for the crank arm/derailleur problem. Total the bike has probably 500 miles from one season of riding and had its tune up at around 250. The crank arm only hits the FD when its positioned for the big ring, so if I ride in the middle or granny ring its fine. Any ideas suggestions? I realized its not a quality bike but I want it to be rideable so that I can find it a new home since it has since been replaced by a flat bar road bike.

Homebrew01

Probably just need to turn in the limit screw a bit. Shift off the big ring, then turn the outer "high" limit screw clockwise (in) about 1/2 a turn. The screw may have an 'H' next to it. It's usually further outboard than the "low" - "L" limit screw. The 2 screw limit how far the derailleur can move in each direction. If 1/2 turn does not fix it, repeat and try again. Don't turn the screw while in the big ring because you'll be putting a bit too much stress on it as it pushes the cage in.

If the chain stops shifting into the big chainring, then you turned the screw in a bit too far and need to reverse the process.

One other cause could be that the Fd is crooked, with the "tail" sticking out a bit. It should be pretty much parallel to the chainring.

There's a bunch of repair info at parktool.com

NoBrakeNate

It seams like the cage of the derailer is twisted heal out, it should be parallel with the chainrings.
If it is straight then you may just need to adjust the High limit screw a bit.

Mondo734

Ya know I'm pretty sure I checked both of those things a while back. But since I cant remember for sure I will definitely recheck the alignment and also the limiter screws.

FBinNY 

There's limited clearance between the right crank and the chainring. So the FD must be adjusted to be parallel with the ring, so no part of the cage sticks out any more than necessary. Then a correctly adjusted outer limit screw will allow the FD to move out far enough to shift & trim properly, yet not so far as to touch the crank arm.

If you'e not familiar with how it's done, there are plenty of good tutorials available, both print with pictures and video. Search "how to adjust front derailleur".

Mondo734

I am familiar with how to do it but am not going to claim to be proficient at it. Plus the other bike I work on has much more pedal to fd clearance. Also the fact that the Columbia has grip shifters really throws me off (even though they work fine).

FBinNY 

The basics are all the same, but older bikes have narrower clearance than more modern bikes. The Campagnolo Record FD cage and cranks on my old road bike (1967) have less than 1mm clearance when on the outer sprocket.

Homebrew01

Wouldn't hurt to also check that your crank is tight.

zukahn1 

Have you tried turning the front DR slightly so it is a little offset away from the crank and readjusting setting both DR's.

Mondo734

I intented to check the fd alignment and limiters last night after work but found myself to tired to want to. I will probably not get another change to do so until tomorrow morning. But As I mentioned earlier I am pretty sure I checked all that. As for checking the crank how does one go about doing that? I noticed that it seems there is more space on the non drive side of the crankset than on the drive side. Now I know this is partly due to the fact that the drive side has the cogs but it still seems off to me, even when compared to m other mtb, and the two road bikes I have.

Homebrew01

Put the right pedal at about the 2 o'clock position, with a light load on it, then wiggle sideways. You should not feel any movement anywhere. If you do then the crank or BB might be loose. Most likely just the FD adjustment is needed.

Mondo734

Thanks for all the input so far. I finally found the time to go and check it over. Here are the findings. First its not the fd that the crank arm is hitting its actually the bike chain. The front and rear derailleurs were both slightly off and have since been adjusted. However the drive side crank arm near the pedal actually strikes the chain on both passes (top and bottom of chain). The crank doesn't seem to have any play to it at all. Given the new info what do you all think can be done to fix it?

jsharr

Sounds like you may have a bent crank arm.

FBinNY 

Most definitely. Odds are that if you put a level on the pedal, you'll that the pedal points down at the bottom of the stroke and up at the top. Even if the crank didn't hit anything, you'd find it hard on your feet and ankles after a short while.

Mondo734

If this is indeed the problem is there anything that can be done to fix it inexpensively?

FBinNY 

Steel cranks can usually be saved by slipping a pipe over the end and unbending. If you have a bubble level, you can use the pedal as a guide. It's straight when the pedal axis is parallel in the top and bottom positions.

If it's an aluminum crank it's toast. You might be ale to straighten it without it cracking, but it would be very risky to use for anything more than near zero load tooling around on flat ground. Even then you risk fracture with injury if you forget yourself and commit some load.

Mondo734

I am pretty sure that the crank arms are steel but Ill definitely check up on it. I take it that replacing the crank for such a cheap bike isn't work the money?

FBinNY 

there's at least one good bike co-op in Denver. That would be your best bet, as they probably can sell you a used crank of a salvaged bike. Easy to kow a steel crank from aluminum. First of all if it has a cotter pin it's steel, or by color, or with a magnet.

Mondo734

Well it almost sounds like more trouble than its worth. Maybe Ill recycle the frame and remove all the parts as cheapy backups or post em on craigslist for a few bucks.