Trek 5200 build - FD fitting problem?

arlowood

Making reasonable progress with the build of the 2002 vintage Trek 5200 frame I sourced recently.

New headset fitted plus stem and bars. Also BB, crankset and brake calipers(Ultegra and 105 respectively). Status at present:-



However I don't know if front derailleurs have changed their design in any way over the past 14 years. Problem I have is that when I drop the FD to it's lowest point allowed by the slot in the braze on bracket, there is still at least 5mm between the bottom of the derailleur cage and the teeth of the large chainring. As per photo:-



The recommendation is for the gap to be 1 - 3mm. Will this still work or will I have to consider filing the clamping slot a bit longer to allow the FD to drop a bit more. Bit worried about weakening the bracket if I have to file 2-3mm extra into the slot.

Any other work around or am I obsessing a bit too much and the FD will still work OK with that larger gap?

majormantra

Is that a compact chainset? The frame was probably designed for a standard double - compacts weren't common back then.

It will probably work, just not optimally. Depending on how much meat there is on the braze on I'd probably file it a bit.

The braze on isn't removable is it? If it is you might be able to run a band-on instead, although that would also depend on the tubing profile.

arlowood

Hi MajorMantra

Yes it is a compact so that probably accounts for the lack of adjustment scope.

The braze-on bracket appears to be attached by two contersunk allen bolts so it's possible I would be able to remove it and substitute a band on FD. Will need to check the seat tube diameter to see if it's suitable for any of the current band-on clamps. Bit gutting though as I've only recently bought the new braze-on FD.

On further inspection there is scope to file the slot maybe 1-2mm longer so I guess every little would be a help

Might just carry on and see how it performs and then worry about alternatives strategies at that stage if the front changing is cr*p.

keef66

That's a jolly tidy garage you have there!

I'm assuming they made the carbon tubes a bit beefier in 2002; there's no way I'd clamp my CR1 by the top tube :shock:

arlowood

keef66 wrote:

I'm assuming they made the carbon tubes a bit beefier in 2002; there's no way I'd clamp my CR1 by the top tube :shock:

Not really clamped - just held steady for purposes of taking the pic.

Just had a quick google and found that I can get a braze-on to band-on adapter if worst comes to worst. They come in 2 sizes - 34.9 and 31.8mm. Hopefully the seat tube dimensions will be a match for one or the other

majormantra

Should be possible. Just make sure the seat tube is really circular, otherwise the clamping load may be uneven. From the pics it looks pretty circular.

Ben6899

OR...

Fit a standard double and a slightly bigger cassette?

keef66

arlowood wrote:

keef66 wrote:

I'm assuming they made the carbon tubes a bit beefier in 2002; there's no way I'd clamp my CR1 by the top tube :shock:

Not really clamped - just held steady for purposes of taking the pic.

Just had a quick google and found that I can get a braze-on to band-on adapter if worst comes to worst. They come in 2 sizes - 34.9 and 31.8mm. Hopefully the seat tube dimensions will be a match for one or the other

You're right. My first bike came with what I thought was a band on front mech (also 105), but when I came to transfer the components to a different frame I found it was a braze-on FD on a band-on adapter. Shame I didn't spot it earlier; I'd already bought and fitted a new braze-on FD for the new frame.

Your main tubes are I think perfectly round / parallel until they start to fatten up where they are joined, so you should be OK

arlowood

MajorMantra wrote:

Should be possible. Just make sure the seat tube is really circular, otherwise the clamping load may be uneven. From the pics it looks pretty circular.

Yeah - was wondering about that. Bearing in mind the general paranoia about clamping any part of a carbon frame in a workstand I thought that using a band on mech might be a no-no.

Any other thoughts or experiences out there?

BTW the seat tube takes a standard 27.2mm seat post and looks to be uniformly circular at the point where the band-on mech would be fitted.

majormantra

Plenty of carbon frames take a band-on, but you want to make sure you aren't having to deform the frame to get it to stay put. A little carbon compound would help.

arlowood

MajorMantra wrote:

Plenty of carbon frames take a band-on, but you want to make sure you aren't having to deform the frame to get it to stay put. A little carbon compound would help.

Have tracked down this as an option

http://www.chainreactioncycles.com/rati ... -prod61287

Seems to address the problem posed by a split metal type of band on clamp where there may be a danger of uneven compression being applied to the carbon seatpost at different points

majormantra

Seems like a good idea. You just need to be sure the diameter matches near as damn it perfectly.

keef66

arlowood wrote:

MajorMantra wrote:

Plenty of carbon frames take a band-on, but you want to make sure you aren't having to deform the frame to get it to stay put. A little carbon compound would help.

Have tracked down this as an option

http://www.chainreactioncycles.com/rati ... -prod61287

Seems to address the problem posed by a split metal type of band on clamp where there may be a danger of uneven compression being applied to the carbon seatpost at different points

Looks very similar to the Dog Fang I have clamped round the seat tube of my CR1 (came with the frameset). Although it's not done up very tightly; it doesn't have to resist the forces a front mech does.

arlowood

Gonna have a go at filing the bracket first and see how that works out. If I hit problems then I can fall back on the various band on conversion options. Will update when a solution is found.

Ben6899 wrote:

OR...

Fit a standard double and a slightly bigger cassette?

Yes Ben I suppose that would be one logical approach but I'm already running a 12-30 cassette with the compact on my other bike and jumping to a 52 or 53/39 would probably be a bit too much for these old legs of mine (approaching their 3 score years and 10 anniversary this July).

Suppose I could consider the Shimano SLX HG81 11-32 cassette( http://www.on-one.co.uk/i/q/CASHHG81/sh ... d_cassette) coupled with a standard chainset but I think the gaps between sprockets would make it a bit "lumpy" for a comfortable cadence. In addition to which it's more expense over and above what I've paid out already on components.

Ben6899

arlowood wrote:

Gonna have a go at filing the bracket first and see how that works out. If I hit problems then I can fall back on the various band on conversion options. Will update when a solution is found.

Ben6899 wrote:

OR...

Fit a standard double and a slightly bigger cassette?

Yes Ben I suppose that would be one logical approach but I'm already running a 12-30 cassette with the compact on my other bike and jumping to a 52 or 53/39 would probably be a bit too much for these old legs of mine (approaching their 3 score years and 10 anniversary this July).

Suppose I could consider the Shimano SLX HG81 11-32 cassette( http://www.on-one.co.uk/i/q/CASHHG81/sh ... d_cassette) coupled with a standard chainset but I think the gaps between sprockets would make it a bit "lumpy" for a comfortable cadence. In addition to which it's more expense over and above what I've paid out already on components.

I see. Fair enough.

keef66

Know anybody in light engineering? If the current bracket does simply unscrew, you may be able to get a longer one made up?

arlowood

Just a quick update on progress. After some judicious filing I managed to lengthen the slot on the FD braze on bracket. FD is now in a much better position vis-a-vis the large chain ring. Gap looks to be identical to that on my other 105 kitted bike and the front shifting is fine on that. Pic of final set up below



Have pressed ahead and fitted the wheels, rear derailleur and STI's and have cabled the brakes.



Taken a break now and will tackle cabling the front and rear derailleurs in the next few days. Then it's the chain and gear set up and hopefully everything should be ready to roll in a week or so's time.