I just tried installing a Jubilee FD with a clamp stamped "28,6" onto a bike with 28.6 seat tube. The Clamp fits snugly, without even closing the hinge, and doesn't want to close beyond the first ~2 threads of the clamp post. It almost seems like it is really a 28.0 clamp mis-labeled as 28.6. Can anyone provide photos of the clamp area of their Jubilees to give me a visual reference for how tightly the clamp is supposed to close? I am hesitant to tighten the clamp bolt any more because I know the clamp hinge pins on these are notorious for snapping. I'm also concerned that having the clamp bolt threaded on by two turns may mean that it can easily work its way loose.

The derailleur is otherwise very nice and I'd like to use it if at all possible. Is it possible to sand the inside face of the clamp slightly to bore it out? Or would that be a futile effort?

Sorry I don't have any pics, I will try to get some tonight.

Thanks!

Hi Southpaw -

You say you're concerned about cracking yours?

I thought they all came cracked from the factory like this:



- And that's why you see them with a big ol' screw right through it, and the Seat Tube:



But at least the front side is netted out and it isn't going anywhere...

If it turns out to be a 28.0mm clamp, will you look to replace it or modify it? It looks like soft enough aluminum that some time with sandpaper would make it work just fine.

Tonight I will test fit it to my jeunet (28.0 ST) and see if it was made for 28.0. If so, I may try sanding it to a wider bore.

If the inner curve/diameter of the clamp seems to match your 28.6 seat tube, you might just have to get a longer bolt to secure it better. Two turns of the bolt does not sound secure enough. Please note that you should not expect the end of the clamp to make full contact (a reamining small gap is normal with the FD body you are screwing it tor as that would most likely make it to tight and lead to the clamp busting on you. The point is to just get the clamp tight enough to grip the seat tube adequately, so it does not get pulled down by the shifter cable or easily misaligned from getting bumped around by the rider or pressure from the crank rings when shifting. the FD.

Chombi

^ Which was the underlying point of my prior post: - The gap of course should be at the front side of the clamp, not at the fractured hinge.

The clamp appears to be two pieces, one of which is the main derailleur body. Is the size stamped on both of them?

.6 mm diameter will add up to almost 2 mm circumference, with the result that a longer bolt won't align properly. I imagine that's how Auchencrow's ended up modified.

I like the diplomatic way rhm described my DR as "modified".

I'm relatively sure this is the original clamp on this bike -(a '74 Moto Grand Jubile).
The O.D. of the seat tube mikes out to 28.3.

This RD was received in a trade, and it was suggested to me from the person with whom I traded that the powder coat on my bike frame could be causing the tight fit, and that the derailleur had in fact come off of a bike with a 28.6 seat post. I think I'll take my caliper to it tonight as see if that's the culprit. Come to think of it, this was a problem I had on another powder coated frame, but the problem was with the clamp-on shifter.

I can't extend the bolt because it's integrated with the clamp band. I think I'm just going to try to sand 0.1-0.2mm off the inner face of the clamp. As long as I can get a couple more turns of the nut I'll call it good. I'll take before and after pics tonight.

I agree that the powder coat could very well be the culprit (or at least it doesn't help). If this is the Shogun, the cream color looks thicker than some, not as thick as some others. My plan of attack would be the same as yours: elbow grease with sandpaper; dry fit; repeat as necessary.

Yep, it's the Shogun, but the PC job on this bike is generally thin. It's thinner than either my Jeunet or my Raleigh Comp, and about the same thickness as my previous Blue Shogun (which was thin). However, I did notice some thick areas around the seat cluster and BB, and I suppose it's possible that the seat tube got it a little thicker than normal as well.

I'll probably use the dremel with mini-belt sander attachment. I try to avoid elbow grease when possible .

Way to use that brain!

Okay, so it turns out the FD is fine, it's the powder coat that's causing the problem. ST measures 29.2mm where the FD clamps on. So, I removed some material by sanding, and managed to get the bolt threaded by at least 5-6 full turns. I think it's fine, and I don't want to take off too much material and turn this FD into a 29.2 in case I want to use it on another bike!

Have you ever seen a front derailer marked 28.0?

No, but I assumed they exist for French bikes? So is there no such thing as a 28.0 FD clamp? My metric Reynolds Jeunet seat tube measures out at 28.4mm with powder coat, so I would assume that a 28.6 FD would fit loosely.

It wasn't sarcasm. I'm asking because I've never seen it. I know that the same Simplex derailers were used on French 28 mm tubes and British 28.6 mm tubes.