Seat Tube Woes - 1989 GT

[beadlesabout]

Right. First I measured the 27.0mm seatpost and it’s bang on.

Then I measured the seat tube which is difficult as the caliper doesn’t go very deep but it came out around 27.2 side to side but 27.0 front to back. So as expected it’s somehow become ovalised.

I tried a couple of 27.2 seatposts and there is no chance of getting one in.

After doing that though, it’s even harder to get the 27.0 to stop moving and I’m actually not sure I can without busting the clamp, which I really don’t want to do.

I hate to say it but I think I need an expert to take a look at it and make the call on if it should or can safely be reamed for a 27.2 post.

If you lovely folks agree, I’m looking for recommended frame workers, ideally local to me in Sheffield as I don’t drive, or someone I can ship the frame to.

Oh god, I’m absolutely gutted about this. I’ve spent a lot of money on nearly new or NOS parts for my dream build and I’ve gone and cocked it up. Not only that but it’s a special frame and must be saved. Man, I am kicking myself.

That’s if it was me cleaning the tube that did it, which it feels like it must have been. Everything I read said ball hones were safe to use to de-bur.

Feck

 

[bikeworkshop]

It's not a problem, don't stress.
A decent bike shop with staff who worked before we were all buried in carbon will have the tool and the know how.
It's no big deal. it's what the tool is for, and why you have one hanging up.
You could put a straight edge on the seat tube to check it's not bent, then away you go.
A well fitting post will add more strength than you've lost with .1mm wall thickness.

 

[27motorhead]

Right. First I measured the 27.0mm seatpost and it’s bang on.

Then I measured the seat tube which is difficult as the caliper doesn’t go very deep but it came out around 27.2 side to side but 27.0 front to back. So as expected it’s somehow become ovalised.

I tried a couple of 27.2 seatposts and there is no chance of getting one in.

After doing that though, it’s even harder to get the 27.0 to stop moving and I’m actually not sure I can without busting the clamp, which I really don’t want to do.

I hate to say it but I think I need an expert to take a look at it and make the call on if it should or can safely be reamed for a 27.2 post.

If you lovely folks agree, I’m looking for recommended frame workers, ideally local to me in Sheffield as I don’t drive, or someone I can ship the frame to.

Oh god, I’m absolutely gutted about this. I’ve spent a lot of money on nearly new or NOS parts for my dream build and I’ve gone and cocked it up. Not only that but it’s a special frame and must be saved. Man, I am kicking myself.

That’s if it was me cleaning the tube that did it, which it feels like it must have been. Everything I read said ball hones were safe to use to de-bur.

Feck

Heh @beadlesabout. 100% message @danson67 to get his thoughts/opinion.

To measure it properly you need some telescopic gauges that will go deep enough vs. the inside jaws on your digital/vernier calipers.

There will be a way to fix it, but you might end up losing some paint, but if it's not original it's not an issue apart from a bit more money to get it repainted in that local area.

Not all is lost. Chat to Dan and go from there

 

[beadlesabout]

It's not a problem, don't stress.
A decent bike shop with staff who worked before we were all buried in carbon will have the tool and the know how.
It's no big deal. it's what the tool is for, and why you have one hanging up.
You could put a straight edge on the seat tube to check it's not bent, then away you go.
A well fitting post will add more strength than you've lost with .1mm wall thickness.

Thanks, appreciate it. I’ll see if I can find someone locally to take a look.

Heh @beadlesabout. 100% message @danson67 to get his thoughts/opinion.

To measure it properly you need some telescopic gauges that will go deep enough vs. the inside jaws on your digital/vernier calipers.

There will be a way to fix it, but you might end up losing some paint, but if it's not original it's not an issue apart from a bit more money to get it repainted in that local area.

Not all is lost. Chat to Dan and go from there

Thanks, I’ve sent him a message. Why do you think I would lose paint? Just thinking the other suggestion is just to ream it to 27.2mm which wouldn’t affect the paint. What did you have in mind?

 

[Suprachrgd82]

May be work a try before going at it with tools. I have noticed that some seatposts are "slippery" while others snug into place without closing in on the pedals.


https://www.parktool.com/en-us/product/supergrip-carbon-and-alloy-assembly-compound-sac-2

 

[27motorhead]

Thanks, appreciate it. I’ll see if I can find someone locally to take a look.



Thanks, I’ve sent him a message. Why do you think I would lose paint? Just thinking the other suggestion is just to ream it to 27.2mm which wouldn’t affect the paint. What did you have in mind?

I would be looking to make the tube profile as round as possible again before removing any internal material.

It's a shame it doesn't have a removable seat collar because a thought is, is to clamp the top of the seat tube in tube/frame blocks that are the same DIA as the OD of the seat tube and roll the frame around inside them to help reshape. If you had no QR lugs in the way this would work really well, but this isn't the case. But you could clamp just below and see if you could still re-shape. They use this technique to remove dents from frames and it removes most of the dent, then you fill with a bit of silver solder or braze and sand back to a dent free finish. That's why the paint could get damaged from friction/rubbing in the blocks.

Once more round I'd then assess what to do next, such as ream to a known DIA.

Hopefully Dan will get back saying the exact opposite to what I'm talking about!