Seatpost clamp recess is deeper than frame will allow

[Manc33]

My frame has a notch on it so you can only put a seatpost clamp flush to it if the seatpost clamp is 10mm, or less.
My (Salsa Fliplock) QR clamp has a depth of 15mm so it's only covering two thirds of the surface area to clamp it.

Should I just not use this clamp and only use one that's 10mm or less, or is covering 2/3 fine?

For what it's worth I am going to have about 19cm of post sticking out of the frame and about 22cm inserted.

Thanks in advance.

[tim-b]

Hi
If I'm reading this correctly then you'll have a moat of rainwater collect around the top of the seat tube ready to funnel down, although there is a slot to relieve the effect.
I would guess that providing you can fill the moat in (a slice or two of inner tube?), and the QR lugs are below the top of the seat tube then you will be ok. I'd wait for an engineer's perspective though
Regards
tim-b

[Manc33]

Loads of clamps appear to be 15mm so I think it must be my (carbon) frame thats a bit funky.

If I had the right tool I could shave 5mm off the frame maybe, but it would be really hard to keep it flush with the tube.

Something like one of these things:



It's got a shim in the seat tube that takes up 2mm of space, but there's still a 3mm gap.

The top edge of the QR clamp bolt is about 1mm under the top of the 2 corners on the gap/split part of the seat tube at the top. I think as long as that bolt is fully covering it, it should be OK.

[cyclop]

That tool is a hole cutter; you would not use it to cut a frame tube.

[Manc33]

That tool is a hole cutter; you would not use it to cut a frame tube.

It's not to cut a hole, it's to shave 5mm more off to create a notch 5mm lower:



I'm not going to do it but I reckon it would work.

It's easier to just find a QR clamp thats 10mm deep, not 15mm.

If I'm reading this correctly then you'll have a moat of rainwater collect around the top of the seat tube ready to funnel down, although there is a slot to relieve the effect.

Yep.

providing... the QR lugs are below the top of the seat tube...

Yeah I thought this, the bolt on the QR is fully covering the 2 squared off bits on the split part of the tube, with about a 1mm margin.

[Manc33]

Done a pic...

[AndyA]

That tool is a hole cutter; you would not use it to cut a frame tube.

Actually lots of framebuilders use them to mitre frame tubes on a milling machine


For Manc33's use they'd be less than ideal as they're usually out of round by at least a mm, it would be very hard to cut the notch well I think. An annular cutter would be much better. But still madness!

I've never seen a QR clamp as shallow as that. You could definitely cobble something together using an old QR skewer and an allen key clamp by cutting down the skewer to approx the length of the screw and threading to m5 on a die

I'd use a non QR clamp, it's what the frame was designed for and they're lighter too

[Manc33]

But still madness!

Yeah it would be impossible to line up. Especially when it's an entire frame that needs clamping in... whatever would be used.

I'd use a non QR clamp, it's what the frame was designed for and they're lighter too

I'm going to have to I think. It's definitely the most sensible solution. I know I've got one somewhere....

EDIT: Found that, its 12mm deep, but the bolt if anything is in a worse place than on the Salsa clamp.

In fact, it being more shallow isn't going to help where the bolt is because on a shallow clamp, that means the bolt on a 10mm deep clamp is going to be central to its own clamp at 5mm down, but on a 15mm clamp it's going to be central at 7.5mm down. Having 2mm of shim isn't helping matters. No clamp can rest fully where it should.

I'll just chance it with the Salsa, I'm under 200lbs.