I’ve got two Inbreds, an old DN6, now the run-around/shopper, and an 853. Both are fitted with Thomson posts and 30mm Salsa boltup seat clamps. The odd thing is that on the DN6 bike with the clamp well tightened there’s a gap of about 3mm between the clamp jaws, on the 853 with the collar at the same torque the jaws of the clamp are almost touching. I’ve swapped the posts and collars around with the same result, so it’s definately the 853 frame.

The post is nice and snug in the 853, so it’s internal dimensions seem right, it’s as if the metal in the seattube is slightly thinner giving smaller outer diameter. Would the walls of an 853 seattube be slightly thinner than a 4130? I’ve ridden the bike well for around 18 months and nothing’s cracked, slipped or misbehaved, so I guess that there’s nothing to worry about (I assume that the clamping force is the same if both are torqued similarly, irrespective of where the jaws are), it just seems odd.

Did you not post an exact same question as this about a year or so ago?

If it’s good, don’t worry 🙂

I think that I probably did. I’ve just been re-greasing the seatpost and noticed it again. It’s certainly not causing any problems (and I’ve over 15 stone).

I assume that it’s not a case of needing a 28.6mm (as per the mech clamp)?

Just checked my 853 (also in sand if it helps) and there is about a 3 mm gap between the clamp jaws and therefore clearly your 853 is faulty and I would contact On-One asap before serious injury results 😉

If it’s that much of a problem, just shim it with a neatly cut piece of coke can. Done this loads of times before with seat clamps and posts and you won’t see it once fitted.

Cheers, I do seem to have a bit of a reputation for worrying. I’m not worried about the aesthetics and everything’s held up for long enough with my 15+ stone bouncing around on top for it to seem pretty sound. It just gives the impression that the metal in the seat tube of the 853 is slightly thinner than the DN6.

The butting in the tube is visible too with the 28.6mm mech clamp fitting well around the thinner diameter part of the tube, so I’ll just ride the thing.

the metal in the seat tube of the 853 is slightly thinner than the DN6

TBH I’d agree: Before I switched to the On-One QR ‘Salsa’-style seat clamp, I was using an On-One bolt on seat clamp and had to file off the lip of the collar or the lip would clamp on to the seatpost well before the collar would clamp the seattube to the seatpost.