Mechanics and Fixing Any Questions Answered

Tester will put it in more technical language.

Not sure about that, but the principle is the same as stem clamps on steerers and I've explained that in non technical language more than once on here.

Is this still the case if the top of the clamping area sits above the bolt on the seatpost collar?

Yes, because #everythingisrubber. The part of the clamp which is supported by the seat tube is strained, but the unsupported part wants to taper back to its original unstressed diameter, resisted only by shear in the clamp. Imagine a rubber hose pushed onto a spigot with a diameter greater than the relaxed bore of the hose.

There's no upward pressure on the clamp

Hoop stress plus the induced taper makes an inclined plane generating a small upward force. In a static situation, this doesn't matter because the taper angle is far below the maximum for a self locking system (something something sinθ something something coefficient of friction) A seat post is about the worst possible deviation from a static assembly, as it has large cyclic eccentric loads applied.

In real life, you're unlikely to have a problem, I'm just explaining why the design is theoretically problematic.

Hoop stress…induced taper… inclined plane generating a small upward force. In a static situation…taper angle …coefficient of friction…deviation from a static assembly…cyclic eccentric loads applied.

There it is!

I should really have said you’d explain it properly as I could not.

I'm very confused.
I bought this second hand frame and installed a new BB, I noticed a small gap on one side and it's not in straight...
I found out that I can screw a driveside bearing in there by hand (this is the non drive side)....
How is that possible? Did the previous owner force a BB in there the wrong way around? How I'm I still able to get the correct BB cup in there anyways (on an angle)?

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Threads might be right but the facing off?

No it's perfectly straight and strange enough if I screw the wrong side cup in there it's nice and flush

Is it a french BB or something similar?

Most likely someone has chased the threads and done the wrong side by mistake

Yes I'm afraid this is it:(

Just use two of the same cups then?

Not sure I quite follow with the dremel instructions though, do you mean dremel the bottom of the clamp to make sure it sits flush (ish)?

Nah, I was saying that if I was you I'd have a go at making that upper lip only 1mm deep instead of 3mm deep by removing metal from inside. Aside from the effort involved, it would be the perfect crime because the sins would be hidden, and removing a tad extra (to increase the ID just under the lip) would leave the upper 2mm of the seat tube unclamped.

Ah I seeeee! My mistake then, the upper lip is normal sized, but the body of the clamp is taller, so there's 'empty space' between the top of the seat-tube clamp area and the lip of the clamp.

Thanks Tester, I understood maybe 30% of what you've said, but will digest. I'll keep my eyes peeled on any movement in the seatpost.

Replying to myself, #7118
11-32T works like a charm with no modifications and no road link whatsoever. B screw had to be adjusted a bit, that's it. Thanks for all the replies suggesting to just try it, it's indeed the way to go!

Update on my post #7230 on the top of this page.
I bought a bb thread tap and could fortunately save the frame. I had to cut away quite some material... The previous owner probably forced a bb in there the wrong way around.
Bb cups sit nice and flush now, happy days.

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That's good news.

You might want to think about getting it faced at some point too, especially if running an external bearing bb as they are a bit more sensitive to parallelism.

If you get it faced, carefully run a file around the external corner of the BB tube down to the metal first so the tool doesn't chip your paint.

That's a great tip

Thanks guys, good advice!

I want to run a front axle mounted rack, but the fork isn’t drilled for the top mount. Previously I fitted a starnut to the bottom of the steerer to hold guards. Will I do a die if I run a bit of flat stock from this to the rack? I see no big issues as most of the weight will be on the axle and it’s only for a duffle bag, but?

Is it one star or two on the nut?

If a single, maybe double it up with another and use a long bolt?

It’s a double thumbs 👍

I saw a mate for his 60th last night, few beers and wine at and then near a pub, introduced him to the joys of cazcabel, good times. I guess the bit that makes it bad is if the birthdayee is a twat.

Fatties don't quite fit fine on my surly steamroller fork.

While the clearance is just about there for my 700c*40mm tyres, there is very very slight rubbing on the inside of the fork crown while I'm riding. There also isn't room for a mudguard which would be desirable.

I'm mooting angle grinder the lawyer lip off the fork and then supergluing some snipped spoke bits in the fork end to create a tad more clearance between tyre and fork crown. I've got a mate who's made an old school Canadian track iron work with 25mm tyres very well by doing the same, albeit without needing to grind off the lip.

The front wheel is a track wheel so I'm not concerned about the wheel being insufficiently clamped in place, as I can torque it down snugly with a 15mm.

Go ahead and tell me if you have a better idea. And yes I know it's a bit gross on the headset cups etc

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