"SONIC boom" (aka Yokel-Motion 2.0)

Thanks.

Very much function over form, but I'm there to look pretty! :)

90mm/350mm >>>>>

80mm/400mm<<<<<

Gaining me 29g of butt-confidence and losing the crick in my neck from being too low at the front.

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Just been sent this pic from last Sunday's 25.

As pictured, my gooch was yowlin', but I couldn't rotate my hips and get on the nose for long, without putting a lot of weight on my shoulders and my hands slipping over the ends of the extensions.

Since then I've lengthened the extensions by 1cm and moved the saddle back by the same amount. After one ride, I think the saddle needs to go back further still.

Currently trialling 56x14 and have 160mm cranks en route from Eire, thanks to the generosity of @boredom.

First evening 10 on Thursday...

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Speaking of generosity, honourable mentions to @mdcc_tester and @umop3pisdn for contributing to what you see above.

Nice legs. Get a skinsuit.

Yeah, skinsuit is on the list along with wheels and another saddle (although I think fettling could improve my comfort on the current one).

However, first on the list is a decent run of work.

Will be back there on Bank holiday Monday for a 10, when I'm planning on joining the ton-up club with 104"...

PS Reported for grooming.

DNS today on account of the steerer bung not holding... again.

Steerer and bung have been keyed, cleaned with acetone and a two-part epoxy used, left to cure for ~five hours before tightening.

The problem seems to be that the bung is such a tight fit, that the epoxy is being pushed down the steerer by the bung, leaving insufficient to form an adequate bond.

Reduce the diameter of the bung? Score some grooves in it?

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Something else is awry if you're pulling the preloader out with normal riding loads. I'd be looking at the steerer shim to see whether it is gripping properly on both the inside and outside diameters.

What bung are you using?

That is also a problem: even when the bung has held long enough to allow proper assembly, the HS eventually develops play.

Assembly paste on either side of the shim, which I hold open when fitting, and torqued to the max. recommended.

A shim is a shim is a shim, so not sure what else I can do (aside from a 1" stem).

However, the photo above is the result of assembly only, no riding. Presumably I reached 2.5Nm when the bung hit the top cap.

A shim is a shim is a shim

...ish

Is the slot in the shim still open when everything is tight? Is the shim cold rolled (hard smooth surface with no grip) or turned (soft, rough, grippy)?

Anyway, shims aside, it should be possible to get enough pull-out strength on a glued in bung, so as you suggest your bond is the problem. Mine have less bond area and hold 5Nm of post-assembly belt-and-braces over-tightening. Stick it in your drill chuck and give it a good linishing with coarse grit paper, you're probably looking to remove about 0.005" on the radius to go from a light interference fit to a decent clearance. Spread the glue on both surfaces when you get to that stage of proceedings.

4mm slot when fitted before the stem and it's fairly snug then, so it won't be much less than that when tightened, and cold rolled based upon your description.

Are there better bike-specific choices, or should I head for the model railway shop?

"Linishing": every day's a school day!

Are there better bike-specific choices, or should I head for the model railway shop?

I had some turned, but I wouldn't go chasing after that as your solution. Maybe touch the shim with some of that coarse grit paper while you have it, but bond strength at the bung is going to be the key.

"Linishing": every day's a school day!

Strictly speaking, you hold the workpiece against a moving abrasive for linishing, but you can get the same effect on solids of revolution by spinning the workpiece and holding the abrasive.

Right-ho!

Thanks for your help.

re shims - the readily available alloy ones can slip and develop play in my experience. The one I'm using at the moment that holds very well is steel and a quite a tight fit. Can't say where to get one though as it was on the bike when I bought it. might be worth looking out for one?

OK, cheers!

How long is the shim relative to the stem? If it's significantly shorter, you'll have the same problem of the stem trying to walk up the sleeve as you get with steerers which stop short of the top of the stem.

5mm shorter: it's from another bike which had a low stack stem.

The centreline of the stem's top screw is right on the edge of the shim.

New shim then.

At least you have a valid excuse to go for a black one now ;)

With a dash of "Spirit Of The Forum" and three bottom brackets later, YM 2.0 gets a 160mm, short-stroke update.

With a 56t chainring, the difference in gain ratios between 170mm and 160mm cranks is one tooth (give or take), which is refreshingly straightforward.

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Just in time for tomorrow's 50...

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looking good, ss, knock it out the park tomorrow!

Good luck. Ended up going for 107" tomorrow, btw.

Any hydration?