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Going button head.

Stainless steel Button head bolts and Spring washers from eBay.

Ever since I installed clipless pedals to my A-bike, my trousers often gets catched by A-bike’s top-tube bolts around my thighs. It wasn’t anything fatal — Each catch only lasts for just a fiction of a second. However, it was utterly annoying!!

One of the causes for this nuisance is A-bike’s wide top-tube. While conventional bicycle (including MTB) has less than 5cm width for their top-tube (including outer cable), A-bike’s top-tube width is vast 7cm+!! The socket head bolts sticking out from the side of the tube definitely contributes here.

If you pay attention to your pedaling next time you ride A-bike, you may notice either the bolts scratching your thighs or your feet are on rather outer side of the pedals to avoid the bolts. As long as we use normal pedals, our feet are free, so the wide top-tube isn’t much of a problem. That’s why I never realised this until I went clipless.

Clipless pedals force our feet to be positioned right in the center of the pedals all the time. Thus, it’s more difficult for our thigh to pull out evasive maneuvre.

Anyway, I didn’t want to give up my Eggbeater pedals over this, so I replaced some of the top-tube bolts (edgy socket head), which interfere with my thigh movement, to smoother button head bolts .

Well, I replaced only 3 of 4 bolts so far…. I cannot remove the last one!! I’ve been applying Acetone to the stiff bit, hoping it would break the seal. Soaking the bit in acetone for overnight does extract some brown stuff (grease? Threadlock?), but the bolt is still as hard as a rock. Oh, A-bike factory, what have you done to it!!
I still seek advice on this at this topic in the forum.

At the moment, even though the mod isn’t completed, minimized top-tube width and smoothness of the button head works great. 95% less chance of my thighs get catched!!
(the 5% is the remaining bolt of course.)

The replacement parts for this modification are;

4 x “M5″ size “0.8” pitch button head bolts (2 x 16mm length and 2 x 8mm length)
4 x “M5″ size Spring washers
4 x “M5″ large washers (ext. diameter 15mm)

(I chose rust resistant stainless steel.)
*’Bolts’ are sometimes labeled as ‘Machine screws’ in some shops.
*10mm length M5 bolt canbe used instead of 8mm M5.
*Be careful not to mistake ‘large washer’ as ‘penny washer’. They are different.

Please note, button head bolts have somewhat weaker tightning strength than the socket head bolts of the same size, due to the size of the hex-key they use and the depth of their socket. I would not recommend to this bolt replacement mod. for other part of A-bike at the moment.

(Left) New button head bolt and A-bike original socket head bolt. (Right) Short bolt assembly for top-tube/seat-tube joint.

While A-bike original bolts are for 4mm Hex-key, button head bolts need smaller 3mm hex-key.

The screw assy. here is glued, but still manageable.

(Left) My A-bike with 3 bolts replaced on the left and normal A-bike on the right.
(Right) Soaking in acetone… please! get unscrewed!!

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