Alu frame with dropouts for belt drive - sheared dropout screw(?)

[keyboardmonkey]

An acquaintance has an 7005 alu double butted frame with a belt drive. Whilst trying to fix a slow puncture the nearside bolt/dropout screw(?) was sheared. I'm sure a similar question has been answered elsewhere, but what are the best DIY options to fix this, please, before the owner gives up and tries a bike shop that will take on the job? Cheers.

[alexnharvey]

If the other end of the bolt is visible you may be able to drive it from that side although it will be fiddly within the dropout. Either put two nuts on and lock against each other or use a capped Acorn nut, then use a socket on this to drive the screw through. If you are able to lock the nuts on, you may be able to "pull" the screw through (towards the rear of the bike). If not you may have to push it back towards the sheared side and then when enough is visible on the other side you can use various methods to remove the remaining bit, locked nuts, cutting a slot or mole grips.

Unfortunately corrosion between the aluminium frame and the steel screw is likely to make the removal quite tricky. Heat, penetrating lubricant and patience are likely to be necessary. He will be much more likely to remember to use anti seize in future when he is done. If the screw won't move then it will have to be drilled out.

Is that corrosion bubbling on the side of the drive side screw hole?

[slowster]

If you use the two nuts locked together as detailed above by alexnharvey, and are able to start the bolt turning in the direction of the sheared end, you might find then that you can reverse the direction of turn to withdraw the bolt from the dropout side, i.e. a shorter distance.

In any case I would probably replace the screws with a Surly Tuggnut on one or both sides, athough that would also necessitate a longer security skewer for the hub to acommodate the thickness of the Tuggnut(s). That would eliminate the risk of it occurring again.

[keyboardmonkey]

Great suggestions, folks. Thank you very much. First thing is a bit of a clean I reckon.

[iandusud]

If you need to resort to drilling the screw out do it from the front (the sheared off end). You may well find that as the drill grips and the screw heats up that it free up and be driven out.

[Jupestar]

In any case I would probably replace the screws with a Surly Tuggnut on one or both sides, athough that would also necessitate a longer security skewer for the hub to acommodate the thickness of the Tuggnut(s). That would eliminate the risk of it occurring again.

+1 for this. I had a bike with those types of screws breifly and it drove me made everytime i had a puncture. I retired them, and used a chain tug.

[keyboardmonkey]

Thanks again for the further input. It hadn’t occurred to me without having the bike in front of me that it wouldn’t be possible to get started with a capped acorn nut because the skewer is in the way.

If the bolt/screw is drilled out would it be suitable to have a square captive nut slid in to the dropout and a locknut or something threaded on from the head end of the bolt so that the two nuts work against each other to hold the bolt in place? The Surly Tugs are quite a price!

[iandusud]

Thanks again for the further input. It hadn’t occurred to me without having the bike in front of me that it wouldn’t be possible to get started with a capped acorn nut because the skewer is in the way.

What is preventing you from removing the skewer?

[rogerzilla]

If there's anything to grab with mole grips, heat it up and try that first. Otherwise, alum will dissolve it out.

[alexnharvey]

Thanks again for the further input. It hadn’t occurred to me without having the bike in front of me that it wouldn’t be possible to get started with a capped acorn nut because the skewer is in the way.

8AF421F0-5046-4BB0-89EC-2C2F62890A1B.jpeg

If the bolt/screw is drilled out would it be suitable to have a square captive nut slid in to the dropout and a locknut or something threaded on from the head end of the bolt so that the two nuts work against each other to hold the bolt in place? The Surly Tugs are quite a price!

As @Iandusud says I assumed you would remove the skewer (and wheel) to allow better access?

If you do have to drill the screw out you would aim to centre the drill in the bolt so that the body/shaft is removed and the screwthreads and some slivers of metal are left. These are then extracted or cleared with a tap, leaving the hole usable. Since this hole is not blind, the twisting action of the drill and the heat generated will hopefully drive the screw out towards the rear of the bike.
In a blind hole, or if the skewer can't be removed, you could use a 'left handed' drill as this has an unscrewing rather than screwing action.

If the threads are damaged during removal then you could potentially use nuts to secure it but of course if one nut is on the inside, access to it within the dropout is very limited. A threaded insert (e.g. helicoil and other thread repair systems) is often used to repair damaged threads, unfortunately they require a larger hole to be drilled and you may not have enough thickness in the dropout to allow this without weakening it.

While you and your acquaintance are pondering how to proceed, if you can get the wheel out, you should immerse that dropout in some penetrating oil solution, or even just old motor oil.

[keyboardmonkey]

My understanding is that the bolts need to be unscrewed a few turns so that there is sufficient slack in the chain to pop the wheel out. The owner accidentally partially unshipped the chain belt with a trouser leg snagged between the belt and chain wheel, but doesn’t believe the belt will come off fully. And even if he could get the belt off he wouldn’t be confident about getting the belt back on without first shifting the wheel forwards a little first. Is he wrong in this belief?

[alexnharvey]

Probably he is wrong in his belief.

Are we wrong to assume that the drive side screw still functions? If so the NDS side can move backwards while the DS moves forward to release belt tension (the wheel skews to one side rather than moving straight forward). Even if this is not the case a partially derailed belt should be possible to fully derail. Certainly this is normally true of chains unless they were very tight beforehand but I suppose the higher tension on a belt may make it a bit more difficult?

Even if that's not an option I think that he is probably not being drastic enough, if the wheel cannot move why not remove the chainring or entire crank to release the belt? I think whatever route he takes it is much easier with the wheel out of the way. Frequently I find the quick way ends up taking longer. Can the repair be easily completed with wheel in place? Yes? carry on; no? accept that it must be removed one way or another and get on with it. Why is he worrying about getting the belt back on at this point
Sometimes you have to accept that the whole front bumper has to come off just to change the headlight bulb. Such is the life of the diyer and professional mechanic alike, although the latter is more likely to know how long a job should take and the necessary steps to complete it.

[Jupestar]

The Surly Tugs are quite a price!

Cheaper versions which do the same thing exist.

https://www.planetx.co.uk/i/q/FSOOCT/on-one-chaintug



I'm a bit confused. If your trying to get that stuck screw out without taking the wheel off, then i reckon you are on a pretty impossible mission.

If it was my bike.

I would take the skewer out, release the drive side bolt. hope that gave me enough movement in the wheel to unhook chain/belt off. then take the wheel off. If it was really stuck i would probably take the chainring off to release, but doubt it would be needed.

Then i would get both of those frame bolts out and chuck them in the bin.

Add 2 chain tugs of choice.

Reseat the wheel, research and try and work out how to get the right tension on the belt. Then when i got it wrong and the belt was damanged. Replace it for a chain drive.

The fact it has a belt and is not my bike means i probably won't touch it at all, as the tension on the belt means it needs someone who knows what they are doing with the belt (not me). in my experinece its not nessecarily a bike shop either.

[keyboardmonkey]

Thanks once more for the detailed responses. If the bike belonged to me I might be tempted to give it a DIY bash and then try to offload on to a shop if things didn’t work out. But then I have a spare bike or two to use while one is off the road, unlike the chap who has this as his only bike for getting to work. I’ll pass on the comments here and thanks again on behalf of the bike’s owner.

[nirakaro]

I think whatever route he takes it is much easier with the wheel out of the way.

In the communal washroom on a campsite the other day, someone remarked on how hard it is to brush your teeth with a mask on. Easier that, I would think, and more sensible, than trying to deal with that screw with the wheel still in place.