Author Topic: Thorn Audax Mk3r dropout spacing wider than expected  (Read 396 times)

u2v2w2

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Thorn Audax Mk3r dropout spacing wider than expected
« on: October 05, 2021, 02:35:05 PM »
Due to wider than 132.5mm dropout spacing freehub is developing uneven drag when QR sqever is tightened accordingly.  Last time I measured it was 135mm or even wider as far as I can remember. To avoid that there is no other choice but to set the pressure on it really lightly. When the dropouts are squeezed then ther aren't parallel anymore which bends the axle and causes to pawls rub
against the aluminium hub body due to insufficient wiggle room. Last time found some aluminium shavings and score marks next to the engagement ring. Anyone else experienced anything like this before?

B cereus

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #1 on: October 06, 2021, 10:57:21 AM »
Welcome to the forum.

I'm struggling to understand the exact nature of your problem here. I'm not a big fan of 132.5 mm rear spacing but I see no reason that it should lead to the problems that you describe. A few more details might help.

Is this a new bike?
What make and model is the rear hub?
Where exactly are the score marks that you saw?, a photo would be useful.

You say that you are tightening the QR “lightly”, do you perhaps mean tightly? I'd be surprised if you could tighten the QR enough to bend the axle, although it is certainly possible to compress it enough to apply excessive preload to cup and cone wheel bearings. This might lead to the “uneven drag” that you describe, and seems to be a more likely explanation than anything to do with the freehub.

JohnR

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #2 on: October 06, 2021, 01:57:51 PM »
If the dropouts are wider than the hub then I would put a washer on each end of the axle.

u2v2w2

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #3 on: October 06, 2021, 09:42:33 PM »
The frame is nearly two years old. The hubs are 130mm OLD budget grade Chosen ones with cartridge bearings. Another alternative option to washers could be 135mm end cap adapters or longer end caps, since respacing chainstays would require dropout facing to make them parallel.

B cereus

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #4 on: October 07, 2021, 09:13:19 AM »
I'm still not clear how and where the  pawls are binding against the hub body. In a conventional freehub this wouldn't be possible.

Here are a few thoughts:-

Have you tried simulating the axle compression with the wheel removed from the frame. Use the the QR skewer with a suitable thick penny washer next to the cam end  to compress the axle and see if the bearings and freehub run free.  This should tell you if the problem is frame related.
 
A good frame maker should charge around £20-£25 to cold set the rear spacing to whatever dimension you choose, and would correct the alignment of the dropouts at the same time.

If the parts to re-space your existing axle to 135 mm are readily available then this might be the best option but wouldn't address the problem of misaligned dropouts. You can check and correct alignment with a couple of old axles or two lengths of 10mm studding. Use nuts and washers to lock the axles/studding into the dropouts and sight along them to check alignment. Gently tweak the dropouts until the ends of the axles are in perfect alignment.

u2v2w2

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #5 on: October 09, 2021, 11:51:08 PM »
I'm still not clear how and where the  pawls are binding against the hub body. In a conventional freehub this wouldn't be possible.

Here are a few thoughts:-

Have you tried simulating the axle compression with the wheel removed from the frame. Use the the QR skewer with a suitable thick penny washer next to the cam end  to compress the axle and see if the bearings and freehub run free.  This should tell you if the problem is frame related.
 
A good frame maker should charge around £20-£25 to cold set the rear spacing to whatever dimension you choose, and would correct the alignment of the dropouts at the same time.

If the parts to re-space your existing axle to 135 mm are readily available then this might be the best option but wouldn't address the problem of misaligned dropouts. You can check and correct alignment with a couple of old axles or two lengths of 10mm studding. Use nuts and washers to lock the axles/studding into the dropouts and sight along them to check alignment. Gently tweak the dropouts until the ends of the axles are in perfect alignment.

The dropouts are quite thick on the Tnorn Audax Mk3r so aligning them with alignment tool would be impossible. The only option then is to file them down a bit. Got the frame to avoid issues like these but what can you do.

B cereus

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #6 on: October 11, 2021, 10:14:31 AM »
Most steel dropouts are amenable  to straightening using the right tool. You can improvise with a large adjustable wrench, or this Cyclus offering  should be up to the job and can be bought for less than £50.

Failing that it might be cheaper to entrust the work your local bike shop.

mickeg

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Re: Thorn Audax Mk3r dropout spacing wider than expected
« Reply #7 on: October 11, 2021, 01:49:26 PM »
I am not familiar with the Audax bike, can't comment on specifics.  But I can say that on my rando bike (non-Thorn) with a steel frame, the frame was 130mm.  Before I bought the frame, I verified with the manufacturer that I should have no problem using a 135mm hub.  The manufacturer only had one concern, when I drop the hub into the frame, I would have to pull the stays out a bit for the hub to drop into place.

For five years now I have been using a 135mm Shimano steel axle XT hub from a wheel that I built in 2004 in that frame that was designed for 130mm hubs.  It has been trouble free.

Yes, you are trying to do the opposite, putting a narrower hub in a wider spaced frame.  But I would think that it should not be a problem unless there is something unusually weak about your rear hub that a bit of alignment error causes something to rub that should not do so.  Are you sure that the hub is not the problem?