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Identification of cycle thread.

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Alan .20412/10/2018 11:39:50
282 forum posts
9 photos

Hi chaps, I’ve a young boy who’s just bought himself a BMX it’s the sort with stunt pegs front and rear, only problem is the front ones don’t fit, what I should say is the threads in both pegs are, shite is the best word I think, anyhow I’ve measured the spindle on the wheel and this is what I get, OD .368 or 9.32mm it looks closer to 26 tip than it does to a 1mm pitch, so this is what I think 3/8 x 26tpi before I buy a tap I though it would be a good idea to ask first as I’ve never had any dealings with cycle threads before, thanks in advance.

Alan.

David Colwill12/10/2018 11:44:58
559 forum posts
32 photos

Look up cycle threads. I believe they are 26tpi which would make sense.

David.

David Colwill12/10/2018 11:47:20
559 forum posts
32 photos

Here is a link to the wikipedia page

**LINK**

David.

not done it yet12/10/2018 12:25:18
2379 forum posts
11 photos

It may be prudent to check other threads on the machine, if these parts are OEM, to confirm if made with imperial or metric dims.

Clive Foster12/10/2018 12:49:05
1507 forum posts
34 photos

UK cycle thread TPI, size and applications were standardised many, many (100?) years ago. Like BSP such standards were often followed in metric using countries. Many bike makers still follow them. In my experience if its crappy but close it usually is standard cycle. Unfortunately poor ones are often cut rather than rolled which can give issues.

Clive

JasonB12/10/2018 12:53:45
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14028 forum posts
1319 photos

Park tools list the most common bike threads

Neil Wyatt12/10/2018 16:02:31
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15010 forum posts
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3/8" by 26tpi is the standard thread for bike axles.

Neil

Alan .20412/10/2018 18:27:32
282 forum posts
9 photos

Thanks chaps it’s what I thought but better to ask though if your not sure, I’ll get a tap ordered pronto.

Regards Alan.

Howard Lewis12/10/2018 19:36:48
1525 forum posts
2 photos

As Neil says 26 tpi, is the standard for UK Cycle threads; BUT the thread form is 60 degrees.

(B S Brass is 26 tpi, but Whit form)

Howard

Neil Wyatt12/10/2018 20:49:02
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Just a thought, a pair of new pegs will be much cheaper than taps... unless you need an excuse

JasonB12/10/2018 20:55:01
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14028 forum posts
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Or get unthreaded pegs that are held on by the existing nuts then you don't have to worry about threads, whatever they may be.

Alan .20413/10/2018 00:19:16
282 forum posts
9 photos

There made of ally so I bought a cheap set of taps they were only 10 quid delivered, the other thing is they match the other set on the back so they will all look the same, I’ll bore them out press a new bit of ally round in drill and tap, also will drill and fit a long grub screw on the join line so they stay put, shouldn’t take much to do and the boy will be smiling again.

Thanks chaps.

Neil Wyatt13/10/2018 09:36:50
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Posted by Alan .204 on 13/10/2018 00:19:16:

There made of ally so I bought a cheap set of taps they were only 10 quid delivered, the other thing is they match the other set on the back so they will all look the same, I’ll bore them out press a new bit of ally round in drill and tap, also will drill and fit a long grub screw on the join line so they stay put, shouldn’t take much to do and the boy will be smiling again.

Thanks chaps.

I would want them to be solid myself - they will be taking his full weight and a failure could be an >ouch<. Could you thread them from the other end?

Bazyle13/10/2018 10:11:16
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4206 forum posts
171 photos

no way will an alloy press fit stand the force of a young boy jumping on it.

Alan .20414/10/2018 20:46:27
282 forum posts
9 photos

The pegs are hollow so you can’t redo it from the other end, that’s how there made so they should be strong enough, he only 11 so it should be ok, as for making them solid I don’t see the advantage as they screw on to about 15mm of thread, I agree though it doesn’t seam a lot, pressed in with a 2 to 3thou press fit should be strong enough, I’ll test them myself if it holds me ok he will be fine, I’m 18 1/2 stone, should have said there must be around 40mm in length I can bore out, I haven’t had chance to measure it yet, thanks chaps for the advice.

Alan.

Neil Wyatt14/10/2018 22:36:06
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You can get them off the 'bay at £2 a pair if you get stuck...

Hopper15/10/2018 03:48:51
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3024 forum posts
50 photos
Sounds bloody dangerous to me. Press fit alloy will loosen up under repeated shock loading. Do the right thing by lads safety and buy new good quality pegs.

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