Fixing a square taper

[a111r]

So this is progress: bikes were invented and used in England 150 yrs ago, the workshop of the world...now, every time we use them, we have to check the pedals aren't falling off...

Cotter pins!

 

[jerrytug]

Cotter pins!

That was my one of my youngest childhood mechanical lessons; sometimes precision machined, threaded and hardened components need to be battered with a hammer!

 

[Sbc]

Is it the drive on none drive side arm as you can buy just the left arm. Only about 10-15. But be careful of the orientation of square on the arm as some some are square on and others are dimond on. It is quite a common problem so would be very surprised that you local bike shop would have one. Once they have come loose a couple of times there is not an easy way to keep the arms on. Any play in the arm on the spindle just wobbles the nut/bolt out the spindle even with 50-60 nm on them.

 

[fzr phil]

Last year i had a similar issue on an onza rip trials bike (that i needed). I tried shimming by sacrificing a feeler gauge without success, aluminiun tape, no, finally i wrapped the square taper with masking tape and believe it or not it does seem to have worked
Good luck
Phil

 

[fzr phil]

Last year i had a similar issue on an onza rip trials bike (that i needed). I tried shimming by sacrificing a feeler gauge without success, aluminiun tape, no, finally i wrapped the square taper with masking tape and believe it or not it does seem to have worked
Good luck
Phil

It also had a damaged thread on the securing bolt. I got a new bolt from a bike shop and had to re-tap the hole.

 

[Pete.]

That was my one of my youngest childhood mechanical lessons; sometimes precision machined, threaded and hardened components need to be battered with a hammer!

One of mine was 'don't remove them by bashing on the threaded end'

 

[a111r]

That was my one of my youngest childhood mechanical lessons; sometimes precision machined, threaded and hardened components need to be battered with a hammer!

Snap!
Or more accurately "Bend!" (then Junior hacksaw it off, fill with Isopon, then Araldite on a decoy nut and thread). Exorcised!

 

[graffian]

I have fitted a few that didn't look great.
I picked a looked unused bottom bracket with a perfect taper to fit the crank to.
I blued the taper and stuck it in the cranks and used a rifler file on the cranks
to fit the two.

 

[Morrisman]

file it into an hex then create a hex into a square adaptor

the hex shape will give it more strength compared to a square

That’s quite possibly the most complex, convolute, complicated solution I can think of.

Does it tighten down purely onto the taper, or is there a shoulder?

I‘d try heat, get it hot, tighten it down, and it should adjust its molecules to fit where it should.

I once had to machine a tapered, shouldered, keyed shaft to take a pulley. The most ridiculous job I ever did when I worked in the machine shop. It was for a farmer......

 

[Morrisman]

That was my one of my youngest childhood mechanical lessons; sometimes precision machined, threaded and hardened components need to be battered with a hammer!

And battered out..... ahem, my earliest engineering lessons involved putting nuts on cotter pins when removing them.
My father did give me some useful guides in life, in between the more common insults and bellittement.

 

[DSR]

There are two schools of thought.
Grease the square taper or don't!

Would be interested to know the thoughts on here. The "Don't do it" school says that if you grease the tapers before you tighten the bolts, the grease might allow you to tighten too much and the steel axle will split the alloy cranks.

Is that likely? Perhaps if you used a scaffold tube as an extra lever?

I run a light covering of grease - normally copaslip. Wrench then up to F then check that they are still F after a hundred miles or so.

I've a clunk from both my bikes now - in both cases it's the bearings. I think the genuine Shimano sealed BB's are the way to go - on one bike I have destroyed the LH sealed bearing in under 1000 miles twice. I'm not heavy and don't push hard, I do ride in all weathers and I think that the seals aren't up to the job on the cheap Chinese bearings. Same with the 5 quid chains - actually snapped one just before Christmas - 200 miles :-(

On the expensive bike, it's SRAM GXP external and that has started clickinging again when I'm putting pressure on going up hills. A check of the torque and clean/regrease normally works but apparently they are not a good design and get panned regularly. When it wears out the chainrings, I'll replace it with Ultegra. I've lost faith in SRAM and think they're a bit lile Apple - all style and marketing and no substance.

 

[Kayos]

Id stick a bottom bracket in and change the cranks if needed

I bought some M8 hex head bolts for cranks, about 12p each from Ali Express, identical down to the packaging and stickers for the £8 per pair ones in my local shop. I know they need to make a profit but really?

 

[VeryFEDUP]

I run a light covering of grease - normally copaslip. Wrench then up to F then check that they are still F after a hundred miles or so.

I've a clunk from both my bikes now - in both cases it's the bearings. I think the genuine Shimano sealed BB's are the way to go - on one bike I have destroyed the LH sealed bearing in under 1000 miles twice. I'm not heavy and don't push hard, I do ride in all weathers and I think that the seals aren't up to the job on the cheap Chinese bearings. Same with the 5 quid chains - actually snapped one just before Christmas - 200 miles :-(

On the expensive bike, it's SRAM GXP external and that has started clickinging again when I'm putting pressure on going up hills. A check of the torque and clean/regrease normally works but apparently they are not a good design and get panned regularly. When it wears out the chainrings, I'll replace it with Ultegra. I've lost faith in SRAM and think they're a bit lile Apple - all style and marketing and no substance.

I usually try to go Shimano UN72 if I can. The one on my original mountain bike must have been on there since early/mid 90s? Still smooth.

I'm going to have a go at mine tomorrow perhaps in between trying to learn a Topcon total station.

 

[a111r]

When it wears out the chainrings, I'll replace it with Ultegra. I've lost faith in SRAM and think they're a bit lile Apple - all style and marketing and no substance.

A friend replaced a worn out Ultegra 11 spd large chain ring (after about 3 years / poor maintenance / 150 miles a week)
It was nigh on £100!
The '105 / Ultegra / Dura ace' ££ per gram gradient is likely flat-ish only on a log scale!

 

[Kram]

What I was getting at with the copper.

in my head from the op it’s like this:
View attachment 294561
No amount of bolt tightening will fill that gap

Part of the problem and perhaps why its a common issue, the bottom bracket male tapers always have large radiused corners, while the female are cut square, it seems wrong, encourages a sloppy fit. Its very tempting to tig it up and grind it sharp square corners, if it wernt for that it would cook the bearings.

Evans, who I bought the bike from had previously cross threaded and ruined the bottom bracket thread, I replaced it, but thats best left alone while it works.

I had a good look at this today. I needed the puller tool to get it off. I think I'd done less than half a mile with a lossening crank but it had put reasonable burrs and damage in, a ridge that will stop it going on further - unless it was from last time. Filed it square/flat. Got it ******* hot and tapped it on with deadblow. I had a meter length of tube handy so that was my allen key extension. I do not think it will come off again.

While it was off, Im fed up with my crank cadence sensor magnet moving around. Drilled and tapped m4, next job to turn a 9mm long, m4, magnet holder.

 

[graffian]

If your replacing BB and cranks try Hollowtech, or has that got hard to get.

 

[DSR]

If your replacing BB and cranks try Hollowtech, or has that got hard to get.

The SRAM BB Force groupset on my good bike is CF cranks and SRAM's equivalent to Hollowtech - the spindles are slightly different so you can't easily fit another BB from Shimano etc. It's the first (and last) bike I will ever have SRAM stuff on. I have a CF Ribble Sportiv with Shimano Ultegra and Triple at the front and it's streets ahead of the SRAM in shift quality and use.

I've had less trouble with cup and cone BB's than I have had with the GXP BB

It's already out of date of course - they're going x1 drive

 

[Stupoty]

Is it the drive on none drive side arm as you can buy just the left arm. Only about 10-15. But be careful of the orientation of square on the arm as some some are square on and others are dimond on. It is quite a common problem so would be very surprised that you local bike shop would have one. Once they have come loose a couple of times there is not an easy way to keep the arms on. Any play in the arm on the spindle just wobbles the nut/bolt out the spindle even with 50-60 nm on them.

yeah when I worked fixing bikes we would fit a new ones, we used to stock generic left cranks for basic level bikes.

You can try putting it on with waaaaay to much torque , it might stay on , they rarely do once the taper is wallowed out though.

Stu

 

[VeryFEDUP]

Part of the problem and perhaps why its a common issue, the bottom bracket male tapers always have large radiused corners, while the female are cut square, it seems wrong, encourages a sloppy fit. Its very tempting to tig it up and grind it sharp square corners, if it wernt for that it would cook the bearings.

Evans, who I bought the bike from had previously cross threaded and ruined the bottom bracket thread, I replaced it, but thats best left alone while it works.

I had a good look at this today. I needed the puller tool to get it off. I think I'd done less than half a mile with a lossening crank but it had put reasonable burrs and damage in, a ridge that will stop it going on further - unless it was from last time. Filed it square/flat. Got it ******* hot and tapped it on with deadblow. I had a meter length of tube handy so that was my allen key extension. I do not think it will come off again.

While it was off, Im fed up with my crank cadence sensor magnet moving around. Drilled and tapped m4, next job to turn a 9mm long, m4, magnet holder.

Bit late now but, I tried some cheapish cadence magnets from the Bay. They attach to end of the pedal axle. Only any good I suppose if you have steel axles rather than titanium or something. On my rollers setup I have Speedplay pedals and so far the magnet has stayed put despite average cadence of over 110.

For the money, I am impressed.

 

[Munkul]

Solution to problematic square taper crank set:

1. remove sq.taper bottom bracket
2. throw the BB and the crank set in the bin
3. buy a hollowtech type crank set and BB - Pinkbike is good for 2nd hand parts
4. fit them
5. ride off into the sunset and never bother with square taper ever again