Threads stripped in cranks…

[p3eps]

This isn’t eMTB related, but hopefully someone can point me in the right direction…

My mate has been borrowing my heavily upgraded 2017 Stumpjumper (Specialized Stumpjumper FSR Expert Carbon 6Fattie (2017) review - MBR) and coming out for rides with me. I’m on my Levo SL, with the power off.

Anyway… tonight, we were just about completing an 11 mile ride, and he said the pedal felt a bit weird. 5 mins later, he stopped - and pretty much pulled the pedal out of the crank. Both the thread on the pedal axel and inside the crank are ruined. He then pulled the other one, and it came out with little effort too. He only had to walk about half a mile back to the house thankfully.

I had upgraded that bike with Eagle X01 a few years back, so the cranks are carbon X01… but I’m not sure what the the fitment is.

2 questions…

How did this happen? Is it something he’s done? I’ve been riding bikes for a long time, and I’ve never seen this before.

What do I need to buy? The shop upgraded my whole bike groupset… so I don’t know what ‘type’ of crank this is other than an it’s a 170mm SRAM X01 carbon crank.

Clearly, I’m going to need a new set of cranks, and a set of new axels for the DMR Vaults that were on it (or some alternative pedals).

 

[p3eps]

All the ones I find say they’re DUB, but I’m sure these are from before DUB was a thing. What’s the difference?

Also, my friend is about 105kg, and the pedals say they’re suitable for riders up to 85kg. Perhaps that’s the problem?

 

[wenna]

Did the pedal bearings seize? Although I think you would feel that immediately, unless they were over-torqued and the threads already were done for. Or maybe the pedals were loose and "wiggled" eating away on the threads.

If it´s not DUB it would be GXP. DUB uses a 29mm axle and GXP uses a 24mm drive side and 22mm non-drive side.

 

[RustyIron]

This didn't just happen over the space of one ride. It's been going on for a while. When you get the new cranks and pedals, install them yourself and follow the instructions exactly. Use your torque wrench, and always pay attention to the handedness of the threads.

 

[p3eps]

Did the pedal bearings seize? Although I think you would feel that immediately, unless they were over-torqued and the threads already were done for. Or maybe the pedals were loose and "wiggled" eating away on the threads.

If it´s not DUB it would be GXP. DUB uses a 29mm axle and GXP uses a 24mm drive side and 22mm non-drive side.

I wasn’t riding the bike, but the pedals still spin freely on this axels just now… so they haven’t seized. Also odd how they both ‘went’ at once.

They were torqued up to about 45Nm, but haven’t been touched for years. I didn’t think pedal threads could come loose - since they’re the opposite way to they spin when you ride?

I also didn’t realise how expensive they were as I bought them as part of a groupset. Looks like about £300 for a direct replacement

This didn't just happen over the space of one ride. It's been going on for a while. When you get the new cranks and pedals, install them yourself and follow the instructions exactly. Use your torque wrench, and always pay attention to the handedness of the threads.

Probably not. He’s probably done the last 4 ride on the bike, and has lost weight since he started.

I take my pedals off my Levo SL every 150 miles or so, and clean out the axels / re-grease, and fit a rebuild kit to them every 1000 miles or so. They’re HT ME03T pedals and are also weight limited to 85kgs (I’m about 84kgs with riding gear and full hydration pack). They weigh next to nothing (under 250g for flats pedals IIRC) so need well looked after.

Sadly, the DMR Vaults on my Stumpy have been fitted and left for several years. Most of their mileage is on a Kickr through winter though.

 

[p3eps]

I guess the easiest thing I can do I remove the cranks just now and take them into my LBS to identify. I don’t want to buy another set and find out they’re the wrong thing.
All photos of SRAM DUB ones say ‘DUB’ across the axel, and also have ‘DUB’ on the self extracting nuts - and mine don’t.

 

[p3eps]

Here’s what I have now I’ve removed the cranks. Is that GPX then?

 

[wenna]

I guess the easiest thing I can do I remove the cranks just now and take them into my LBS to identify. I don’t want to buy another set and find out they’re the wrong thing.
All photos of SRAM DUB ones say ‘DUB’ across the axel, and also have ‘DUB’ on the self extracting nuts - and mine don’t.

Yes it´s hard these days to find parts for GXP. I have a gravel bike with Sram Red GXP carbon crankset and a power meter spider. I want shorter crankarms for it but I can´t find any mainly because I want to be able to keep the power meter.

In your situation I would look at swapping the BB to DUB and get a DUB crankset.

 

[p3eps]

Yes it´s hard these days to find parts for GXP. I have a gravel bike with Sram Red GXP carbon crankset and a power meter spider. I want shorter crankarms for it but I can´t find any mainly because I want to be able to keep the power meter.

In your situation I would look at swapping the BB to DUB and get a DUB crankset.

I figured that would probably be the way forward. I’m sure someone else manufactures a decent carbon crankset other than SRAM, as all the X01 ones I’ve seen are about £300.
If this was my main bike, then I’d pay it… but since it’s used on occasion, then I kind of grudge an expensive repair.

 

[wenna]

I figured that would probably be the way forward. I’m sure someone else manufactures a decent carbon crankset other than SRAM, as all the X01 ones I’ve seen are about £300.
If this was my main bike, then I’d pay it… but since it’s used on occasion, then I kind of grudge an expensive repair.

you could try to save the crankarms with helicoil insert.

 

[p3eps]

you could try to save the crankarms with helicoil insert.

What's that - tap out the existing thread, and put a new insert in? I saw kits on eBay - approx £50 for a LH and RH tap, and then £12 for inserts. Certainly cheaper, but expensive if it doesn't work.

I guess the other thing I have to consider is I'm either going to have to pay my LBS to remove the GPX BB and fit a DUB one, or buy the correct tools myself

 

[wenna]

What's that - tap out the existing thread, and put a new insert in? I saw kits on eBay - approx £50 for a LH and RH tap, and then £12 for inserts. Certainly cheaper, but expensive if it doesn't work.

I guess the other thing I have to consider is I'm either going to have to pay my LBS to remove the GPX BB and fit a DUB one, or buy the correct tools myself

There´s usually small kits that aren´t too expensive. Or you take it to a workshop and let them install new threads.

This is Helicoil

 

[RustyMTB]

Can you get Helicoil big enough for cranks? I've just helicoiled a bunch of stripped valve cover threads on a Mini Cooper & the kit goes up to M12. Never measured crank diameters but they look wide to me.

 

[p3eps]

There´s usually small kits that aren´t too expensive. Or you take it to a workshop and let them install new threads.

This is Helicoil

According to the video, the Helicoil's are much stronger than the originals... so might be worth a shot.

Can you get Helicoil big enough for cranks? I've just helicoiled a bunch of stripped valve cover threads on a Mini Cooper & the kit goes up to M12. Never measured crank diameters but they look wide to me.

That was going to be my next question - what size is required!
I see kits like this:

HeliCoil Eco Thread Repair Kit 8-32 UNC A560019237| at Zoro

HeliCoil - Eco Thread Repair Kit 8-32 UNC available at Zoro.co.uk - UK's Leading Supplier of DIY Tools and Supplies'

www.zoro.co.uk

But there's no mention of LH and RH threads?

 

[Hardtail]

Helicoil works great on cranks, I have done it before and you can get a set just for this.

A helicoil repair is also stronger than the original aluminium thread.

Or buy an alloy crankset, no need for carbon on a shed banger.

 

[Paulquattro]

Can you get Helicoil big enough for cranks? I've just helicoiled a bunch of stripped valve cover threads on a Mini Cooper & the kit goes up to M12. Never measured crank diameters but they look wide to me.

Yes i did mine a few years ago
came as a kit for L+R sides with a drill bit and taps with coils included
i had access to a milling machine and clamped the arms square to drill and tap
Any one doing this just make sure you drill square or the pedals are going to be horrible to ride
There's also companies that will repair and hellicoil them for you

 

[RustyMTB]

Ah cool. I like them as a repair option, they've certainly got my fat fingers out of jail a few times.

 

[Hardtail]

Bicycle crank arm pedal thread repair service (for stripped & damaged threads) | eBay

This guy does it as a service, worth it at that price.

 

[wenna]

According to the video, the Helicoil's are much stronger than the originals... so might be worth a shot.


That was going to be my next question - what size is required!
I see kits like this:

HeliCoil Eco Thread Repair Kit 8-32 UNC A560019237| at Zoro

HeliCoil - Eco Thread Repair Kit 8-32 UNC available at Zoro.co.uk - UK's Leading Supplier of DIY Tools and Supplies'

www.zoro.co.uk

But there's no mention of LH and RH threads?

If the threads are aluminum then a helicoil repair will be stronger. I know people who intentionally drill out aluminum threads to install helicoil for taking higher torque.

If you can´t find a decent kit then your local bikeshop, if half decent, should have helicoil toolset for their workshop and can put in new threads for you.

I used to have an expensive kit with all the drills, taps and threads from m4 up to m12. Used it a few times and then it got lost when I moved to a new house

 

[p3eps]

Ok - will check with my LBS and see if they can do it... if not, the guy on eBay for £30 could be worth a shout.

One other thing... the self extracting Hex bolt in the crank has maybe seen better days. When I took them off this morning, it was tricky to get the Allan key back out, as it had turned more than it should.
Can these be replaced?

 

[Paulquattro]

Ok - will check with my LBS and see if they can do it... if not, the guy on eBay for £30 could be worth a shout.

One other thing... the self extracting Hex bolt in the crank has maybe seen better days. When I took them off this morning, it was tricky to get the Allan key back out, as it had turned more than it should.
Can these be replaced?

Yes you can renew the end caps and extraction Bolts

Just google : self extracting crank bolts there is loads of options .

 

[wenna]

Ok - will check with my LBS and see if they can do it... if not, the guy on eBay for £30 could be worth a shout.

One other thing... the self extracting Hex bolt in the crank has maybe seen better days. When I took them off this morning, it was tricky to get the Allan key back out, as it had turned more than it should.
Can these be replaced?

I think this is the one you need. Can be found almost everywhere for around 10 euro.

M15/M22 GXP crank bolt

If you find M18/M30 I think its for DUB cranks.

 

[p3eps]

Awesome - thanks all! Hopefully I can get this all sorted for about £40 rather than £400 for cranks, a new BB and either tools or the shop fitting it.

I'll also need new axels for my pedals, but that's a different issue. The cheap stainless steel ones will probably be best, since they don't have a low weight limit!

 

[p3eps]

I’ve sent them to the guy on eBay. Didn’t realise it was £30 per crank though! He offered the second one for £22 (assume since he can ship both back in 1 package), so a bit of a saving. £52 vs £300-400 though!

I’ve cleaned up the threads on the pedals, and they’re actually fine. They just looked mangled because of all the shards of the crank thread mixed in with them. I’ve also opened them, cleaned and re-greased the axles… which look fine too.

Hopefully the re-built Helicoil cranks and the £10 nut I’ve ordered solve everything!

 

[bram.biesiekierski]

Put a Re-coil in. These are helicoil style inserts and are typically stronger than the base threads when installed correctly.

Don't use a solid style insert. Use a coil style insert.

I just did a e13 crank after the threads failed, and have a Sram crank that has been repaired with a coil insert that has held up for a number of years like that on my other bike.

The re-coil brand kit is very high quality. The tap is a pilot nose, which means it screws in directly to what ever is left of the old threads and pulls itself in straight as it goes.

 

[bram.biesiekierski]

Recoil is an Australian brand. 34096-20 is the part number for the left and right kit. But you can also buy just the left or right individually aswell.

The pedal threads are UNEF 9/16 - 20. Left and right hand threads for left and right pedals. Which is a very unusual size, except on bicycles. You won't find that size in a large kit. You will have to purchase that size specifically.

 

[gaba]

I have the unior helicoil kit. Works pretty well. I suspect you might have put the wrong pedals on the wrong cranks (cross threaded) for them both to go at the same time. I mark my right pedal with a permanent marker for quick reference.

 

[bram.biesiekierski]

I have the unior helicoil kit. Works pretty well. I suspect you might have put the wrong pedals on the wrong cranks (cross threaded) for them both to go at the same time. I mark my right pedal with a permanent marker for quick reference.

From what i understand. Unior kit isn't actually a coil type insert. It's a solid insert.

Coil inserts (eg helicoil, recoil and many others) are coils like springs, not a solid insert with a larger outer thread.

Coil inserts are superior for thread repair, and even superior to just threaded holes. They actually stronger than the original thread is without a coil. In industries like aerospace for example it is common for Coil inserts to be used from new because they are superior.

What makes a Coil type insert superior has to do with the way a fastener will stretch when tensioned. When you tighten up a threaded fastener, the forces are never spread equally along the length of the fastener. Instead, the majority of the force is distributed into the first few threads, and progressibely less along the length of the fastener. So the strength of the threaded connection is only going to be as strong as those first few threads.

Coil inserts are not a solid piece. They have some amount of compliance due to them being a Coil of metal. So when you tighten a fastener up into a Coil insert, it can deform and distribute those forces more equally along the threads.

 

[p3eps]

Posted them off at 16.45 last night, and have had a text telling me they’ve been received and repaired already - and will be in the post back to me on Monday…

Happy days!

 

[darwink1]

A good rule if thumb is to check all the bolts on your bike periodically especially after you've fitted new parts such as cranks or pedals. Even after being torqued correctly they may come loose after a ride or two.

May be overkill but I literally put a wrench on most every bolt before every ride. Cranks and pedals see a lot of stress and are the most likely to come loose especially if you ride a lot. Hell, I've had rear derailleur mount bolts come loose after them staying tight for weeks at a time.

Funny but my buddy just broke a front chainring on his range vlt last weekend due to losing 3 out of 4 mount bolts (104 bcd shimano). I've had a crank arm fall off half way through a ride on my bigfoot vlt fattie.

If you get in the habit of checking your bolts it literally takes 3 minutes at most and can save you a ton of hassle.

D