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I fitted a new set of GRX810 crank arms using my old GRX400 rings, all went well. However I 've rounded off one of the crank pinch bolts badly and can't remove the cranks. Hammering in a torque head just makes it worse. The other bolt is completely loose, is drilling it out the only option?
Tighten the loose bolt up to torque setting , and hammer in a torx head to try again
No it's no good! What a mess!!
Post a pic but drilling/removing the head will be easy enough if you have a decent drill (not one with a wobbly chuck/head) and suitable drill bit
Or you may be able to get a thin hacksaw blade in the “pinch” area of the cranks and cut the bolt
As a last resort you could slide a small hacksaw blade between the crank arm joint and cut through bolt
The head should just fall off and the the tension will be relived on the arm, you should then be able to put a small screwdriver through the crank arm's bolt hole with a dab of glue on the end, once its stuck to the bolt it should easily unwind
Dont ask me how i know this!
The head's pretty much gone. Hacksawing's going to be an issue due to the retaining tab thing.
"Hacksawing's going to be an issue due to the retaining tab thing."
Does the retainer tab not pull out if you fully remove the other bolt? By the looks of things it rotates around the other bolt
I'd be tempted to put the other bolt back in tightly then drill a small hole and use an easy-out (or similar) to try and remove it. However I'm guessing that is still not hugely guaranteed to work if you couldn't get it out with what you have already done
And if fitted properly the retaining tab is surplus to requirements.
Though killing the bolt like that doesn't scream fitted properly...
I need to go to work so I'll try tomorrow. I'm pretty careful with my torque wrench and ensuring that tools are properly seated but this one just seemed to go!
Hammer in the smallest torx bit that doesn't fit
As somafunk said up there just drill the head off.
Looks like it's half way there already.
Once the head is gone the arm will come off, you can the just wind the stub of the bolt out the back with a small drill bit.
Just remember you only need to drill slightly larger than the bolt shaft size not the whole head size so should be able to get that off without damaging the cranks.
Sorry my reply seems to have got delayed.
Thanks. I need to calm down, go to work and forget about it. I'm sure it's solveable.
Annoyingly everything was fitted perfectly, they were upgrade GRX810 arms to replace my GRX400 arms (just a whim) whilst retaining the existing rings.
I noticed that the peg on the outer chainring was digging into the back of the crank arm so decided to do it properly and sort them. What a mess!
Sorry to sound a bit blunt but it might be better in future to get someone else to fettle what needs fettling. Some people are just not mechanically minded. That's OK but they perhaps should avoid trying to fix stuff.
Maybe try a Dremel cutting disk if you have one. Lots of care needed but will make short work of the shaft of the pinch bolt. Best to remove the plastic tab spacer first.
Sorry to sound a bit blunt but it might be better in future to get someone else to fettle what needs fettling. Some people are just not mechanically minded.
I'm certainly not a pro-mechanic & can be a numpty, but I have put together a number of bikes & fitted a fair few cranks. My problem is that if something goes wrong I can panic & make it worse.
This bolt nipped up nicely by hand & was finished to 12Nm with a torque wrench. It was when I loosened it off that things went awry.
Anyway I've taken a step back & realised that I need to take the best, rather than quickest panic driven approach. I've an extractor set on order (meant to get one ages ago) & I'll sit tight until that arrives.
Hopefully the cranks won't be trashed but if they are I'll just have to put it down as one of those painful learning experiences.
Sorry to sound a bit blunt but it might be better in future to get someone else to fettle what needs fettling. Some people are just not mechanically minded. That's OK but they perhaps should avoid trying to fix stuff.
That is a bit blunt, mistakes are made in the process of learning and anyone thinking they are not "mechanically minded" sounds like a self-limiting belief.
After you've drilled and removed the bolt with a reverse thread extractor. Maybe invest in a torque wrench and some new hex bits?
You're welcome 😁
Every day is a school day, no matter how old you are. Just chalk this off as a lessons learned and move on.
That's what I do when I spend many an hour tinkering, like putting more brake oil on the floor than into my brakes 😁
I've an extractor set on order (meant to get one ages ago) & I'll sit tight until that arrives.
Forget about consumer rated screw extractor sets - they're shite, they cause more issues than they are worth especially in your case with such a small m5/m6 ? sized bolt as you'll never manage to drill squarely in the middle if the seized bolt thread, you'll never get a cheap extractor to bite and on the off chance you do, it will snap, especially on your crank arm as the bolt will be under tension unless you fully tighten the other bolt, and that may cause issues.
My bolt/screw extractor set with 6 bits cost £160 and that was over 15 years ago.
Supposedly hex plus Allen keys are less prone to rounding bolts.
https://www.screwfix.com/p/wera-950-9-sb-metric-hex-plus-1-ball-end-long-l-key-set-9-pieces/181tx
Please just drill the head off the bolt.
No need to make it worse with screw extractors.
If you're anywhere near me I'll do it for you.
Supposedly hex plus Allen keys are less prone to rounding bolts.To be fair, just some halfway decent hex keys will get 75% of the way there.https://www.screwfix.com/p/wera-950-9-sb-metric-hex-plus-1-ball-end-long-l-key-set-9-pieces/181tx <
And not using the ball end...
Ah, so £8.99 isn't going to cut it then. I'll have a go drilling the bolt out and see how that goes.
I'm not prone to rounding off bolts but I had another crank pinch bolt go some years back. On the other hand I've done plenty of stem swapping recently and not had issues with the dainty stem/faceplate bolts Thomson uses.
I guess it must have been something I did wrong but I'm not entirely sure what.
I'll have a look at those hex+ keys although my set is a Pedros one, so reasonable quality.
although my set is a Pedros one, so reasonable quality.Maybe, but a lot of the bike branded stuff is fairly mediocre, but dressed up nice paint/packaging with a premium price.
I tend to buy/recommend non-bike brand stuff at a similar price point.
did you use antiseize on the thread? some folk say it can cause catalytic corrosion but I have never seen that happen and I am a big user of copaslip. Every thread gets it
Before resorting to drilling a set of these has proved most useful for removing damaged hex socket head screws https://amzn.eu/d/j6saBGK
Too late for your example though 😕
The head's pretty much gone.
Quite impressively so! Did you use an electric screw driver on it's high speed drill setting? I've often forgotten to return mine on slow speed screwdriver settingl, although now I'm in the habit of using non electric tools to loosen first.
Please just drill the head off the bolt.
No need to make it worse with screw extractors.
I agree with Stu.
Screw extractors are great ,but it's easy to make more of a mess with the small ones if you don't get the drilling straight.
If you can't get a clear shot at what's left of the cap head,I would go at it with a junior hacksaw (new blade) through the gap as suggested above.
Good luck,and at least you didn't go in (Kryton style)with an angle grinder . 😉 🙃
I don't usually hold with telling people not to do things themselves, but the thing with a knackered bolt is you only really get one or two good attempts at each method and it gets worse and worse as you rule those out so it's definitely one of those things that can escalate. That head is really bad, most of the better options are already out the window tbh so even as a skilled diyer person I'd be approaching it with basically horror and trepidition 🙂
The big question is always why did it happen. Is the bolt just mangled or was it extremely stuck? Because lots of techniques are fine for "removing a bolt with a bad head" but quite poor at "removing a bolt that is so seized that the head stripped" And you've still got to deal with that, if it is. I suspect this is where most bolt extractions go wrong tbh, people get fixated on one thing and miss the other. Drilling the head off gets the arm off the bike which is very helpful but still leaves you needing to get the stub out, you need a plan for that too.
(aside but imo trying to hacksaw this is basically insanity because of the access, you're going to have to vinegar stroke your way through the whole thing. Drilling the head off is about a million times easier and way less likely to cause collateral damage)
Traditional screw extractors can instantly make things much worse and leave you with a bolt with a broken off super hard bit of steel in it, I hate those. But they can work. Reverse drill bits are quite useful too, sometimes you can just walk a bolt out while drilling the hole, lovely.
Those Lazer ones that fruitbat linked are fantastic btw, every mountain biker should have a set or something like them, to go along with their disposable hammer-in torx.
Thanks, I appreciated folk taking the time to help out.
The bolt's not seized and nipped up to torque quite happily, the head just seemed to go when I was loosening it off. The head's in that state from hammering in torque heads to try and get a purchase.
I think it was handy taking a step back, with hindsight I could see myself walloping the frame with a hammer blow going astray. As it stands, if I can get them off, the RX400s can always go back on.
The crank arms are new (Ebay) removed from a bike (I could always pretend that there was rounding already there) and £50 so a tough, but not catastrophic loss if they end up trashed (hopefully not though).
I've taken onboard that the cheapo extractor kit is a no no, so I'll take it slow & steady & see how it goes.
Looks like multiple attempts, either that or at some point someone has lost/damaged the original bolt and grabbed the nearest one that fits...Did you use an electric screw driver on it's high speed drill setting?
All these people with well calibrated torque fingers…. Most important thing to do is not panic 🙂
Given the head on that is totally gone you’re best off drilling it like singlespeedstu says (assuming you are happy with that) I think last time I used a 6mm drill bit in the head and go slow. You’re only going far enough to weaken the head so that the bolt will weaken. Go slow. And when you get near to the crank you should find it “pops” as the pressure is released. Then you’ll be able to wind out the remainder.
Somehow I have managed to mangle several pinch bolts this year, I have put it down to my “upgrade” to wera hex plus keys.
if you’re nearby happy to help.
Does anyone have a source for high quality replacements? While I'm always careful with these, and have never had one fail yet, (jinx!) I really don't think the hex head is a good fit with most tools.
To answer my own question, probably these from SJS Cycles. https://www.sjscycles.co.uk/oem-stock-bike-build-only/shimano-clamp-bolt-washer-m6-x-20mm/?geoc=DE
I got a little bag of spare shimano genuine ones (including washers) a few years ago. They're labelled as XTR/D-A but fit everything. Only used one when i went to refit a crank and one of the bolts was missing... (It'd been on a shelf for 5 years, so i might have repurposed it myself!) Cost me about 25 euros for 10 IIRC
I could always pretend that there was rounding already there
Not sure I think this is a good or fair idea?!
If it rounded whilst being loosened then I would suspect bad fitting tool/seized bolt/already damaged head or a combination of all three?
2nd hand? Previous owner probably damaged same bolt removing them so replaced with a Temu special. Could easily be a bit of galling on the threads and that would explain it locking solid despite all else done correctly. I would definitely chase the threads out with a tap when/if you get remains of bolt out.
Well I can't begin to describe how nerve racking that's all been, but it is now resolved (before the extractor set turned up as well). The drilling took ages but it was great when it finally went (more of a loud crack than a pop) and nice to see the washer sat on the end of the bit. I've replaced it with one of the very same JTek bolts mentioned above.
The cranks seem to have survived except for the graze on the back of the drive side arm (other thread) so all now reassembled and seems fine but re-torquing the pinch bolts was rather stressful. Hopefully they won't need undoing now until the BB goes.
I could always pretend that there was rounding already there
Not sure I think this is a good or fair idea?!
Not entirely serious there (hence the pretend) they were new crank arms removed from a bike and in tiptop condition until I got my hands on them.
Anyway all resolved but nursing a bruised ego & confidence.
Great work!
Surely the better way to look at this is the enhanced confidence you can deal with this for yourself or any of your riding friends who happen to be unfortunate enough for this to happen again! 🙂
(and yes, that’s why the little washers are good!)
I've read this thread with interest and I'd like a bit of an assessment of what I've found with a couple of sets of HTII cranks.
Torque wrenches can be misleading with these, especially if using the original plastic preload thingy and the cranks are old. As you tighten each bolt, gradually and sequentially, I think you can easily go over the recommended torque setting as tightening one will apparently make the other a tiny bit looser again, so more turns can be wound on before the wrench clicks. The plastic preloaders can also deform to help this bad process along - eventually being spat out of their threads. Older cranks that have had more cycles of release and re-tightening may be more prone to it.
Nowadays I use Burgtec metal preloads (which use a 8mm allen key, not the silly unique tool that you can never find like the plastic ones). Then I tightening it to about the maximum I can manage using one hand, in no discomfort, and one of those triangular 3/4/5 mm allen key tools. This is a setting I rate as 'tight' or 'T'. Above this there are settings designated as 'FT' and 'RFT'.
And anyone who designs or markets a product for a pedal bike where the recommended torque is over 25nM (SRAM Dub, I'm looking at you) has done something wrong. In my opinion, obvs.
And anyone who designs or markets a product for a pedal bike where the recommended torque is over 25nM
Ever fitted a cassette, threaded bb or pedals. All well above 25nm though I bet you just use RFT.
Torque wrenches can be misleading with these, especially if using the original plastic preload thingy and the cranks are old. As you tighten each bolt, gradually and sequentially, I think you can easily go over the recommended torque setting as tightening one will apparently make the other a tiny bit looser again, so more turns can be wound on before the wrench clicks.I don't think you know how to use a torque wrench.
The plastic preloaders can also deform to help this bad process along - eventually being spat out of their threads.😯 Nope, that would take a *shed* load of torque, unless you've destroyed the preloader when installing it. I've fitted (and refitted) hundreds (possibly thousands?) of HTII cranks and never had one pop out, or fail for that matter.
Then I tightening it to about the maximum I can manage using one hand, in no discomfort, and one of those triangular 3/4/5 mm allen key tools.Ah, yes. They are meant to be finger tight, snugged up. 0,7 to 1,5Nm. You're looking at probably 3 or 4 times that with what you've described.
Agree with what Mert says re the 'preload'. Well actually it's supposed to be just taking up the clearance of the bearings, as the type of bearings used, deep groove rollers, are not designed for axial loading.
The plastic tools with a knurled edge are designed so nipping it up with your fingers is all you need.
You can't go over torque of you're using the torque wrench properly, that's the exact point of the tool! And yes, the sequential tightening of the opposite bolt does exactly what you said and release the tension on the other one.
Ah, yes. They are meant to be finger tight, snugged up. 0,7 to 1,5Nm. You're looking at probably 3 or 4 times that with what you've described.
What you're quoting there is the torque for the plastic preloader, though, not the pinch bolts to which I was referring with the hand-tight triangle Allen key thing.
Shimano have the recommended tightening torque for the pinch bolts as 12-14 nM which is into FT territory.
As for the plastic preload being spat out due to damaged threads - yes, to be honest, I can believe that. Perhaps this is where I went wrong as the knackered threads allowed the thing to be pushed out as the pinch bolts were overtightened.
In any case, the metal preloaders guard against this to some extent.
I do think that the torque values for the pinch bolts is high @ 12-14Nm, especially for such small bolts (compare with bigger calliper bolts @6-8Nm).
I think that this might be part of the issue I had although I have since noticed that the collar on my torque wrench was loosening and could slip in use upping the torque setting.
I am wondering whether I ought to stock up on pinch bolts & replace them each time I remove the cranks
How often do you do that??
Just make sure you never get a SRAM GXP crank as that is around 46nm from memory. I just have to guess at it when tightening as my torque wrench doesn't go that high.
Caliper bolts are M6 as are the pinch bolts on HT2 cranks
How often do you do that??
Quite often if you use lower end Shimano BBs and ride in the UK in anything other than high summer.
What you're quoting there is the torque for the plastic preloader, though, not the pinch bolts to which I was referring with the hand-tight triangle Allen key thing.
Ah right, I misinterpreted that. Although I still maintain that plastic thing is not a pre-loader. If you've got the crank installed properly you would be fine taking that out after, same as a headset top cap. Shimano wouldn't have persevered with the same basic design all this time If it was fundamentally flawed.
How often do you do that??
Quite often if you use lower end Shimano BBs and ride in the UK in anything other than high summer.
Well, there's a very simple answer to that, don't put even the cheap Shimano BB's in, XT level as a minimum, it's not like they're massively expensive compared to the low end ones or even push the boat out and fit an XTR one for £40, they literally last forever / 2 or 3 years.
Caliper bolts are M6 as are the pinch bolts on HT2 cranks
Thanks, I'm clearly misremembering, still lower torque though.
It's only the second pinch bolt I've rounded & the first that's needed drilling, but I"d rather not have to do it again.
Well, that's why I use Hope 24mm BBs.
Although I still maintain that plastic thing is not a pre-loader.
Probably splitting hairs now, but...
It acts to pull the non-driveside crank onto the spindle which does preload the bearings. Otherwise there is play across the BB. In this sense, I would say it is very much a preloader. Just because it could be safely removed once another locking clamp has been applied (pinch bolts in the case of both stem and HT2 crank) doesn't make it not a preloader.
But I'm happy to believe one thing and let you believe another.
FWIW, the plastic end cap should really just be used to take the float/clearances out of the bearing. Actual preload on the bearings should be as near to zero as is possible.
And there is an even simpler way to make your bottom brackets last longer, fit them properly.
Faced and chased bottom shells, proper adjustment, the usual. Think my oldest one in regular use is well over a decade and a half old, and used year round. That was pretty much the cheapest one i could get and i'm amazed it's lasted that long.
I still have an original XTR (M960) on one of my old race bikes. But that hasn't really got the mileage, despite being nearly 25 years old!
FWIW, the plastic end cap should really just be used to take the float/clearances out of the bearing. Actual preload on the bearings should be as near to zero as is possible.
Exactly! As I said before, the standard plastic tool about 40mm diameter for finger tightening is all the torque you need.