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Ruined allen socket head on a crank bolt. How to remove?
The bottom bracket of my Trek Liquid 20 is making a cracking noise. My
first guess, and the Barnett Guide's advice is that it's most likely a loose crank. (This has happened to me before on other bikes). Today I decided to remove the cranks and then re-tighten them. In preperation, I even bought a torque wrench so that I can tighten the cranks to the correct specification. Not thinking clearly, I removed the cranks from the wrong Liquid 20. Didn't really matter, I'll regrease and re-tighten them too. But then I realized I'd made another mistake. When I bought the torque wrench I forgot to get a 3/8" square to 8mm allen key socket. The 8mm allen key is needed to remove the crank bolt that holds the crank tight against the splines of the bottom bracket. This precludes me from retightening the cranks to the correct torque. Oh well, I might as well remove the cranks from the second (creaking) bike. First one came off fine. The second one was a serious nuisance. For some reason I couldn't get good purchase and it wouldn't budge. Then I noticed that the allen wrench was slipping. Before long I can see that the allen key head of the bolt is rounded off and I can't get any purchase on the bolt. It's stranded. I'm screwed. I took the bike to a local bikeshop that seems happy to get down and dirty. After I refused the guy's offer to "do a total rebuild of the bike -- take it all apart put it all back" (it doesn't need it) I think he grew cold on me. And when I came back thirty minutes later said it was impossibly stuck and my best bet was to chisel it out. For heaven's sakes. I've seen references to adjustable pin spanners, but the torque necessary to break free the crank bolt from the bottom bracket is immense. I can't imagine them standing up to the task. So two questions? 1) How do I get this bolt out? Currently my only idea is to have someone weld a socket directly on the bolt that I can torque free. 2) Where do I find a replacement crank bolt? |
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#2
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stuck bolt, yuck:
consider this as last ditch desperation advice, unless someone with more than half a brain supports it: take the bike to a reputable auto repair place, ( i would take it to someone that specializes in bmw, but thats just cause i have found they all seem to really know thier stuff ) have them use the mig welder and weld a nipple on the end of the screwed screw. this will allow you to use a pair of vice grips to spin it with the advantage that the heat transfer into the bolt will help break it free from being seized. this is comonly done in engine blocks and etc when you break a head bolt. the heat transfer to the bottom bracket spindle and the crank should be miminal, as MIG is used when welding heat treated metal without taking the temper out of it. Mr. Bill Michael Slater wrote: The bottom bracket of my Trek Liquid 20 is making a cracking noise. My first guess, and the Barnett Guide's advice is that it's most likely a loose crank. (This has happened to me before on other bikes). Today I decided to remove the cranks and then re-tighten them. In preperation, I even bought a torque wrench so that I can tighten the cranks to the correct specification. Not thinking clearly, I removed the cranks from the wrong Liquid 20. Didn't really matter, I'll regrease and re-tighten them too. But then I realized I'd made another mistake. When I bought the torque wrench I forgot to get a 3/8" square to 8mm allen key socket. The 8mm allen key is needed to remove the crank bolt that holds the crank tight against the splines of the bottom bracket. This precludes me from retightening the cranks to the correct torque. Oh well, I might as well remove the cranks from the second (creaking) bike. First one came off fine. The second one was a serious nuisance. For some reason I couldn't get good purchase and it wouldn't budge. Then I noticed that the allen wrench was slipping. Before long I can see that the allen key head of the bolt is rounded off and I can't get any purchase on the bolt. It's stranded. I'm screwed. I took the bike to a local bikeshop that seems happy to get down and dirty. After I refused the guy's offer to "do a total rebuild of the bike -- take it all apart put it all back" (it doesn't need it) I think he grew cold on me. And when I came back thirty minutes later said it was impossibly stuck and my best bet was to chisel it out. For heaven's sakes. I've seen references to adjustable pin spanners, but the torque necessary to break free the crank bolt from the bottom bracket is immense. I can't imagine them standing up to the task. So two questions? 1) How do I get this bolt out? Currently my only idea is to have someone weld a socket directly on the bolt that I can torque free. 2) Where do I find a replacement crank bolt? |
#3
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Would welding heat up and destroy everything in the area? How about
drilling out the bolt head, removing the crank and then using a gripvise on what's left of the bolt. You probably would mess up the crank a bit when drilling out the head. (Michael Slater) wrote in message . com... So two questions? 1) How do I get this bolt out? Currently my only idea is to have someone weld a socket directly on the bolt that I can torque free. 2) Where do I find a replacement crank bolt? |
#4
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"Michael Slater" wrote in message om... The bottom bracket of my Trek Liquid 20 is making a cracking noise. My first guess, and the Barnett Guide's advice is that it's most likely a loose crank. (This has happened to me before on other bikes). I've seen references to adjustable pin spanners, but the torque necessary to break free the crank bolt from the bottom bracket is immense. I can't imagine them standing up to the task. pin spanners are commonly used on cup and cone bottom brackets. I wouldn't count that option out. -- Derek Hodges Toronto |
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Woogoogle wrote:
Would welding heat up and destroy everything in the area? MIG welding doesnt use any flame so the heat is extremely localized. my guess is the crank wouldnt heat up much at all, and would not become hot enough to burn your fingers the heat will only to into the bolt directly, although some will be transferred to the bottom bracket spindle and the crank but not that much. Mr. Bill |
#6
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Michael Slater wrote:
Oh well, I might as well remove the cranks from the second (creaking) bike. First one came off fine. The second one was a serious nuisance. For some reason I couldn't get good purchase and it wouldn't budge. Then I noticed that the allen wrench was slipping. Before long I can see that the allen key head of the bolt is rounded off and I can't get any purchase on the bolt. It's stranded. I'm screwed. 1) How do I get this bolt out? Currently my only idea is to have someone weld a socket directly on the bolt that I can torque free. I once ran into one of these that had been wrecked by a worn-out Allen wrench. In the end, I used a tool commonly known as an Ezy-Out, or generically, as a "screw extractor." This is a tool that looks sort of like a left-hand threaded tap, with tapered helical grooves. The normal way to use an Ezy-Out is to drill a specific sized hole into the bolt then insert the Ezy-Oyt. However, I didn't believe that an Ezy-Out skinny enough to fit into the bolt shaft would be strong enough to undo this particularly recalcitrant bolt. I also didn't relish trying to drill out the bolt. Instead, I used a considerably larger Ezy-Out, the biggest one that could fit into the remains of the 8 mm Allen socket. (Sorry, I don't recall the specific size.) The Allen socket is not so deep, so the largest size that would fit in was too loose to even get close to getting a grip. I got around this problem by grinding the point of the Ezy-Out off. You need a serious bench grinder for this, and it is important to quench the Ezy-Out very frequently in water so it doesn't overheat and anneal the hardened steel it's made of. This took a while, but in the end it worked. 2) Where do I find a replacement crank bolt? Any bike shop. Sheldon "Sparky" Brown +-------------------------------------+ | Don't drink and drive: you might | | hit a bump, and spill your drink! | +-------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.com http://sheldonbrown.com |
#7
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Michael Slater wrote:
The bottom bracket of my Trek Liquid 20 is making a cracking noise. My first guess, and the Barnett Guide's advice is that it's most likely a loose crank. (This has happened to me before on other bikes). Today I decided to remove the cranks and then re-tighten them. In preperation, I even bought a torque wrench so that I can tighten the cranks to the correct specification. Not thinking clearly, I removed the cranks from the wrong Liquid 20. Didn't really matter, I'll regrease and re-tighten them too. But then I realized I'd made another mistake. When I bought the torque wrench I forgot to get a 3/8" square to 8mm allen key socket. The 8mm allen key is needed to remove the crank bolt that holds the crank tight against the splines of the bottom bracket. This precludes me from retightening the cranks to the correct torque. Oh well, I might as well remove the cranks from the second (creaking) bike. First one came off fine. The second one was a serious nuisance. For some reason I couldn't get good purchase and it wouldn't budge. Then I noticed that the allen wrench was slipping. Before long I can see that the allen key head of the bolt is rounded off and I can't get any purchase on the bolt. It's stranded. I'm screwed. I took the bike to a local bikeshop that seems happy to get down and dirty. After I refused the guy's offer to "do a total rebuild of the bike -- take it all apart put it all back" (it doesn't need it) I think he grew cold on me. And when I came back thirty minutes later said it was impossibly stuck and my best bet was to chisel it out. For heaven's sakes. I've seen references to adjustable pin spanners, but the torque necessary to break free the crank bolt from the bottom bracket is immense. I can't imagine them standing up to the task. So two questions? 1) How do I get this bolt out? Currently my only idea is to have someone weld a socket directly on the bolt that I can torque free. 2) Where do I find a replacement crank bolt? Get a stripped bolt extractor kit ;-) Basically a hardened screw with a left-hand thread. Drill a small hole and screw the tool in. The bolt will come out. Replacement crank bolts are widely available in aluminium, but these are useless for actually fitting cranks (they work OK for holding them in place once they have been torqued up with a steel bolt). Anyway, the good news is that most bottom brackets use standard M8 threaded bolts, so you can use one of those (with a suitable washer to protect the crank), fit the crank, then remove and replace with the alu bike jewellery. |
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#9
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On Sat, 11 Sep 2004 19:44:58 +0100, Zog The Undeniable
wrote: ...Anyway, the good news is that most bottom brackets use standard M8 threaded bolts, Ahem. M8 fine thread. That's M8x1.0 The more common size of M8 is the M8x1.25, which most hardware stores have. I have found few hardware stores in the US have 8x1.0 stuff, but far too many of them have brain-dead staff who will look at the bolt and incorrectly identify it as 5/16NF, which it closely resembles. Buying this bolt at the lbs is a good idea in my opinion. so you can use one of those (with a suitable washer to protect the crank), fit the crank, then remove and replace with the alu bike jewellery. Eh, I suppose, but I figure that substance overrules form, so I just go with the appropriate steel bolt and knock the plastic cap in to cover it. -- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts. |
#10
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Sheldon Brown wrote:
Michael Slater wrote: Before long I can see that the allen key head of the bolt is rounded off and I can't get any purchase on the bolt. It's stranded. I'm screwed. 1) How do I get this bolt out? Currently my only idea is to have someone weld a socket directly on the bolt that I can torque free. I once ran into one of these that had been wrecked by a worn-out Allen wrench. In the end, I used a tool commonly known as an Ezy-Out, or generically, as a "screw extractor." This is a tool that looks sort of like a left-hand threaded tap, with tapered helical grooves. Another approach would be to drill out the socket with a drill at least 8mm in diameter (preferably a little bigger) until the bolt head comes off the thread. After the fastener's tension is released, the stub remaining in the spindle should turn out with no significant torque required. Left-handed drill bits are especially good for this because they tend to spin the fastener out as soon as the tension releases. Chalo Colina |
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