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Stumped by Thun Crankset

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Stumped by Thun Crankset

Old 07-30-15, 05:52 AM
  #1  
matto98
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Stumped by Thun Crankset

Hi there, this is my first post.

I hope somebody out there can help me as I am well and truly stuck.

I am in the middle of renovating my bike as part of a summer project, It was going very well until I was confronted by this. I have no idea how to remove this crankset.



I have found some useful information in these forums:
Old Falcon MTB Crank Removal | BikeRadar Forum
CTC Forum ? View topic - Crank removal issues
But I haven't managed to find a solution yet .

My crankset remover doesn't fit, I have taken it to bike shops and halfords to have a look at it, they are only willing to help if they can charge 45 + an hour on it. Which in my opinion, is not worth it.


I have read something about screwing in a bolt, but no one has been sure about size, between 12-16mm, I believe.
Other solutions have been to use a hammer, but as you can see, I have wacked it to bits already with no success.

As both the bottom bracket and the crankset need replacing I don't really mind causing them damage.

If anyone has any useful information out there it would be much appreciated.

Thank you

Matt
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Old 07-30-15, 06:38 AM
  #2  
dabac
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Left side:
- cut BB axle with angle grinder
Or
- use a "pickle fork" tie rod separator. Hammer it in between arm and BB cup.
Or
- a generic 2-arm bearing puller
Or
- FB's favourite method of chuck wedges
Right side:
- cut/split crankarm from BB axle with a hacksaw
Or:
- try the pickle fork/chuck wedges here too.

Or:
With bolts loosened but not entirely removed, ride some hills. Out of saddle. Straining hard. With luck, one might break free.
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Old 07-30-15, 06:42 AM
  #3  
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Are you sure the frame/bike is worth the effort? I suspect that a frame equipped with such a mess is of low quality, and likewise the rest of the components.
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There's no such thing as a routine repair.

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Old 07-30-15, 07:59 AM
  #4  
matto98
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Thanks for your replies so far.

I probably won't use an axle grinder, a bit out of my comfort zone and to buy rent one, I might as well buy a new bike.
I'll certainly look into wedges / arm puller / pickle fork, thank you very much.

Normally, I would agree with you, that at this point, the bike isn't really worth the effort.I wasn't aware how cheap the parts really were until I had stripped it down.
Unfortunately the bike is actually fairly sentimental to me, and the reason I started the project in the first place / I have already put a lot of effort into stripping and painting the forks / handles and buying replacement parts (of better quality).
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Old 07-30-15, 08:02 AM
  #5  
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Live and learn.
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There's no such thing as a routine repair.

Don't tell me what "should" be - either it is, it isn't, or do something about it.

If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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Old 07-30-15, 09:50 AM
  #6  
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Agreed, very unlucky. After further inspection / whacking , seems the bike is so cheap, that they are actually apart of the bottom bracket.
I think I will give up with this one.
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Old 08-02-15, 11:17 PM
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Thun made some truly wretched parts BITD. They were pretty much the cheapest parts available in Europe.
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Old 01-26-16, 02:37 PM
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I have just got an old bike with one of these crank sets and of course it has to come off ! BB loose. I had some experience with one of these last week, if its the same, inserted a large bolt, think it was 12mm. It can cause damage to the BB, but in a way it works in almost the same way as the other crank extractors except one bolt screws in, instead of a bolt within a threaded "bolt" Plenty of penetrating oil and yanking etc rather than just turning the bolt.
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Old 01-26-16, 06:20 PM
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From those pictures, (#1 and #4 ) it appears the non-drive side arm is already cracked at the bottom bracket end. If that's the case, the crank is a throw away already and destructive removal can't do any more damage.
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Old 01-27-16, 12:55 PM
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Originally Posted by HillRider View Post
From those pictures, (#1 and #4 ) it appears the non-drive side arm is already cracked at the bottom bracket end. If that's the case, the crank is a throw away already and destructive removal can't do any more damage.
The Thun crank on my Finnish Helkama city bike, with a single ring, also has the same line visible. I determined that it's just a crack in the plastic coating (!) on the crank and not a real problem.

I was also baffled when I pulled the bolt and the typical crank extractor threads weren't even close to fitting. I ultimately finished repacking all the other bearings and left this one all as originally found since I couldn't feel any problems, except the horribly rusted chainring, which still works okay. If, and when, its day comes, I'm going to just go insane caveman on it and hope I can remove the bottom bracket. And if that doesn't work, I'll find another frame. All of this is okay, because I'm pretty sure it'll be stolen eventually.
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