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Post by Deleted on Jul 10, 2015 17:27:15 GMT
Ok a little update, I used the recommendation of leaning the bike and pushing the crank to see the flex and indeed it shows! I put a little video www.youtube.com/watch?v=il_KP60GcD0So it seems that the flex is indeed coming from the crankset area instead of the frame (if you look carefully it appears like the frame is moving also, but it is just the tires being compressed to one side). I cannot tell precisely which part is flexing, it looks like the crank and the chainring are moving together so does that mean it is the BB? I might get some help to film another angle with better lighting later but if you have any guesses let me know. Also does the flex look reasonable or is it showing something's wrong? On the other hand I noticed that even though the limit screw is almost hanging by a few threads, I could get a few mm more space by unscrewing it and adjusting the cable tension. This could potentially solve the noise but now I'm worried more about the flex
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Post by r0b1et on Jul 10, 2015 18:48:41 GMT
looks like mostly the BB to me. The stock one was rubbish anyhow, and that looks very flexy, I'd replace it if I were you.
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Post by Radchenister on Jul 10, 2015 18:59:45 GMT
Blimey must be made of lead or something - fair enough, that's a flexy BB alright; ripe for replacement, as Rob says.
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Post by Rocket on Jul 10, 2015 22:08:18 GMT
Having watched the video linked by the OP I did the same test on my own bike. Hell, even my 105 5800 setup flexes and I'm only 70Kg but its not to the amount here.
I would pull the cranks off the bottom bracket and make sure that they are seating correctly. I'm thinking that the cranks have been off before and the puller may have deformed the cranks as we know they can and so they are not seating correctly on the taper of the bottom bracket
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Post by Spoakes on Jul 12, 2015 7:34:16 GMT
Hm is that vid showing a lot of flex then? If so I better get shopping for a new bb. ?
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Post by chas on Jul 12, 2015 7:48:46 GMT
As stated by others you'll always get flex to some degree and it's not necessarily a problem, a lot depends on your weight and whether you're a masher or a spinner. If it's not worried you before I wouldn't start now.
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Post by taffytim on Jul 12, 2015 21:26:00 GMT
Get a new BB from here if you haven't done so already www.wiggle.co.uk/shimano-bb-un55-bottom-bracket-british-thread/68mm thread by 115mm length Shimano UN55 Square Taper Bottom Bracket Be careful when removing the cranks as some pullers have a plunger that is too fat and you end up pulling the threads out not the crank itself. Offer it up first to make sure you can see the cranks will pass the pullers plunger.
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Post by Radchenister on Jul 13, 2015 9:53:24 GMT
Ditto, that's the BB I've put on my T3.
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Post by Deleted on Jul 13, 2015 16:32:50 GMT
Wouldn't I be better with a 110mm or 113mm BB considering my chainline is way off spec? I don't remember now but I think it was ~55mm instead of 45mm. That would help with the fd adjustment.
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Post by jondxxx on Jul 14, 2015 6:24:16 GMT
Is it possible the installed BB is actually wrong?
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Post by stevo on Jul 14, 2015 9:34:17 GMT
I can't see the T3 frame bending, as far as aluminium frames go, it is better than a lot of 'named' frames costing twice as much!!
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Post by taffytim on Jul 16, 2015 21:11:24 GMT
Wouldn't I be better with a 110mm or 113mm BB considering my chainline is way off spec? I don't remember now but I think it was ~55mm instead of 45mm. That would help with the fd adjustment. Ive only changed the bb once and i kept it as above but theres no harm in trying, i cant see 5mm having a massive effect positive or negative. Let us know how you get on if you do try it.
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Post by chas on Jul 17, 2015 9:52:50 GMT
Wouldn't I be better with a 110mm or 113mm BB considering my chainline is way off spec? I don't remember now but I think it was ~55mm instead of 45mm. That would help with the fd adjustment. Ive only changed the bb once and i kept it as above but theres no harm in trying, i cant see 5mm having a massive effect positive or negative. Β Let us know how you get on if you do try it. You can run into several problems fitting a shorter bb, end of cranks hitting chainstays, inner ring scraping frame, front mech not moving close enough to shift to inner ring. It may be possible the one fitted is wrong?
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