# new crankset problems



## nufc (9 Aug 2009)

I damaged my Crankset an RPM unit with rivetted Crank wheels. I bought a Shimano Alivio unit to replace, however when Ive fitted it the crankset is out of alignment with the deraileur meaning i can only get low (smallest) gear. Due to the stops on the deraileur I cannot see a way of getting it to work. I can push the deraileur across with my fingers, but the most it will reach in the middle crank, but i cannot get the cable to do it.

The changer is a Sram gripshift, mind as i say its the deraileur that seems to limit the movement.

I thought the cranksets would be interchangeable and have the same offset, is this a daft mistake?? or is there someway of getting this to work?


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## MichaelM (9 Aug 2009)

A different chainset may require a bb of a different length (e.g the old lx required a 118mm bb). It could be that the bb you have is too long. 

According to this (if it's the same one) you need a 113mm.


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## peanut (9 Aug 2009)

Welcome to the forum Nufc you'll find lots of help here 


Have you put the axle in the right way round ? square taper axles usually are handed with one end being slightly longer than the other, unless its a cartridge BB in which case you can't put it the wrong way round.
measure from the centre of the BB to the end of the axle on the chainset side and let us have the measurement.

silly question I know but have you fully adjusted the front mech to maximum travel?


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## Mr Pig (9 Aug 2009)

Hi there and welcome :0)

Is the new chainring pulled fully onto the axle? Maybe you've just not tightened it enough.


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## nufc (10 Aug 2009)

Thnaks for the welcome guys

Michael, thanks for that, definitely a strong chance yor right...I didnt realise the axles had different lengths. Pity many places dont tell you that when buying replacement parts.

Yes the crankset is fully tightened, and yes Ive tried fully adjusting the mechanism. 

Off to measure the axle length tonight. Can you just buy the axle or do u need a complete BB?


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## simon_brooke (10 Aug 2009)

nufc said:


> Thnaks for the welcome guys
> 
> Michael, thanks for that, definitely a strong chance yor right...I didnt realise the axles had different lengths. Pity many places dont tell you that when buying replacement parts.
> 
> ...



These days you'll almost certainly have a cartridge bottom bracket which is a single assembly, so no, you have to get a complete BB. However, compared to other bits of bike kit BBs are surprisingly cheap.


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## peanut (10 Aug 2009)

yes you can still buy bottom brackets with a loose axle and bearings and cups. However BB's are so cheap it would be a good investment to replace yours with a cartridge type for many years troublefree cycling. Don't get one with plastic cups ,heres one for as little as £6.00

Is the front mech for a double or a triple chainset ?


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## nufc (11 Aug 2009)

Its a triple chainset, Peanut, did you try to put a link into a BB? nothing appeared. Had a quick look and theres a few shimano units UN26 and 27 are these any good? Also seen Campagnioli....does any one rate these?


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## peanut (11 Aug 2009)

sorry the link was missing wasn't it 
Campagnolo are excellent BB's I have two real cheapos mirage I think that have lasted years. All metal you see.
I would recommend you steer clear of the Shimano U26 U27 U54 range they are all plastic cups with an internal toothed fixing which gets chewed up in no time . Many people have ruined their frames completely trying to drill them out .

This is a good quality part although there are cheaper.
http://www.chainreactioncycles.com/Models.aspx?ModelID=26067

http://www.ribblecycles.co.uk/productdetail.asp?productcatalogue=STROBTBR300


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## MichaelM (11 Aug 2009)

Maybe I'm wrong but you may find that not all squre tapers are equal (something I read somewhere a long time ago), for that reason I'd stick with a Shimano bb. Don't forget to check the shell size (68 or 73), a couple here:

UN26 (113mm) £7.15

UN54 (113mm) £13.75


Michael


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## peanut (11 Aug 2009)

MichaelM said:


> Maybe I'm wrong but you may find that not all squre tapers are equal (something I read somewhere a long time ago), for that reason I'd stick with a Shimano bb. Don't forget to check the shell size (68 or 73), a couple here:
> 
> UN26 (113mm) £7.15
> 
> ...



thats a good point Michael however the two Campag BB's I have recommended are compatable 

I have already recommended that the OP *does not* use these Shimano BB's they are poor quality with weak plastic cups which are very easy to strip out . Those prices are surprisingly cheap from Parker


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