Hi

Please need help guys , i have looked at various videos and read articles but nothing helps . Recently my chain snapped so had to replace but due to obvious wear i needed to replace the cassete and aslo the whole crank/chain set.
My problem is now my front derailer will not put the chain onto the largest cog, i have raised the derailer as i was guessing new cogs where different size no luck , i have tighted the cable no luck and alos played around with the H & L screws.

It is almost as if the new crank / chain set is not on tight enough as only need like an extra 5mm out for the chain to go on the cog. But this is on as tight as i can get it with out cross threading the screws.

Please any help , advice .

Sorry about spelling

its a bit hard to tell without looking at it but your guess could be right, perhaps you haven’t pushed the drive side crank on far enough.

little tap with a plastic faced hammer or mallet and see if it moves?

is it a 2 piece crank? if you fitted a new bottom bracket maybe you put the wrong number of spacers in and it is all shifted a bit further to the right than it should be

Hi you didn’t say but if your using a square taper bb and the crank isn’t the same as the one you took off its not uncommon for cranks to have a different off set… so a new bb would be needed.

Thanks for reply i will try that tomorrow but dont think it is as was very tigtly fit, also did not change the BB just straight swap of old for new, just very confusing as even with pushing the derailer as far as it could go would only go about 4 mm over the large cog

@ Howie it a square tapper BB , also used same crank set shimna avio (sP)

pompom – did you get the same axle length? square taper units come in different sizes eg 73/113. 73mm shell (frame) and 113mm axle. Sounds like you’ve got a longer axle.

You shouldn’t need to raise the derailleur unless you get bigger chainrings. You may be able to get around it by winding out the H-stop and tightening the cable, but first stop would be checking the BB.

If you measure the distance from the centreline of the bike (centre of the seat tube) to the centreline of the middle chainring, it should be about 47 – 50mm. If it’s more than this then you will need a shorter BB. The instructions with the cranks would have said which axle length is suitable, but you could work it out from how far off the current one is.

Thanks guys, seems a lot more complicated than i thought . Thought it would be a straight forward job of changing cranks.

Cant check BB now but willl do it in the morning , i will read the instrcuctions that came with the chain set .

Did not think i would have had to touch the BB, starting to become an expensive job £100 including tools for a £300 bike. should have listerned to the wife and sent it to the LBS , but liked the idea of hanging out in the man cave tinkering with it, obviously not as easy as i had thought

just re-read your post. you shouldn’t need to replace the BB. odd. let me think…

On a like-for-like replacement you shouldn’t need a new BB.

Two possibilities;

1) you haven’t fitted the new drive side crank arm correctly so it’s not sitting on the spline properly.

2) It’s not the same as the one it replaced – has it def got same model number and chainring teeth?

Personally, I’d go to parktool.com and carry out all the steps for fitting a crankset and then do their ‘new front derailleur’ bit from scratch too.

Hi thanks for all the help and advice, i managed to look at the instrctions after much digging in the bin . There seems to be two varaiations of the new crank i got ,, one takes a 113mm spindle and the other 118 mm , but with out checking my BB cant tell which one i need , but hopefully this is the solution . just which thhey made all cranks the same or at least say when u buy them what size spindle instead of just what type of spindle it is either sqaure tappered or octalink.
Thanks again all