Bottom brackety things on trainer

[jjlynn27]

When it comes to bikes, I'm lazy and my knowledge on the subject could be summed up with sweet FA.

Now, I have an old falcon bike permanently strap into the trainer. One of the pedal mounting thingies is messed up so you can't fix crank arm properly to it (it wobbles).

The question is; how easy difficult would it be to replace that bottom bracket, and is it worth it or should i just buy a new cheapie bike as a trainer. They don't get used much as, once again, I'm lazy.

Thanks.

[anonymous-user]

It depends

Could be a tenner, could be a score for the parts

Could be a score or two or three for labour

[Paul Drawmer]

Does the BB spindle have square tapers that fit into the cranks?

What is actually loose? If it's the crank rattling on the spindle, it might be that the crank is now rubbished. Is there a bolt underneath a cover in the crank arm that can be tightened up?

[jjlynn27]

Thanks for the replies.

The faulty bit is the square part of bb that pedal crank attaches to.

ETA: even if you tighten the bolt as much as you can the crank is still not tight. There is very significant wear on the square part that crank attaches to.

I guess my question is; how big job is this, and how easy is for a numpty like me to get wrong part/mess up the installation.

Edited by jjlynn27 on Saturday 18th November 16:23

[mikey P 500]

Bottom bracket is easy to change but does require a specialist tool (about £5 for tool) or pay shop to fit. Bottom bracket it's self will be about £10. Sometimes though it's the crank arms that are rounded off (as alloy against steel) so might need new crank arms, which would cost more, but sounds worth fixing of only issue with bike.

[Get Karter]

Are you sure its not the square hole in the crank that has worn/stretched?

Square taper bottom bracket spindles tend to be made from steel, whereas the cranks are soft alloy.

Therefore it is more likely you need a new crank.

[Barchettaman]

Get Karter said:

Are you sure its not the square hole in the crank that has worn/stretched?

Square taper bottom bracket spindles tend to be made from steel, whereas the cranks are soft alloy.

Therefore it is more likely you need a new crank.

+1, your crank arm has rounded off. You may well need a new bottom bracket; you definitely need a new crank arm.

[jjlynn27]

Thanks for all replies. The crank arm was 'rounded' but was replaced, but now, the bb thing is rounded off too. The whole bike is probably worth £5, but it's useful as trainer.

Thanks again, for all replies, I'll get it to halfords so they can replace brackety thing.

[jjlynn27]

OK. I had enough of Hfords BS. The brackety thing that they've replaced is making loud metallic grinding noise. Is it possible that they've fitted wrong size/type of bb as I can't believe that the new unit would fail after 30-40mins of use.

[anonymous-user]

jjlynn27 said:

OK. I had enough of Hfords BS. The brackety thing that they've replaced is making loud metallic grinding noise. Is it possible that they've fitted wrong size/type of bb as I can't believe that the new unit would fail after 30-40mins of use.

A bad halfords could have fitted the wrong part, or the correct part incorrectly

Either could result in the problem you now describe

Take it back is the obvious option, but your expectations of their ability to fix it might put you off doing that.

Any photos to help us to identify the set up and be a bit more specific with advice?

[Barchettaman]

Replacing a square-taper BB is a doddle. I can't see how they could have cocked that up.

Was it maybe a loose-ball BB that they have repacked incompetently?

Photos would definitely help.

[jjlynn27]

Thanks for the replies really appreciated it.
The thing is it's a trainer (read; really really cheap) bike as I'm too lazy to put the normal bike in and out of trainer and clean the tires all the time (it lives in spare-room-home-gym). After speaking to Halfords today they agreed to have another look on condition that if it's user fault I'll have to pay again. I'll try to get a picture of bb later.tomorrow.