Bottom bracket and gear troubles

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Tcr4x4

Veteran
Location
Gloucester
Replaced my bottom bracket today, all went smoothly, except when I came to test and couldn't change gear of the front derailler. I've spent the last two hours trying everything I can to get the damn thing to work, but I just can't do it. It seems stuck on the granny ring, I can get it to jump to the middle ring only by pulling with all my effort on the cable, the shifter seems to have no effect at all. I've tried tensioning the cable as much as I can, but still nothing.

Is it possible for a bottom bracket to mess the gears up? My theory is the bracket is for whatever reason slightly longer than the old one and thus means the derailler hasn't enough "reach" to push the chain from the small ring to the middle and large rings.

The bottom bracket looks like its for a mtb, but I was assured it would fit my bike. It went on with no issues, although I did use all the spacers as per the instructions. Tomorrow I may try removing a couple to see if that makes any difference as it may make the whole assembly "shorter" and allow the derailler to reach better.

Failing that, I'm taking it to a shop to be sorted as I've had enough of it today and I'm soaked through, thanks to the rain.
Was really looking forward to trying my new spd pedals too :-(
 

RecordAceFromNew

Swinging Member
Location
West London
Replaced my bottom bracket today, all went smoothly, except when I came to test and couldn't change gear of the front derailler. I've spent the last two hours trying everything I can to get the damn thing to work, but I just can't do it. It seems stuck on the granny ring, I can get it to jump to the middle ring only by pulling with all my effort on the cable, the shifter seems to have no effect at all. I've tried tensioning the cable as much as I can, but still nothing.

Is it possible for a bottom bracket to mess the gears up? My theory is the bracket is for whatever reason slightly longer than the old one and thus means the derailler hasn't enough "reach" to push the chain from the small ring to the middle and large rings.

The bottom bracket looks like its for a mtb, but I was assured it would fit my bike. It went on with no issues, although I did use all the spacers as per the instructions. Tomorrow I may try removing a couple to see if that makes any difference as it may make the whole assembly "shorter" and allow the derailler to reach better.

Failing that, I'm taking it to a shop to be sorted as I've had enough of it today and I'm soaked through, thanks to the rain.
Was really looking forward to trying my new spd pedals too :-(

Do you have a Shimano road chainset and a Hollowtech 2 mtb bb? Chance is your current chainline is 50mm when it should be 45mm - if so you should remove the spacers. Whatever you do, don't force the shifter/cable unless you would like to break it.

BTW road and mtb HT2 bb's are not identical, although in most instances they interchange fine.
 
OP
OP
Tcr4x4

Tcr4x4

Veteran
Location
Gloucester
The chainset is a shimano fcr-553, the bb that came off was labelled BC1.37x24 road, its a 68mm shell and I believe a clamp on derailler if that means 1 bolt holds the assembly onto the tube.
The instructions said I needed 3 spacers on the chain side and one on the other.

I've since read that my chainset my require a different spacer on on the non chain side, which I took off but wasnt sure if I needed to refit. I'll try again tomorrow with different spacers and see.
Trouble is, I spent so long fiddling with the gear adjustments, it will take me ages to find out if removing the spacers actually worked!
 

RecordAceFromNew

Swinging Member
Location
West London
The chainset is a shimano fcr-553, the bb that came off was labelled BC1.37x24 road, its a 68mm shell and I believe a clamp on derailler if that means 1 bolt holds the assembly onto the tube.
The instructions said I needed 3 spacers on the chain side and one on the other.

I've since read that my chainset my require a different spacer on on the non chain side, which I took off but wasnt sure if I needed to refit. I'll try again tomorrow with different spacers and see.
Trouble is, I spent so long fiddling with the gear adjustments, it will take me ages to find out if removing the spacers actually worked!

The beauty of chainline is you can measure it once installed. It should be 45mm, especially if you have a road front mech.
 
OP
OP
Tcr4x4

Tcr4x4

Veteran
Location
Gloucester
Thanks...
Next question,
How would one measure the chain line? Where/what do you measure?

Complete newb to bike maintenance so talk to me like Im an idiot!

*edit*

Nevermind, google is my friend. I'll measure it tomorrow and fiddle with the spacers to get it to 45mm!
 
Last edited:

RecordAceFromNew

Swinging Member
Location
West London
The chainset is a shimano fcr-553, the bb that came off was labelled BC1.37x24 road, its a 68mm shell and I believe a clamp on derailler if that means 1 bolt holds the assembly onto the tube.
The instructions said I needed 3 spacers on the chain side and one on the other.

Since the bb that came off says road, as the Park link I gave earlier says, "The Shimano® Hollowetch II road cranks require no spacer between frame and bottom bracket bearings.". The instruction you have probably says 2 spacers on the drive side for 68mm bb shell, not 3, and it says so only because it is a mtb bb AND mtb chainline is generally more than 45mm.
 
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