Shimano CT90 BB

[michael franks]

Just managed to extract one of these but - wait a minute - cartridge srews into left hand side of BB shell, loose cup into right. Front mech is BB mounting. Threads in BB shell are as you would expect. I can't seem to find a replacement for it so is there any reason why I couldn't replace it with a normal UNxx for example or does the BB mounted front mech need one of these 'reverse' units? Never seen one before.
Thanks in advance for your help and advice.

 

[mikee]

should be fine mike

i have no doubt theres a reason for it ,but bicycles shouldn't be complicated

 

[cce]

you need an E-Type BB to mount a BB mount front mech, EG UN-53E

 

[marc two tone]

bb

ignore the 'reverse' unit thing. Some factories simply installed 'em like that. When you get your new one install as you'd expect. Metal majority to chainset side(wind in anti clockwise) cup to the other side wound in clockwise. a smear of grease on bb thread is a good idea, no need on cup side if vinyl. And yes, if you are sticking with bb mount front mech then 'E' type is on the menu.

 

[michael franks]

Thanks for the help fellas - much appreciated. I'll probably keep the front mech and use an 'E' type bracket as suggested although I can't see the benefit in having the front mech secured with a half-ton steel bracket as opposed to a few grams of alloy clamp :?

 

[cce]

on the posh ones it was carbon fibre.

 

[michael franks]

on the posh ones it was carbon fibre.

What is this 'carbon fibre'? We're talking Shimano Altus here

 

[cce]

i had an XTR e-type briefly. the idea was to provide mechs for difficult full suspension bikes

 

[michael franks]

cce wrote:

to provide mechs for difficult full suspension bikes

That I can understand but this is el cheapo rigid Claud Butler :shock:

 

[michael franks]

cce wrote:

to provide mechs for difficult full suspension bikes

That I can understand but this is el cheapo rigid Claud Butler :shock: