E-type BBs

[kona kid]

are there any differences between normal and e-type BB shells? and if so how do I tell which my BB shell is?

If I'm not using a e-type front Mech can I use any BB, so do I still need to use an e-type on but with a spacer? and if I need a spacer what size is it?

 

[P20]

I think you can just use a normal bottom bracket set up as its the bottom bracket that compensates for the chainline adjustment. (the axle is offset) Is this for the P20?

 

[kona kid]

it is for the P20, I had a nice ritchey BB and a Ritchey compact crankset but hadn't appreciated that the compact crankset requires a shorter BB than the regular one. Although my main worry now is why the cranks seems to be offset (see http://www.retrobike.co.uk/forum/viewtopic.php?t=16849), i'm hoping it because its a cup/cone BB and the axel might be the wrong way around?

sheldon brown lists it as needing a 110-113mm axle length for a compact and 120mm for the non-compact

for the front mech I've got a 34.9mm dia 953 top swing front mech and shimmed it which seems fine for the heavily ovalised seat-tube, as you prediceted getting an 953 etype is a bit difficult!

 

[ssmike]

There is no difference in the bb shell between a frame that requires an e-type and one that doesn't. Both will be 68mm.

The difference is that the e-type front derailleur must be mounted between the flange of the fixed cup side and the bb shell. The thickness of the e-type mounting plate is 2.5mm.

On a comparable length BB, there will be 2.5mm less axle extending past the flange on the e-type to accomodate the 2.5mm plate, so it will seem offset.

 

[kona kid]

okay, so seems that although my frame is designed for a 68-110 e-type bottom bracket I can use a regular 68-110 BB and a regular front mech and still get the correct chainline?

in which case does anyone have a nice 68-110 or 113 BB?!

 

[P20]

The Ritchey Specs are here: http://www.oldmountainbikes.com/catalogs/
Lists the bb length and the chainsets used in the catalogue scans. Hope it helps

 

[ssmike]

okay, so seems that although my frame is designed for a 68-110 e-type bottom bracket I can use a regular 68-110 BB and a regular front mech and still get the correct chainline?

Does your frame have the braze-on mount on the seat tube for the e-type front derailleur? If it does, a standard clamp-on front mech won't work.

 

[P20]

The frame does have a brazed mount for the front mech. I saw them built the sachs plastic mechs which did clamp round the frame. I think the demo bikes had this set up, although they were mainly 2X9 set ups.

 

[kona kid]

the front mech seems to fit so long as it's a top swing, and I'm using a shimmed one which maybe makes it even more complient (but I checked with my old unshimmed DX one first)

P20 - those cats don't seemt o help me with BB length as the bikes seem to come with non-compact (hence me purchasing the correct 120mm BB for the non-compact chainset) and it only seems to mention that the compact ones need a shorter BB, but not actually the size... please correct me if I'm wrong or missed it!

 

[ssmike]

Isn't the bottom of the seat tube ovalised on P-Series frames?