How important is length & width??????

[thejackal]

Good afternoon

I am replacing the bottom bracket on my current bike, and having measured the length in-situ (with a vernier guage) - it measures in at 117.2mm? What axle length should I go for??? Could I use a 116mm? There's a nice one e-bay at 115mm?????

Similarly, I used the same guage to measure the seast post diameter, which came in at 25.5mm - does that sound right? Looking on flea bay for a Campagnolo post I keep seeing 27.2mm, 26.6mm etc and various other sizes..... but no 25.5mm ones?

If it is any help whatsoever, my bike is a mid 80's Raleigh.....

 

[Old Ned]

Axle length is generally dictated by the cranks you are using. Are you keeping the same ones? If so, then do they fit well on the current axle with the correct amount of clearance (ie a few millimetres) between the rings and the chainstay? If the answer is yes then you will need the same length. If there is loads of clearance then you may get away with a slightly shorter one.

Presuming you are using square taper axle and cranks, there are 2 slightly different tapers, ISO and JIS. This can affect the amount the cranks slide onto the axle as can wear on the crank internal taper.

Are you intending to replace the cups as well? Another thing to be aware of is that different brands of cups can have a variation in wall thickness (and axles can have variation across the bearing surfaces) which might affect the amount of axle that sticks through - and correspondingly the amount of thread available to screw in the adjusting cup on the other side.

If you let us know the cranks and BB you are using then more assistance may be possible and there are websites with useful related info.

Regarding the seatpin, there is a 25.4 size. What is the frame and/or tubing?

All said and done though, it's not really the minefield that the above may suggest

 

[thejackal]

Thanks Old Ned

It's a Raleigh from the early - mid 80's. It's not a team cadet, but it is in the Raleigh Panasonic colours of the day. It's only 18 - 23 steel frame tubing, nothing exotic like 501, 531 tubing etc, but it's the bike I had when I was a lad, and way back then I dreamt of having Campagnolo parts on it!!!!

Now I'm a little older, I have tracked the bike down, and am trying to purchase to period correct Campy parts for it! Brakes are bought, as is the crank. Was hoping to utilise a Campy BB, bit didn't want to commit to buying one, and end up with the wrong size. Same story with the seat post.

Many thanks again

 

[bm0p700f]

Push still make 25.4 mm seat post and if you £70-£80 spare you could have a Thomson Elite seat post. Very strong and light posts. Most seat posts are now 27.2 mm or a couple of larger sizes which is why you are finding it hard to find one.

 

[ianfoot]

I just got a 25.4mm System Ex seatpost from Wiggle a few weeks ago for my 80's Raleigh rebuild.......

They've one left apparently in silver.......

http://www.wiggle.co.uk/system-ex-alloy-seat-post/

 

[ianfoot]

in fact, you can have mine for a fiver + postage. it's now up for sale after a cracked head tube lug finished my project......