Just before I do something I will regret.......

Just before I do something I regret, like buy a part I somewhere thought would fit, but now have my usual doubts, could someone please check I have got this right, or am totally wrong.

My bottom bracket woes, I have found a Shimano UN54 with a 68mm shell and 118mm axle length at an affordable price. The BB advertised has the length 68 on it.

Now, the BB I have removed from my Saracen says the following ;

BB-LP30

VIA 73 RD

BC 1.37 X 24


The BB I was hoping to purchase says the following ;


BB-UN54

68

BC 1.37 X 24

Now, I understand the axle length, mine being 118mm and the BC 1.37 X 24, that being British BS thread, so am ok on that, but the figure of 73 on my existing bracket, the LP30 bears no relationship to the cartridge sealed bearing shell length, which is 68mm. Am I right in thinking the UN54 I have listed is the correct replacement for my LP30 ?

If the bracket you removed fitted ok then it looks like you have a 73mm shell, have you tried physicaly measuring the shell width on the frame with a ruller ?, a 73 bracket in a 68 shell will be obvious as the non flanged cup will stick out the frame 5mm.

Ihave recently owned two old saracens and they both have 73mm bb shells.

Right, I have just measured the BB shell on the bike and come up with 73mm. The LP30 with the plastic end cup put back on is 80mm, the threaded portion is 74mm, so with it all screwed in, the LP30 with the marking of 73 would be correct, I had got it wrong, I need a UN54 with a length of 73 not 68, phew !

Thanks guys !!!

Just got to find one now, as it seems 68's are popular, although a 68 will do at a push, might reduce the clearance between chainset and BB, but I will not go there if I can at all help it.

http://www.chainreactioncycles.com/Mode ... elID=17473
http://www.wiggle.co.uk/p/Cycle/7/Shima ... 360027179/

take you pick
shop around some more. put un54 73 113 into google.co.uk
no cheap though for a low end bottom bracket :S

www.petracycles.co.uk, wait till they are back up think they where £15 there, not sure of P&P cost, or search ebay.

Do we get to see the build in the Early Saracen Lovers Anonymous thread?

silverclaws":2iudkf8r said:

Just got to find one now, as it seems 68's are popular, although a 68 will do at a push, might reduce the clearance between chainset and BB, but I will not go there if I can at all help it.

Click to expand...

A 68mm in a 73 shell wont alter the gap between the chainset and BB, only thing you will find is the non flanged cup will sink into the BB shell as you tighten it, i did this years ago when i didn't know BB's were different widths, the splines on the tool only just manage to grip the cup.

my mate had a the opp for is rockhopper, a bike shop fitted a 73mm in a 68mm shell, with it sticking out the side.

jimihendrix":2m83z0ql said:

silverclaws":2m83z0ql said:

Just got to find one now, as it seems 68's are popular, although a 68 will do at a push, might reduce the clearance between chainset and BB, but I will not go there if I can at all help it.

Click to expand...

A 68mm in a 73 shell wont alter the gap between the chainset and BB, only thing you will find is the non flanged cup will sink into the BB shell as you tighten it, i did this years ago when i didn't know BB's were different widths, the splines on the tool only just manage to grip the cup.

Click to expand...

Yep, you're right, I was thinking of the situation reversed, but even that is wrong, an oversize cartridge will alter the chain line unless there is a bit of mucking about with installing the thing off centre, either way, a bodge worth avoiding.

As to a shop doing this, that is unacceptable if there are parts still available, makes you wonder if they were just trying to rid old stock.