...whats 0.5mm between friends!

wookiee

wookiee

Retrobike Rider
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Hi guys

Looking to replace a knackerd cone/cup BB for a sealed cartridge one...I know from the old one and the chainset that I am fitting (Deore LX M550) that I should need a 122.5mm one. My question is this...I can get 122mm ones cheaper than 122.5mm so will 0.5 mm really make any difference???

Thanks

Doug
 
You will be ok with 122mm, wook. the difference is negligible as alloy cranks will open by that much at the taper closing the cranks in by atleast 0.5mm. yes, buy one ;)

un51/52/53/54 are pretty much the same. un55 looks better manufactured but....no real diference 'til un71>
 
Thanks guys as far as I understand it the differences between the un's is this:

UN51 = solid axle
UN53 = solid axle
UN54 = hollow, plastic NDS cup
UN55 = hollow, alloy NDS cup
UN72 = hollow, ?? cup
UN73 = hollow, alloy NDS cup
UN91 = hollow, alloy NDS cup

In the end managed to get a un51 122.5mm from crc for £7.99 free post! A bit heavier but its for my wifes bike (another 1991 Marin Eldridge!) so weight not really a mega issue!

Cheers anyway guys

Doug
 
Remember that lad who bought a 122 instead of a 122.5? His dog bit him, wife.left him, and he got arrested for cross dressing in the ladies loos. It's jot worth skimping that half a mm!
 
marc two tone":2h85g9ef said:
UN72 twin alloy cups. both removable, one seems fixed but isn't. ;)
Click to expand...

Indeed, and it's the cups that are different between 68 & 73mm widths, not the body (have two here of the same axle length).
 
Chopper1192":1vtd2xtd said:
Remember that lad who bought a 122 instead of a 122.5? His dog bit him, wife.left him, and he got arrested for cross dressing in the ladies loos. It's jot worth skimping that half a mm!
Click to expand...


That was my fear...hence I went for the 122.5mm!
 
wookiee":ugjlmmlk said:
Thanks guys as far as I understand it the differences between the un's is this:

UN51 = solid axle
UN53 = solid axle
UN54 = hollow, plastic NDS cup
UN55 = hollow, alloy NDS cup
UN72 = hollow, ?? cup
UN73 = hollow, alloy NDS cup
UN91 = hollow, alloy NDS cup

In the end managed to get a un51 122.5mm from crc for £7.99 free post! A bit heavier but its for my wifes bike (another 1991 Marin Eldridge!) so weight not really a mega issue!

Cheers anyway guys

Doug
Click to expand...

There's a few numbers missing from theatre. un54/55 are the same bottom bracket apart from the cup change. I asked Shimano what the change was.
In the scheme of things they are lighter than the previous 5x's but still don't get the axle coating of the UN7x and 9x series.

Chances are 122 is the same as 122.5 anyway.
 
Chopper1192":1oqli5r8 said:
Remember that lad who bought a 122 instead of a 122.5? His dog bit him, wife.left him, and he got arrested for cross dressing in the ladies loos. It's jot worth skimping that half a mm!
Click to expand...

You forgot what happened after he was released.

He tried to get home by bike, but the 0.5mm increased the friction on the bearings so much that they overheated.
His bike caught fire while he passed a petrol station and the resulting explosion caused 3rd degree burns in the genital area.

To top it off, the incident was classified as an act of terrorism, which means he now is on the no-fly list as well.
 
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