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  • Shimano UN55 Square Taper Bottom Bracket
  • Shimano UN55 Square Taper Bottom Bracket
NOW$19.99
  • RRP$29.99
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Select  Colour
Select  Option
English Thread
Italian Thread
Select  Size
73 x 110mm
73 x 113mm
73 x 118mm
73 x 122.5mm
70 x 107mm
70 x 110mm
70 x 113mm
70 x 115mm
68 x 113mm
68 x 110mm
68 x 118mm
68 x 115mm
68 x 127mm
68 x 122.5mm
73 x 107mm
68 x 107mm
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Shimano UN55 Bottom Bracket

Shimano Road UN55 model has super-accurate bearings for smooth operation and improved durability

Features:

  • Durable, hard-wearing sealed cartridge bottom bracket.
  • Maintenance-free sealed cartridge bearing assembly keeps out dirt, mud and water for long bearing life
  • Fast and easy installation without adjustment
  • Hollow Axle

Buy Shimano UN55 Bottom Bracket at Chain Reaction Cycles, the world's largest online cycling store.

  • Colour: Silver
  • Size: 73 x 110mm, 73 x 113mm, 73 x 118mm, 73 x 122.5mm, 70 x 107mm, 70 x 110mm, 70 x 113mm, 70 x 115mm, 68 x 113mm, 68 x 110mm, 68 x 118mm, 68 x 115mm, 68 x 127mm, 68 x 122.5mm, 73 x 107mm, 68 x 107mm
  • Option: English Thread, Italian Thread
Rated 4.6 out of 5 by 37 reviewers.
Rated 4 out of 5 by Easy to fit and works well A solidly performing bit of kit from a reliable company, its made my bike good as new. 17 July 2014
Rated 4 out of 5 by Solid and durable bb A quality replacement part. Needs a little breaking in to start with. 13 June 2014
Rated 5 out of 5 by Update your bike with this I acquired an old Raleigh Trail for free (1980s or thereabouts). The bottom bracket was completely wrecked, but I persisted in riding it. Eventually it got so bad, that I was going to call it a day. The local repair guy pointed out the excellent 501 frame and the excellent wheels. A bit of research on the web and I found out you could replace the old ball-bearing setup with this sealed unit. Replacing the old set-up myself would have proved very difficult and costly with several special tools needed. The bike guy showed me how to measure the old spindle etc and I bought this (English thread for Raleigh). He did it for £20. My bike works like new now - for a total cost of under £35. I was planning to buy a new bike but with this my old bike works like new again. I've just saved £500. Very pleased with website, product and speed of delivery. 04 June 2014
Rated 4 out of 5 by Does what it's meant to Ordered as a cheap but good quality replacement for an old loose ball bearing bottom bracket (BB). I've used these BBs on my main commuting bike for years without issue. Arrived in the post very quickly and fits perfectly. As far as I know, this is the cheapest shimano BB with an aluminium non-drive cup, as opposed to plastic. 21 May 2014
Rated 4 out of 5 by Buen producto y Buen precio Buenas prestaciones del producto, no obstante el eje que tenía antes era el UN26 y tenía las mismas prestaciones de fluidez de giro del eje. No merece la pena gastarse el doble de precio por el UN55, por el hecho de que algunas piezas de cierre, en vez de plástico sean metálicas. Con el antiguo eje no he tenido problemas con las piezas de plástico. 04 May 2014
Rated 5 out of 5 by It's cheap and it works!! Can't fault this bottom bracket so far. Replaced a completely trashed original part and it has put up with everything from being immersed in flood water too being thrashed along dirt tracks! Runs smoothly enough for me and at the price I really can't find a negative! 30 April 2014
Rated 5 out of 5 Bullet proof Great value strong bottom bracket. For the money you can't go wrong. 26 April 2014
Rated 5 out of 5 by Bomproof classic These are the weapon of choice for MTB tourers for a reason, they are solid, bombproof and pretty much fit and forget. I switched all my external bottom brackets to these this year as I find externals aren;t all they are cracked up to be. The thing i like most is these spin round and round for ages with no resistance, like your bike did as a kid! and how often did you change the bottom bracket on your old street bike? never?..... exactly.... I've heard of these being replaced at 80,000 on world tours! good enough for me! 25 April 2014
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26 Questions : 40 Answers

Product Q&A

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3 answers

Does this come with crank bolts?

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Answer: 
Crank bolts are not included with this bottom bracket; the suggested bolts below are compatible.
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Answer: 
Yes comes with plain hex head steel ones
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Answer: 
No, no crank bolts comprised.
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2 answers

Sizing

I have a Specialized Allez that I need to replace the bottom bracket on. The size is 68x113mm, but you only do that size in the Italian thread, will that fit my bike as I purchased it in the UK?
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Answer: 
I bought this this and a week later the sealed bearings were knackered n thats with the right size. so i would get another mate
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Answer: 
'Italian' is not in regards to the origin of your bike- it is a thread descriptor- it is very unlikely that your bike frame needs an Italian threaded bottom bracket- double check with your bike maker but I'd suggest it will need a British (ISO) bottom bracket- 99.9% sure.
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Will this fit my 2013 GT Karakoram 3?

I have 2013 GT Karakoram 3 and it has a sealed unit that looks like this. Do you know whether this would be suitable and what size would be required? Thanks
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Answer: 
It will fit your frame but what you need to establish is the length of your axle- take your pedals off and measure it or remove the bb and simply read the axle length from the bracket itself.
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Answer: 
Yes this bottom bracket will fit the frame; however the exact cartridge size and spindle length are not measurements we can advise on as there are many variations.

Simply measure the current bottom bracket width's in relation to the diagram here - http://i.imgur.com/hfNhAM9.jpg

The 68mm, 70mm, 73mm are in relation to the cartridge width and the frames bottom bracket shell (http://i.imgur.com/qfhqzHT.jpg) and the other measurments of 107mm, 113mm, 118mm etc. are in relation to the spindle length.
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Answer: 
This is perfect:
http://www.chainreactioncycles.com/it/it/weldtite-shimano-bottom-bracket-cartridge-tool/rp-prod86711
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Answer: 
The suggested square taper tool suggested below is required for fitting this bottom bracket. For future reference; the crank puller will likely be required to dissemble it again.
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Shimano un55 bottom bracket

Hi i need a replacement bottom bracket for my Trek 7.2 FX the old one is a un55 but the label says 68 but on the length it as the letters D-NL not numbers. Can you tell me which bb i need.

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Answer: 
You can simply measure the bb yourself my friend- use the ruler or callipers and buy the relevant axle length. The 68 is teh BB shell compatibility- you can buy 73 and use a spacer when needed too.
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Answer: 
The 68 refers to the shell width, but you can double check the required length by measuring the end to end of the existing bracket (image below).
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Answer: 
Это JIS Taper.
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Answer: 
Из того, что я помню, 99% Shimano квадратного конуса является JIS (единственным исключением является Dura-Ace).

Так что я ма на 99% уверен, что это JIS.
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Answer: 
You can determine the width you need by either measuring your existing bracket, or across the shell on the frame (68 or 73mm is English thread, 70mm is Italian).

Axle length is determined by the chainset you intend to use; check with the manufacturer of your cranks to confirm what axle length you should be using. If re-using your original cranks, simply check the axle width on the previous bracket (image below)
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Answer: 
British (ISO) thread will do you good.
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I’ve been using UN54’s (68 x 122mm British Thread) for a number of years, they now appear to be either discontinued or out of stock. Is a UN55 (68 x 122.5mm British Thread) a compatible replacement? If so what actually is the difference as they appear to be identical

Thank you
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Answer: 
The UN55 is perfectly compatible as a replacement for the UN54 - forget about the 0.5mm numeric difference! I think the UN55's left cup washer was slightly redesigned (different shape and, I think, different material) to eliminate some creaking that the UN54 could suffer from.
HTH
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Answer: 
The difference is the axle length and bearings. The axle will be ok with only 5 mm difference. The bearings- you will never notice the difference.
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My current Japanese vintage bike's BB is signed 1.37x68. Which size should I choose for this BB to replace it well?
Many thanks.
3 weeks, 5 days ago
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Anonymous
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Answer: 
Your required axle length will depend on which cranks you intend to use. Try searching the web with your crank's brand and model number to find the right length.
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Answer: 
You'll need a standard (aka British aka ISO) bottom bracket. 68mm will fit directly in. If you get 73mm bottom bracket make sure you get the spacer.

You will also need to measure the axle length (sometimes written on the bracket itself) to make sure that your chainline remains unchanged.
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Can I replace old UN25 with UN55?

Looking at the ticket on the side of the old unit it states 68 BC1.37x24 MM110 however on the UN55 the only option English thread is for 70 BC1.37x24 MM110. The only option that seems to match (68x110) states that it is Italian thread.

Which of these do I need?
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Answer: 
Our sku271953 is the 68x110mm English Thread bracket. This should be fine to replace your UN25.

FYI, 68/73mm is English Thread, 70mm is Italian Thread.
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Answer: 
Get a 73mm version and get a spacer for the bottom bracket (the bracket itself does not come with the spacer sometimes)- ask your LBS for the spacers and you'll be sorted. When getting 68mm you're limited to 68mm only. When getting 73 you can get it into the 68 shell with spacers or directly into the 73 shell.
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