Shimano UN55 Square Taper Bottom Bracket for Secure Bike Crankset Performance

andrea f.: Non c'è nulla da fare, le cartucce sono più fluide e scorrevoli dei movimenti di ultima generazione. Sono anche di installazione più facile.

Italy on Dec 14, 2023

Mr. Paul R. Collins: When the motor on my eBike conversion failed, I decided to revert my Surly Disk Trucker to being a normal push bike and so needed a bottom bracket. Its a quality bike with mostly Shimano components. Although inexpensive, this UN55 model is a really nice, solid and - crucially - all metal option. It is definitely a cut above anything cheaper, but feels so smooth that I would expect diminishing returns from spending more. In short, the BB-UN55 represents the "sweet spot" for anyone in the market for a JIS threaded BBB.

United Kingdom on Feb 27, 2021

Laimtoh: I bought this for daily commuting along a sandy, sea salt laden cycle route.

The no-brand bottom bracket that came with the bike had developed play after about 3 years, so had to be replaced. So far the Shimano unit has remained as smooth as the day I installed it, and will probably remain that way for years to come, as the square taper type BBs usually outlast the Hollowtech external bearing BBs many times over.

Used with a new Shimano Acera chainset, there are no creaks whatsoever. I recommend you fit Shimano to Shimano when it comes to chainsets and bottom brackets, to avoid the dreaded crank-creak problem.

United Kingdom on Jul 26, 2020

BERSON Yves: En un mot: Métamorphose !!!
C'est comme si, de mon ancien vtt je passais à un neuf ! Une onctuosité de pedalage incroyable. Le tout pas cher, conforme à la description, tout en métal respirant la qualité.
J'en suis ravi

France on Jul 09, 2020

Marty61: Great upgrade for Cup and Cone bearings. Quick and easy to fit. Smooth bearings and excellent quality. FYI no bolts supplied with mine?

United Kingdom on Jun 18, 2020

bob bobbob bob: Once I pulled this crank set out and inspected for wear, it was in serious need of replacement. I chose the easiest and most inexpensive way to replace the cup and cone originals. The sealed bracket was the way to go. I measured the axle end to end and ordered the same size, within a half millimeter. The sealed bracket performs easily. I suggest rechecking both sides for proper torque after a hundred miles or so. The drive side has a tendency to loosen. This old Bianchi is going to be restored to its proper status.

United States on Jul 23, 2019

Charleston Jeeper: Bought first of these to build up a 2010 Fuji Nevada 5 hardtail frame I scored locally. That worked out very well - the bike came with a generic Chinese cup/cone bottom bracket, which was VERY gritty and a tad loose. I measured the bottom bracket shell and the axle width (with the cranks removed) and it went right in. The only trouble I had was user error in getting the drive side installed straight. Be careful, don't force it, and make sure you lubricate the threads with grease (or better yet, antiseize) so that when you have to replace the BB cartridge in a few years you don't have to deal with corrosion- ESPECIALLY if you're dealing with dissimilar metals.

You will need a special tool to install this. Search for a Shimano square taper cartridge BB tool, it's less than 10 bucks.

Liked that so much, when I went to rehab some of my mid-90s mountain bikes and realized they had 25 year old grease in them, I merely pulled the cranks and measured axle width and shell width. 68x123, as it happens. Hardest part about installing the unit in that bike was removing the old school cup/cone bearings. The Fuji used the same tool as this BB uses, but the old...

United States on Jun 16, 2019

Dean Dicorcia: I only have one ride in with this BB so far, but already I can tell it's a night-and-day improvement over the vintage BB it replaces.

I tooled up to overhaul the old BB on a ca. 1990 Trek, and that went well except for the condition of the spindle; it had already become pitted from foreign objects grinding around in there.

The new UN55 is butter smooth and feels more solid, too.

My only reservation is the spacing. I measured slightly under 113mm on the old spindle, so figured the 113mm UN55 would be the tiniest bit wide. In fact it was a tiny bit narrow, as the chainrings lined up slightly to the left of where they were. I adjusted the limit screw and tension on the front derailleur and the bike seems to work fine now. Not sure whether I should try a wider BB or what; I'm new to proper road bike mechanics. Also I didn't actually measure the new spindle to verify that it really is 113mm; I only noticed the discrepancy after I assembled the whole thing and I didn't want to back out all the parts just to measure....

My UN55 was shipped from Bell's Bike Shop and it was missing the bolts. I had to go to a local store and get a couple of...

United States on Aug 27, 2015

Ivan: I bought this item to put it on my vintage italien "Alpes" bike.I have chosen spindle lenght of only 115 mm. in order to bring front crank chainrings 42/34/24, as much in line with rear Freewheel(14-28T 6 speed) as possible.I must say that my bike, built in 1958 was monospeed one and I did not want to "kill" it, since it was part of my childhood memories.That means frame was not designed to accept easily all this modification.
But everything went well, ShimanoBB-UN55 BottomBracket 70 x 115 Italien thread (36 mm)with alloy left cup, fitted
perfectly.Both threads, left and right side are right hand ones.
I could have bought 118 mm. spindle instead of 115, wouldn't be any worse.Front 3 speed derailleur only had to be adjusted properly to new position of the crank.
Now, it works perfectly with no chain noise at all, shifting runs smoothly too.
So far I have made only 100 km, but it seems to me that this bottom bracket and entire system could last for ever, or at least another 5o years!Very happy.

United States on Oct 27, 2012