Shimano Deore UN53 Bottom Bracket

Advantages: built in external BB, good quality
Disadvantages: None

...I bought this to replace the SR Suntour cranks and stock Shimano Bottom Bracket on my Trek 4300. A fantastic upgrade, extremely sturdy, nice stiff cranks, excellent machine work. And to top it off, no internal Bottom Bracket is needed. Something I dont think a lot of the adverts for the item make enough of. You don't need to bother measuring your spindle as you just need to remove the entire bottom bracket and fit the M532 with the inbuilt external BB. You will need additional tools to fit this, but they can be picked up relatively cheaply and you never need to worry about wearing out any bearings in the bottom bracket again. It took me 15 minutes to fit, simply remove your old cranks, remove the BB and slot this in place. It comes with various spacers to adjust the width depending on your frame size and once fitted it'll feel like... Read review

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Advantages: Great for downhill
Disadvantages: suspension no good for road.

...for the road due to the suspension on the back. You can adjust the suspension for the road but you have to fully wind it in and is not a quick action. Another problem with the bike is the bottom bracket (the bearing where the peddles are) to offer a bike like this at a reasonable price, cheaper than its makers for instance, parts like this are of poor quality, the bracket is made of plastic so soon wears out and will need to be replaced with a decent one. Again you can pay a varied amount of prices for them and they usually cost about £10 to fit. I replaced mine with a Shimano and have not had any problems since. The pads on the Tektron are not of decent quality either and Im finding they get spongy not so longer after I have adjusted them. The seat is quite comfy as its larger than a normal Carerra stiff tail seat, one fat arse in padded shorts... Read review

Ciao members have rated this review on average very helpful

Advantages: Cheap, extremely durable, abuse tolerant
Disadvantages: Poor crank choice, may not be suitble for extreme use

..., and now the latest big thing are external bottom brackets. X-type from Race Face, Hollowtech II from Shimano, and GXP from Truvativ. While they have different names they are all interchangeable, as they are all made to similar specifications and similar dimensions. Each "improvement" has led to stiffer and lighter BB's, with a marked decrease in durability. The latest BB's can last as little as 3 months on a mountain bike, if ridden in wet and muddy conditions. ISIS are particularly bad in this regard, but the new external BB's are in a class all of their own. Mounting the BB outside of the frame, makes them extremely vulnerable to water penetration and early failure. The UN54 will give you an average service life of around 18 months to 2 years, and this reason alone may be enough to persuade you to stick with square taper. My last one a UN... Read review

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