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Square Or Isis


Adrian

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i've heard that the bearings in isis bb are weaker than square taper and so more prone to breaking. That's why raceface etc have started to do their bb's with the bearings on the outside of the frame so that they can make them larger. I don't know if this is a major problem though??

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Hi :)

I recommend Square Taper myself, for the reasons pointed out above - the bottom bracket bearings tend to last much longer. A good square taper crank like a middlesburn pro trials, put on correctly should last a very long time, and so should the BB (Y)

~Gaz

edit: changed smiley!

Edited by ghosts_cloak
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To sumemrise:

ISIS:

Good:

Strong, stiff axle

Strong, stiff Interface

Due to the above two very little flex, and stronger than square.

Bad:

Due to oversize axle, smaller bearings are used than square. Some people have experienced reduced BB life due to this, as has been mentioned can be improved with use of external bearing bb's.

As the splined interface is not tapered, repeated removal of cranks (or running loose) will damage interface and it will never be tight again.

Sqaure:

Good:

very common fitment if you need parts in a hurry

good bearings, long bb life.

due to tapered interface cranks can be tightened on further after frequent removal, or slight damage.

Bad:

taper can be damaged easily in extreme use

axles are weaker due to smaller size

feel more 'flexy' due to small interface and axle, alowing more movement.

Its swings and roundabouts, but overall ISIS has proved itself better in extreme riding applications such as trials, despite the bearing problems.

Edited by nmt_oli
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I have a cheap shimano un square bb and midleburn cranks and have ran them for nearly 2 years now and had no bother at all they never slacken. The good thing about square is easy to get lenghts and standard bolts for them and are cheap got mine for about £12.

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I have a cheap shimano un square bb and midleburn cranks and have ran them for nearly 2 years now and had no bother at all they never slacken. The good thing about square is easy to get lenghts and standard bolts for them and are cheap got mine for about £12.

shimano un bb (N)(N)(N) espcailly not if you want to do drops!!! i had 1 which i cant remeber which model it was but it was the holow axle 1. did a 6ft drop and snapped the axel. so i bought the solid axel 1 which was ment to b alot stronger but also alot heavey went for that 2 months later snapped that axle. i know what you are think you must be a heavy/harsh rider. well no i am not i am not a harsh lander and only weigh 10 stone. you can only take my word on that but must people i have riden with have agree i am not harsh and defo not heavy.

Cheers Glynn Hope It Helps

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