Is this finally the end of the square taper............

plugp7

I notice now on the CRC website that the latest version of Shimano's "top end" cartridge square taper bb, UN55, is given as for road use.
I've resisted the change to the external bb cranks etc on the basis of "if it aint broke, dont fix it".
So my question is, should I take a deep breath and go for the external bb crank set up?
I've been told that there is less flex on these but I ask myself, based on the group test done by WMB mag a while ago, will I actually notice small amount of reduced flex and is the faff of servicing and changing the bearings anually, really worth it? Are there any other benefits I'm missing?

The Rookie

You still have ISIS (just don't), Octalink, Powerspline amd Hollowtech1 before you have to go external BB......

I did notice a difference going from Deore square taper on an RPM BB to Truative Powerspline (everything else even the rings were carried over), not much, but a definate feel of less 'flex'.

Simon

warpcow

I'd take "road use only" with a pinch of salt. There doesn't seem to be any difference betwen the UN55 and UN54. I still use squaretaper on my commuter, simply because they last well in all weather. I made the change to external BBs on my mountain-bikes a couple of years ago and, while I'm not sure I could say I noticed any extra stiffness, I do like the ease with which everything can be stripped. I seem to have had pretty good luck with my BBs too. My current MegaExo is about 18months old, and my Shimano SLX is over a year old now, and neither show signs of dying yet.

bobgfish

I still run ISIS and it is fine. Until I've worn out the two Cranksets I have that take ISIS I won't replace. I've had one set of bearings refitted to the BB in 8 years.

There are two many old bikes out there for them to dump square taper. The axle and bearing will be the same but sometimes you can (or have to) reuse the old cups to make it fit.

Neal_

I fitted a UN55 to my bike in October and have so far done 660km without any maintenance in some pretty grim conditions and it's as smooth as the day it was fitted, ignore the road use tag.

njee20

Shimano square taper has been obsolete for 9 years now! They'll keep making the parts, as said there are so many bikes out there, but they'll just do lower end parts (like you can't get UN73s anymore).

Personally I find external lasts as long, is cheaper to replace, lighter, stiffer and easier to fit. Not much contest for me!

rockmonkeysc

You will notice the reduced flex with hollowtech, especially when climbing. Also XT & Saint bottom brackets seem to last forever, I haven't changed one in two years.

Thewaylander

njee20 wrote:

Shimano square taper has been obsolete for 9 years now! They'll keep making the parts, as said there are so many bikes out there, but they'll just do lower end parts (like you can't get UN73s anymore).

Personally I find external lasts as long, is cheaper to replace, lighter, stiffer and easier to fit. Not much contest for me!

This bar the only one downside, being slightly more exposed, but with some half decent seals its niether here nor there, time to change over

plugp7

Just as a matter of interest, what exactly flexes where?

rockmonkeysc

Most of the flex is in the shaft of the bottom bracket. Although a square taper BB has a solid shaft it is fairly small. Shimano Hollowtech 2 cranks have a large diameter shaft which is much stiffer.
Also having the bearings further apart stiffens up the crank as well.

leaflite

Changed from a truvativ powerspline crankset to an external bb xt shimano one. I could definately feel the increase in stiffness, but that may have been because the truvativ one was rubbish-I havent tried any other powerspline, isis or other setups.