Square Taper BB's – UN54 or bling?
As I’ve just gone back to the old school with some Middleburn cranks, is it worth getting something posh in the bottom bracket department or just bung in a Shimano UN54 ‘cos they’re cheap and they work pretty much as well as anything else?
I think I’ve probably answered my own question, but let’s hear your thoughts anyway…Posted 5 years agoteacakeMember
Standard Shimano square taper. Think mine is a UN73? Fitted 3 and a half years ago and never had any problems – just beginning to feel a slight bit of play. I ride on average 15 miles offroad a week. Every week, so I rate them!
Square taper BB’s are so reliable that they had to invent other “standards” or “improvements” to keep their business growing.Posted 5 years agoti_pin_manMember
LX and above will do fine and pretty much bombproof so should last an age, I think the XT are UN72’s. I couldnt find one for my cross bike and fitted the UN54 which, if memory serves, is the LX version.
I also have a couple of bikes with ancient Royce BB, one of which has been in for 8 years, serviced occasionally, but still going strong!
you pays yer dosh and makes yer choice. If it s bling build buy a bling BB, if not Lx/XT will be fine.Posted 5 years agowoodsmanMember
I’ve got some exprience on this one!
I’ve been using UN54 and UN72/3 for the last ten years or so. I do ride a fair bit and find either of the above last me the same – one year no longer and they’re grindy and have play. As I’ve said I ride a fair bit!
Recently, I’ve bought some new Middleburn’s and decided to go with a bling Royce BB. It is massively lighter for a start, feels absolutely smooth and yes it really is very noticable when riding – just makes me want to go faster! The down side is that there can be problems getting them to bed in to the crank taper. Mine creaked and squeaked for a year despite following the set up instructions religiously! Now, it doesn’t make a sound, but I have also noticed that some play in the bearings is developing after two summers use. In summary this product is nice but can be temperamental and may not last any longer before it needs bearings (serviced at Royce) than replacing a UN54/72/3 but it does feel incredibly nice when riding. I’ll probably take a chance and get another for my next build!Posted 5 years agoroverpigSubscriber
I’ve been using a couple of UN54 and UN72 BBs for around ten years on various bikes (on and off road) and they still feel smooth. The tricky bit, I find, is working out what axle length you require.
I’m running the UN72 with some old Truvativ Compact drive triple cranks on a Five and they sit a bit too far out, so I’d be interested to know where to go to get a new one. Mind you, the current setup does allow me to run 22/36 and a bash ring without fouling the pivot on the Five.Posted 5 years agocoolhandlukeSubscriber
Ditched them external BB’s on my main bike a few years ago and got some Middleburn cranks and chain rings
The BB (UN54) has been in for about 3 years now? and last time I rode, it sounded a bit squeaky. if its goosed, its still lasted about 2 and a half years longer than the external BB’s did
Just bought a new UN55, to be sure.
Wouldn’t go back to external BB’s. not worth the grief for weight saving.Posted 5 years agodizcostixMember
Had an UN54 then moved to phil wood.
The phil wood definitely spins a lot better (smoother) and I noticed it while pedaling.
The adjustable cups mean you can shift the BB 5mm within the frame, improving chainline alignment if that makes a difference to you
EDIT: UN54 is still ok in my eyes though!Posted 5 years agoStonerSubscriber
Another square taper devotee here.
All 6 of my bikes run them.
Unfortunately Ive only got one UN72 left in one of the bikes, one sitting in the shed thats 108mm – and one next to me on the desk that I took the grinder to to see what the axle looks like. (The BB had died I promise, I got it second hand 10 years ago…)
TBH Ive compared the weight with a plain non-hollow axle and the weight penalty is negligible so I guess some of the savings must be in the shells/bearings?
Ive resigned to using UN54s for now as I just cant justify £100 for saving about 100g. I still keep a weather eye on eBay – probably just like 100s of other UN72 junkies 🙁Posted 5 years agoandy3877Subscriber
I’ve just built up a Whyte 46 with square taper (UN55 and FSA crankset). The BB has been in my bit box for several years and still runs smoothly.
I still ride my Giant Track (1989) with its original UN?? BB as my rigid bike and the combination of BB and XT cranks is still a joy to ride (original XT Thumbies too…)
So another vote for shimano here.Posted 5 years agocoolhandlukeSubscriber
Just took my UN54 out to replace with a UN55 because I thought it was a bit creaky. It’s just over a year old, checked purchase history on CRC.
Anyway, it still feels smooth as silk but the crank ams weren’t exactly tight. Cleaned the outside up, put a bit of grease on it and popped it back in, but with the metal collar from the UN55 instead of the plastic one.
Probably good or another year at least.
Got a spare UN55 in the toolbox now anyhow. It won’t go off.
I’d probably have replaced external BB’ at least once by now if I hadn’t gone ack to square taper.Posted 5 years ago
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