Bicycle Mechanics - BB spindle length confusion
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04-30-08, 08:07 PM
I have a Shimano UN-52 bottom bracket and was looking to replace it (starting to grind, ten years old). I ordered a new one and went for a UN-72, but for some reason seemed to have ordered the wrong spindle length.
Using Verniers I measured the two spindles:
New UN-52 spindle length = 107.95mm (I'm guessing it is a 107 mm, since that is a standard length)
Old UN-72 spindle length = 111.3mm
My question is, should I be after a 111 mm spindle? (Do they even make one?) I know they make a 113mm one. I measured carefully, but maybe I was off a bit? But two mm's....that is quite a bit to be off and I don't think I was.
I also checked out Sheldon's database here:
I have a 105 double crankset and the database says I'll need either a 113mm or 107mm. But, that is for an "SC". My cranks are stamped Shimano FC-1056.
I'm confused (and depressed I can't get out riding tomorrow.)
Anyone know what length spindle I need? I know I need a 68mm shell width. Do they make a Shimano UN model (such as 72) in a 68x113? Or a 68x111?
04-30-08, 08:17 PM
"New UN-72 spindle length = 111.3mm
My question is, should I be after a 111 mm spindle?..."
Sounds like you already have one?
04-30-08, 08:27 PM
Hey, Bill...made a mistake there, thanks for picking up on it. My old BB spindle measures 111.3 mm. I'm confused by that. I thought the lengths were either 107 or 113. Do they make a Shimano square taper BB in 111mm?
EDIT: It looks like they make a 110mm Shimano. I'm guessing that is closer than the 113mm. I'll measure again, but I tried to be as precise as possible.
04-30-08, 08:59 PM
I changed a spindle type to a cartridge a couple months ago. My measurements were off a couple MM from what it was supposed to be too.
Are both spindles symmetrical? A=C
Even if they are, it'll change your chain line by 2MM. Not a major amount. Cog spacing is close to 5MM, depending on how many cogs in your cassette.
If they aren't, use the end that matches up best.
BTW, it seems they don't match up perfectly anyway. I guess a crank that's been on/off a few times may have a bit of wear plus machining tolerances etc. With that slight of a tapper, ,001" difference on the "square" is going to allow a "few" .001" difference in chain line.
05-01-08, 01:58 PM
Assuming you had the 105 crankset on before, get a cartridge with a spindle length closest to what you had. If you're putting a new crankset on, and are going with the database, I suspect the smaller length is for a double and the larger for a triple.
05-01-08, 02:51 PM
Tellyho, you are saying I should upgrade to a cartridge bearing BB? What are the pros of that? (that the BB is rebuildable in the future?)
I am not updating the crankset. An older bike and while I'd love to upgrade things, I'm going to sit on my hands and bank account and just save my money to get an entirely new, modern road bike in a year or two. This one suits me pretty well, as I ride for fun/leisure/stretch my legs.
What type of cartridge BB do you suggest?
I'm having trouble finding a UN-72 in 68x110/111mm. Anyone know a source?
(I can find lots of UN-52s, but not the UN-72)
05-01-08, 05:16 PM
If you're going to be replacing the bike in a couple years...why not just go with the UN-52?
Oh...and it sounds like you're already using a "sealed cartridge BB."
05-03-08, 08:54 AM
You are right, I am using a sealed BB. For some reason I was thinking in my head that cartridge meant like a cartridge hub bearing, one you can replace. Yeah, my Shimano BB is sealed and all I can do it swap it out.
As for why I want to upgrade...the UN-72 is only slightly more expensive and it is lighter and a bit nicer. Though I have my eyes on a new bike, this is still my only true road machine and I like keeping it as nice/light/happy as possible.
I just have to find one...
05-03-08, 09:08 AM
AFAIK, the UN-72 series bottom brackets are out of production and you will have to find an NOS one if you can.
Otherwise, the UN-52 is the best commonly available and current production square taper cartridge bb Shimano still offers.
05-04-08, 04:19 AM
i am pretty sure the un-72 is being phased out as well, it's successor being the un-54? or at least you can use a un-73... either way they are both hollow spindle and come in sizes from 103 all the way through 113+. remove it from the frame before you try and measure it, it will save you headaches of eyeballing a tape measure and being off by 1 or 2mm. when in doubt, hit up your LBS with old bb in hand and leave it up to the guys who play with that stuff for a living. they are cheap as fock and available at any shop thats worth its existence. hell even nashbar sells them for under 25 bucks. oh and unless you have the LBS install it, you'll need a park tool bbt-2 (i think is also discontinued, may be the same as the bbt-22 now...) bottom bracket tool which hooks onto a standard 3/8" ratchet or can be cranked by a (i think) 32mm hand wrench to screw in the "cups." good luck.
05-04-08, 05:47 AM
I tried and tried to find a reference that listed cratridge BB sizes. I thought it would be nice to know the distance from the right face that bottoms out against the frame to both the left and right spindle ends. That way you could campare BBs and figure out what you needed. You could even move the crank arms a known distance. Alas I have never found such a thing. I think the advice about the LBS is your best bet when unsure. You can walk in with an old BB and line it up right next to the new one to make sure it is what you want.
05-05-08, 10:17 AM
Wait, the UN-54 and UN-73 are hollow axle as well? That is why I was after the UN-72...I thought it was an upgrade from the UN-52 because it was lighter due to the hollow axle.
Are you sure about that, Cizzlak? I have not seen any of those at Nashbar nor Performance.
I have the tool and can uninstall and reinstall myself. I did measure it while it was removed. Measures at 111mm with a Vernier. I have seen 110.5, but I'm sure I'll be okay with a 68x110. I know Harris Cyclery has some, but I am trying to find out which ones, but they don't take phone calls and are slow on emailing.
05-07-08, 10:15 AM
Any confirmation on the UN-54 and UN-73 having hollow axles?
I've heard the same thing about the UN-54s having a hollow axle. I'm not sure what the difference is between the 54 and the 7x now. Maybe bearing quality?
As for the OP, the length of the bb spindle is usually stamped on the drive side near the bearing, or on either a sticker or stamp on the bottom bracket shell if you pull it off the bike. The biggest issue with bb length for a geared set-up is chainring/chainstay clearance. If you have plenty now, the bb won't make a huge difference. If the chainring comes close to hitting the chainstay, you'll probably want the longer spindle just in case.
05-07-08, 07:18 PM
I have a sec of 105 sc and i matched it with a dura ace 112 simetric. Regarding 111? bettween 111 and 112 there is no big difference, in a matter of fact maybe be even a 107 sealed might work fine.
Between the 112/111 and the 107 that is a bb more likely to be able to be found (a 109 also) u have like 4 mms difference, that means 2 mms per side.. that doesnt make big difference my friend. Specially when we talk about shimano.
If you are going to use a bb that is ISO it will make a big difference because the crank will go further (if im not wrong) in the axle... If the crank is jis you need a jis bb, well technically u can use a jis cranks and a iso bb, but the lenght of the axle needed will change too much, more likely u might need a longer axle. Again, the idea is not to mix jis and iso but that doesnt mean it wont work (little tiny differences)
Have fun :)
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