Joined: 26 Sep 2013Posts: 591Location: somewhere up north
Hey Guys,
After getting rad last night, I was peddling up a hill heard a clink and then almost lost it. My bottom bracket is toast, and now my non-drive side crank arm spins freely.
Do I need to measure for a new bottom bracket on a modern bike, or do they come in a standard size?
Its a square tapered sealed bottom bracket as far as I know.
langston
Posted: Fri Oct 02, 2015 9:21 am
Joined: 25 Jul 2005Posts: 5547Location: Columbia City
They are indeed different lengths, you'll want to roll into your LBS of choice and have them help sort you out as the easiest way of fixing this right the first time.
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jimmythefly
Posted: Fri Oct 02, 2015 9:27 am
Joined: 10 Jan 2007Posts: 1491
IF it is square taper, there are 4 measurements you need to know to order a replacement:
1. Your frame's BB shell threading. If your bike is truly "modern" and is not from an Italian manufacturer, it is 99.9% certain that you have what's called "BSA" threading or "British" or technically known as 1.37"x 24 TPI.
2. Your frame's BB shell width. If your bike is truly "modern" and is not from an Italian manufacturer, it is 85% certain that you have a 68mm wide shell. If your bike is a MTB it is very possible that the shell is 73mm wide.
3. The spindle length of the BB. Because various crank arms are not all made teh same and for other factors, your BB spindle length could vary quite a bit. you can measure the old one, or look on the old BB itself to see if it says, or you can google what crank you have an likely get a recommendation.
4. Spindle taper. It is 99.99% certain you want a JIS standard spindle taper. But if you have Italian or French or other retro parts you might want to check for sure.
If you walk into a shop and ask for a "square taper bottom bracket" you will be handed a British threaded, 68mm wide, JIS taper BB and the only question you will really have to answer is what spindle length.
But since I don't know what cranks or frame you have it's a lot tougher to say for sure.
whitenhiemer
Posted: Fri Oct 02, 2015 10:55 am
Joined: 26 Sep 2013Posts: 591Location: somewhere up north
jimmythefly wrote:
IF it is square taper, there are 4 measurements you need to know to order a replacement:
1. Your frame's BB shell threading. If your bike is truly "modern" and is not from an Italian manufacturer, it is 99.9% certain that you have what's called "BSA" threading or "British" or technically known as 1.37"x 24 TPI.
2. Your frame's BB shell width. If your bike is truly "modern" and is not from an Italian manufacturer, it is 85% certain that you have a 68mm wide shell. If your bike is a f'n mtb it is very possible that the shell is 73mm wide.
3. The spindle length of the BB. Because various crank arms are not all made teh same and for other factors, your BB spindle length could vary quite a bit. you can measure the old one, or look on the old BB itself to see if it says, or you can google what crank you have an likely get a recommendation.
4. Spindle taper. It is 99.99% certain you want a JIS standard spindle taper. But if you have Italian or French or other retro parts you might want to check for sure.
putting my 2012 Giant Escape in to the googles comes back with a Shimano UN-26 even though I have a SRAM VIA groupset.
Hopefully the measurements will be written on the BB
Rogelio
Posted: Fri Oct 02, 2015 12:52 pm
Joined: 31 Jul 2007Posts: 3092Location: Pos, aya, por la Corona-Alta-Madera y que no.
If you need help swapping it out or don't have the tools, one of us can help out. (In which I volunteer as default, but there might be someone that lives closer to you that might be up for it.)
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walker
Posted: Fri Oct 02, 2015 2:33 pm
Joined: 05 Aug 2015Posts: 1855Location: beastcake
I'm at 80th and Greenwood if that's close to you. I have a stand and everything you'll need except the BB tool. I've got a crank puller if you need one. If you can hunt down a BB tool, I'll be wrenching most of Saturday, and am happy to help.
whitenhiemer
Posted: Fri Oct 02, 2015 2:34 pm
Joined: 26 Sep 2013Posts: 591Location: somewhere up north
walker wrote:
I'm at 80th and Greenwood if that's close to you. I have a stand and everything you'll need except the BB tool. I've got a crank puller if you need one. If you can hunt down a BB tool, I'll be wrenching most of Saturday, and am happy to help.
You are close to me, I'm at 143rd and Aurora
I"ve got a bottom bracket tool.
walker
Posted: Fri Oct 02, 2015 4:00 pm
Joined: 05 Aug 2015Posts: 1855Location: beastcake
PM'd
whitenhiemer
Posted: Tue Oct 06, 2015 4:51 pm
Joined: 26 Sep 2013Posts: 591Location: somewhere up north
Walker thanks for the offer, I ended up getting caught up by family stuff last Saturday and it ended up being too late for me to get a hold of you.
I did end up getting the bottom bracket off by myself and found out it is a standard 68mm bottom bracket and is a 113mm spindle length.
This is my option as far as I can tell, unless yall have a better idea.
I like how that product page features 6 different shots of the box, and none of the contents.
YEP IT'S THE TOP OF A BOX ALRIGHT
The box top really had a decisive effect on my purchase.
Andrew_Squirrel
Posted: Wed Oct 07, 2015 9:27 am
Joined: 01 Mar 2010Posts: 2098Location: Greenwood
+1 for the UN-55
If you are doing this yourself remember to use a liberal amount of grease on the cup threads when installing. You also might want to borrow a torque wrench for both the BB and reinstalling the cranks.
whitenhiemer
Posted: Fri Oct 09, 2015 3:57 pm
Joined: 26 Sep 2013Posts: 591Location: somewhere up north
New BB is installed and seems to work so far. Funny thing is the new one is a solid piece housing while the last one was 2 bearing on either side with a thin metal sleave covering them. Shimano over Chinese knock off from now on.
The new one also ways twice as much as the old one, so I'm going to say heavy BB is sturdier.
joeball
Posted: Fri Oct 09, 2015 6:49 pm
Joined: 24 Jul 2005Posts: 6037Location: Ether
Was the BB that broke the original or had you replaced it once before?
Also, did Jace type your last post?
whitenhiemer
Posted: Fri Oct 09, 2015 8:31 pm
Joined: 26 Sep 2013Posts: 591Location: somewhere up north
joeball wrote:
Was the BB that broke the original or had you replaced it once before?
Also, did Jace type your last post?
Typed my own post. I've never changed my bottom bracket out myself, so it could be the original. I've been having issues with this bottom bracket since I had my bike worked on by one of those mobil bike repair guys. I'm trying to do all my own repairs now. I'm getting better.
joeball
Posted: Mon Oct 12, 2015 7:55 pm
Joined: 24 Jul 2005Posts: 6037Location: Ether
whitenhiemer wrote:
I'm trying to do all my own repairs now. I'm getting better.
That's the attitude.
Also Shimano bike parts are a good benchmark. Your bike probably came with a super crap bottom bracket to begin with. This replacement should last you a while.
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