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Damn BB Problems



 
 
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Old December 5th 19, 09:35 PM posted to rec.bicycles.tech
Tom Kunich[_5_]
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Default Damn BB Problems

On Wednesday, December 4, 2019 at 6:19:42 PM UTC-8, AMuzi wrote:
On 12/4/2019 7:37 PM, jbeattie wrote:
On Wednesday, December 4, 2019 at 2:45:37 PM UTC-8, Tom Kunich wrote:
On Wednesday, December 4, 2019 at 1:46:14 PM UTC-8, jbeattie wrote:
On Wednesday, December 4, 2019 at 1:13:06 PM UTC-8, Tom Kunich wrote:
On Wednesday, December 4, 2019 at 12:29:34 PM UTC-8, jbeattie wrote:
On Wednesday, December 4, 2019 at 9:32:13 AM UTC-8, Tom Kunich wrote:
On Tuesday, December 3, 2019 at 8:30:26 PM UTC-8, jbeattie wrote:
On Tuesday, December 3, 2019 at 4:27:50 PM UTC-8, Tom Kunich wrote:
I have a Redline cross bike and it had an XT crank on it that had a 24-38 rings. The bottom bracket appears to be an XT also but the only thing on it was "mountain" on both sides and the markings are "BB-MT800".

I pulled off the cranks and tried to replace them with a Reynolds 24 mm shaft compact chainset I tripped across while I was looking in my parts bin(s)

When I inserted it, I discovered that the end cap of the Reynolds crank was missing. Also it appears that the crank is about a 1/4th inch too short for that bottom bracket.

Tearing the universe apart I still haven't found the endcap which is smaller thread than the XT crank.`

So I need to figure out what BB the Reynolds is supposed to use. The Reynolds site was no help. Plus I can't find out what the size and thread of the endcap is and they make enough 2nd manufacturer end caps that they probably make one that will fit for $5-6.

Anyone got any information on these things?

Oh Gawd, so all that wasted time on BB386. It is a f****** threaded BB. I was right.

Go buy a 105 crank and put the Reynolds crank back in the parts box or on eBay. Done.

-- Jay Beattie.

Are you saying that BB-MT800 or whatever it is is a BB386? I'm not convinced they are. There isn't a lot width diffeence.

NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO. BB386 is a press-fit format not a threaded cup. You have a plain old regular (probably) 68mm ISO threaded BB shell. The same thing as half the road bikes on the planet. You took a Shimano out, put a Shimano back. This is a two minute process. Just confirm that it is a 68mm BB and not a 73mm, which would be really odd for a CX bike.

-- Jay Beattie.

https://www.bing.com/images/search?v...vt=0&eim=1,2,6

Groan. That is a CONVERSION BB for using BB386 crank on an ISO/BSA threaded BB frame. A standard BB386 BB is a press-fit format for 46mm bore BB shell. https://www.youtube.com/watch?v=U66bVfZeLyk

Don't be opaque. Answer the following two, simple questions:

1. What is the width of the BB shell?
2. Is the shell threaded?

If you have a 68mm threaded BB shell and a BB-MT800 (NOT PF) BB, then throw in a Shimano road crank and stop this insanity. If it is 73mm, use a Shimano mountain crank -- like the one you took out. This should take five or ten minutes tops and not days of bizarre speculation.


-- Jay Beattie.

It is threaded and a 73 mm width. I am not about to put an MTB crank into a cross frame. Shimano makes an "oversize" BB and so they must let a normal crank work.


First, are you sure that there are not a bunch of spacers between the BB cup and the face of the BB shell, which you need when using a MTB crank on a 68mm shell. Are you sure that you are not measuring a bunch of spacers? I ask because I could not find any indication that Redline ever made a Conquest with a 73mm bottom bracket shell. Are you sure it is a Redline -- or is it some Chinese knock-off like a Redlime or a Reedline?

If it really is 73mm, you're screwed if you don't want to use a mountain crank. Maybe Andrew can help you.

-- Jay Beattie.


I read the original post and saw the whole thing as an
obscured sort of tarbaby. Or maybe more charitably an
unresolvable koan.

Redline Cross frame BBs are 1.370"x24t threaded BSC and 68mm
wide. Redline Cross frames are 34.8 FD in aluminum and titanium.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


This is a Conquest. It has an oversize (73 mm) BB shell and a 32.4mm seat tube. I've measured these several times with a digital caliper (General UltraTech) in case Jay was correct.
 




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