BB Question
 

Alright, I have looked around for related posts but had little/no luck. I just got a 1994 Diamondback Master TG and the bottom bracket is absolutely screwed - the worst I have ever seen. (does that say anything?) Anyway, the spindle is 120mm wide but has 4 additional mm on the drive side ~ 120 r+4. I cannot find any such spindle or cartridge bb on the internet for purchase so I am wondering what a good replacement/substitute would be.

Any help is appreciated, Thank you.

lverhagen

I have never seen a 124mm spindle - are you saying that it is 120mm, asymmetric? To get to the bottom of it, I suggest you check out the BB info on Sheldon Brown's website.

Hi on older bikes asymetrical BBs were not too unusual. you need a 120mm asymetrical BB it should not be too hard to find. are the cups really bad? how about the races on the spindle?

try Velo Orange you might find a cartridge style that will work.

OH doe this have bolts or nuts to hold the cranks on? are you only measuring end of the square taper to end of square taper?

what brand and model is your crankset?

Hmmn, in the course of installing a triple chainring setup my recent FrankenVega build I noticed the the BB from the donor bike (also a Univega, c. 1980 Sportour) was assymmetric. I believe it is an SR BB, as the crankset was SR. As an aside, I originally thought the longer side of the BB would be needed on the chainring side to keep the small chainring away from the chainstay, but it turned out that the shorter side of the BB was adequate and made the chain line up better to the rear cogs, considering that the gearing I implemented was single step plus "granny" (not really a granny, the small chainring is actually 36T).

Until the mid-1980s symmetrical BB spindles were only found with single chain ring cranks. 124mm is proper length for a triple crank; a double would be 118-120. Here are a couple possibilities:

http://www.biketoolsetc.com/index.cg...=YS-BB98868124

http://www.biketoolsetc.com/index.cg...TH-7420AL68124

Do you happen to know if the cups are removable on that YST BB???

TIA
-Mark in St. Louis

Thank you for all the responses. My cranks are 1994 Shimano 105 doubles (Part number FC-1055). The spindle is indeed 120 asymmetric, however I am not sure which side the offset was meant to be on. Is there a hard and fast rule for this?

@Bianchigirll - both the cups and spindle are extremely pitted. I do not plan to reuse them at all.

The longer side goes on the drive side.

Check your spindle for a number/letter size code, that will tell you everything you need to know.

http://www.sheldonbrown.com/bbsize.html

scroll down and look at the first chart.

Once again, thanks for all the help. I should be able to determine a suitable spindle using the information given.

Cheers,
lverhagen

Is your bottom bracket casting width 68 or 73 mm nominal? It makes a big difference in BB selection/replacement.

Shimano FC-1055 cranks should be used with a 113 or 115 mm symmetrical bottom bracket spindle. The one currently in your Diamondback is completely wrong.

Not if the BB is 73 mm wide.

Shimano says otherwise.

Well, alrighty then.

I don't think there is a hard and fast rule about BB size, as it depends on variables. The width of the BB, the clearance of the chain stays are the two that come to mind, and then the crankset itself will want a certain length.

I would be surprised to learn that a component manufacturer can specify a BB size and have it work on all random frames. Logic dictates otherwise.

Personally, I would check the fit of what you have and if the crank fits fine, stick with that. If the chainline is off and you have the clearance, then you could use the old one as a starting point and measure from there.