klunker build question---bottom bracket.

[all riders]

So if you are changing over from one piece crank to a three piece, single chainring (square taper cartridge ), and you are going to run a single speed coaster, ---What spindle length range would you be looking at, 107mm? 103?. Yes, I am lazy, and am avoiding some simple measuring, but it really should be the same on many of these kinds of builds--thinking someone has it stored in the memory. Thanks everyone!

 

[Archie Sturmer]

Sunlite makes a conversion kit (#20044), that fits 68mm wide bottom brackets, and has 122mm spindle length. The difference is 54mm, or 27mm on each side, (just over an inch).

 

[all riders]

Thank you for your answer. well, I was thinking that might be the range. When I asked about 107 I was thinking about the Varsity that I had just used to measure the BB shell(same as typical cruiser). But it occurs to me that the chainstay on a cruiser would require more clearance as it does not taper out like those on a Varsity. I have some cartridge BBs around so I'll probably just buy the conversion plates or whatever you would call them.

 

[AndyA]

So if you are changing over from one piece crank to a three piece, single chainring (square taper cartridge ), and you are going to run a single speed coaster...

Out of curiosity, why change cranks with a coaster brake? One-piece crank will work fine.

 

[all riders]

I currently have some three-piecers around. don't have a spare one-piece, But it is in my mind to possibly stay one piece.

 

[Archie Sturmer]

Measured a Redline spindle for a 3 piece crank set last night, it measured about 135mm for use with ~11mm wide sealed type bearings (x2).

 

[all riders]

wow! that'sbig. I have road bikes (2x6) that are smaller than that, but then again there is a difference in how the chainring clears the stay. Thanks for your input.

 

[SKPC]

Many variables to this question. Generally though it is quite easy using older alu forged square taper crank sets, both road and MTB. Just takes some trial and error fitting attempts. The bb spindle width is just one factor but a medium length for me has worked. As you mentioned, just try a few loose ones you have to see if things clear. You can also move the big chainring left to right either side of the arms if after tightening the drive side arm you finding the clearance is too tight. The arm offset is another variable but workable most times by lengthening the spindle..

 

[all riders]

Thanks, I will monkey with it. I built up a lot of road bikes in the past and, as you say, it was often trial and error(lots of error)

 

[all riders]

My thinking, in my original question, is as follows: Your starting with a bike with a 65mm shell(63.8 in my case) Converting that to a width of 68 using a cassette is easy enough. Since a single speed cruiser (of the typical klunker type) has no offset in dishing, then the hub(say a model D) and, importantly, its cog, should always have the same distance out in relation to the center(or outer edge) of the shell. Originally I was thinking that you should see the same number over and over for the spindle length because variables found in other builds are not there--they are constants. However, the crankset is still a variable, even a single ring, As they too can have more or less offset in the spyder.