How to correctly measure a prewar frame in order to buy a bottom crank assembly Prewar or post war straight leg that will fit correctly.

[mikecuda]

How do I correctly measure a prewar frame bottom bracket in order to buy a bottom crank assembly Prewar or post war straight leg that will fit correctly.

 

[49autocycledeluxe]

you don't.

tell us what kind of bike you are working on and which parts of the "bottom crank assembly" you need. then we can go from there.

 

[mikecuda]

you don't.

tell us what kind of bike you are working on and which parts of the "bottom crank assembly" you need. then we can go from there.

Sears Chief frame. I have coming to me the feather chain ring. I just want to use a straight leg crank arm assembly that will fit in the Chief's bottom bracket. The bike will be another display bike for me. How do I measure??? Across the bottom bracket??

 

[49autocycledeluxe]

Sears Chief. Sears did not make bikes, making a picture worth 1000 words so we can see what it is.

again, there is no measuring. nobody advertises bike parts like that with measurements. they show pictures and say what bike it came from.

parts like the crank will interchange from many different bikes depending on what bike it is.

are we speaking of a teens bike here?

 

[49autocycledeluxe]

1915 to 1919 Sears Chief - Documentation & Bike Thread | Antique Bicycles Pre-1933

There always seems to be a ton of interest around the 1915 to 1919 Sears Chiefs so I thought I'd start a thread specific to documenting these great bikes. I know there are several threads with a lot of data on these bikes but this is intended specifically to be a "documentation" thread. I am...

thecabe.com

 

[mikecuda]

Sears Chief. Sears did not make bikes, making a picture worth 1000 words so we can see what it is.

again, there is no measuring. nobody advertises bike parts like that with measurements. they show pictures and say what bike it came from.

parts like the crank will interchange from many different bikes depending on what bike it is.

are we speaking of a teens bike here?

Yes. Motobike. I'll try to unbury it and take a photo. I'm seeing on Ebay 6.5" and 6.75" bottom bracket crank assemblies prewar and post war.

 

[mikecuda]

Here is my Sears Chief frame and fork

 

[49autocycledeluxe]

the inside measurement here is what you need to get proper bearing races and associated bearings and whatnot. the width is slightly less critical as there is a degree of adjustment.

I am assuming this is all you have?

 

[mikecuda]

the inside measurement here is what you need to get proper bearing races and associated bearings and whatnot. the width is slightly less critical as there is a degree of adjustment.

I am assuming this is all you have?

View attachment 1535320

I have more stuff off the bike, I just can't find them at this time. Packed way for same keeping. I own two head badges and more. 3 speed Sturmey archer back hub and the Sturmey archer shifter.