Measuring correct stem size??

[bigred407]

Hey guys 'n' gals...

My project Moulton had a really small one-piece handlebar & stem unit which I have removed and want to replace using an alternative size of stem & bars.

My problem is I'm not sure what size or type of stem will fit. The bike has on old school threaded headset and threaded forks. With the original stem removed, I measured it using a micrometer and it came out at 19mm or 3/4" outer diameter. Is this the correct way to measure, or should I be measuring the internal diameter of the forks steerer tube? So if it's 1" dia i would be looking for a 1" stem?

Hope someone can help, I'm confused?! :banghead:

 

[deorman]

Best to measure inside the steer tube. In my experience, 15/16"/21.1mm is the smallest common size.

 

[Bicycle808]

I'd take a look at the quill on the original stem. If you don't have calipers, you can tighten an adjustable wrench on the quill and measure the space between, in mm, as close as possible. That will get you close enough to any of the common 1" quill sizes, which are (as Deorman said) 21.1 (late 50's thru 70s American bikes, some ceap imports), 22.0 (French), and 22.2mm (most everything else-- same as 7/8").

I've seen photos online of Moulton F Frames with standard Nitto stems installed. Nitto stems are almost always 22.2mm (the exceptions I've seen were bullmoose bar/stem combos, available in both 21.1 and 22.2) but I have no way of knowing what mods, if any, were done to the stems or the steering tube.

HTH

 

[bigred407]

My bike is a Moulton but it's a Mini, was 7/8 of size of a normal Moulton. I have measured the quill on the existing stem with a micrometer and it measures 19.5mm.

 

[mikeeebikey]

I would measure the I.d. of the fork tube.
The stamped stems are so sloppy in the tube I never felt warm and fuzzy for them!

 

[bigred407]

I had managed to find a fixie style Moulton Mini on google images which runs a different bar and stem setup, but there is no build information on it anywhere

 

[LukeTheJoker]

Something interesting going on with that stem...

Luke.

 

[bigred407]

I can't really figure out from the pic if it's a quill stem or an Ahead stem fitted to an adaptor. Also not sure why the big bracket on the head and down tube is there. Wondered if it's had some extreme surgery...

 

[LukeTheJoker]

I can't really figure out from the pic if it's a quill stem or an Ahead stem fitted to an adaptor. Also not sure why the big bracket on the head and down tube is there. Wondered if it's had some extreme surgery...

Totally agree, that may be some extra bracing for some reason, there may be a fair amount of stress in that area.

I am guessing they cut the bars off the original stem and welded on those two side plates with the adjustable piece between them for angle adjustments.

Luke.

 

[bigred407]

I thought the stem was an old elastomer suspension stem form an MTB from days of old?

 

[Bicycle808]

ooooooooooh. 19.5mm? You'd better hold onto the original....

As for the red bike you linked, looks like the bike originally came with the Moulton Wishbone quill:

...and then he kludged something different on the handlebar part of it....

 

[bigred407]

My Moulton isn't like the one you have pictured. The bar and stem is one-piece on mine. The bar cannot be seperated from the stem.

 

[LukeTheJoker]

I thought the stem was an old elastomer suspension stem form an MTB from days of old?

You are right, that does look like it!

Luke.

 

[Bicycle808]

Yeah, that does look to be the one...

 

[kingfish254]

Isn't the Moulton stem similar to the Raliegh Twenty stem (same designer)? Check out the work of SixtyFiver over on bikeforums.net

 

[bigred407]

Isn't the Moulton stem similar to the Raliegh Twenty stem (same designer)? Check out the work of SixtyFiver over on bikeforums.net

It was Alex Moulton whi originally designed the Moulton which was latterly made under license by Raleigh. The RSW was their answer to the Moulton design.
I think the problem is mine being a Mini, everything is smaller than a standard Moulton. I will look him up though, really need to find a solution to my problem.

 

[mikeeebikey]

In the past, when I was a boy, I used a belt sander and a caliper to get a stem to size. I actually made the quil rounder than it was when I started!

 

[bigred407]

In the past, when I was a boy, I used a belt sander and a caliper to get a stem to size. I actually made the quil rounder than it was when I started!

Could be a way of doing it, although this must weaken the stem somewhat by reducing the material thickness that's there. The replacement stem would have to be fairly thick material to turn it down to 19mm.

 

[mikeeebikey]

Yeah, I don't think I'd use a cheapo! A bmx stem, quality one, should have enough metal.

 

[bigred407]

If only I'd picked a model that's easier to deal with for my first rat rod project...