Cheseldine

Hey everyone,

I have an older fillet brazed Jamis Diablo (1988) that I'd like to rebuild from a rigid mountain bike into a dirt drop/commuter setup. It has a threaded, rigid fork, and Tioga headset.

I assumed that the quill stem post (where it inserts into the steerer tube) diameter should be 22.2mm. When I got out the dial caliper and measured at multiple points, I am getting exactly 22mm - if I open my caliper to 22.2mm I definitely have a minute amount of play between the caliper arms and the stem.

Is this typical? I know some older French bikes like my Motobecane take a 22mm stem, but was suprised to get a 22mm reading on a late 80s mountain bike. Do stems vary by a couple tenths of a mm typically?

I am getting measurements of 22.0mm stem diameter and 25.4mm clamp diameter for the stem (which makes sense).

I'd prefer to get a nice 22.2mm Nitto dirt drop stem with a 26mm clamp size to fit the Nitto Dirt Drop bars, but if I really have to go with 22mm options I'll be stuck with a threadless adapter.

Thanks for any insight!

Wilfred Laurier

Is there no marking on the stem? And do you have another stem to try? Because that would be weird if it were specced as 22.0mm.

Cheseldine

Unfortunately I don't have another 22.2 quill stem lying around I could try. The stem has no markings other than "Jamis" on the neck and the marks for the minimum insertion depth.

Wilfred Laurier

Have you measured the ID of the fork? Maybe there is space for a 22.2mm quill but the OEM stem is just undersized.

Cheseldine

^I hope this is the case - I had just repacked the bearings and correctly tensioned the headset and locknut when I decided to actually measure it before ordering parts last night. I couldn't get a good measurement of the ID of the fork steerer with the locknut installed as there is a rubber washer in there to prevent grime from getting in. I am unsure if the ID of the locknut is the exactly the same as the ID of the fork as well. I guess I'll have to pull it apart and check that next. I was wondering if maybe it was common for 22.2 quills to measure closer to 22.

Andrew R Stewart 

Another possibility is that some early MtB bikes used the "American" (these days I should really say "USA") 21.15mm stem diameters, a left over from decades of US bikes and Wald/Schwinn like products. (Ross was another who used this spec). With a simple caliper the measuring is easily drifted a bit from the actual. This is why afterr the thousand of assumptions and the one measurement, a trial fit tells all. Andy

cecu

another possibility is that the caliper is not 100% accurate?

Andrew R Stewart 

Agreed. The cheap calipers tend to have a bunch of slop in their movement. Additionally don't forget that if you ask 10 people to measure something with the same device it's often that you end up with 11 different claims Andy

Miele Man

I've seen the odd bike with a 22.2" steerer tube but with a top lock nut from a 21.5 headset.

Cheers

Andrew R Stewart 

Yes so have I. But when one says they measured a steerer ID you have to hope that they know the difference between the steerer and the top nut Andy

Miele Man

I've seen far to many who measure at the top lock not and assumed it was the same as the steerer tube. I NEVER assume what people might do when it comes to working on a bicycle.

Cheers

Andrew R Stewart 

Yes, My reply was a tad tongue in cheek. I should have added more then a smile to indicate that. Andy