Gods lonely man

After tightening the quill stem on the drop bars, there is this small gap , the stem is tight enough so I can twists the bars and there is no movement , should I use a shim ? Is it safe enough? Maybe the stem clamp is not perfectly round , both are 25mm clamp , a pretty rare and obsolete size.

Iride01 

If the bars won't rotate in the stem clamp when you push on them with all your might, then it's probably okay. I'd be careful the first few rides when hitting big bumps. Those sometimes will have you putting more sudden force on the bars than you can do by muscling them.

It'd bother me though what is out of round or why this is happening. So I'd probably change out the stem, the bars or both. Though I wouldn't let that stop me from riding it until I can find what I want.

The pic is with the clamp tightened... isn't it?

Trakhak

A photo of the opening at the bottom of the stem clamping area taken from below will likely show the stem is fully closed. If the stem and bar were compatible, you'd see a gap of a few millimeters. The absence of a gap would mean that the handlebar and stem were designed for two different diameter standards.

Yes, insert a shim. One or two layers of aluminum cut from a soda can should do it. Aluminum works very well as shim material.

First, though, examine the inner and outer surfaces of the stem clamping area. Here's hoping tightening it as much as you did to clamp the undersized bar didn't create any cracks.

Hondo6

This should be obvious, but since Trakhak didn't say it and it's safety critical I will.

If you find any cracks on inspection, do not ride that bike until you have replaced whatever cracked (bar or stem, but I'd guess most likely the stem).

A bar or stem breaking while you are riding is a seriously bad thing.

icemilkcoffee 

I doubt they are both 25mm. The previous owner could have reamed the stem out to the common 25.4mm opening.

Gods lonely man

Thanks for the replies, I am going to test it carefully without a shim, here is a pic from the bolt clamp

Gods lonely man

The bars are Alsasua from Razesa, Spanish maker , their old stuff had a lot of metric sizes, quill stem is Super Akront.

Gods lonely man

No cracks before and after installation, and I hope none after a test drive.

grumpus

Looks fine. I'd just listen out for any clicks or creaks that suggest the assembly is moving under high load - you don't want to wear a groove in the handlebar.

SurferRosa

Go for a quick and fast ride without traffic and slam on the brakes with both hands on the bars. If they don't rotate, you're good.

alcjphil

That bar does not fit that stem. I can see daylight between the bar and stem. That is a dangerous failure possibility

dsbrantjr

The stem clearly does not fit the bar correctly for whatever reason. Perhaps someone tried to force an oversized bar into the stem, bending the upper part, or forced the opening wider to insert/remove some drop bars.
Regardless, I would not ride it until the fit is rectified. I suspect that it will be prone to loosening under shock/vibration. It is only funny in cartoons when the bars come loose.

Andrew R Stewart 

Either the bars or the stem clamp are not round. Tha the bars can seem secure but there's still a gap as shown proves this. I would be more nervous if the stem clamp had been deformed (as can happen if its pried open too far) than if the bars are a tad oval. Why? Because when a bar catastrophically fails generally only one side breaks off. When a stem goes bad both sides of the bars become loose.

It's possible that careful measurements can gain more insight. But if the stem is the culprit I would stop riding the bike and replace the stem. Andy (who laced a pair of Akront alloy rims for a friend for his Honda 550/4 sport bike way long ago)

Gods lonely man

Chances are the stem clamp is compromised, (so is my safety) i think the shim option may be a nice try , I really wanted to use this bars/stem combo, if I try sprinting up a hill and come back with all my teeth i would leave it like this
No that bad from this angle

The bars are in great shape though

Gods lonely man

Almost forgot Akront is well known in vintage motorcycle circles.
The stem clamp does have some scratches from the previous owner, nothing too serious, so it may have been forced into bigger bars in the past.

Soody

Have you got a thin film of grease on the mating parts and the bolt thread? Will help it tighten and not creak.
I think it's fine. Agree to put a small beer can shim in there, maybe just in the gap. Make sure it protrudes slightly past the edges of the stem so it does not cut into the bar.

The can should be Estrella or similiar.

Soody

Also, in my experience, bars and stems are often the full spectrum of sizes between 25.4 and 26.4. Old ones have very very commonly been bent or shimmed to fit each other. They're bent open on installation with most drop bars.
Anyone riding an old quill stem is taking a similar risk to you. It's not a crazy one. People ride carbon steerers, crashed, 2 bolt faceplates that will let go if one bolt breaks.

GamblerGORD53

Those gouges on the bottom side of the bar look like trouble to me. Gonzo IMO.
The top side pic in post #14 does look better though.
I've had a steel bar break in half going slow up a hill. Had to walk it home.

Gods lonely man

Add to the list riding with the quill up above the minimum insertion line , same with seatposts, I know two guys who cracked a frame that way.

Gods lonely man

I thought It looked ok...and breaking a bar climbing sounds better than breaking it bombing the hill

smd4

I can see some daylight between my Cinelli bars and Dura Ace stem (though not at the clamp). Probably most folks here would, if they ever shined an LED flashlight and checked it out. I think you'll be fine.

Hondo6

OP says in comment #7 above that it's a Super Akront.

urbanknight

Since you seem confident that both are 25mm size, I'm wondering if the previous owner of the bar tried to fit it into the wrong size stem and squished it out of round.

oldbobcat

It looks very much like somebody at one time or another pried the clamp with a chisel or screwdriver to squeeze an oversize handlebar in there. The shape of the gap on top suggests the stem was originally machined for a smaller radius, and the gap on the bottom is wider than it should be. It was obviously not made for this size handlebar. After what it's been through I would not trust it..

Gods lonely man

Update, thanks for the replies, I got another stem with a 25 mm clamp, ( and 22.0 quill!) it was noticeable harder to fit it on the bars but I managed to do it without scratching the handlebar engravings, now bars and stem are tight tight without gaps and the new stem is shinier so win/win situation.