cyclotoine

A beautiful 25.4mm stem I really want to use with a 26.0 bar.

1. Should I do it? Why and why not?
2. Have you done it? If so, what was your method and how did it turn out?

I plan to just use a seat tube honing/clean-up brush tool (is there a proper name for it?) in the drill and or emery paper wrapped around rags, wrapped around a large drill bit (actually used this variously for cleaning up seat tube and stems which I sprayed easy-off on to remove anno and then I needed to get the white crust out of the clamp area.

What do you think?

unworthy1

the Flexhone® is a wire brush thing with lumps of silicone carbide on the bristles...use oil if you use one. I have used an adjustable reamer to do this, but you get much smoother results if you fabricate a plug of aluminum to fill the gap in the stem clamp. It doesn't have to be fancy, but it keeps the tool (any tool) from "stuttering" at every rotation when it hits a gap.

old and new

YES.. affectionatly called an "ugly hone" , a mess of wire and pebble-like balls, like a funky tree.
These and 2 stone flat hones,the old style both are used to do brk. wheel cylinders & clutch slaves in cars. Luckily the range in these are similar to bike tubes 1".
It's not critical and these hones aren't "precission". You don't want precission anyway. Go by feel.
Believe me, ZERO risk in such. I used to hone stuff for fun when working in a shop.
Reamers are trickier, they can bind. Honing is to be done LESS than you'd expect.
Tubes are near foil thin so back-off prior to guessing you're done, no worries.

cyclotoine

Bingo, hmm now to fabricate the plug... got some thinking to do on that one... what kind of oil? something very light I presume?

old and new

See if you can filch a bit from a machinest, a little will do. I reluctanly would use a cutting,grinding stone oil, foul smelling, milky stuff. OR just ask the man.
We used Sunnen, so not warrented for your job.
Use lightweight, low viscosity motor oil, 20wt is best, beat it half-way with karosene or diesel fuel, it works. Too thick o' mix will make the stone spin at worst.
Honest, myself and another more skilled machinest preferred the mix, the official oil causes pimples and smells bad. (don't snitch on us)

old and new

If it all seems pesky, use a little Marvel Mystery oil or the like and toss the rest in your cars engine or don't. We ground alot so we used the cheaper stuff, they were HUGE grinders and engine hones. For brakes, what little brk. fluid residue that remained worked fine.

randyjawa 

Two questions come to mind. First, the component was engineered to accommodate predefined stresses. Removing material would negatively impact the components strength. How much, I do not know but I do know that fooling with engineered stuff can backfire sometimes. Anyway, unless you are a really big strong guy who rides very aggressively, the modification will probably be of little consequence. However...

The second question that enters my mind, is - should I irreversibly modify a vintage piece to suit my own personal wants? For me, the answer so far has been no. But that is just me.

miamijim

Hone it. Stems are a plenty.

Road Fan

Sorry, as one who is always on the lookout for 26.0 Nitto Tech Deluxes in my lengths, I think stems are NOT a-plenty! Unless I want just generic crap on my bikes.

T-Mar

I can fully appreciate where Randy is coming from, having had both Cinelli XA and 1R stems fail due to extra machining of the clamp to accommodate their recessed logo plug. While the risk may appear low, the potential consequences are severe. To me, the solution is simple and no risk. Use a 25.4mm bar.

Old Fat Guy

Ken,

You could just break down and buy a new one. They are readily available.

infinityeye

I'd thin out the bar first. Maybe go halfs. I'd probably just open up the clamp a little and the try to get it in place.

txvintage

Too easy and implies the use of logic, and there is no place for that here. Don't make me come over there.

unworthy1

The "plug" I made was just a piece of flat AL stock about the width of the gap (1/8" of so) and I drilled a hole for the clamp bolt to pass thru and keep it in place, trimmed the edge that would contact the hone so it was "close" to flush...the rest just hung out all over since that wasn't critical.
Flexhone sells their own brand of oil, but I use 20W motor oil: no problems...you just have to use some sort of lube with them, same with the brake-cylinder 2-or-3-stone style. If I was doing a lot of this I'd probably opt to use a cutting fluid specifically for Aluminum alloys...but I don't do a lot of it.
Since one only removes about 0.6mm of material, I sincerely doubt there's much chance of dangerously compromising the strength of a stem, but if you have any fears about the safety of it: DON'T do it.

Bianchigirll 

wouldn't a Flexhone get 'clogged' from the aluminum? I thought you were not to use stones to gring and shape aluminum? atleast that is what I was tought both in the Marines and in the shops i worked in

tuz

It'd remove only 0.3mm (12thou) on each side so I don't think there is a big risk. You can probably remove half that and the bar will fit okay. And it's a good idea to put a plug: I was honing a slotted tube once and the hone disintegrated as it got caught in the slot.

unworthy1

yeah, true....while that's "technically" the best practice, I have violated the rule numerous times. In my case, however, I used a reamer to enlarge the stem hole, no stone, and I went very slowly as you must do with a reamer in Aluminum.

cyclotoine

thanks, I don't have any flat stock so I'm gonna gut a hunk of old crank arm to fit in there.

Bianchi Girl, I think the fluid help the hone to stay clean.

Others, It's a dia-compe gran compe stem which I guess is sort of rare, it looks like a nitto pearl. It's like the 1A and there is a lot of material there, I'm not the least bit concerned that it will weaken the component, do you guys see how thin they make alluminum today? Granted the metallurgy has changed, but I think these old stems were pretty burly.