curiousabe

So I bought a EM Corsa Motorola with Columbus tubing but am unable to fit both stem and seatpost...

I cleaned the inside of both the seat tube and head tube with steel wool mounted to a drill so inside is clean and looks good but Im confused as to what the correct size seatpost and stem is supposed to be since I cannot fit a 27.2mm seatpost and a 22.2mm stem (tried multiple stems), also took it to an LBS close by and he only had a caliaper top measure with and would not give any recommendations for "old bikes" and the previous owner isnt replying when I asked ghim what size seatpost he ran...

Measurements taken with digital caliper in multiple places
Seat tube, inner diameter: 26.14mm to 27.15mm
Seat tube, outer diameter: emasures 28.83mm

Head tube, inner diameter: 21.80-22.05mm
Head tube, outer diameter: 32.25mm

Acccording to serial nr this is Corsa, size 54, from 1992-1993

I tried bending the seat post binder back and forth to enlargen the hole so the "slit" ran vertically all the way. Now should I continue enlarging the hole to fit a 27.2mm seatpot or could a 27mm or even 26.8mm seatpost be the correct size?

Given that it is a Columbus SL from 92 I would assume that the correct sized seatpost would be 27.2mm and maybe the previous mounted a smaller seatpost and squezed the seat post binder too much? If I recall correctly Columbus SP seat tube would take 27mm but then again the sticker could have been mounted

The head tube is confusing me though, somehow Id be surprised if indeed was a 22mm one I managed to squeeze in a 22.2mm stem a few CM but I really had to force it in which didnt feel ok? Please note that the headset was mounted just yesterday so that should not be an indication of correct diameter (not sure if yuo can mount a 22.2mm headset on a 22.00 headtube?)








Seatpost binder bolt is only inserted with the on the first thread so isnt compressing seat tube.

repechage

Time for some telescoping bore gauges. A caliper is what I would use to measure those.

all looks quite messy, the leftover seat tube paint shows some reaming took place.

I would not expect the tubing transfer to be 100% definitive.

Kabuki12

I wouldn’t be bending it around too much until someone can give a definitive size that it is supposed to be. I think the bore gage idea is a good one as well as checking with 3 point internal mics. The difference between the telescoping internal gage and the 3 point mics will give you an overall picture of the ID of the tube. It could be that the seat tube needs reaming , which is the way I would do it once you know what it should be.

curiousabe

I dont have telescoping bore guages and LBS only had a caliper he told me...Will maybe bring it to a different LBS.

curiousabe

Thanks, yea I dont feel comfortable doing any more bending tbh! Quickly googled teleescoping bore guages and prices locally range from 30-300 eur, it seems like a precision tool so 30eur maybe is a waste of money then, the 3 point internal mic costs more than the frame but maybe a better equipped LBS have all these.

repechage

a three point gauge would be a very good way to go, doubtful a bike shop has one, doubtful even a frame builder.
the cheap telescoping gauges can work well enough, just the locking off of a reading really needs to be double and maybe even triple checked.

SurferRosa

For clarity, you're interested in fork steerer size, not head tube.

Mr. 66

There are times that I use a steel seatpost, here is one of them. My steelpost has a nice rounded end that help fit into a misshapen lug. I carefully install, the steel post has a more give than an alloy. Get it to a minimum insert depth and I rotate the post to help reshape the inner. I'll do this a few times with the steel and then switch to the user post.

On the steertube/stem, have you tried inserting the stem without the locknut. There are times when the top of the steertube and the locknut don't align giving the appearance of not fitting 22.2. On one Italian I ended up setting the stem, and then the locknut because the stem would not insert when following normal building processes. On another I ended up filing down a little bit of the locknut opening for the stem to clear install.

Bummer that your seller ghosted you, he should not have done that.

curiousabe

Very helpful, thanks! Had a second look at the headset and the locknut has some rubber grommet that is quite thick, hard, and protruding like a tiny but from the steerer tube, maybe thats enough to make it hard to mount the stem, will with locknut removed.

Not sure I have a steel seat post lying around though, but even if I had I wouldn't know if its the correct size I'm squeezing in there.

curiousabe

Plot twist, the guy who sold the frame to the previous owner(whom I bought it from), reached out on a local forum where I posted photos of the frame so I asked him. According to him, when he bought it, that owner had used a 27mm seat post since had been hard to fit a 27.2mm, he did however belive that the intended diameter was 27.2 and had made sure to convey this into when he sold it.

Anyway, will bring this to a different lbs across who used to sell itsedan steel frames back in the 80s and let him work some magic.

randyjawa 

For the seat post I added the OP's three diameters and divided by three to get 26.6mm approx. Does that seem to make sense? This is how I determine if a seat lug is out of round. If out, I cross my fingers and with great care, round it out to get equal measurements.

curiousabe

Hm Ive never heard of columbus SL seat tube that takes a 26.6mm stem, but then again I havent heard alot of things either. Maybe seat tube is not SL?

repechage

could be inverted. 28.6 - 1.8 to 2.0 could get you 26.6
test, don’t guess, measure the bore below the heat effected zone of the seat tube.

PhilFo 

Is the fork original?

repechage

Just thought, Hambini I recall has a three point bore gauge or more- digital readout.

the “aged 5” YouTube engineer presenter who gets excited “trashing” bikes.

jethin

Maybe it’s a Varsity in disguise?