# Reaming the seat tube?



## mikesnowdon (Sep 25, 2009)

Hi. 

One for the frame experts....

I have a 1997 Kona Cindercone. This is a double butted cromo frame. It takes a 27.0mm seatpost which really limits my choice on a new post. 

Is it safe to ream it out to 27.2mm?


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## cannonballtrail (Sep 14, 2004)

*Been there, done it, wish I hadn't*

Been there, done it, wish I hadn't. Back in the day when I was young and dumb, I didn't use a seat tube reamer, rather I put 27.2 bit in an industrial press and drilled it out very slowly. I made it about 5 weeks until a crack appeared on the seat tube.

Would you have better luck with a reamer, maybe. Should you do it? No. IMHO, you are removing way too much material. You should still wait for a pro like walt or dave to answer, but from someone who has a long history of stupidity through trial and error, I can say these things just never end as intended.


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## Hubcap Cycles (Sep 6, 2009)

If you know someone with a 27.2 reamer it should not be a problem, you are only opening it up .008" on the diameter.
Cheers,
Hub
http://hubcapcycles.com


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## Walt (Jan 23, 2004)

*Do some measuring*

First off, the frame is really old. Do you need the latest fancy carbon fiber post that only comes in 27.2? Only you can answer that, but a 27.0 Thomson is a nice post and will last at least as long as the frame.

If you do decide to ream it out, measure the inside diameter (presumably a little over 27.0) and the outside diameter, after scraping the paint away around the top (the seat collar is going to cover up the paint damage, don't sweat it). Subtract one from the other, divide by 2, and you've got your wall thickness. You can also (if you've got nice calipers) just measure the wall thickness directly, but it's not going to be as accurate.

If it's 1.3mm or thicker, you're probably (IMO) ok to ream. If it's around 1.2mm, it might be ok, but I'd avoid it. Thinner than 1.2mm, forget it.

-Walt


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## mikesnowdon (Sep 25, 2009)

Thanks guys. 

and Walt...

I think I'll go with a Thomson. I'll keep you advice for reference should I ever want to change the post though. Thanks mate.


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## problematiks (Oct 18, 2005)

If you're looking for a cheaper seatpost, you can solve this another way.Cheaper and mid-range seatposts are usually relativelly thick walled, so if you have access to a lathe, it's going to be easy to mill the seatpost down from 27.2 to 27.0 and it won't compromise the strength of the seatpost.

Marko


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## Linnaeus (May 17, 2009)

I don't know where the Cindercone sat in Kona's range, but many older, low end steel frames have plenty of extra material. I recently did a 26.6 -> 26.8 conversion with an expandable reamer, which are very versatile should you decide you need to buy a reamer.


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## mikesnowdon (Sep 25, 2009)

Linnaeus said:


> I don't know where the Cindercone sat in Kona's range, but many older, low end steel frames have plenty of extra material. I recently did a 26.6 -> 26.8 conversion with an expandable reamer, which are very versatile should you decide you need to buy a reamer.


Low end? Are you kidding? You have offended the old girl!

According to the Kona catalog from back then its a good mid-point in the steel framed Kona line up.I've checked and the seat-tube wall's are too thin by my reckoning. This frame may not be made of fancy named steel but its very light for a 19" and its got that 'Kona thing' in spades. (If you get that you'll understand). Its being built up with some very nice parts and will make a super bike that I defy anyone not to love. IMHO its thoroughly deserving of the Thomson, Middleburn, Hope, Easton, XTR, and Crank Bros, SID items waiting to go on her. Ive had her modified to run a disk brake and the weight is around the 2100g mark. Not too bad for 19" steel mtb frame eh? With the parts I have selected I'm expecting to hit the 23lb mark.

Thanks you.


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## Linnaeus (May 17, 2009)

Sounds like a good 27.0 post is in order then!


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