# IRO vs. KHS frame sizing.



## slappypants (Sep 24, 2008)

Hello I want to buy a KHS flite100. While I was shopping around I noticed that my size for an IRO mark V is 56cm, and naturally I thought the KHS 57cm would be the right size for me. My stand over is about 31 inches. The KHS 57cm is 33 inches and the 53cm KHS is 31.5 (stand over) way more similar in measurement to the IRO 56cm. and the 59cm IRO is more comparable to the KHS 57cm. 
Is it normal to be that different in measurement? I am 5 10' and didn't think I'd have to buy a 53cm bike. If anyone could help or check out the geometry on both and give me some advice. I'd love to ride both but the flites are sold out until november. Anyone else have either of these frames and what did you end up buying? 
thanks.


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## Dave Hickey (Jan 27, 2002)

Forget standover and look at top tube length..standover is meaningless when determining frame fit..


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## slappypants (Sep 24, 2008)

*thanks*

thanks for the reply. I don't know which size frame I would be.


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## Dave Hickey (Jan 27, 2002)

Do you ride a road bike now? If so and it's comfortable, measure the top tube from the center of the seat tube to the center of the head tube.. It should be measured in centimeters...

Once you determine the top tube length, check the charts for the KHS and IRO and find something similar...


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## slappypants (Sep 24, 2008)

Dave Hickey said:


> Do you ride a road bike now? If so and it's comfortable, measure the top tube from the center of the seat tube to the center of the head tube.. It should be measured in centimeters..
> 
> 
> Once you determine the top tube length, check the charts for the KHS and IRO and find something similar...


This will be my first road bike. I know it's hard to say without ever being on the bike. I'll check with my lbs.


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## slappypants (Sep 24, 2008)

thanks for replying


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## slappypants (Sep 24, 2008)

*Frame size*

I should have titled this thread bike frame size, doing a little research on potential bikes I would buy I notice that although their numbers in terms of top tube and seat tube etc. are relatively close in measurement they all label the size of their bikes differently which I don't understand, I've read some Sheldon Brown size fitting and Peter White's how to fit a bicycle I don't understand how a fame is labeled with a certain cm. Why is a 56cm bike a 56cm, just want to know where they get that number?( Not specifically 56cm). I found that I fit a 53cm khs flite100 and a 56cm IRO Mark V.


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## Dave Hickey (Jan 27, 2002)

The 56cm refers to seat tube size...

Depending on the manufacturer, seat tube are measured

1. From the center of the bottom bracket to the center of the top tube
2. From the center of the bottom bracket to the top of the top tube
3. From the center of the bottom bracket to the top of the seat collar
4. On compact frames(sloping top tube), size can be from the center of the bottom bracket to a virtual horizontal top tube.

The above is why you can't just buy a 56cm XXX bike because a 56cm YYY bike happens to fit you... 

It's best to look at the geometry charts and not go by size and please forget standover as a way to determine fit


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## BIGBOB (Jan 29, 2004)

As stated, go by top tube length. That is the most critical dimension. Seat posts can be raised to accomodate. But T-T lengths and stem can only be stretched so far. 


Size by TT length. Then fit stem etc.
Most stems in a bike that fits properly will fall in the 11cm range. (110mm) 

IME, Bob


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