Frame Sizing of a Road Bike

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Frame Sizing of a Road Bike

Postby MichaelB » Thu Feb 22, 2007 8:57 am

Quick question - is there a simple way to calculate what frame size you need for a given height/leg length ?

I'm 184cm tall and inside leg length is ~ 90cm.

What frame measurement would I need to be looking at ?

The reason is, I am looking at some s/hand bikes at the moment, and want to know if any are too small/large

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by BNA » Thu Feb 22, 2007 9:16 am

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Postby europa » Thu Feb 22, 2007 9:16 am

It's brand specific and sometimes model specific. Different manufacturers use different methods of measure up for size. The only way to tell is to throw your leg over the thing. However, as you get a bit of experience, you'll start to get a feel for the numbers.

There are size calculators on in the internet - they've been linked to before on here so a quick search won't hurt, but don't take them as gospel.

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Postby Mulger bill » Thu Feb 22, 2007 9:28 am

G'Day Michael, you could try competitivecyclist.com, they've got a calculator.

Looking at the review pane, I see Europas got in first :o
The quick and nasty way:
Stand over the top tube, feet flat on the floor. Is there 30-50 mm of space between the boys and the frame? If so, sit on it and grab the bars. Are you too cramped or stretched? If not, it's test ride time :)

As an example of company sizing, I have a Giant MTB and Roadie, the MTB is sized 17inch and fits, the Roadie is sized 50cm and fits :?

Good luck

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Postby MichaelB » Thu Feb 22, 2007 10:04 am

Mulger bill wrote:Stand over the top tube, feet flat on the floor. Is there 30-50 mm of space between the boys and the frame?


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Postby MichaelB » Thu Feb 22, 2007 10:21 am

From a very quick rough measurement from competitive cyclist it says that the seat tube c-c should be 58.3 to 58.8 (for their version of it).

So does that mean that a bike witha 52cm frame is not ideal ?

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Postby sogood » Thu Feb 22, 2007 10:42 am

MichaelB wrote:From a very quick rough measurement from competitive cyclist it says that the seat tube c-c should be 58.3 to 58.8 (for their version of it).

So does that mean that a bike witha 52cm frame is not ideal ?

Just have to make sure that 52cm frame is also measured centre to centre. And if it's a compact frame eg. Giant et al, then it's centre to imaginary centre.

If the reference of measurement is corrent, then yes, 52cm is a long way off from 58cm and you shouldn't take it.
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Postby mikesbytes » Thu Feb 22, 2007 10:55 am

I use to be very picky with frame sizes in the past and had frames built to my body shape.

Now days I just buy a medium or large frame and adjust it carefully to position my legs correctly and adjust the handlebar postion if applicable.

I'm 181cm and 56cm frames seem to be about right for me.

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Postby LuckyPierre » Thu Feb 22, 2007 11:26 am

I'm a bit shorter than Mike (178 cm) and I find that 56 cm seat tubes / top tubes are about right too.
The boys might beg to differ, because that doesn't give them a lot of clearance on a traditional frame!
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Postby mikesbytes » Thu Feb 22, 2007 11:32 am

Looks like you are roughly a 58cm frame. But check the measurements on that site where ever it is.

And like everything theres a degree of personal preference.

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Postby europa » Thu Feb 22, 2007 12:36 pm

These slanting top tubes make it hard. In the good old days, of horizontal top tubes and not a lot of choice in frame sizes anyway, it was fairly easy. But there's more choice now and with the top tube doing all sorts of weird things, you have to look very carefully at reach as well as height.

Don't buy on the numbers. Stand over the top tube and see how high you're voice'll be if you slip off the seat. Sit on or ride the bike and see how far you have to reach (or not). That's the only way to tell. The major revisions I had to do to the Sow's Ear to get her to fit indicate it can be done with a too small frame, but it's not pretty and not good.

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Postby gururug » Thu Feb 22, 2007 6:21 pm

Mulger bill wrote:The quick and nasty way:
Stand over the top tube, feet flat on the floor. Is there 30-50 mm of space between the boys and the frame?


I have an Small sized avanti, "the boys" are 4mm if that above the frame and this is even with their angled bar.

I guess if I wanted something lower I would need to get something custom made?

What problems should I anticipate from this (I already know I need to probably change some parts (crankset165,stem60)). Anything else operational maybe?

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