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PostPosted: Thu Dec 16, 2010 9:49 pm 
Retro Guru

Joined: Sat Aug 13, 2005 2:59 pm
Posts: 2253
Location: Bridport Dorset
how do i workout what would be the correct size roadbike frame for me? do i go by standover height or what is the best way?
had a 23" Peugeot frame which seemed ok to ride but was way too tall on standover.


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 Post subject: frame size
PostPosted: Fri Dec 17, 2010 12:11 am 
Retro Guru

Joined: Wed Nov 04, 2009 9:57 pm
Posts: 641
Accepted old fashioned way is -----
inside leg in stocking feet -- XX inches
frame size is XXinches - 9 1/2 inches
so 32 inside leg would be 22 1/2inches.
tip of saddle is usually set 1 3/4 to 2 inches behind centre of the bottom bracket
stem length is usually 11cm
or, arm length from elbow to tip of finger , from front of the saddle to rear of the handlebars ,plus 1 inch.


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PostPosted: Fri Dec 17, 2010 7:08 am 
Devout Dirtbag
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Joined: Tue Jul 21, 2009 5:27 am
Posts: 100
Location: Sydney
Never heard of any of those ways, but then again, I've never used imperial measurements.

On a roadbike you should aim to have around 3cm standover clearance, but that's only for safety, so you can comfortably stand at the traffic lights, etc.

For calculating frame size and seat height, I like the simple Greg Lemond formulas:

a. Your centre-to-centre seat tube will equal (inseam x 0.65).
b. Your centre-to-top seat tube will equal (inseam x 0.67).
c. Your bb-saddle height will equal (inseam x 0.883).

There is also a rather detailed calculator available online at Competitive Cyclist. There are lots of explanations too. However, I find that the Eddy fit and the French fit given on this website are too big for me.

All this is for proper traditional frames though. Modern "compact" frames are designed to get everyone to fit on just 4 frame sizes. It's a way of cutting costs for the manufacturers. The seat height calculations are still good, but the rest of the calculations are a waste of time if you intend to ride a compact frame.


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PostPosted: Fri Dec 17, 2010 10:02 am 
Retro Guru

Joined: Sat Aug 13, 2005 2:59 pm
Posts: 2253
Location: Bridport Dorset
i will just be looking for a cheap bike to build as a singlespeed commuter,so wont be too modern. thanks for the tips.
Pug is way too big and i thought it was!


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PostPosted: Fri Dec 17, 2010 10:41 am 
Old School Hero

Joined: Wed Aug 11, 2010 4:54 pm
Posts: 165
If you are a 32 inside leg for a traditional size I would look out for a 56cm with sensible angles and clearences.I strongly disagree that online calculators can give accurate set ups and should only be used as a guidline
Sombody showed me a photo of a famous sportsman the other day having a pro fit, I nearly wet myself laughing at the end result


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PostPosted: Fri Dec 17, 2010 11:21 am 
Retro Guru

Joined: Wed Dec 10, 2008 9:19 am
Posts: 2095
Location: Sheffield, top city
top tube centre to centre is the clincher. Saddle height is altered via the seatpin length. For top level pros where handling is critical, that is their prime measurement.

Unfortunately, these days, seat tube has become the prime measurement cos we all want the amount of saddle sticking out to look right.
Consider this .. a short frame with a long stem will handle totally different to a long frame with a short stem. Its all about weight distribution on the front wheel. One might descend like a breeze - the other you will be fighting it. However, if youre pootling around on flatlands or just commuting, it probably wont matter. For me, where the majority of my rides are in the peaks, it makes a helluva difference.


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 Post subject: Frame measurment.
PostPosted: Fri Dec 17, 2010 12:12 pm 
Retro Guru

Joined: Wed Nov 24, 2010 4:38 pm
Posts: 1468
Location: The Lovely Lincolnshire Wolds and by the sea in Sussex
I agree with the traditional way...standover height is nonsense (ok not nonsense it you just a casual cyclist on a roadster type bike).

For the enthusiast cyclist with/or wants a decent bike...go the traditional route.

No pro or a"cat"amateur ever worried about standover height.

Compromise is the handmaiden of mediocrity (Henry Royce).

Roadking.


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