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How to measure frame size?

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How to measure frame size?

Old 05-22-24, 05:36 PM
  #26  
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Originally Posted by zandoval
Still chasing this as I have had a few young-uns ask about what size bike to buy. I agree that the most important measurement would be Effective Seat Tube Length. I would also say REACH from the ESTL would also be important. But of the frames I see advertised on modern bikes these measurements can be elusive. I have plugged in some numbers on some of the bicycle web site Bike Fit Algorithms. Wow... What a mess... No wonder people are spending the money for personal bike fitting.

I guess if I were going to buy or sell a frame these days these would be the some important measurements to include in its description.

There is no perfect math equation for this. The easiest thing is to look at the website of the brand and check the recommendations based on height.

In general, if the sizes are "classic", you can match things up like this:
5'4" - 50cm
5'6" - 52
5'8" - 54
5'10" - 56
6' - 58
6'2" - 60

This is roughly what you'll find on bike manufacturers' recommendations pages.
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Old 05-23-24, 02:08 PM
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Originally Posted by Iride01
Why not?

If you can measure effective top tube length then you know were to measure to for effective seat tube length.
With some bikes using extended head tubes for comfort, effective seat tube length hardly has any meaning now. My 58 cm H2 Trek Madone has not a single dimension that measures 58 cm, and using your method would designate it 60 or 61. About the only thing you can say about its size is, "It seems to fit like a 58 that was built in the late 1980s or '90s." My advice for riders who don't know where to start on sizing is to read the manufacturers' recommendations and geometry charts and know your basic body morphology. If your arm or leg length is not average for your overall height, understand that some models will be a difficult fit. Bike dealers are getting more sophisticated in sizing bikes to customers.
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Old 05-23-24, 03:03 PM
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Originally Posted by oldbobcat
With some bikes using extended head tubes for comfort, effective seat tube length hardly has any meaning now. My 58 cm H2 Trek Madone has not a single dimension that measures 58 cm, and using your method would designate it 60 or 61. About the only thing you can say about its size is, "It seems to fit like a 58 that was built in the late 1980s or '90s." My advice for riders who don't know where to start on sizing is to read the manufacturers' recommendations and geometry charts and know your basic body morphology. If your arm or leg length is not average for your overall height, understand that some models will be a difficult fit. Bike dealers are getting more sophisticated in sizing bikes to customers.
The OP has a bike from his/her teen years and wants to know if it's too small. It's thought by them to be a letter size, either X or XS.

My suggestion to the OP was that if nothing bothered them when riding it, then it really didn't matter whether it too small from what the manufacturer or other might suggest for the OP's current size.

The other stuff is just the usual bickering among the rest of us. I never stated that effective seat tube length is the one and only way to size a bike. It's just one of several.

The OP is 161cm and has a 72cm inseam. If it's a S or Small size frame, then it's probably the proper size or the OP is only a cm or two of it having been the correct recommended size. Still, to me, it doesn't matter what size it is. The OP either is able to ride it comfortably or is not able to ride it comfortably. Not anything different than those cyclist claiming to have properly size bikes but still can't seem to ride comfortably.
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Old 05-23-24, 04:29 PM
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Originally Posted by Iride01
The OP has a bike from his/her teen years and wants to know if it's too small. It's thought by them to be a letter size, either X or XS.

My suggestion to the OP was that if nothing bothered them when riding it, then it really didn't matter whether it too small from what the manufacturer or other might suggest for the OP's current size.
Yep, whether its a S or XS, it should still fit. Most women stop growing in their later teen years anyway. If it's still a concern, she should ride down to here local bike shop and get a 10-minute eyeball fit instead of asking a bunch of strangers who can't even see how she sits on the thing.
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Old 06-02-24, 06:52 AM
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I had a problem understanding Giants frame sizing. Im 510 but with relatively shorter legs for my height (29 inseam). There were three sizes M(57-511) M/L(59-61), and L(510-63) that could have technically fit

I ended up going with the M bc of my inseam and it seems to fit well!
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