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# How do you determine frame sz. these days?

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# How do you determine frame sz. these days?

10-23-07, 08:54 AM
#1
steve91562
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How do you determine frame sz. these days?

How do you determine proper frame size these days given the sloping top tubes of most bikes? Are the old formulas of .65 x inseam for c-c and .67 x inseam for c-t in any way relevant?

My inseam is about 86 cm and I've been sized on anything from 53cm to 56 cm. I know that there's a range of frame sizes most people fit, but is there a formula used now days for the sloping TT? Thanks.
10-23-07, 09:15 AM
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SEAtrain
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There are a number of online calculators that get you in the ball park. I like competitivecyclist the best because it calculates three different fit styles.

https://www.competitivecyclist.com/za/CCY?PAGE=HOME
https://www.wrenchscience.com/Store.aspx?stylecode=R
https://www.peterwhitecycles.com/fitting.htm
https://bikefitkit.com/bicycle_riders...t_position.php
10-23-07, 09:21 AM
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PhilThee
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They use the virtual top tube size when determining the correct size on a sloping/compact frame.
Check this out https://www.litespeed.com/bikes/2005/sizing.aspx

Wow an 86 inseam and they put you on a 56?
If your 6ft+ I'd think a 56 would be the smallest.

Just how tall are you?
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Last edited by PhilThee; 10-23-07 at 12:39 PM.
10-23-07, 09:29 AM
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PhilThee
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Originally Posted by SEAtrain
There are a number of online calculators that get you in the ball park. I like competitivecyclist the best because it calculates three different fit styles.
I like competitivecyclist and I liked wrench science before they changed it a bit.
I think it showed a bit more info before.Seems like it's geared more tward a sale now.
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10-23-07, 09:53 AM
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Zouf
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Most important measure is virtual top tube length, that's what drives most of the fit. You can move the seat up and down, but you can't cut or stretch the top tube... There is a bit of play with stem length, but not that much.

Second important sizing point is head tube length, in terms of how low/high the bars can be set relative to seat position.

I did my last frame selection based entirely on TT length; I came up with different sizes from different manufacturers, so don't stick on a frame size number.
10-23-07, 10:00 AM
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botto
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tt or 'virtual' tt.
10-23-07, 12:19 PM
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Zouf
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Originally Posted by botto
tt or 'virtual' tt.
Good point - virtual, otherwise it's whatever the manufacturer feels like that day.
10-24-07, 07:22 AM
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steve91562
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Originally Posted by Zouf
Good point - virtual, otherwise it's whatever the manufacturer feels like that day.
How do you determine what is the best TT length? Is there some formula one can plug in measurements? Or is it something done strictly by comfort?
10-24-07, 07:39 AM
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merlinextraligh
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^ It's the length that gives you the right extension to the bars, using a reasonably sized stem.
10-24-07, 11:11 AM
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PhilThee
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Originally Posted by steve91562
How do you determine what is the best TT length? Is there some formula one can plug in measurements? Or is it something done strictly by comfort?
Yes use these fit calculators.They are not the end all but mearly a guide.

https://www.competitivecyclist.com/za...LCULATOR_INTRO

With the wrench science one you have to join to get the info.It wasn't like that before.
You need to follow those links provided and fill out the forms.
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10-24-07, 01:48 PM
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kraftwerk
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It is a good question with no solid answer....

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