# How to measure top tube length?



## Damitletsride! (Oct 19, 2007)

I got my new frame delivered, and the top tube is shorter than i thought it would be by 2cm. How do most manufacturers measure it? I assumed it was center of seat tube to center of headtube. 

Thanks, Mike.


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## TurboTurtle (Feb 4, 2004)

Damitletsride! said:


> I got my new frame delivered, and the top tube is shorter than i thought it would be by 2cm. How do most manufacturers measure it? I assumed it was center of seat tube to center of headtube.
> 
> Thanks, Mike.


You are correct unless it is a 'compact' frame where they might give the 'virtual' which would be center of head tube at the top tube juction to center of the seat tube (or seat post) staying level (not at the seat tube - top tube junction). - TF


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## Damitletsride! (Oct 19, 2007)

I see, as if there were a spirit level running along the top of the bike from the head tube. Yes it is a slight compact design. I was a bit shocked when i measured up the frame though.


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## C-40 (Feb 4, 2004)

*horizontal TT length...*

The only TT length that should ever be used for comparing the fit of a frame is the horizontal TT length. Sloping frame geometry charts sometimes list both the sloping and the "virtual" or "effective" TT length. These terms are misnomers for horizontal.

When comparing the fit, both the TT length and the seat tube angle must be considered. Steeper STAs make the reach longer by about 1cm per degree.


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## Richard (Feb 17, 2006)

C-40's right, but I wouldn't call "effective" tt length a misnomer.

On my sloping tt 56cm Masi, the tt measures 55cm. But the effective tt is 57cm, making the bike fit the same as my "classic" (i.e., horizontal tt) 58cm steel bike.

So, "effectively" speaking, they're the same size.


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## Kerry Irons (Feb 25, 2002)

*Specialized bikes?*



C-40 said:


> seat tube angel


Does this seat tube angel have anything to do with the Specialized angel (seen at bike races) and does this angel do something to protect your seat tube from the devil? Inquiring minds want to know


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## Mosovich (Feb 3, 2004)

*I strongly agree with C-40*

I purchased a new bike that was 1//2 a CM longer TT thinking that it would be no big deal WRONG! So far I've switched to a 1 CM shorter stem and still feel stretched out! I got the saddle dialed in perfectly just like I did on the other bike, making sure my knee was over the spindle, etc. and the bike is just too long.. I'm very discouraged.. Now, my cross bikes are 1.5 cm shorter, and feel perfect, almost like the road bike that was 1/2CM shorter than my current road ride. So, seat angle and head angle mean alot.. Problem is, on higher priced model bikes, you can't test ride a frameset..


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## Damitletsride! (Oct 19, 2007)

Thanks, all of this is starting to make sense. Well after reading this i decided to bite the bullet and get my new frame built up.. instead of sending it back to the shop. It is 2cm shorter than my older ride ( a bianchi ) but i'm convined its the right size now. ( i was measuring it wrong lol). It's a principia revolution frame set, stealth black colour combo. Can't wait now


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