Bicycle Mechanics - sloping top tube stand over height

Where is the stand over height measured on a bike with a sloping top tube?

I ask because I am contemplating purchasing a new bike over the net and can't really test ride one.

Thanks

I believe I've read that they take the average height of the top tube, which means measuring at the center of the top tube where most people tend to stand over their frames anyway.

Another I've heard is about six inches forward of the intersection with the seat tube.

Where is the stand over height measured on a bike with a sloping top tube? I ask because I am contemplating purchasing a new bike over the net and can't really test ride one.

Thanks

DO NOT GO BY STANDOVER HEIGHT.

Go by top tube but even then you should really test ride or atleast know what size you need.

Regardless of the correct answer though, you shouldn't be selecting a frame based solely on standover height. Virtual top tube length of a sloping TT frame is a much more important measurement to consider.

Another I've heard is about six inches forward of the intersection with the seat tube.
That sounds about right. It's where you would stand when straddling the bike.

The old, if naive, rule of choosing a frame size by standing over the bike and being sure you have at least 1" of clearance was based on a level top tube. A sloping top tube will let you pick a much larger frame and you are likely to have a way too long top tube if you size it that way.

Thanks for the responses.

I understand that the top tube length is more important assuming you can straddle the frame with some margin of safety. In the case of the frames I am comparing the top tube length is 0.4" different when comparing the 2" difference in sizes I am looking at. given the increased length of exposed seat post with the smaller frame this seems like it probably is close enough to not worry about. The larger frame would likely provide a more upright riding position, at least with whatever stem it comes with, which is preferable for me.

Maybe a better question is if a rider that wears 34" pants is cutting it too close with a mountain bike that has a 32.5" stand over height.

Thanks

Thanks for the responses.

I understand that the top tube length is more important assuming you can straddle the frame with some margin of safety. In the case of the frames I am comparing the top tube length is 0.4" different when comparing the 2" difference in sizes I am looking at. given the increased length of exposed seat post with the smaller frame this seems like it probably is close enough to not worry about. The larger frame would likely provide a more upright riding position, at least with whatever stem it comes with, which is preferable for me.

Maybe a better question is if a rider that wears 34" pants is cutting it too close with a mountain bike that has a 32.5" stand over height.

Thanks

DO NOT USE PANTS INSEAM.

measure your actual inseam.

you are setting yourself up for disaster. why can't you go to a local bike shop?

Maybe a better question is if a rider that wears 34" pants is cutting it too close with a mountain bike that has a 32.5" stand over height.

Yes, IMO, unless being very upright (handlebars above saddle) is a very important concern of yours. My assumption is that you, like most guys, wear pants that a generally an inch or two longer than your real inseam.

DO NOT USE PANTS INSEAM.

measure your actual inseam.

you are setting yourself up for disaster. why can't you go to a local bike shop?

I am looking at a bike from an online retailler that is not available from any of the local shops and trying to compare sizes with my current bikes. My current mountain bike is a 10 year old Gary Fisher Hoo Koo e Koo 19" frame, and it is about right or maybe a bit small, but I have not been able to find details on the frame geometry online, so I will take some measurements.

Standover height is from the ground to a level line through the intersection of the axis of the top tube with the axis of the head tube and through the seat tube.
The top tube length measured along the same level line is just as important.
Another reason I prefer a bike with a level top tube.
Al

I hope you aren't spending a lot of money because its very likely you won't get something that fits. As others already have said, don't use standover height or inseam (alone) as a way to size. If you have to do it online and can't test ride it first, at least use a couple on line guides.

Here's one. Do a search and find at lreast one more. Each varies a little.

http://www.coloradocyclist.com/bikefit#introduction

its very likely you won't get something that fits.

If you know what fits, it's very unlikely that the bike won't fit you. He has a baseline in his current bike so as long as he doesn't stray far from it's measurements (mainly just TT length), he should be fine.