How to read geometry chart

[plandy]

I just copy and paste two different geometry charts. (just use them for references only ) Doesn't matter what model.

My problem is if the chart doesn't have the stand over height listed, it will confuse the hell out of me. Reason being that different bike models even listed as the same size ( for example 52cm for giant bike is different from 52cm Cannondale ) the cannondale will have a higher " stand over height ".
Many times, people usually ask how tall i am to figure out if the bike fits me or not. (I'm 5'9" with 30 1/2 inseam), but usually when people hear that I am 5'9" then they will recommend a size 54cm bike for me. The truth is, I can barely handle a 52cm. So knowing how to read a geometry chart without the " stand over height " listed will be a great help.

Someone please help me how to figure out the " stand over height" of a bike if the geometry chart doesn't have it on there. Thanks

g1.jpg

g2.jpg

[Louis]

The problem with quoting a standover height on a frame like this (the lower image) is that it varies based on how far fwd or back you're standing. With a horizontal TT bike it's a constant, so given the frame and wheel + tire radius information, a legitimate number can be calculated.

Good Luck

[mhespenheide]

Your point is exactly why most people on this board think of (effective) top tube length as the more important starting point for sizing a bike, rather than seat tube length. Compact frames mean that the seat tube length isn't nearly as meaningful as it used to be with horizontal top tubes.

And standover height can change not only with where you measure it fore/aft on a bike with a sloping top tube, it can also change depending on the size of the tires you are running.

The "best" sizing measurements are probably stack and reach, but they're pretty obscure to a beginner, and can need a little trigonometry to calculate if the manufacturer doesn't specify them.

[R3awak3n]

Originally Posted by Louis

The problem with quoting a standover height on a frame like this (the lower image) is that it varies based on how far fwd or back you're standing. With a horizontal TT bike it's a constant, so given the frame and wheel + tire radius information, a legitimate number can be calculated.

Good Luck

well the standover height on a compact frame should be measured on the effective TT line I would say.

The standover height, AFAIK, on the bottom geo would be stack + bb drop (BBH). approximately. however I don't thing stand over height really matters much, reach and stack, much more important

[cadence90]

As Louis points out, on a level tt frame standover will be the distance from the ground to the top of the top tube.

For a sloping tt frame, one could get close via two means:
A) Add BBH plus ETT (Effective Top Tube, the measurement from the bb center to the top tube center-line, parallel to the ground) plus half of the top tube diameter.

B) Add BBH plus Stack minus the dimension from the top of the head tube (where stack is measured) to the top of the top tube.

R3awak3n just beat me to line!

[R3awak3n]

Originally Posted by cadence90

As Louis points out, on a level tt frame standover will be the distance from the ground to the top of the top tube.

For a sloping tt frame, one could get close via two means:
A) Add BBH plus ETT (Effective Top Tube, the measurement from the bb center to the top tube center-line, parallel to the ground) plus half of the top tube diameter.

B) Add BBH plus Stack minus the dimension from the top of the head tube (where stack is measured) to the top of the top tube.

R3awak3n just beat me to line!

ahah, musta been seconds

[ultraman6970]

IMO u cant judge the size of a frame based in the stand over height, because if the BB is higher or lower and u are used to get frames based in the stand over height as a main measurement u can end up with the wrong frame size bike time. The same can happen if a manufacturer decides to get the front tube longer. u can end up in the wrong size, specially if the frame has sloping top tube as many pointed out.

Actually some manufacturers have the bad idea of posting the stand over height in their tables of sloping frames, if the angle of that top tube is ridiculously sharp, u end with the wrong size again.

Virtual top tube, reach is what you have to know how to read, many times the front tube will help you a lot.

Im talking of decently designed stuff here, if we go to wackly designed stuff you will find the weirdest sizes that I would advice you to run away from them because are really hard to fit aswell. For example some of the trek low end aluminum stuff or some wackly 6 foot tall front tube road bikes that really make my eyes hurt when i see them.

Hope this helps.

[plandy]

To my understanding, SOH refer to the middle of the top tube to the ground.
So it doesn't matter wether it's a horizontal or sloping top tube.
We want to know the height from middle of top tube to ground.
Correct me if I am wrong.
So knowing that if I can clear the SOH is very important to get a proper fit.

[cadence90]

Originally Posted by R3awak3n

ahah, musta been seconds

Yep. Micro-seconds. The width of a standover chart.

I was Zabel, you were Friere.


.
.

[cadence90]

Originally Posted by plandy

To my understanding, SOH refer to the middle of the top tube to the ground.
So it doesn't matter wether it's a horizontal or sloping top tube.
We want to know the height from middle of top tube to ground.
Correct me if I am wrong.
So knowing that if I can clear the SOH is very important to get a proper fit.

Then the only thing to do is know your standover, and ask for the SOH on every frame you considering, and hope that those people all measure SOH the same exact way (unlikely).

by Sheldon "The Long & Short Of It" Brown

Generally, when you see a single number listed as a frame's "size" that number refers to the length of the seat tube.

A further complication is that nobody knows how to measure a bicycle's seat tube any more. Even leaving the inches/centimeters question out of things, there is the question of where the seat tube ends:

• The old standard system was to measure from the center of the bottom bracket to the very top of the seat tube.
  
• Some manufacturers have decided that this is too easy, so now many bikes are measured instead to the intersection of the centerline of the top tube with the centerline of the seat tube.
  
• Some other bikes that have seat tubes that protrude farther than normal above the top tube measure as if they were measuring to the to the top of a seat tube with normal protrusion.
  
• Some bikes are measured to the top edge of the top tube, even though the seat tube protrudes higher up.
  
• Some bikes with slanting top tubes are measured as if there were a level top tube, they use the length that the seat tube would be if it was as high as the head tube.

Anarchy reigns; I know of one bicycle line that made a running change in the middle of the year. You could have two bikes of the same make, model, year and nominal size, but one was 2 cm larger than the other! The only way to know was to measure them.

An additional complication is that the height of the bottom bracket varies over a considerable range, typically anywhere from 10.5" to 13"! Thus even frames that use the same system for figuring the top of the seat tube may have widely disparate stand-over heights.

Bottom line: seat tube "frame size" numbers are nearly meaningless unless you know how they are measured!

.
.

[dave thompson]

Stand over height is probably the last number I look at when considering a frame, it's the least important.

[djdj]

If a typical road frame (I'm excluding trick and clown frames here) fits in other respects, the chances of having a problem with standover height are minimal.

If you want a rough idea whether it may be a problem, compare your saddle height to the seat tube length. If you would have a lot of seat post showing, standover height won't be a problem.

[Bob Ross]

Originally Posted by R3awak3n

The standover height, AFAIK, on the bottom geo would be stack + bb drop (BBH).

Wait, wouldn't standover height be stack minus bottom bracket drop, then plus one-half wheel diameter (including tire)?

[bobswire]

Originally Posted by dave thompson

Stand over height is probably the last number I look at when considering a frame, it's the least important.

[OtayBW]

Originally Posted by R3awak3n

The standover height, AFAIK, on the bottom geo would be stack + bb drop (BBH). approximately.

You mean BBH, not BB drop, right? They're two different things.

Originally Posted by plandy

To my understanding, SOH refer to the middle of the top tube to the ground.
So it doesn't matter wether it's a horizontal or sloping top tube.
We want to know the height from middle of top tube to ground.
Correct me if I am wrong.
So knowing that if I can clear the SOH is very important to get a proper fit.

Good advice already mentioned here: I think SOH is a red herring. I tend to evaluate effective ST length first and then ETT on a compact frameset. Better yet, get fitted - or have someone recommend a bike to you of the proper size and get fitted correctly - and you'll know whether you're comfortable with the SOH. Don't put the cart before the horse...IMO....