Compact frame dimensions?
 

Back in the day, top tubes were universally parallel to the ground (from head tube all the way back to the seat tube). The stand over height was easy to measure.

But with the advent of "compact frame geometry" (curse it to the hell where it so richly deserves to be), things are no longer so clear. Different manufacturers, so far as I can tell, measure standover in a variety of ways. This means that one brand's "56cm" frame has 32.5 inches of standover height, while the next brand's "60cm" frame has exactly the same. In other words, there is absolutely NO way for the consumer to tell from the specs whether or not ANY %^$^)(*&^%*&$#$%*&^(! compact frame will fit or not.

If you buy a frame that you can safely stand over where the top tube meets the seat post, you're in for painful surprises if you have to dismount close to where the top tube meets the head tube. Further, having a slanted top tube makes it nearly impossible to accurately measure the distance from the seat post to the head tube...

Now that I've finished my rant, allow me to ask pertinent questions:

1. How & where is the standover height supposed to be measured for a compact frame?
2. How does one assess CF top tube length without a jig and bubble level?

As to relying on manufacturer's specifications, I've found them to be not only unreliable, but also to have no consistent match between manufacturers. Unless I can learn to discern what the specs mean, I'll never, ever even consider another compact frame.

Two words, stack and reach.

For some reason different manufacturers measure their frames using different standards. Even on conventional frames with level top tubes this has been a problem. With some manufacturers they measure from the center of the crank to the top of the seat tube, some measure from the center of the crank to the top of the top tube, and others use the center of the crank to the center of the seat tube.

With a compact frame, I look for the standover height, AND the effective seat tube height. The effective seat tube height is the height that the seat tube would be if the top tube was parallel from the head tube to the seat tube.

While I don't own any right now, I have been thinking about trying a compact frame to see if I can improve on my standover height probem, since I have short legs and a long torso. 56cm, frames usually have the top tube length I need, but the standover is a bit long. 54cm frames usually have a good standover for me, but the top tube can be too short. I'm thinking I need to try some compact 56cm, which should get me into a good length top top at a lower standover height.

You're making this overly complicated.

No matter what, a compact frame's standover height will be LOWER than a standard frame of the same size. So you cannot lose compared to a classic frame and the only question is how much you can win.

In any case, it frees people from worrying over standover height unless they have specific issues like problem hip joints that limit what they can step over (not stand over). It also means that we are free from trying to hit a narrow target between the limits of short seat posts and standover clearance.

The long posts, combined with sloping top tubes means that we can focus on the actual issues of fit, including head tube height and saddle to stem length, which is measured in the classic way - parallel the the ground from seat tube (or post) to the steering axis whether it's the head tube or stem.

As far as standover height goes, I'd take it at the center (or so) of the top tube, which is about where one is likely to stand over it. More info might be useful, such as the height of the tube a the seat tube (frame size in many, but not all cases) and head tube height, but standover height is unnecessary unless one is in that minority for whom it would be an issue.

Standover height always was a crude way to measure frame size even before the advent of compact frames. This isn't a new issue. I currently ride a frame that is 4 cm smaller than the frame of my first good road bike, and my current bike has a level top tube just like that first one. The point is finding a bike that is comfortable. I did a couple of very fast centuries on that first good road bike, under 4 hours and 15 minutes. I won a national level time trial on it. But it would probably be too big for me now, I can't stretch out the way I could then, because that was the only way I could be aerodynamic on my old bike. There is nothing wrong with a sloped top tube, it can help riders with short legs and long torsos fit on a bike. It just means that you have to do a bit more research when you look for a bike

OK - Now I'm confused. "Stack Height" according to Sheldon Brown's site it the vertical space taken up by the headset. "Reach" is the extension of the stem. How do these affect standover height in any way?

OK virtual top tube length = reach, the length between, as if the top tube were level .

Jig? I Dont care what Music you Dance To, as you run a tape measure between, the axis center line of the fork and seat Tube/post :lol:

Stack and reach no longer have the same meaning. What you are interested in is the position of the handlebars relative to the saddle once you have figured out where your saddle position should be relative to the bottom bracket. Then you need figure out whether the handlebars can be adjusted to a comfortable position without having too many spacers under the stem or having to have a stem that is unreasonably long for the frame size

I won't argue that, but a simple tape measure would quickly reveal both the standover height AND the top tube length. Not quite so simple with a compact...

I will argue this. Since manufacturers measure differently, there is no way to "do a bit more research." It's like comparing apples to toilets! The manufacturers specs are random numbers with no relationship to anything outside of that individual manufacturer's specs. Yes, IF one can visit dealers and try the bikes in person, a fit is possible, but when buying over the internet (as so many do these days), the potential to end up with some misfit that you never anticipated is HUGE. Even if you do ride the bike before buying it, assuming that you can change a few bits to make it fit "right" after the sale is no sure thing with compact frames. To add sewage to the pot, the advent of "compact rear triangles" adds even more unexpected changes to the steering...

I am sorry, but if you look carefully at any frame geometry chart you can figure out which size will be the best fit, no matter whether the top tube is sloped or level. The thing you have to factor in is head and seat tube angles. Seat tube angle in particular will affect where you have to locate your saddle. Once you have done that, everything else falls into place

Thank you - That makes sense. The last frame that fought me to insensibility needed a "riser stem" to get the height right. THEN the reach was so excessive that I'd have needed to reverse the stem to use the bike at all. Without an extreme "set back seat post," my knee was a few inches in FRONT of the pedal spindle at the 3:00 position of the cranks. All this despite the fact that I could barely stand over the compact frame. The thing handled like a pig too.

This was the second compact frame that I've not been able to fit on. The first was selected by the bike dealer for me (supposedly a 60cm, which I couldn't stand over). The second was a CL find, but it could at least be stood over. Neither were ever comfortable. This may be less than fortuitous circumstance. I understand that many love the compact frame geometry. I still, however, find it confusing, less than consumer-friendly, and FAR more difficult to fit to the rider than older frame styles.

Ah - but many manufacturers do not provide frame geometry charts.

Well then, if there is no frame geometry chart, don't buy that brand of bike unless you can try one first

Sometimes they may be hidden away, but as someone who has done quite a bit of online bike shopping the last five years for myself and my growing family, the only times I can recall *not* being able to find geometry charts for road and mountain bikes has been for very small boutique or custom frame builders...

Walk int the LBS we have a tape measure on hand already .. a Cloth Tailor's tape is a Small Investment, and are Fractional and Metric marked

For some, you're right. But for what is currently the biggest bike seller in the USA (Electra), no geometry is given. I'm not considering another Electra just now, but I'd like to be able to compare, for example, Trek, Raleigh, and maybe Giant without getting confused. Not so easy as one might suppose...

When you asked "Trek, Raleigh, and maybe Giant" how they measure stand-over height, what did they say?

With "compact" frames, standover height is less of an issue. Proper fit is accomplished by adjusting the seat post height, elevation of the handlebars with respect to the seat height using various stem angles and steer tube spacers, and distance from the seat to the handlebar via various stem extensions.

It seems to be his wont. ;)

With Electra (why bring them up if you're not considering one??) it's just as well, since their crank-forward/"flat-foot" geometry won't compare directly to other bikes anyway. If they're truly the biggest bike seller in the USA, it shouldn't be hard to find a store and try one out.

I just checked, and Trek, Raleigh, and Giant all provide geometry data, so that complaint is out the window. They even provide standover height and effective top tube lengths (the horizontal measure from the head tube to the seat tube), so there ya go. You *can* compare these directly with the classic bikes of old. :thumb:

Some random links:
Shift 1 - Trek Bicycle (click "fit and sizing")
Envie Advanced Tri (2015) | Giant Bicycles | United States
Raleigh Bicycles - Detour 5.5 (click "size guide")

The Trek, Raleigh, and Giant dealers say they don't rely on the factory measurements at all, but rather deal with it on a customer by customer basis. But the last time I let a dealer "fit" me to a bike, I ended up with one I couldn't stand over, except on my tip-toes. At the time, I didn't know enough to object - I assumed that this must be standard any more. I tolerated that bike for an entire miserable year before I got fed up with it and sold it.

I'm guilty as charged of over complicating things, but in this case, my gripe is legitimate. It may be that in theory "...with compact frames, standover height is less of an issue," as Mr. John D. Thompson says, but in my experience, it's just the opposite. I strongly suspect that I'm not alone.

Since I'm in the minority here, though, I'll shut up about it.

You can always ask them:
Support | Electra Bikes

I've e-mailed companies in the past about geo specs,and so far have always gotten answers.

Not even close.

You may be right, but their web page advertises otherwise.

Well, I don't think anyone's saying to "shut up about it", but I think there are still some misconceptions at play.

Standover height is measured fairly consistently -- almost always from the midpoint between head tube and seat tube, and in the case of Surly, they'll even throw in the tire diameter used when measuring.

It makes sense for a dealer to make an educated guess as to frame size and then try you on bikes they have on hand, rather than taking specific measurements of you and running to their charts first. The factory measurements and geometry charts (weren't you just asking for them?) are invaluable for those of us doing our own research at home. I know through trial-and-error that 32.75" is about my limit for standover, so it's easy to use that when looking at bikes online.

I would still imagine that your standover issues would have been worse on a horizontal top tube frame with the same geometry -- the dealer probably tried to get you onto the bike that would fit and handle best while riding. There is never a time when you need to stand over the top tube with both feet flat on the ground.

Yes, there are some misconceptions. Kona measures standover at the seat / top tube junction: KONA BIKES | 2015 BIKES | TRAIL 29" HT | UNIT

Raleigh doesn't say how they measure theirs - they only give a rider height to recommended size chart (ignoring limb length): Raleigh Bicycles - Revenio 2

Trek gives a measurement to somewhere closer to the seat than the steerer tube, but doesn't quantify where: Madone 7.9 - Trek Bicycle

Giant gives a stand over height, but doesn't say where it's measured: Avail Advanced SL 0 (2015) | Giant Bicycles | United States

Specialized gives a stand over height, but doesn't say where it's measured: Specialized Bicycle Components

Felt gives a stand over height, but doesn't say where it's measured: Z2 - Felt Bicycles

Bianchi doesn't even specify a stand over height: Cortina | Bianchi USA

These are the first I looked at and they were at random. NOW do you want to tell me how consistently standover height is measured? Not a SINGLE manufacturer specified any such thing as "from the midpoint" of the top tube.

chasing rainbows.

Surly and Soma use the midpoint of the top tube, and Trek's measuring point is close enough to it if you ask me.
ECR | Bikes | Surly Bikes
Soma Fab Double Cross


Kona seems to expect that if you're going to stand over the frame, it'll be right in front of the saddle. I think that's fair. Perhaps the other companies on your list would share more about their standover measurements if you asked them.

Looks like I was wrong about how consistent manufacturers were in measuring standover, but I'd stand by a second pass answer of "somewhere between the top tube midpoint and in front of the saddle, where you are likely to stand over the frame" -- if that isn't enough to go by after adding the traditional inch or two, it's a good sign that you should be trying out bikes in person and insisting on what makes you most comfortable before handing over your money.

You're right, sir. I agree completely.

A few comments.

If one is frustrated by how bike manufactures label their geometries then either measure all their bikes yourself and make your own charts or create your own brand and label the geometries the way you think is right. This issue is really one for those who shop without trying. I don't accept the excuse of "at the last shop I had fit me I ended up on a bike I couldn't stand over". Bad fitting session/communication, not bad geometry information. This is why the LBS is the best source for information about how a bike feels. That's the only place you can touch, stand over, ride BEFORE buying. This should be worth a lot, but is discounted frequently because in the interweb age we are all experts...:)

Manufactures measure their geometries differently because they can, like tire size labels. It makes exactly what the OP is complaining about happen, the on paper info isn't completely transferable between brands. The brands that sell through (the listed Raleigh, Trek, Giant and most others) the LBS chain really want their potential customers to go to their dealers. For better or worse this is the distribution model they have invested in.

Stand over can be measured at the front top point of the top tube. This is a more realistic location for human parts to be located near then the middle of the TT. Remember that the seat takes up some of the TT length then there's one's butt and body before the front equipment is going to touch a TT. Lastly when dismounting it's common to lean slightly forward, further bringing the human parts close the front of the TT. Now not all brands do this measurement this way, just saying some do for a reason.

While stack and reach (the new/current dimensions) do describe a better set of fit aspects they don't speak to the seat/pedal relationship at all. If one has a good grasp on the classic geometry data these two new ones don't add more info. If one doesn't have a good grasp of classic geometry data then these two alone aren't going to insure a good fit.

Not directly mentioned yet (but alluded to indirectly) is BB drop. A large drop (or low height) VS a shallow drop makes a big difference in how "big" the bike fits.

One of the advantages that was trumpeted when the current wave of sloping TT bikes came about (and I say current because any student of bike history knows that sloping TTs have been around for 100+ years and were the standard a century ago) was the increased frame stiffness. Maybe an issue for the taller sized bikes (and I even question the stiffer is better claims) but for the sizes that I ride stiffness isn't the issue. Fitting a second water bottle, or rack, or seat bag is. Andy.