https://inventors.about.com/library/i.../blbicycle.htm

These people were visionaries, the rest of us are just expressing ourselves thru a particular style.

You noticed that too ? I just didn't want to be the one to point it out.

but the OP is talking about buying a high-end frame. high end track frames have track geometry. i agree that there are a lot of FIXED GEAR frames that have very close to road geometry, but those are generally not really high-end frames.

p.s. how straight the top tube of a bike is has NOTHING to do with geometry.

as for a chain tensioner, it in no way creates inefficiency in the drivetrain, that is a myth. a "direct drive" is a rod-driven bicycle, has nothing to do with bicycles who use chains. the OP has also mentioned that he wants a single speed, NOT a fixed gear. they are two different things; one of which a tensioner is totally acceptable for, the other of which it is not able to be used. furthermore, eccentric hubs are HEAVY. my rear hub plus the tensioner weigh less than a WI eccentric hub would. i also do not have any additional links in my system. the tensioner simply takes up the excess slack in a different way than the eccentric hub does.

i think top tupe angle has a little to do with "geometry." granted, it doesn't necessarily affect the headtube angle, fork rake, or wheelbase, it will certainly affect the ride quality, as the more level the top tube, theoretically, the less flex between seat tube and head tube than a downward sloping tube.

for an exaggerated example, consider two bike frames, made of identical tubing, with identical wheelbases, head tube angles, and fork rakes. (and we'll assume same size frames for equal centers of gravity). one of these frames is a standard mens frame with horizontal top tube, and one is an old school womens step through frame. (for sake of argument, we'll say that both tubes are straight, as if it's just a VERY sloping top tube.) All of the components are the same.

I'd wager either of these bikes will feel/ride noticeably different from the other...

if it affects the ride quality of the bicycle, and it's directly attributed to the geometry of the tubing, i think it's fair to consider it a part of the frames geometry.

and OP:
Well, that's the abridged version of the quote, and some points I'd like to comment on.

Your exuberance toward fixed gears and single speeds is certainly appreciated, but patience, young grasshopper. your torrid love affair with FGSS will soon pass, and you wont want to fix everything that moves. your relationship will blossom into a more stable, practical endeavor.

-changing out single speed freewheels is about the same as changing out a cassette on a freehub: either a cassette removal tool, or a freewheel removal tool. one tool vs the other, and neither method is particularly labor intensive.

-internal routing does look cleaner, but by running a single-speed, you're inherently limiting the top speed of the bicycle, and putting a cap on how much of an advantage it is. Aero advantage on the road really only comes into play when racing (when not racing, an aero disadvantage can help training, like swimmers not shaving til race-day), in which case, you'd be on a road bike. Aero advantage on a track is good too, but in that case you'd be riding a fixed gear with no cables to route anyway.

-carbon may be lighter than steel or aluminum, but weight is the biggest factor when climbing. by not running gears, you're putting a limit on the overall climbing ability of the bike.

-Even with track dropouts, with some time and practice, centering the wheel requires virtually no effort. it's not a big deal. really.

-i forget who said it here before, but they quoted a song that went something like "not doing something because it's popular is just as lame as doing something because it's popular." this applies here. at the end of the day, you should be riding your bike because of how it feels riding your bike. when you're sitting on it, you really don't have to look at it all that much.

ride what you like riding. if that really means riding something that looks a certain way, then fine, but if you ride your bike, you might find that many of these roadie vs ssfg differences do serve a functional purpose beyond asthetics.

[/novel]

no, any upslope up to about twenty degrees will be stiffer and lighter than level, not theoretically, in actuality.

seejohnbike, I think the guy responding to my post is confusing straight vs flat top tube line. Of course the top tube itself is straight, but whether the tube is level in relation to the horizon is what I was referring to. And the top tube is part of the frame's geometry as it happens to be like you indicated effected by all other dimensions of the frame.

Wearyourtruth: As for chain tensioner inefficiency, I subscribe to it, whether you do is your belief:

https://en.wikipedia.org/wiki/Single-...ain_tensioning

"If neither of these are an option, when working with an existing frame not originally designed for single-speed use for example, some kind of idler pulley, such as the Surly Singleator[3] , can be used to take up chain slack."

Just me, but running a chain thru the tensioner, there is additional friction, friction = resistance, you can't tell me that with that resistance, that no matter how minute the inefficiency is, it is occurring. And not a myth when compared with a system that has no tensioner in the drive line. And if we go by a direct drive definition that you indicated, I'll disagree with that definition as there wouldn't even be a drive shaft, it would be 1 or even 2 gears interfacing at the tooth level with nothing in between, shaft, belt or chain. I say 1 gear, because a unicycle is a direct drive. 2 gears interfacing with each other to drive the wheels is a true gear driven drive train. Otherwise there is a shaft drive with universal joints in between, or a belt or a chain that can have derailers and tensioners involved.

ah. good catch.

That makes sense and even getting out the yardstick, as the closer to forming a 90* angle with the seat tube and or head tube the top tube is a shorter length. But what are we talking there, 1/4" of top tube ? Hard to measure or describe how much stiffer or what the feel translates to the road, but it's a "jnd" or so (just noticeable difference) ?

the tubing length difference around the two triangles could be a foot. at the end of the day, its all rider.

Not necessarily ? I'm thinking the triangles of the rear tires are/could still be welded and designed relatively independent of the main triangle, which may not even be a triangle if there is any 4th side, it's then a trapezoid.

https://www.bikemania.biz/ProductDeta...Merry_SomaRush
https://en.wikipedia.org/wiki/Trapezoid

Parallel sides being the seat post and head tube.

if you make the top tube horizontal, you wont have the seat stays seven inches lower.

if you make the top tube meet seven inches lower on the seat tube, youre not going to put the seat stays seven inches above that.

your trapezoid talk is inane.

Haha. Of course Ill ride it because of how it FEELS. Riding it becasue of how it looks is obviously secondary. But the FEEL of the RIDE is given. At least to me. No one rides a bike that doesn't feel good....unless its their only one or they're just tryna look cool.

But thanks for those good points. The centering of the wheel for me is more an issue of patience.

And just to comment on the debate about top tubes......I don't like sloping top tubes lol.

But whatever.

THanks again.

..

The Trek District Carbon, I think, is what you're getting at. Madone framed single-speed. If money were no object... Ah well. I can dream.