Cyclists - does compact geometry matter?

[dd74]

Here is a Trek OCLV 120 Carbon:


and here is a Giant TCR Composite 2:


The Trek is traditional, the Giant has a sloping top tube - or what is also called "compact geometry." Both bicycles are carbon fiber, use similar Shimano components, and cost about the same. Their weights are about the same.

The notion of a compact frame, however, is what interests me. For those who might know, is there a noticeable difference between a compact frame and a traditional? I've heard the idea of the compact frame is simply to produce less frame sizes to fit more riders of varying height. That aside from this, which is decidedly a marketing scheme, one bike handles, accelerates, climbs and stops as well as the other when both are similarly equipped.

Does anyone here have any real world experience with a compact frame and can compare it to a traditional frame?

Thanks.



PS: ironic, isn't it, that my 11,000th post is bike and not Porsche-related.

[nostatic]

The mtn bike world has been making "compact frames" since the 80's. The main advantage there is increased standover clearance. That is a very real advantage for technical terrain. The other claimed benefits (from the road community) is a stiffer front and rear triangle (shorter tubes) giving better acceleration. The longer seatpost can give some extra compliance over bumps, but you also have to have a more robust post lest you snap it.

Beyond that, there shouldn't be a difference (assuming the other geometry measurements stay the same). In the end for the road I think it comes down to looks and maybe a few ounces.

[turbo6bar]

I prefer the traditional frame, because the top tube is a great seat while waiting at stoplights.

[John Rogers]

I would think the use of the bike would decide which type of frame to buy. If you were to do a lot of moutain road racing where you are sitting down and working hard with the bars and pedals, then I would want the larger frame and shorter seat post to reduce flex. On the other hand, for criteriums and short circuit races the small frame would probably be better since you will be sprinting a lot while out of the seat. For just plain fun riding, it would make no difference I suspect.

[argonaut]

Finally a topic I feel qualified to contribute to! I have been in the bike industry for quite a while. I think Nostatic is right on with his input.

Additionally, while there is nothing inherently wrong with compact frames, I do have a problem with manufacturers selling them as fitting a larger number of riders. This is simply manufacturers cutting their tooling costs and passing the disadvantage down to the consumer. Standover height is a terrible way to fit frames. Cockpit length is cockpit length, no matter which direction the tubes connect. Get a bike that fits, less compromise the better.

I get the opportunity to ride a wide variety of bikes for work. I would say with the prevalence of carbon fiber, engineering and construction will have a much bigger impact on how a bike feels than frame style. I would go with the one that you feels best, 'eyes closed'.

[BGCarrera32]

I can't ride compact geometry in a road frame; I have a tall torso and average leg length. So by riding compact geometry I might have a 55 seat tube and a 54 top, which causes me to need a 135-140mm stem at the bars which is too long in my opinion. It screws up the balance of the bike when cornering and in a sprint. If I have a 55/55 and can run a 130 mm stem with the correct steerer tube geometry, the balance is much better. Not something the average rider will notice on a 30 mile occasional ride perhaps, but the Cat 3 on up definetly starts to pay attention to.

Think of it like 50/50 balance in a road car, and with compact geometry (in my case anyway) there is too much weight shifted over the front end of the bike.

You might consider being fit by a custom frame builder, or a pro shop has a size-cycle. The average bike shop has kids working there who although may ride a lot, can only tell you what feels good to them, not necessarily what is right for your body measurements.

[argonaut]

I disagree. Compact and standard frames do not really dictate fit. Measuring the actual tube lengths on different frames is a bad way of sizing a bike, and the reason people freak out about compact frames. You have to measure like-for-like. If you measure the length of your top tube on a standard frame on the horizontal, you need to compare that to the 'virtual' horizontal top tube length of the compact frame. Otherwise you are looking at different angle in relation to the seat tube.

Another way of thinking of it. Curved vs straight bladed forks. You can achieve the same steering geometry either way. Its just how the tubing gets from point a to point b that changes.

[nostatic]

in the case of forks though, the way the tubing gets from point a to point b does matter since the blades have significant flex. For a tube that is joined on both ends, I do agree that it is less of an issue.

Also, note that I didn't say anything about fitments when talking about standover...only that mtn frames went to a "compact" geometry (ie sloping top tube) to get more standover for confidence in technical terrain. Fit is a somewhat complex mix of a lot of variables on the bike including top tube length (usually measured as parallel to ground, no actual length of the tubge), stem length and rise (or drop), seat setback, and crank length. I'm a big fan of Grant Peterson's emphasis on ground-to-pubic bone as a "critical measurement" of the body, and then matching that to a saddle-to-peddle (at bottom of spin) length.

[island911]

Originally posted by nostatic
. .. The other claimed benefits (from the road community) is a stiffer front and rear triangle (shorter tubes) giving better acceleration. . . .

Yeah, that is wrong.

edit . . .for the same wall tube, the larger triangle will be stiffer. Though, torsion may be improved, w/ shorter tubes . ..but that not the triangle stiffness.

[argonaut]

Originally posted by island911
Yeah, that is wrong.

edit . . .for the same wall tube, the larger triangle will be stiffer. Though, torsion may be improved, w/ shorter tubes . ..but that not the triangle stiffness.

Yes! That is a great point. I think that some mfgs have used compact geometry as a cheap short cut to lower frame weights without informing consumers of the drawbacks (why would they). Its left to shop employees to try explaining the difference to a customer. Hence the mass confusion and varying opinions on the subject.

[dd74]

Unless I'm reading Island incorrectly, he brings up a point that goes against all the advertising about compact frames being stiffer, because with the sloping top tube, the triangle is smaller, right?

I ride an '02 Lemond w/ Reynolds 853 tubing. It fits somewhat poorly on me, even as I have a long upper torso, which is whom the frames are designed. Nevertheless, I'm fairly much a steel guy. My previous steed was a Colnago Super with SL tubing - best riding bike I've ever had.

What I'm truly looking for is a Colnago that is similar to my old Super. I love the head and seat angle, and have been looking at the latest Colnagos - but my God. They're PRICEY!

I've only entertained a carbon and/or titanium bike because they're a bit more common, and a lot less expensive than steel. There are other steel producers out there, but I have no idea if they're quality manufacturers. My Colnago easily has 100,000 miles on it.

I've also seen compact steel bikes; Bianchi makes one.

Any advice, guys? Also, what steel tubing is favored amongst you?

[island911]

Cyclists seem to be the biggest engineering misunderstanding marketing-fed messed-up group in the world.

When I teach, I always ask if any are cyclists. Then we go in to the whole "strongest material per weight" disscussion. That of cousre splinters into stiffness per weight, and then toughness per weight . .. and finally stifness due to geometry. (structures & statics)

So here again, in our example, cyclist grab hold of some marketing re-speak, of some kernel of truth, uttered by an engineer, somewhere -- "stiffer when shorter triangle legs."
Well, at the consumer point, all details are lost . .. WHAT exactly is stiffer? . . . the triangle? . . . the twist? . . .AND, is it stiffer per weight, or just plain stiffer.?

Be careful out there. Marketing does bad things to engineers words. --- beyond the bad things we do to them ourselves.

[argonaut]

Originally posted by island911
Cyclists seem to be the biggest engineering misunderstaning marketing-fed messed-up group in the world.

The cycling industries total disregard for established terminology doesn't help. The word monocoque is my personal favorite. Generally this is perverted for any carbon frame that does not have lugged construction. Monocoque is the opposite of a truss frame, not just something made from one piece or all in one mold. Most modern aircraft fusealges are monocoque, but nobody in their right mind would believe a 747 made as a single piece. Most any bicycle you see at your local dealer is a truss.

Perfect example of this: http://en.wikipedia.org/wiki/Monocoque

quote
-----
"Some racing bicycles are using carbon fibre Monocoque diamond frames, in order to reduce the overall weight of the vehicle."
------
end quote

Just because a single tube is a monocoque doesn't mean an assembly of them is.

Not a monocoque.

Monocoque for the most part.

Sorry for the rant.

[krichard]

Screw compact vs. traditional, get one that is so comfortable you will never own another bike period:

http://www.softride.com/product.asp?p=14

[turbo6bar]

Originally posted by dd74
Any advice, guys? Also, what steel tubing is favored amongst you?

What about custom steel in your preferred geometry?

Search roadbikereview.com "frames" forum for plenty of custom steel builders at reasonable prices. I know there are plenty of choices in the sub-$1500 range (several under $1000). I was considering this last year, but I ended up grabbing a cheapo used Serotta Ti. I'll ride it for a while, but I do believe the next one will be steel.

Can't help you on the tubing choice.

[Mojo]

I don't think carbon will go 100,000 miles nor will aluminium.
Get a good 853 reynolds or ti bike, make sure the geometry works for
you, and off you will go a happy camper, oh ya Ti is great it dosen't rust

[dd74]

Monocoque has me baffled to the point that I think of it as just another ploy. So yes, Island and Jason, I'm being very fastidious, and knew I should pose questions here first before on a cycling forum - the brain trust of engineers and cyclists is very beneficial.

Turbo6 - yes, I've been thinking along those lines. I'm taller and bigger since my Colnago days, though still, that bike fits me better than the LeMond, and the Colnago is 21 years old. What do you think of the Serotta ti. I never knew they were American built.

Seven is the only personal framebuilders I know of that are truly touted here in L.A. But I've seen Steelman and others.

I found this link which shows a list of the frame builders in the U.S. Can anyone recommend anyone from this list?

http://www.sandsmachine.com/fbplist.htm

[JavaBrewer]

Good God...ride a few bikes and pick the one that talks to you. In the end it all comes down to your lungs, legs, and courage. The two best bikes I've ever owned were an 80's Land Shark (crit bike) and a mass produced Trek 2300 alum/cf combo bike. There alot of good all-round bikes but if you're looking for the best then you need 3 bikes... a crit bike, a distance bike, and a climbing bike.

[dd74]

Originally posted by dmoolenaar
Good God...ride a few bikes and pick the one that talks to you.

I've done that a million times.

[greglepore]

David, check out Carl Strong www.strongframes.com or one of the other custom builders out there. They still do steel, some of it suprisingly light, and relatively inexpensive. You can have a custom frame built to your dimensions for as little as $1200. You can also get built bikes.