Compact Frames - I call bullsh*t

Triathlon Forum
1

“I call bullsh*t” is my new favourite phrase so I’m gonna use it…

This question is purely ainmed at fitting, not ride characteristics etc - Ive seen it posted many times that bike manufacturers claim they can fit the same amount of people with a reduced number of sizes in a compact framed bike, presumeably because of the sloping top tube. How teh hell does that work??!

My feeble mind says how a frame fits is based on the position of the headset, bottom bracket and saddle, in relation to each other in terms of distance and angle. So surely a limited number of frame sizes in a “traditional” frame will fit people just as well/equally as badly as a limited number of frame sizes in a compact style - right?

Im no expert on bike fit (Im too ashamed to post a pic of my aero position here!! I look like a bag of spanners :slight_smile: ), so Im more than willing to be proved wrong by minds greater than my own!

PS - I know/train/race with Bobby who posts here, and Im getting abit concerned about all his questions about farting and p*ssing in the pool…

2

I think you’re correct. What matters for a bike position is wheel position, bar (hedset), crank and seat. Compact frames have production advantages.

On a traditional frame where only 4-5" of the seatpost is visible, the estethics of the bike is spoiled if the seatpost is just a bit too long or short. While on a compact frame with 10" visible seatpost, a few inches don’t make any estethic difference.

3

I just helped two guys with long torso/short legs syndrome (LTSLS) find nirvana on compact frames. Standard frames just wouldn’t give them enough crotch clearance. Compact frames are perfect for people like these two. For more normally-proportioned people, I don’t think the compact frame creates a disadvantage to fitting positions. SO, I say the compact frame companies are correct, the compact frame does, indeed, provide correct positioning for more body types than a standard DD frame.

4

You’re right. You don’t know much about bike fit. You have three contact points with the bike. Your ass, your hands and your feet. Whatever works to keep those three things in their proper relationship will work. What difference does the headset location make when you can vary stem length and stack height? NONE (if we’re playing by your rules and eliminating riding characteristics from the equation). And what does anything about the frame have to do with where the saddle is? In this day and age, you can get saddles with all kinds of setback, or none at all. And the last time I checked, with the turn of an allen key, you can raise and lower it quite a bit.

As for the bottom bracket, I’ve never heard it mentioned as a variable in compact versus conventional frame design. They’re all pretty much the same unless you’re looking at a cyclocross bike.

All this is not to say that compact frames aren’t driven more by manufacturing economics than customer demand. I believe they are. But they offer certain advantages to certain people and they DO offer some differences in riding characteristics … though you didn’t want to focus on that.

BTW, I have a conventional frame bike and two compacts. As far as fit, if I were blindfolded, I wouldn’t know which bike I was on. As far as ride, well, there are some very notable differences. Each bike seems to be better at different things and I love riding them all.

Bob C.

5

With integrated threadless headsets, the head tube of modern bikes end up being about 6 centimeters lower than old 1" threaded and quill stem bikes.

Given that bike companies are now building those 6cm back into the head tubes, a horizontal tube extending from the top of the head tube back to the seat tube would result in a frame that would not provide any standover clearance, and offer confusing sizing parameters, leaving no true measurement with which to name the frame size.

3 sizes really is not enough, but the Conago method of offering a frame in 46.5, 47.5, 48.5, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, and 65cm sizes is confusing to 95% of consumers. A happy medium of 5-7 sizes per model and an understanding of those sizes by the fitter(shop) is important. Knowing their limitations and how they compare to other vendors is a huge lesson few have learning.

-SD

6

Thanks for all the replies and feedback - at this risk of sounding organised, I’ll go through the responses one by one…

ajo - totally agree that there are obvious production advantages for bike mfctrs in producing a limited size range - less cost outlay, less unsold bikes at end of year etc etc

titan - hadnt thought of that point about “crotch clearance” (is that when the missus allows monthly acces to the naughty bits?!?!) for long torsoed/short legged riders, totally valid one

psycholist - again I totally agree with your points, esp that I know nada about bike fit! However all your points lead to the fact that pretty much any frame can be fitted to any person within reason, with a combination of stem length, stack height, seatpost height, layback etc - it might not be ideal but it would work to a certain extent - again all totally valid, but it doesnt answer my question how one can say that a range of compact frames in a limited number of sizes can fit the general populus “better” (whatever that means) or even the same as a trad frame in more, closer together sizes…

Super Dave - Thanks for your points, again all valid, good points, but I still dont feel that my question has been answered.

Maybe this will be like my seemingly endless quest to find out how teams can plan cricket for five days and still end in a draw - surely one team must score more runs than the other??? However many times people try to explain it to me, I just dont get it…maybe I have ADD…

Non PC joke alert: Q: How many kids with ADD does it take to change a lightbulb? A: Lets all go and play on our bikes!!

Cheers for the responses and dont take my post as a complaint/attack - just trying to better my (already established as limited) understanding…

PS - just had a thought that my “rule” that we are not talking about handling characteristics doesnt help - when we talk about bike fit I guess we mean a combination of comfort, power output, aerodynamics and handling/ride characteristic…

7

“Standard frames just wouldn’t give them enough crotch clearance. Compact frames are perfect for people like these two.”

Why does the compact frame have anything to do with this? You’re honestly saying that someone on a properly sized traditional bike couldn’t touch the ground when straddling the top tube?

I think compact frames are all about looks. People want to ride 8 inches of seatpost like the pros, but they want their bars level with their saddle too. So, bike companies have created a granny crusier geometry that looks really aggressive to stroke the ego of fat old men.

8

I sort of agree.

But I think compact geometry frames look better for even normally proportioned fit people! Purely an aeshetic opinion, but a horizontal top tube just looks old fashion and unappealling to me.

I don’t believe there is any real difference between compact and normal frames except to satisfy different preferences in terms of looks.

Given the current offerings in the world today I have no plans to ever own a bike with a horizontal top tube.

9

The problem with the current compact offerings is that riding a trully aggressive postion gets tough. Since the headtubes are so tall you can’t get the bars low enough on frame with a “normal” toptube length. The only thing you can do is downsize from a 58cm frame to a 54 or 52 and ride a 130-135mm stem. (Take a look at the Healthnet squad, that’s what they’ve all done). A tiny frame and long stem effects handling.

10

caleb asked: You’re honestly saying that someone on a properly sized traditional bike couldn’t touch the ground when straddling the top tube?

Correct.

Oh, they could tiptoe and not bang the boys on the top tube of some properly fitted standard DD framed bikes. They could also fit on a TitanFlex since the top tube is lower, as long as the TF was correctly sized for road riding…not enough front to center distance even the smaller size range TF for these two guys, and when they stepped up to a larger size to enable the handling to be stable enough when in an aero position they ran into the clearance issue again. A couple of other lower-top-tubed bikes were close to being OK, but, both of them were much better served by the lower compact top tube standover height.