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Aerodynamics- Another advantage to compact frames?(24 posts)

Aerodynamics- Another advantage to compact frames?peloton
Sep 28, 2002 5:47 AM
Watching the Vuelta this morning, and some of the riders decending in the hills, and I had this thought. Is the compact frame with it's lower top tube a better frame for the riders to get aero on when decending? I'm talking the type of decending with the hands on the stem, and the hips in front of the saddle with knees and elbos in- trying to get as small as possible. Watching Oscar Laguna decending on his compact frame in a breakaway, he was able to get down very low on the top tube. Much lower than one could get if the top tube were of the higher traditional variety. My theory/observation is that he can now get his back more flat by being able to lower his hips more. Getting the torso close to the thighs would also decrease the 'pocket' of air caught by the legs. He seems to create a lessened frontal area by being able to get his body in a tighter egg shape. His center of gravity would also be lower, and therefore more stable. On a traditional frame with a higher top tube it would seem by observation that he hips would be higher, and his body less compact. He would be higher and less stable, and create a bigger frontal profile with his higher hips, and legs catching more air.

I wonder if any wind tunnel testing has been done comparing these two positions. Any thoughts?
I don't think so.jaredhartman
Sep 28, 2002 6:11 AM
You say when descending riders get in front of their saddle, but they really get behind it to stretch their bodies out. The photo shows this despite him being in the drops. The top tube is not a limiting factor in how low a rider can get; the saddle is.
The photo did't post. Here it is.jaredhartman
Sep 28, 2002 6:14 AM
different decending technique than this picturepeloton
Sep 28, 2002 6:26 AM
The technique I'm talking about is when the rider slides forward on the bike, and either grabs the bars by the flats or the stem. The upper body is more over the front wheel, and the hips are in front of the saddle. We are talking about two different positions on the bike. Sliding in front of the saddle is better for pure speed on straight, smooth roads than the position in the pic.

BTW- This pic isn't from today's stage. :)
Like this?Ken of Fresno
Sep 28, 2002 9:40 AM
Steve Bauer at 65mph.
Like this?peloton
Sep 28, 2002 11:07 AM
More like that position. Watching Laguna in the Vuelta this morning though, it was very striking how low he was getting on some of the decents early in his break. He really had his hips in front of the saddle, and right on the top tube of his frame. I would compare the difference in position between the higher position of behind or above the saddle to his like that of a ski racer in a high or low tuck. In the low tuck the hips are lower, and there is less frontal area. That is what it looked like when he was in this low tuck on his bike today.
yeah, laguna had the tip of the saddle right in his backrufus
Sep 28, 2002 3:36 PM
i saw that tis morning, and while i guess it wasn't why the compact frame was designed, it sure did allow him to get low. he was like the bauer pic, but pretty much sitting on the top tube with the saddle sticking him in the middle of his back.
Silly Roadie...jrm
Sep 28, 2002 7:19 AM
Trying to descend like a Dirt Head. Give it up..
Sep 28, 2002 6:18 AM
They really do get in front of the saddle when trying for maximum aerodynamics on smooth roads. The behind the saddle technique probably means more curves in the road, or rough pavement. Watch the stage again tonight when it is replaying, and you will see Laguna employ this technique early in his break.

It is faster to hand in front of the saddle than off the back, but it's harder to control the bike. When using this technique, the top tube and not the saddle is the limiting factor in how low you can get.
well, based on the picweiwentg
Sep 28, 2002 10:15 AM
I would say that since the nose of the saddle is between Bauer's legs, the saddle is still the limiting factor.
I can't say that descending that way is rational for me. the risk is too great. recently, I've started descending MTB-style (since I got an MTB). no doubt Cipo would say I have problems descending :)
ther is NO advantage unless you are short or a manufacturer ...Spirito
Sep 28, 2002 10:21 AM
frame makers benefit from making frames in 4 or 5 sizes which lowers production costs significantly.

short people 48 - 53cm can have a few fit advantages.

if you think there are other advantages then you are falling for the marketing schtick.

the goal is to save on production costs by making far less sizes and this also makes it easier for distributors, wholesalers and retailers to move stock as 4 sizes is a lot easier and generalised than the 8 - 12 for each model that had to be stocked previously. if we all rode compact frames their life would be easier and ours uglier.

what next? .... one day it will be just a matter of swapping parts as your frame will be a road/mtb/bmx/hybrid and all frames will be extruded plastic made by 3 international giants. super pricey to setup but cheap once running and then all will be rebadged and us dumb consumers will be arguing over the merits of one to another even though they are the same.

don't beleive the hype.

Ok Ok .... one more advantage of a compact frameSpirito
Sep 28, 2002 10:43 AM

Spirito, do ya think Specialized will paint a frame to match?NFMSpunout
Sep 28, 2002 11:05 AM
of course ... saddles, bartape, cages, helmets too ;-) NmSpirito
Sep 28, 2002 11:30 AM
not an argumentfiltersweep
Sep 28, 2002 10:48 AM
I get what you are saying about stocking sizes, however, my guess is compact frames will simply carry a lower price, and it will be like paying a premium for a "full-sized" frame.

Personally, I'd find it a bit odd to see the top tube a foot beneath my saddle...

It will be interesting to see what happens in five or ten years... compact frames have already made it into the pro peletons.

Twenty years ago, ergo bars would have looked very odd... quill stems were the norm (I thought the first threadless stem looked VERY bulky).
i say in no jest ....Spirito
Sep 28, 2002 11:16 AM
10-20 years and its just 3 or 4 manufacturers (industrial giants) of frames from extruded plastics. they will be light, stiff, long lasting, multi-compliant and much cheaper than we pay now. they will cost zillions to design and build the tooling for but once running they will have the ability to pop them out 24/7 in the 4 or 5 sizes needed to cover the size spectrum.

of course you will be able to buy them labelled under 100 different names. they will be great to ride but will have little in the way of individuality or style. consumers will be able to ride a TdF winning bike for 1/2 the price or less than they do now.

im not trying to be orwellian but smaller frame manufacturers will not be able to compete and will find it hard to sell their frames to a fickle price motivated market. some will stay around but few will stock their stuff and high manufacturing costs and a lack of distribrutors will send many to the pastures.

you will still be able to buy a handmade custom specced small company bike but you will have to be rich and there will be no reason to do so if you are concerned about getting from point a to point b fast.

I'm hoarding Columbus steels now Dr. Spiritodesmo
Sep 28, 2002 12:00 PM
Eef ur predicshons are right, I should be a vey rich man ven ur doomsday scenerio plays out. You vant individuality? ya, we haf but you must pay. Hahahahahaaaaahhhhh..cough, cough, ahhh.
Are the pro's falling for the marketing schtick too?fbg111
Sep 28, 2002 4:23 PM
I find it hard to believe that so many pro's and pro teams are falling for that schtick too. Don't they test out all their equipment religiously and only change frames if they're absolutely convinced something new truly offers an advantage? Or do the big sponsors have their racing teams wrapped around their fingers, financially?
Are the pro's falling for the marketing schtick too?divve
Sep 28, 2002 10:27 PM depends how you look at it. During the TdF there was a small bit on Belgium TV regarding pros and their basically boiled down to that they long gave up caring about whatever manufacturer's bike they were riding...the most important part was that it fit and did what it was set out to do...whether it was made by Mongoose or Colnago...they couldn't care less...most got 3-4 new bikes a year with whatever features they wanted...most of it was about looking good for marketing purposes. The general consensus was that love for bikes was more part of the "hobbyists" experience of cycling than for pros. This basically holds true to almost every product in existence...when you can get as much as you want of said product you start looking differently at it...or stop looking at it at all:)
Sep 29, 2002 3:06 PM
Another conclusion from that could also be that modern bikes are so close in performance regardless of frame design, material, or manufacturer, that any differences or advantages are negligible to the pro's. What do you think?
Short riders and compact frames...jtolleson
Sep 28, 2002 4:31 PM
Actually, the assumption that compact geometry is good for short riders is in fact something of a myth. Compact bikes offer a longer effective tt usually for their mythical standover than the standard geometry bikes.

They ARE good for riders who are shorter in the legs but average to longer in torso... you can get the good standover without having the bars too low or the tt too short.

Contrary to popular belief, compact bikes present problems for some women because they tend to be longer legged and shorter torsoed.
Ultimate compromise...?divve
Sep 28, 2002 11:31 PM
Ah yes, the 2003 R7000filtersweep
Sep 29, 2002 8:53 AM
Great spy report... ;)
re: Aerodynamics- Another advantage to compact frames?Spunout
Sep 28, 2002 4:18 PM
a) As much as Steve Bauer is a God around these parts, eh, I can't see descending like that is any good. A bit of brakes and yer over the bars.

b) With any normal (standard) geometry frame, if you are impeded by the top-tube in an aero position, I still can't visualize that. The whole bike is too big for you then.

But, those are only my observations. Anybody have a wind tunnel at their disposal? I thought most tests showed that on the seat, flat back, chin above the stem, was most aerodynamic. Sitting on the top tube (or where one should be, if you're riding a mixte frame) can't be any better (or safer, or more comfortable).