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Compact Frames and Handling Characteristics(10 posts)

Compact Frames and Handling CharacteristicsFez
Sep 6, 2002 8:41 AM
I know compact frames are becoming more commonplace.

But could you explain the difference between a compact geometry sizing system like GIANT where people choose between small, medium, and large compact frames and then get longer seatposts and stems to get a decent fit as opposed to if Cannondale hypothethically sold their CAAD 5 frames in only 48, 52, and 56 standard sizes and then told us to get longer posts and stems and we also got cranks and bars to match.

I had the misfortune of riding a bike a little smaller than my ideal size and I must say I hated it. I rode it for an entire week, and it was the same model bike I ride, just a smaller size. The biggest difference was it was twitchier and rougher riding, despite adjusting the seatpost and stem length to get a pretty close fit.

Do the compact frame bikes ride like a too small bike, or are the compact geometries engineered so that it rides identical to a conventional bike, just less tubing?
re: Compact Frames and Handling Characteristicslegs
Sep 6, 2002 10:05 AM
there is a fundamental flaw in the queston because it assumes all frames with sloping top tubes have similar characteristics.. and that would be the same as saying all conventional frames handle the same.. it just doesnt work that way...

fit is an issue with all frames...
but things like fork rake, wheel base, seat tube angle, etc.. affect ride characteristics.

get a frame that fits no matter what the tt is doing... also read an article on the spectrum site by tom kellog about his peceptions regarding the merlin/spectrum compact... from my experiences i couldnt agree more with him.

Sep 6, 2002 10:38 AM
my question is a lot more general. What have compact frame manufacturers done differently to make their frames 1) be more compact and 2) fit a greater range of people simply by adjusting the stem and seatpost. I wanted specifics and was comparing it to the idea that a manufacturer like Cannondale offering 3 of its existing small to medium sizes and telling the whole riding population to choose a post and stem to fit those sizes.

Litespeed, Specialized and Merlin for example produce conventional and compact frames. Does a compact frame from each respective company ride differently than choosing too small of a conventional frame and using a longer post and stem?
Sep 6, 2002 11:06 AM
I took my mesaurements off my trek and matched em up on my giant. the effective top tube, seat height and reach to the stem are the exact same. the 2 bikes fit the exact same regardless of how the tubes are put together. carbon vs AL tubes makes the ride different feeling but the fit is the same
Sep 6, 2002 11:22 AM
I ride a merlin xl compact...
as my main bike for training and racing..
of the 5 or seven or whatever sizes.. most of them have the same seat tube height... this matters only in relation to head tube height.. as in either too much or not enough drop.. with a medium i use one small spacer to get a three inch drop..(perfect for me)
I chose the size based on top tube length... i like a long top tube.. so just using that criteria the bike fits exactly right...(at 55).. i ride standard frame measurement of about 53 for seat tube.. so i like standard frames that are 53x55 or 54.5

seat tube hieght isnt an issue because that measurement regards stand over clearance.. it becomes a rote point on a sloping frame...

even on standard frames.. for all the different seat tube measurements.. the top tube lengths change manufacturer to manufacturer...

and often times in an odd relationship to seat tube hieght...
so i would argue that riding a too small standard frame is just like riding a too small sloping frame.. and riding a frame that fits is like riding one that fits..

I think stem length becomes the important factor with sloping frames...and in the most general sense a stem between 110 and 120 suggests a good fit.

the bike fits like a glove....
Sep 6, 2002 12:19 PM
so what I am trying to say is no.. a compact frame is not like riding a frame that is too small ..
There is no difference!!!!Kerry
Sep 6, 2002 4:40 PM
It is all about geometry, tube material, tube shape and thickness, etc., not whether the top tube slopes. All that the compact frame does is slope the top tube (making it a little shorter) and save a little weight on the frame. Then you put in a longer seat post, which comes close to canceling the weight savings. Whether the frame rides softer or not depends on the stiffness of the seat post. THERE IS NOTHING ABOUT "COMPACT GEOMETRY" THAT ALTERS THE HANDLING OR PERFORMANCE OF A BIKE!!! Repeat that three times.
There is no difference!!!!Fez
Sep 6, 2002 8:05 PM
Then why only 3 or 4 sizes in compact? Some say cost savings to keep the bean counters happy, but why don't they start reducing the number of sizes on the std geometries?
There is no difference!!!!legs
Sep 6, 2002 8:38 PM
because the essential measurement is the top tube.. and there is no hard science about top tube length.. so there is room to compensate in a range of appropriate stem lengths....(110-120 for example)
but also .. the amount if sizing varies between manufacturers... (some have 6 or more sizes)
and there is a subtle diff in ride quality regarding a perceived lower center of gravity... usually only noticeable out of the saddle..(this is from experience)
no one is insisting you have to like a compact.. but i can tell you that i will always choose one over a standard...

most people buy a standard frame based on their ability to straddle the top tube.. that is not an efficiant way to size a bike (there is so much more to it than that)..
so the perception that compacts are a manufacturing cop-out is not always true.. one needs less sizes because stand over is no longer an issue in sizing...
again the emphasis is on the tt length...

but its true .. many stock compacts dont fit everybody.. but you can get a sloping frame in any size in the world....
also.. sloping frames seem to give builders a chance to make a taller head tube make more design sense.. and this can help with regards to ahead style headsets.. by reducing spacer crimes....
Another thread on this:fbg111
Sep 7, 2002 5:31 AM