Road Cycling - Compact frames/carbon seat stays

Need some info on the advantages/disadvantages of compact road frames. The bike I'm looking at (K2 Mod 4.0) comes equipped with a carbon fork and seat stay, and Ultegra components. I currently have a 16 year old steel frame made from Reynolds 531c and like the smooth ride, but want the performance of Aluminum w/out the harsh ride....Plus, it's time to upgrade.....components have seen their better days and the K2 weighs about 4 lbs less. Unfortunately I didn't get to test ride the bike for any significant distance, but liked the way it felt. I'm a little concerned with the bonding process between the stay and frame. Any feedback would be greatly appreciated

I just put a compact frame on the road and I am real crazy about the bike. I have about 500 miles on it which barely gives me any credibility to talk about these type of bikes. My old bike was a Cannondale with a carbon fork and a mix of components. The ride was stiff compared to my older Trek 1440, but I could stay comfortably on the Cannondale for 7-8 hours. The new (compact) frame is very stiff compared to the other two bikes. I put it together as a climber and the stiffness makes it work well in those regards. I have a carbon seat post and fork that "dampens" the road bumps. The longest I have been on the bike is 4 hours, so I'm not sure I have any longevity comparisons. At the risk of rambling on too much more, the compact frame is stiff, responsive, climbs well and accelerates like a mutha. It is a very sweet ride. It will work well on those Sierra roads this summer.

Good luck with your selection.

My main road ride is a traditional geometry steel frame; my cyclocross bike is a compact [slightly sloping] aluminum frame. I really don't find that much difference except in the smoothness of the steel. The 'cross bike has a great lateral stiffness for climbs, but I fee that lower in the frame and attribute it to the frame material [Easton Ultralight 7005] rather than the geometry.

The advantages of frame beometry are [imo]:

For the rider: More standover clearance.

For the manufacturer: Use of less materials and the ability to make and stock a smaller range of frame sizes.

All the rest is smoke.

Compact frames are called compact because they are, well, compact!
There is a big difference between a standard and compact frame. The wheelbase is shorter, the rear wheel is tucked in (shorter chainstays) and of course the sloping top tube.
The ride is different and suits itself to out of the saddle climbing where I can find no other perfect bliss than climbing straight up a mountain pass on a compact frame.
I have done 140 fast miles straight with no discomfort.
Steering is usually faster on compacts and I don't like them on high speed descents as it feels too twitchy above 55 mph for me. It can punish the inattentive.
Specialized makes the full range of sizes and all their road bikes are compact so I guess they are sold on the concept.

If you went a bit large with the frame, I guess it would ride more like a standard geometry bike. If you are going with a sm, med, lg, xlg choice--don't buy it unless it fits you properly.

I would say the carbon/aluminum bonding is a non-issue as the factory warranty would cover such things. Legitimate concern, but I would think the warranty info will tell you more than anyone here could.

I don't want to pick on anyone's opinion but I am not biased as to frame material, style, etc. My experience is with the S-Works Columbus SLE5 tubeset. Excellent bike, imo. Very few stand next to that one, compact or standard.
Personally, for ultimate comfort/performance/longevity I would go with Titanium.

If you decide to go with the K2, I would say 4 things:
1. Carbon stays will dampen ride, by how much I don't know. But on the Pinarello Prince, it is magical what a aluminum/carbon blend can do.
2. Make sure you are properly fitted. Compacts are measured differently and those rules need to be respected.
3. Give yourself some time to get used to the ultra-responsive handling. In time, it will be like the bike is reading your thoughts!
4. See what wonders loosing 4 pounds off your bike can do!

No, surely compact frames differ from standard road frames only in the height and angle of the top tube. The points of contact and wheels remain in the same position.
How can you tuck the rear wheel in any more than on a standard modern racing bike. You are limited by clearance from wheel to the seat tube. Once the tyre hits the seat tube, you can only reduce the wheelbase by going to smaller wheels, or sculpting out the section of seat-tube.

A large sized compact frame would be much longer in the (effective) top tube than a medium sized normal bike, even if both have a similar standover height to the top tube.

You mean how Giant scoops out the seat tube of the TCR so the rear wheel fits?
The angles are steeper and the chainstays are as short as possible. This is not done with the standard geometry bikes.
I'm not making this stuff up. It is just how it is. I will stop posting on this since I don't want this to transgress into something other than what the original post was about.

Originally posted by RacerX
There is a big difference between a standard and compact frame. The wheelbase is shorter, the rear wheel is tucked in (shorter chainstays) and of course the sloping top tube.
Not at all. In fact, the only geometric difference between a compact frame and a standard frame is the angle of the top tube. [There may be geometry differences between bikes, but the compact design doesn't create those differences]. For example, this year's Specialized Allez Comp, at 54 cm, has a wheelbase of 977 mm and a chainstay length of 405 mm; a Guru Racelite (a traditional geometry frame) in the same size has a wheelbase of 979 mm and a chainstay length of 405 mm.

The only difference is the angle of the top tube.


Originally posted by RacerX
The ride is different and suits itself to out of the saddle climbing where I can find no other perfect bliss than climbing straight up a mountain pass on a compact frame..
I don't doubt that that's your subjective impression, but there's really no math or metric to back it up objectively, unless you're comparing bikes of different materials... And that's a whole other kettle of fish.

I hope this doesn't come off as confrontational -- it's not meant to. Moreover, I don't think that compact frames are bad; my cross bike has a compact frame and I like it a lot. It's just that there really are no garet differences in ride quaity or performance between compact and standard frames. Which you chose comes down to preference.

RacerX
I believe that the shortened wheelbase is more
of a timetrial/triathalon setup and isn't considered
"compact". I think we could slide down the slippery
slope of semantics here.
The Compact frame is a result of the Mountain Bike
influence on traditional road frames. (no judgement
here, just the facts!).
As more roadies converted to ahead/threadless stems
they had to add headtube extensions to compensate for the
loss of height in stem. Now, too much extension via
spacers is NOT a good thing (think structural failure here).
Compact Geometry allows for a taller front end without a
longer stem or excessive spacers.
An advantage of Compact Geometry is that you get a
"larger" frame, with lower standover height.
you can effectively have a 58cm front end on a 56cm
bike.
Marty

Originally posted by RacerX
The angles are steeper and the chainstays are as short as possible. This is not done with the standard geometry bikes.
It is. And it's actually quite common. You see it a lot in time-trial bikes and in bikes inspired by TT design.

There's the Guru Chrono:

http://www.gurubikes.com/bikes/images/crono_lg.jpg

And the Cervelo P3:

http://www.cervelo.com/images/2002/2002-P3-click.jpg

To name two. These bikes come in 650c and 700c wheel sizes, but the geometry is basically the same.

Thanks for all the feedback. I've decided to go ahead with the K2.....especially after I took it for another ride. It was quite smooth and responsive.
I carefully compared the geometry of many bikes....traditional and compact. The essentials seem to match: wheelbase, effective top tube, head angle, etc.
My hesitation was mainly in the bond between the carbon and the Aluminum....but I've been told this has been done for many years with few overall issues.