Compact vs trad..

fallingoff

Can anyone tell me the differences between compacts and traditional frames..and perhaps uses?Reasons?
Thanks.

Wheelspinner

A traditional frameset has a horizontal top tube, whereas the compact design all use a varying degree of slope from the headtube to seat tube junction. So called "semi-sloping" designs have roughly 6 - 8 degrees of slope angle.

I don't know for sure, but reasons I've seen for it include:

Weight saving - shorter combined tube lengths overall means less weight, even if a longer seat post is required.

Stiffness of frame - shorter frame members means a stiffer frame, although again offset by flex in a longer seat post. Also means you can save weight again to get the same stiffness as the larger frame triangle sizes.

Standover height reduced - good for the vertically challenged rider.

Aesthetics - can make some frames look better proportioned.

I don't think there are any functional use differences though, as in neither is necessarily better at some types of riding than the other.

Garry H

Another reason is economics. Sizing -wise, a compact frame should theoretically fit a broader range of rider. Therefore, you can get away with having to produce less model sizes, leading to smaller production costs. If I recall, Giant were the first to produce compact geometry road bikes and they had four different sizes that they believed would fit all riders.

MichaelW

Advantages of a trad frame:
Easier to carry on the shoulder
More comfortable to sit on the top tube.
Seatstay rack eyelets are placed above the level of the wheel for better triangulation of the rack and stiffer luggage setup.

More advantages of compact frame:
Riders with short legs/long torso can find one to fit.

greasedscotsman

Garry H wrote:

If I recall, Giant were the first to produce compact geometry road bikes and they had four different sizes that they believed would fit all riders.

Dave Lloyd was making compact frames before Giant. I have an old copy of Winning from '89 which has one of his bikes with a slopping top tube. His idea was to produce a more rigid, stiffer frame as previously mentioned in earlier posts.

mrushton

Giant were poss. to explore the commercial aspects of this when they employed Mike Burrows. The idea was that a compact frame would be smaller (obviously) and therefore could be made stiffer. Someone then realised that instead of making 20 sizes of frame, a manufacturer ciould make a S/M/L and adapt the rider using different sized components. The maker can make frames with less inventory saving money. Compare that to Colnago who used to have lugs for prob. each size of C40 as obviously the lugs for a 54cm bike would be slightly different to a 56cm etc. How many lugs did Colnago have to buy/stock. Monocoque frames were even better as now you just needed a mould per size (S,M,L,XL)