Road Bike Geometry - Standard vs Compact

[winjim]

Do we have a thread where we bicker about the pros and cons of standard road bike geometry vs compact? If not, can we start one please?

 

[totallyfixed]

Nothing so ugly as a seat post that starts half way down where the seat tube ought to be. There, that ought to stir someone .

 

[Fab Foodie]

Do we have a thread where we bicker about the pros and cons of standard road bike geometry vs compact? If not, can we start one please?

Go for it .... give us a starter question/statement and then we've got something to bitch about ....

 

[winjim]

Go for it .... give us a starter question/statement and then we've got something to bitch about ....

Nothing so ugly as a seat post that starts half way down where the seat tube ought to be. There, that ought to stir someone .

How about seat stays that start halfway down the seat tube? Giant, I'm looking at you.... well actually I'm averting my eyes.

So is it all just aesthetics?

 

[3narf]

I'm sure there are sound engineering principles at work as well as mere marketing gimmicry. At least, I hope so.

A smaller triangle should be stiffer, but a longer seatpost will flex more. Presumably it's about where the designer wants the flex to occur. A sloping top tube allows more adjustment with saddle height but this is of limited value with a road bike 'cos once you get the correct height you don't really mess with it.

Aesthetics? I think a slightly sloping top tube looks modern and balanced.

 

[3narf]

Of course, geometry is a different issue!

 

[User6179]

I must admit after buying a second hand Giant Defy I don't like the sloping top Tube but I also have a CaadX and the seat post only has a couple of inches on show which looks even worse .

 

[Kestevan]

Surely the whole point of the compact frame geometry is that it allows manufacturers to get away with producing fewer differing sizes of frame.

Just build em all too small with stonking long seat tube.....

 

[Fab Foodie]

Surely the whole point of the compact frame geometry is that it allows manufacturers to get away with producing fewer differing sizes of frame.

Just build em all too small with stonking long seat tube.....

IIRC That was the original goal of Mike Burrows who designed the compact frame with Giant. Their research also showed that men and women are proportionally the same* so that combinations of a longer seatpost, stem length (with height adjustment) and seatpost layback meant fewer frames sizes were required to fulfill peoples size requirements. Just S, M, L In part it kinda worked. Stand-over height is lower too and the frame has less metal and so could be stiffer and hence lighter. In time an XL was added and then intermediate sizes to the point that they pretty-much ended-up going for a regular cm size range.
I have an 2004 vintage TCR1 with a compact frame and it looks great.

I remember the first time I saw a compact frame on a custom built Omega hybrid and it looked like it would take-off and ride itself .... it looked cool. I still like them but not too compact. I could have had the 853 Rourke built as a compact too, but wanted a more traditional look and a tad more forgiving frame from larger triangles so I have a very very mild slope in the TT.

Geometry is another question all together ..... I know this to my cost :-)


*OK, while men and women are on average proportionally the same, there are differences in hip rotation for example and delicate undercarriage parts which means that women's bikes generally have shorter top-tubes. WSD designs might also have shorter reach brake levers etc too in the more petite sizes. However .... a bike either fits or it doesn't.

 

[velovoice]

While I prefer the look of a traditional level top tube, my fit issues require short reach and tall stack. For engineering reasons, this means the top tube must start quite high up on an already tall headtube. For standover reasons, it must then slope quite dramatically towards the seatpost. End result looks a bit bizarre -- even after 18 months of blissful ownership, I have difficulty with it from a purely aesthetic point of view. But it has without exaggeration 'saved' my cycling. (My aesthetic 'win' in the design was asking for, and getting, the same 52 degree angle in the rear triangle at both the top and bottom of the seat post - I hate it when those angles are different - just looks wrong.)

 

[Fab Foodie]

While I prefer the look of a traditional level top tube, my fit issues require short reach and tall stack. For engineering reasons, this means the top tube must start quite high up on an already tall headtube. For standover reasons, it must then slope quite dramatically towards the seatpost. End result looks a bit bizarre -- even after 18 months of blissful ownership, I have difficulty with it from a purely aesthetic point of view. But it has without exaggeration 'saved' my cycling. (My aesthetic 'win' in the design was asking for, and getting, the same 52 degree angle in the rear triangle at both the top and bottom of the seat post - I hate it when those angles are different - just looks wrong.) View attachment 90545

The joy of custom built ..... if you're a non-standard size/shape human the are worth every penny .... V. Nice

 

[velovoice]

The joy of custom built ..... if you're a non-standard size/shape human the are worth every penny .... V. Nice

Thank god, yes. After years of trial and error and pushing the logistical boundaries of several stock geometry bikes, it became the only option left. Otherwise, I would have had to stop road cycling.

 

[samsbike]

What seatpost is on the ti bike and is it mounted backwards?

I am only asking as I need a similar arrangement.

Thanks

 

[midlife]

Compact frames look like you have nicked a kids bike and are escaping....... Happened quite a bit in the 70's

Shaun