Frame Geometry

[Paul J]

I ride an old style bike with a horizontal crossbar (top tube). Most of the modern bikes have a top tube that starts quite low down on the seatpost and rises to the head tube. Can someone point me in the direction of a site that explains why or explain the pros or cons of the new geometry.

Cheers

 

[screenman]

Traditional geometry road frames are often associated with more comfort and greater stability, and tend to have a longer wheelbase which contributes to these two aspects. Compact geometry road frames have a lower center of gravity and tend to have a shorter wheelbase and smaller rear triangle, which give the bike quicker handling. Compact geometry also allows the top of the head tube to be above the top of the seat tube, decreasing standover height, and thus increasing standover clearance and lowering the center of gravity. Opinion is divided on the riding merits of the compact frame, but several manufacturers claim that a reduced range of sizes can fit most riders, and that it is easier to build a frame without a perfectly level top tube.

 

[Paul J]

Thanks for the info and explaining it in simple terms

 

[screenman]

Paulj, I cannot lay claim to it, I only Googled it and thought it would fit well.

 

[smokeysmoo]

Stick with traditional geometry, they just look right

 

[screenman]

No go with compact far more modern.

 

[Smokin Joe]

Compact geometry road frames have a lower center of gravity and tend to have a shorter wheelbase and smaller rear triangle,

Compact frames have exactly the same wheelbase as standard frames.

 

[Banjo]

Even out and out tourers like the Dawes Galaxy are coming out in compact frame geometry. I strongly suspect its the one size fitting a wider range of riders that appeals to the manufacturers.

 

[screenman]

The wheelbase on my compacts are less than those of my normal old fashioned frames.

 

[simon.r]

Didn't compact road frames start appearing after MTBs became popular?

Standover height on MTBs is greater than traditional road frames for practical reasons - quick dismounts on uneven ground don't lend themselves to having little standover clearance. I always assumed that it was as much about fashion (albeit with practical benefits) and tempting MTBers onto road bikes as anything else?

 

[Ian H]

One of the advantages, especially for smaller frames, of compact geometry is that the headtube can be longer. This means less stress on the headset bearings. Otherwise, most of the claims are (as with most cycle fashions) b0llocks.

 

[raindog]

I've got a "traditional" steel framed racing bike and a more modern aluminium/carbon bike and the wheelbase is identical on both - in fact, the steel frame is a couple of millimeters shorter. If you've got a steel frame with a long wheelbase it's got touring geometry.

 

[Smokin Joe]

The wheelbase on my compacts are less than those of my normal old fashioned frames.

That has nothing to do with the frame being a compact.

 

[screenman]

Just stating a fact.

 

[Smokin Joe]

Just stating a fact.

So am I.