Looking for help understanding road bike geometry
03-15-13, 02:10 AM
#1
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Looking for help understanding road bike geometry
I've very recently converted to the world of road bikes, having picked up an old 1982 Team Fuji. I hear people referring to the differing geometries of various road bikes, but I can't quite visualize what is what in my head. Since this is the one baseline that I have, looking at the bike that I have, how would you describe it's geometry?
03-15-13, 07:49 AM
#2
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There are many aspects of geometry which people talk about. The style of frame, sloping top tube or level top tube, is discussed here quite often. The picture is a level top tube, or classic style frame. Sloping top tube frames are sometines called compact design. These things don't mean as much as the other dimensions and angles.
The wheelbase and the steer tube angle can have a profound effect on the way a bike turns and handles a straight line. Long wheelbase bikes, like touring bikes, tend to be stable and usually have shallow angle steering. A shorter wheelbase paired with steep head angle will make a frame steer quicker but can give a nervous or busy feeling on straights.
Of course, frame material and fork construction figure into the way a bike rides, too.
By the look of the picture, that Fuji is probably stable and built the way we used to say was a stage racing geometry.
The wheelbase and the steer tube angle can have a profound effect on the way a bike turns and handles a straight line. Long wheelbase bikes, like touring bikes, tend to be stable and usually have shallow angle steering. A shorter wheelbase paired with steep head angle will make a frame steer quicker but can give a nervous or busy feeling on straights.
Of course, frame material and fork construction figure into the way a bike rides, too.
By the look of the picture, that Fuji is probably stable and built the way we used to say was a stage racing geometry.
03-15-13, 08:09 AM
#3
Senior Member
One thing i've noticed, the older frames which all have that classic look are not as quick or flickable in the handling department as the new stuff, but they track nice and strait with ease.
03-15-13, 08:43 AM
#4
The Left Coast, USA
There are many aspects of geometry which people talk about. The style of frame, sloping top tube or level top tube, is discussed here quite often. The picture is a level top tube, or classic style frame. Sloping top tube frames are sometines called compact design. These things don't mean as much as the other dimensions and angles.
The wheelbase and the steer tube angle can have a profound effect on the way a bike turns and handles a straight line. Long wheelbase bikes, like touring bikes, tend to be stable and usually have shallow angle steering. A shorter wheelbase paired with steep head angle will make a frame steer quicker but can give a nervous or busy feeling on straights.
Of course, frame material and fork construction figure into the way a bike rides, too.
By the look of the picture, that Fuji is probably stable and built the way we used to say was a stage racing geometry.
The wheelbase and the steer tube angle can have a profound effect on the way a bike turns and handles a straight line. Long wheelbase bikes, like touring bikes, tend to be stable and usually have shallow angle steering. A shorter wheelbase paired with steep head angle will make a frame steer quicker but can give a nervous or busy feeling on straights.
Of course, frame material and fork construction figure into the way a bike rides, too.
By the look of the picture, that Fuji is probably stable and built the way we used to say was a stage racing geometry.
For a touring geo, in addition to the elongated wheelbase the frame/fork would be boxed/spread slightly to accommodate larger tires/fenders. I suspect the largest tire that frame would accommodate are 28s.
03-15-13, 08:55 AM
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Actually, touring frames usually steer faster at a given speed, due to the decreased trail resulting from increased rake.
https://www.cyclingtips.com.au/2012/05/whats-in-a-fork/
As far as geometry goes, for fit what matters most is the location of the bottom bracket, saddle, adn bars in relationship to each other. For classic frames like that, the seattube and toptube are almost certainly the same length, and it uses the "classic" 73x73 seat and head tube angles which was the standard for a long time and is a good benchmark to go from.
https://www.cyclingtips.com.au/2012/05/whats-in-a-fork/
As far as geometry goes, for fit what matters most is the location of the bottom bracket, saddle, adn bars in relationship to each other. For classic frames like that, the seattube and toptube are almost certainly the same length, and it uses the "classic" 73x73 seat and head tube angles which was the standard for a long time and is a good benchmark to go from.
03-15-13, 01:46 PM
#7
Senior Member
Actually, touring frames usually steer faster at a given speed, due to the decreased trail resulting from increased rake.
https://www.cyclingtips.com.au/2012/05/whats-in-a-fork/
As far as geometry goes, for fit what matters most is the location of the bottom bracket, saddle, adn bars in relationship to each other. For classic frames like that, the seattube and toptube are almost certainly the same length, and it uses the "classic" 73x73 seat and head tube angles which was the standard for a long time and is a good benchmark to go from.
https://www.cyclingtips.com.au/2012/05/whats-in-a-fork/
As far as geometry goes, for fit what matters most is the location of the bottom bracket, saddle, adn bars in relationship to each other. For classic frames like that, the seattube and toptube are almost certainly the same length, and it uses the "classic" 73x73 seat and head tube angles which was the standard for a long time and is a good benchmark to go from.
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