Frame Geometry

supergrass

More of a generic question just out of interest really... I would class myself as a sportive rider, so i have what is classed as a sportive frame(Bianchi C2C range).. just using Bianchi as an example they also do there B2P range which are classed as more of a race geometry. As im by know means an expert i just wondered On for example a 80 mile ride would you feel the difference on what is classed as a more comfortable Geometry or is it just marketing by the bike companies?

holiver

It really depends on the individual. Obviously the pros do mammoth distances with very aggressive (low and long) geometry for the most part.

How do you feel doing 80 mile rides on your bike?

mfin

It has nothing to do with frame geometry, you could get potentially get a correct fit on a 40ft tall clowns bike. What you are describing is changing your fit. If you want a more upright fit and your current bike doesn't make this possible then you might benefit by buying a new bike with geometry that lets you have that fit.

I'll try to put it in layman's terms a bit...

You have to imagine a perfectly measured drawing where the only things on it are a mark where the centre of the BB is, your saddle and your handlebars. Then you can overlay a bit of tracing paper and draw any bike you want on it, as long as you start drawing from the one point that can't change, and that is the centre of the BB. That must fall directly over the mark for the centre of the BB on the drawing underneath.

Some bikes you can 'draw' won't work for various reasons, like 'can't get bars low enough', 'stem will be far too short or long', 'there will be a ridiculous amount of spacers', 'there will be naff all seatpost showing', 'there will be too much seatpost', etc, etc, etc.

Now, your question "i just wondered On for example a 80 mile ride would you feel the difference on what is classed as a more comfortable Geometry", replace that last word Geometry with 'fit', and you might see where I am coming from. IF you don't then the best thing you can probably do is go for a bike fit, take your existing bike along and hopefully they can fit that to you and you'll get the idea. Oh, and most people use the same fit for 100 miles as they do for 10 miles.

maddog 2

the racier frame will be lower at the front, and usually a bit longer too. Whether or not this more or less comfortable depends on how flexible you are, and how you like to ride. Sometimes a longer/lower front end is actually better, as it places more weight on your hands and less on your backside. But sometimes it's just a pain in the neck. What you don't really want to do is run loads of spacers/flipped stem to get a sportive position from a racey frame. Then it just looks a bit daft.

tomisitt

The Stack-to-Reach ratio is the best way of working out the "fit" of a frame. You divide the Stack measurement (the vertical distance between the middle of the bottom bracket and the middle of the top of the head tube) by the Reach (the horizontal distance between those two points on the frame) to get an STR ratio.

For example, if the Stack is 570mm and the Reach is 390mm, you divide 570 by 390 to get 1.46. Anything around 1.30 is very stretched out and aggressive, anything around 1.55 is pretty upright and relaxed.

The frame size also has an effect — a 48cm frame is likely to have (due to design constraints) a lower STR than a 62cm frame of the same bike. The smallest size Bianchi Oltre has an STR ratio of 1.37 while the largest size Oltre has an STR ratio of 1.52. So saying a frame is a sportive or a race frame is pretty difficult...it can be either (within reason), depending on the frame size.

Of course the physiology and flexibility of the rider have a significant influence on perceived "comfort". But once you know what STR ratio suits you, it's pretty easy to work out which other frames will be comfortable.

woolwich

I agree with the above. Short Headtube, if you are flexible, is not so important. Getting the fit right is crucial. Most fitters tend to be using stack and reach.
However Geometry does play a role in a bikes comfort. Head angle, rake and trail all play in a bikes comfort and the designers use this to the frames advantage. Stack and reach can be identical on very different geometrys.

You could write a book on this, so very very simply. All things being equal, wheels,tyre pressure, fork design etc. Aggressive (race) geometry, steep head angle and short trail figure, tends to transmit more shock to the bars, which can be fatiguing over long days. Sportive bikes tend to have less aggressive head angles/ more trail for this reason. Cyclocross bikes again, less steep to deal with hitting roots etc.

If we all rode around on roads perfectly surfaced like after the Tours been through, it would be less of an issue.
The Pros are starting to more and more use CX bikes ( or hybrids of) in the cobbled classics for this reason.

Another more minor factor is the rear triangle. Again all things equal. Short chain stays and tight rear triangles usually means a harsher ride which is why they lengthen them slightly for Sportive and CX bikes.

All this as well as the fact that sharper bikes generally need a bit more focus from the rider to get the best from them, can add up over a long day.

My favourite bike to admire at the moment is the Genesis Volare. I would simply love to have a go on one. However I would hate to do a 400km Audax on one.