A HYPOTHETICAL: If there were no UCI or other rules limiting you and you were to have the ability to build a completely custom bike frame, would there be any advantage to riding a bike with a slightly more ‘steep’ seat tube angle for general road riding and racing?
For example, say you previously rode and raced on a completely traditional ‘road’ bike with a 73 deg. seat tube and used a traditional seat post with a clamp set-back of 2 cm.
You are a reasonably flexible rider, with no major back or hip pain issues, who likes to get as low and aero as possible (within reason) on your road bike’s drop bars. And your training and racing consists of preparation for 100 km (~60 mile) road races that would include some flats, some rolling hills, two 500-meter (1500 ft) climbs/descents, some pack riding, but also 1 to 4 person breakaways where you might be motoring by yourself or in small groups for 10 to 60 min.
Then you had the option to have a bike built for you that would ride and handle perfectly and would in all important ways be identical to your previous bike except that the builder offered to build the new frame with a 75 to 78 deg. seat tube (the angle would be your choice). You would still use a traditional seat post with a clamp set-back of 2 cm. You would have all the time you needed to adapt to the new angle during training.
Fit-wise, the bike would be the same as your previous bike, except perhaps that the steeper seat-tube might allow you to ride with your torso 2 to 5 degrees lower depending on how steep you had your seat tube built on the new bike.
So the questions are:
Would the typical bike rider develop more power (over the type of road course above) on the new bike?
Would the typical bike rider be more aero on the new bike?
Would the typical bike rider overall be faster on the new bike?
Then, if you had the choice, what seat tube angle would you pick for this new bike scenario?
if you could do anything, rules wise, you’d still have the same road bike geometry underneath you. the ability to displace your weight on two spots, the front and rear of the bike, is what allows for the range and variability of positions on a tri bike. you don’t have that with road bikes, and any attempt to ride steeper just means too much weight on one’s hands.
most people ride too steep on their road bikes, and too shallow on their tri bikes, imho.
So you think that just steepening the seat tube angle by a few degrees (say, from 73) makes a pretty significant difference with regard to the amount of weight that would end up on your hands?
Because to me, it seems that the amount of weight on the hands would be appear to be more affected by a rider’s torso angle (relative to ground level) than by the seat angle. (?)
“it seems that the amount of weight on the hands would be appear to be more affected by a rider’s torso angle (relative to ground level) than by the seat angle.”
the amount of weight on the rider’s hands is determined by one’s center of gravity in relation to the BB. if you moved your saddle forward but kept your torso angle the same, you’d still be pushing your CG forward versus your BB.
That’s not hypothetical for me - that’s reality. However, I have a very long torso relative to my legs, so riding for me in a somewhat neutral position has been what works best for me for road or tri.
Hope you don’t mind my endless questions, as I am trying to fully understand this.
Your center of gravity (cg) argument does make sense. But wouldn’t the amount of weight on the rider’s hands be determined by one’s unsupported center of gravity? In other words the cg of mostly your torso, not really the lower body? Can the amount of weight on the rider’s hands really be affected that much by the position of limbs (the legs) below the saddle? Because it seems that the bike saddle supports quite a bit of your body and interacts highly with weight distribution and (relative) cg balance. Your argument makes complete sense for a rider off the saddle, but would it also work for rider with a lot of weight on the saddle as well?
“wouldn’t the amount of weight on the rider’s hands be determined by one’s unsupported center of gravity?”
you can’t ignore your legs, because they’re supporting your weight as well. when you push down on the pedals, you’re pushing against something, and it’s your body weight. you could, theoretically, ride no hands with a reasonably flat torso. of course your spinal erectors will complain, but you could do so. that’s because the weight aplied to your pedals overcomes the tendency of your torso to fall forward.
why are touring bikes slacker than crit bikes? because you’re exerting less, less of your weight is supported by your pedals. when you stop pedaling hard on a 75-degree crit bike your weight falls to your hands.
i should have added more precision in my original post, and said your weight is distributed over 3 points when using aero bars, instead of two. or even better to say it’s supported in 3 points without the use of sustained muscular effort. when road riding one of those points of suspension requires sustained exertion (the hands position). the beauty of aero bars is that now all three points of contact are supported without muscular effort. however, when you take weight off the pedals it’s transfered to your saddle and, more precisely, to your taint. therefore, tri bikes are not good options when not being ridden under power.
rule of thumb: when riding hard, ride your tri bike. when riding easy, ride your road race bike. it’s not distance dependant, but effort dependant.
From my experience, I have definitely noticed that longer, easier rides do make my rear hurt more than an equal length ride at high speed, as more body weight is supported by the saddle and much less on the pedals. But I personally have never really noticed much difference in how my hands feel (on drop bars) at all based on effort alone. I have noticed differences in weight on my hands on different set-ups, but it to me it seemed all based on my on torso angle and the distance/drop to the bars.
I think Dan’s last point, the rule of thumb, ride the tri bike when riding hard and the road race bike when riding easy, is the best advice you can get. This would help most people make a decision when they’re stressing over which type of bike to buy.