Only now that I have my upgraded Kama folding bicycle I can ride fast in a folding bicycle. No dough the top speed of a folding bicycle on a flat road is slower then a road bicycle.
So my question is how much slower a road small wheeled folding bicycle is in relation to a road bicycle? is it theoretical possible to improve a small wheeled (451 mm wheel and smaller) bicycle to ride side by side with a road bicycle ? how?
I start answering with my own example. Usually I ride in cruising speed in a road bicycle 22-25 km/h, on flat road. Despite I manage to cruise speed with the folding bicycle above 20 km/k I think I ride slower then a road bicycle. The top speed gap is more evident. From triathlon competition I know I can ride on a road bicycle at an average top speed just above 40 km/h on a flat road but on my folding bicycle I hardly manage to keep above 35 km/h. I must refer that I have my folding bicycle drive train with 100 psi tyre 451 X 27 with a single 52 teeth chain wheel sprocket 15 teeth.
rhm
07-05-07, 08:33 AM
Can you compare the respective aerodynamics of your road bike vs your upgraded folding bicycle? My first guess is: that's the biggest factor.
caotropheus
07-05-07, 09:22 AM
You're right about the aerodynamics. Unfortunatley I do not have any wind tunel to compare aerodynamics. If there is an empiric way to measure aerodynamics I am willing to try for both bicycles.
pm124
07-05-07, 10:18 AM
We've gone over this on other threads a lot recently. It seems as if wheel size is not a relevant factor for most people. However, few here feel that small wheels are faster than big wheels. Conversely, there are more people that feel that big wheels are faster than small wheels.
As for me, my 355mm Birdy folder seems to be faster than other folk's expensive road bikes. But I ride the folder all the time, and have probably conditioned myself based on my fit to the bike. I've never actually ridden a road bike that I've bothered to properly fit to my body.
There are some subjective things I've noticed. One is that others tend to blow me away on hills. Most of these people are on $3000+ 14 pound bikes, and I am on a 20 pounder. Also, I'm usually carrying light luggage. The funny thing is that I have no trouble on 20-24MPH group rides. I'm usually breathing less than other folks sucking wind around me. However, I cannot push the pack *at all*. Perhaps that's psychological, or perhaps it has to do with the more aerodynamic drafting of the folder.
Swift claims that 20" wheels are 1% less efficient than large wheels. That is a huge amount of efficiency loss over 100 miles! Bike Friday seems to implicitly claim this in calling their 451 bikes faster. But they also note that there is no disadvantage of small wheels at normal racing speeds. (Go figure.)
All I know is that I can get to work really fast and keep my aging ass up with the roadies on group rides. Yippie.
I think that the real answer is that no one knows. So, ride and have fun!
Bacciagalupe
07-05-07, 11:48 AM
Adding to pm124's comments.....
Performance-wise tire size is probably a wash. Smaller wheels tend to have better aerodynamics, but (*cough* edit) higher rolling resistance; they may even have a slight performance edge overall. However, in almost all cases you have to compensate for the rougher ride by doing something that will adversely impact performance.
Otherwise, pretty much the same factors come into play with any bike: geometry, stiffness, aerodynamics, rider position, gearing etc. Oh yeah. And engine. I've heard that's kind of important. :D
Generally speaking the higher-end models like the Bike Friday Pocket Rockets and the Moultons etc will be right around the same performance as an equivalently-priced road bike. Without sticking a power meter on your bikes, though, it will be very difficult to get any good hard numbers.
I.e., I wouldn't worry about it. Just ride whatever feels comfortable and fun.
jur
07-05-07, 04:12 PM
You can do a good comparison between 2 or more bikes by doing roll-down tests: Find a long shallow slope and time the roll-downs, no pedalling. Maybe pedal just to eliminate freewheel drag, but definitely no power applied.
With a roll-down test you can at least attempt to get the same aero position on the various bikes by hunching over to have the same torso angle for the cases. This then will tell you something about the bike as a whole. Wheel rolling resistance will be dominant, I think, but hub drag will obscure clear distinction between wheel sizes, if hub drag is significant.
Drivetrain efficiency is another matter that will have an effect on speed; obviously a roll-down test won't show anything. For that you would have to suspend the bikes and pedal by hand to get a feel for the drag on the pedals. Maybe some sort of spring scale between the hand and the pedal will yield drive train drag.
So by doing these tests you can see exactly where the difference lies.
caotropheus
07-05-07, 09:23 PM
I will make the slope test because it's easy and very low tech. I will set the same gain ratio for my several bicycles and apply a single pedal stroke to start movement and determine descending time for a given distance. I will make several repetitions randomly with the bicycles and then I will make a statistical treatment of the data with a qualitative linear regression and I will let you know the results.
pm124
07-05-07, 09:37 PM
Wow, you've invented a qualitative linear regression technique, caotropheus. We've been awaiting one in the social sciences.
This may all sound silly to some, but I find it interesting. It's one of those classic problems in which there are a lot of variables and theoretical efficacy calculations, but no real-world effectiveness data.
Was it Bacciagalupe who suggested actual wattage calculations? I think it's an great idea, factors out the rider's psychological factors and leaves only terrain and weather variablility, both of which can be measured and controlled. Maybe we can get old Moulton to fund this. Or Dahon! Come on baby, give us some equipment.
jur
07-05-07, 10:18 PM
Maybe pedal just to eliminate freewheel drag, but definitely no power applied.
I just had a better idea: remove the chain to eliminate freewheel drag.
caotropheus
07-05-07, 10:37 PM
Wow, you've invented a qualitative linear regression technique, caotropheus. We've been awaiting one in the social sciences.
No, I have not invented no statistical technique. It have been invented long before I was born in 1967. I suggest you to read this book.
It is an excelent book, but it does not refer Multi Analisis of Variance (MANOVA) that is a statistical technic frequently used in social sciences.
Pine Cone
07-05-07, 11:34 PM
I will make the slope test because it's easy and very low tech. I will set the same gain ratio for my several bicycles and apply a single pedal stroke to start movement and determine descending time for a given distance.
My daughter and I did a similar test several years ago for her 7th grade science project comparing the rolling distance for a mountain bike and a road bike with a heavy rider (me) and a light rider (her).
I found a low-use country road which had a very small hill and then was more-or-less flat after that. We didn't pedal at all, just started from a point on the hill and coasted from there until we stopped. We then measured the total distance of each ride. Worked pretty well but you need a calm day with no wind and several repetitions. The road surface (smooth or rough) will make a difference as well, so you should pick one similar to the average road in your area and try and ride the same path. We used duct tape to mark the start and stop points, using a marker to record which replication it was on the ending tape.
You might also try a couple of different tire pressures to see what difference that makes.
I'm not sure what happened to the spreadsheet with the data, but as expected, road bikes with high pressure smooth tires roll farther than knobby mountain bike tires at half the pressure. Fat old men roll downhill further than skinny girls.:D She got the top prize for 7th graders and we both had a good time!
I'm looking forward to your results.
caotropheus
07-06-07, 12:44 AM
Pine Cone
In my case I do not have a smooth hill followed by a flat road, but I have a small inclination descend for about 200 m and I am going to set a start and finish line and I am going to measure time between those two lines.
cooker
07-08-07, 07:10 PM
Why make it so complicated? Across the street from me is a 400 m high school track. I will time myself doing ten laps on my tour bike, Bike Friday and mountain bike from time to time over the summer in random order and post the results.
One thing that is different about the smaller wheel is momentum. It accelerates and decelerates more readily than a larger wheel. So unless you pedal at a very steady effort, you repeatedly surge and lag. That may make it feel either slower or faster than it really is.
jur
07-08-07, 07:43 PM
One thing that is different about the smaller wheel is momentum. It accelerates and decelerates more readily than a larger wheel. So unless you pedal at a very steady effort, you repeatedly surge and lag. That may make it feel either slower or faster than it really is.Unless you are going up a steep hill, surges with every pedal stroke is negligible. Momentum of your body is much larger than that of a wheel, unless you have a wheel built for Godzilla.
Dahon.Steve
07-08-07, 08:36 PM
Is it theoretical possible to improve a small wheeled (451 mm wheel and smaller) bicycle to ride side by side with a road bicycle ? how?
It's not only possible, the machine has already been built! Now if we can only get them to design a folder??
Unless you are going up a steep hill, surges with every pedal stroke is negligible. Momentum of your body is much larger than that of a wheel, unless you have a wheel built for Godzilla.
The wheel has low rotational inertia and that means when you increase your effort you can accelerate a bit quicker, and if you ease up you lose speed quicker.