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Old 09-12-10, 02:36 AM   #1
NE Tiger
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The speed gap between bike styles?

Is the speed gap between hybrids and road bikes less than the speed gap between hybrids and mountain bikes?

I was on a flat bike path yesterday, and riding alongside someone of similar dimensions. He was on a mountain bike in the same gear as me, pedaling at the same pace, but on my hybrid with narrow tires, I was going significantly faster.

A guy came by on a road bike and he was pedaling at the same pace, and shot by me. Later I saw him stopped, asked what gear he was riding in, and he was in the same gear as well. And I lifted his older road bike, and I couldn't tell much if any of a weight difference between it and my hybrid.

So..what gives? Why was the road bike that much faster? It wasn't the tires. Doesn't seem to be weight. I wouldn't think it was wind resistance. Maybe rider angle effect on pedaling power? Gearing? I don't get it.
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Old 09-12-10, 03:00 AM   #2
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Where I live, the classification of bikes in just 3 groups is not appropriate. We have road bikes with flat bars, that some people call a hybrid. But we also have bikes with front suspension that are not MTBs and are called hybrid by some. The flat-bar road bikes seem to be as fast and light as a road bike. The ones with the front suspension are heavier but also reasonably fast. The big difference comes when you start to get the wide chunky tires. This gives you not just increased weight but increased rolling weight and gyroscopic effect. So the bikes with heavy wheels can't accelerate or brake so easily. In addition the chunky tires flex considerably as they compress under the weight. This compress-decompress action takes a lot of energy. I frequently find myself coming up behind a dude on a commuter bike with heavy tires, and while he is constantly pedaling downhill a slight gradient, I can just coast past him.
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Old 09-12-10, 04:21 AM   #3
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I haven't done this in a while (haven't had a speedometer/cycling computer for years, last one was on a bike that was stolen :/ ), but I remember a measurable difference between sitting fully upright, no-handed; and riding forward, hands on the bars. Perhaps wind resistance makes more of difference than you think. The prevalence of wind fairings on land-speed record bikes would seem to indicate such.
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Old 09-12-10, 05:51 AM   #4
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Yeah, I think tires make a big difference in speed/rolling resistance (especially the extremes of smooth verses knobby).

Something else to consider, sorry if I'm stating the obvious (and you may have taken this into account already) but the gearing (the assorted sizes of the cassette gears on back and the chain-ring gears on front) of each bike you observed might be much different, so say, if all of you where in the 3rd largest gear in the back and the largest chain-ring on the front, you still might (because of differing gear sizes) be dealing with very different amount of power transfer (I think I've read the term "gear-inches" used when making comparisons between different gearing combinations when this has been discussed in the past).

In my experience mountain bikes don't have as much "high" gearing, you might "run out of gear" if you try to go very fast down a paved hill on a mountain bike. Some road bikes (especially conventional two-ringed chain-ringed ones) might not have the "low" gears some desire for climbing steep hills.

The effect of different gearing is that, with each peddle stroke, the back wheel is rotating at a different rate. Three different people on three different bikes might be peddling at the the same rate (say 70 "strokes" a minute) but with differing gearing the back wheels are turning at different rates and accelerating the bikes at different speeds.
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Old 09-12-10, 06:53 AM   #5
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There are three things that affect your speed on a bicycle: motor, aerodynamics, rolling resistance (in order of importance).

If you have a good enough motor you can forget the other two.
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Old 09-12-10, 09:14 AM   #6
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Quote:
So..what gives? Why was the road bike that much faster? It wasn't the tires. Doesn't seem to be weight. I wouldn't think it was wind resistance. Maybe rider angle effect on pedaling power? Gearing? I don't get it.
The guy on the road bike who blew by you might be on the same gear settings as you, but if you look at his chainrings and cassette closely, I'm willing to bet he has a higher gear ratio (or gear inches) than your hybrid. Typical road bikes might have a 52-tooth large chainring on the front, whereas 48T or smaller chainrings seem more common on hybrids.

Also, tire pressure makes a huge difference. Firmer tires have less rolling resistance. Soft tires balloon out at the bottom as they roll, and this flexing in the sidewalls eats up pedaling power. Typical narrow 700x23c road bike tires are inflated to around 120PSI. Hybrids with wider tires typically have lower tire pressures like 80PSI or so.

The weight of the wheels also makes a difference. It takes more pedaling effort to keep a heavy set of wheels spinning than a lighter set of wheels, and typically road bikes have lighter (narrower) 700c rims and often fewer spokes than wider hybrid wheels.

I own both a front-suspension hybrid (Trek 7200, Bontrager wheels and 700x35c tires, 48T chainring) and a flat-bar road bike (Specialized Sirrus Expert, Ksyrium Elite wheels, 700x23c tires, 52T chainring). Both weigh about the same, but I can top out 5mph faster on the Sirrus than on the Trek due to the Ksyrium Elite wheels, higher pressure 23c tires and bigger chainring.
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Old 09-12-10, 09:28 AM   #7
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Its all in the gearing, wheel weight (my opinion) doesnt matter as much as some say, my daily rider is a 26" MTB i converted to drop bars i run a 50t large up front and a road cassette in rear 11-28 i do lose a little top end with the smaller wheel size but its plenty fast very close to my actual road bike. And like said before they may all be in the "same" gear but different size sprockets. Also different crank arm length, riding position, weight, condition of said bikes(bearings and such), so basically there is a lot that makes for "speed gaps"
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Old 09-12-10, 09:52 AM   #8
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Normally, I'd just say that it's the riding position (assuming that the riders' fitness is about the same). The same rider on different bikes can go faster, or the same speed with less effort, on a bike that lets them use a more aerodynamic position.

But, OP, since you mentioned "the same gear", you're unwittingly bringing up the different gearing usually seen on these bikes. Mountain bikes aren't meant for chugging along on a paved road at 25 mph, just like road bikes aren't made to climb over tree roots at 5 mph. The gearing for each is tailored to the task.

My three bikes -- coincidentally one each of road bike, hybrid, and mountain bike -- all have different gear ranges, and they're just as others have described already. And, even though I'm running the same 50/34 chainring combo on both the hybrid and road bike, the hybrid's cassette is a little wider and gives me a lower low gear.
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Old 09-12-10, 09:56 AM   #9
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Basically, if you and another rider on a different bike are pedaling at the same cadence AND you are going the same speed, THEN you are using the same effective gearing (tire circumference included).

However, OP, you weren't. You would have had to downshift to match the cadence AND speed of the mountain biker, and you would have had to upshift to do the same with the road biker.
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Old 09-12-10, 10:02 AM   #10
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Quote:
Originally Posted by Retro Grouch View Post
There are three things that affect your speed on a bicycle: motor, aerodynamics, rolling resistance (in order of importance).
Yes.

Quote:
If you have a good enough motor you can forget the other two.
No. Aerodynamics remains really important even if you have a great engine. Air resistance is the reason it takes a greater increase in power to raise your average speed from 20 - 22 mph than from, say, 16 - 18 mph. And riding in the drops will make a significant impact on your speed for the same power output; much more, for example, than taking a couple of pounds off the weight of the bike.
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Old 09-12-10, 11:17 AM   #11
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This is a little off the main topic, but since it came up:

Quote:
Originally Posted by LongIslandTom View Post
Also, tire pressure makes a huge difference. Firmer tires have less rolling resistance. Soft tires balloon out at the bottom as they roll, and this flexing in the sidewalls eats up pedaling power. Typical narrow 700x23c road bike tires are inflated to around 120PSI. Hybrids with wider tires typically have lower tire pressures like 80PSI or so.
Jan Heine and Mark Vande Kamp measured the real-world performance of various tires, and they determined that a wider tire (28-30mm on 700C rims) with a supple casing, run at moderate pressure, was more efficient than narrower tires run at high pressure. The higher rolling resistance of the wider tires was more than balanced out by the lower suspension losses from road irregularities. See Jan Heine and Mark Vande Kamp, "The Performance of Tires," Bicycle Quarterly vol. 5, no. 1 (2006), p. 1. (Not available online, unfortunately.)

They also found enormous variation in the performance of different brands of tires, depending on how supple their casings are.

Finally, Frank Berto has calculated that the ideal pressure is that which results in the tire dropping 15% of its width under load. This article from Bicycle Quarterly explains the principle and provides a handy chart for calculating optimal pressure.
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Old 09-12-10, 12:33 PM   #12
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Staying on this tangent..

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Originally Posted by brianogilvie View Post
This is a little off the main topic, but since it came up:

Jan Heine and Mark Vande Kamp measured the real-world performance of various tires, and they determined that a wider tire (28-30mm on 700C rims) with a supple casing, run at moderate pressure, was more efficient than narrower tires run at high pressure. The higher rolling resistance of the wider tires was more than balanced out by the lower suspension losses from road irregularities. See Jan Heine and Mark Vande Kamp, "The Performance of Tires," Bicycle Quarterly vol. 5, no. 1 (2006), p. 1. (Not available online, unfortunately.)
If it's related, I can keep pedaling harder and longer if I'm on a smooth road -- or, if the surface is a little rough, I'm on a bike with suspension.

If I'm on my road bike and am on a rough, crappy, washboard section, or maybe a wooden bridge, I'm spending more effort just to absorb the shocks with my body. I don't get the chance to sit there and pedal. But, if I'm on my FS MTB, I can barrel down a limestone trail, chattering washboard and ruts and all, pounding away on the pedals nonstop.

Back on the road bike -- I think there's a balance between distruptively-bouncy-hard and energy-sapping-soft with tire pressures. If I use the recommended pressure from that BQ article or the pressure from psimet's formula, it works pretty well. I would consider lower pressure for rougher conditions, but then I'd be more worried about pinch flats and rim damage -- which means that I'd rather use bigger tires instead.
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Old 09-12-10, 04:42 PM   #13
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Interesting. Thanks!
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Old 09-12-10, 04:57 PM   #14
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Back on the road bike -- I think there's a balance between distruptively-bouncy-hard and energy-sapping-soft with tire pressures.
Agreed. What's surprising about Jan and Mark's results is that narrow tires don't win, despite the widespread belief that they are faster. I was out on Friday with a couple guys who are about my fitness level. They were on road bikes with narrow (23-25 mm) tires. I was riding my touring bike with 35 mm Panaracer Paselas, which did pretty well in the Bicycle Quarterly test (though they tested a narrower version). All three of us kept up the same speed with about the same amount of effort. I run my front tire at 55 psi and my rear at 75 psi; I didn't ask but they must have been running theirs at around 120 psi. Of course we were on rural New England roads which are not really smooth even when they haven't been patched and repatched a dozen times!

Jan points out too that a lot of riders have been conditioned to think that hard tires feel faster, even if objective measurements show that they are not.
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Old 10-15-10, 09:54 PM   #15
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I read somewhere that geometry may also make a difference, is that true?

Also, all other factors being equal (including the cyclist on the saddle--), is a men's bike with horizontal top tube faster than a women's step-through bike?
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Old 10-15-10, 10:01 PM   #16
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Also, all other factors being equal (including the cyclist on the saddle--), is a men's bike with horizontal top tube faster than a women's step-through bike?
Not in any significant degree if all other factors are equal.

The standard diamond frame is stronger than the step-through frame, however. So the step-through frame is likely to be heavier to compensate. Not that weight on a bicycle means very much unless 1) you're carrying it or 2) you're going up hills (though a few pounds aren't going to mean more than a few % difference in your speed) or 3) it's a race and a tiny fraction of a second may make the difference between winning or losing.

Geometry does matter, however -- it changes how the motor (i.e. you) is situated and therefore your air resistance. For an extreme change, think of a utility bike vs. a recumbent racer. But the existence or non-existence of that top bar doesn't matter, as long as the rest is unchanged.
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Old 10-15-10, 10:12 PM   #17
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Basically, if you and another rider on a different bike are pedaling at the same cadence AND you are going the same speed, THEN you are using the same effective gearing (tire circumference included).
There is a lot of talk here about how to ride faster but it is off-topic from the original question. This quote hits the general idea.

If two cyclists really are running the same cadence, their relative speeds will depend solely on their gearing. Whether or not they are capable of running that speed, which is to say capable of running with that cadence in that gear, depends on all those other factors mentioned, the rider's power, the wind resistance, the tires, etc. So their top speeds or top sustainable speeds may be different. But below that their speeds for the same cadence depend only on the gear (which includes wheel size). Note, two riders may seem to be at the same cadence but not really be identical. So there is some wiggle room in the "was the same as" observation.
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Old 10-15-10, 10:29 PM   #18
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Not in any significant degree if all other factors are equal.
Thanks. Beside the weakness of the frame, what about pedaling efficiency? This article seems to suggest the step-through is not as efficient as horizontal top tube:

"it’s an innately weak and inefficient design compared to the classic diamond frame, because of the way the top tube joins the seat tube far below the seat stays. It’s inherently ’floppy’ by comparison and, other things being equal, requires greater effort from the rider for the same speed."

I can understand the frame weakness due to the lower top bar, but why and how does it affect pedaling efficient/effort?
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Old 10-15-10, 10:32 PM   #19
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Quote:
Originally Posted by brianogilvie View Post
This is a little off the main topic, but since it came up:



Jan Heine and Mark Vande Kamp measured the real-world performance of various tires, and they determined that a wider tire (28-30mm on 700C rims) with a supple casing, run at moderate pressure, was more efficient than narrower tires run at high pressure. The higher rolling resistance of the wider tires was more than balanced out by the lower suspension losses from road irregularities. See Jan Heine and Mark Vande Kamp, "The Performance of Tires," Bicycle Quarterly vol. 5, no. 1 (2006), p. 1. (Not available online, unfortunately.)

They also found enormous variation in the performance of different brands of tires, depending on how supple their casings are.

Finally, Frank Berto has calculated that the ideal pressure is that which results in the tire dropping 15% of its width under load. This article from Bicycle Quarterly explains the principle and provides a handy chart for calculating optimal pressure.
I agree with this completely... this tire "dropping width under load" is called deflection and if a tyre is pressured up to a point where it does not deflect under load it will have a negative effect on performance and handling.
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Old 10-15-10, 10:38 PM   #20
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Finally, Frank Berto has calculated that the ideal pressure is that which results in the tire dropping 15% of its width under load. This article from Bicycle Quarterly explains the principle and provides a handy chart for calculating optimal pressure.
Interesting. According to that, their recommended pressure for my front tire (~40 psi) is probably lower than the minimum recommended by the manufacturer.
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Old 10-15-10, 10:50 PM   #21
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I ride them all... and my road bike idles at speeds I consider decent for some of my other bikes.

It is lighter, is geared higher, has much lower rolling resistance, and is more aero which allows me to ride at much higher speeds while being more efficient.

Conversely... I have bikes that don't look fast that are much faster than appearance would suggest.

Strip all the luggage off this little guy and drop the bars to a more aero position and you have a pretty fast package.

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Old 10-15-10, 11:32 PM   #22
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dont worry about the road bike, im sure he wouldve passed you up even if you were on matching bikes. he was probably mashing a bigger gear as he passed you and changed gears when he stopped and neglected to tell you.

bottom line dude is hybrids are awesome. its the man, not the machine(but having an awesome machine can sometimes help the man).
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Old 10-15-10, 11:46 PM   #23
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I can understand the frame weakness due to the lower top bar, but why and how does it affect pedaling efficient/effort?
Got me. If it flops around, that can sap energy from your pedaling -- but really, it's not going to flop around much.

It is entirely possible that they're just ... wrong.
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Old 10-19-10, 09:15 PM   #24
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Got me. If it flops around, that can sap energy from your pedaling -- but really, it's not going to flop around much.

It is entirely possible that they're just ... wrong.
I asked the question to an acquaintance who is a mechanical engineer. He explained that the frame does not absorb the energy from the "wiggle" or it would get hot! Eventually the energy is returned back to the pedals... weird hah?
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Old 10-19-10, 10:42 PM   #25
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If you were indeed pedaling at the same pace your speed differences can only be attributable to gearing or tire size (circumference, not width). Your legs were moving at the same speed but your wheels were revolving at different RPMs. The gear you all were in may have been labeled the same but the ratio is the variable.
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