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how much faster is a RB over MTB with slicks?

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how much faster is a RB over MTB with slicks?

Old 03-28-09, 04:04 AM
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ssgg
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how much faster is a RB over MTB with slicks?

I've been wondering if anyone know how much faster is a RB over a MTB with slicks on the flat?

Both average speed and top speed.

Thanks for any input.
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Old 03-28-09, 04:09 AM
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depends.

/thread
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Old 03-28-09, 04:09 AM
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the same, except you can really put yourself in a better 'tuck' position with drop bars to lessen the air resistance, which is most of the resistance you encounter while just pedalling along.
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Old 03-28-09, 04:20 AM
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My road bike has a top end of 400 watts
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Old 03-28-09, 04:36 AM
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so mainly an aerodynamic thing because of the riding position?
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Old 03-28-09, 05:21 AM
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Originally Posted by ssgg View Post
I've been wondering if anyone know how much faster is a RB over a MTB with slicks on the flat?

Both average speed and top speed.

Thanks for any input.
Depends on the engine, but for me a lot. You are going to spin out a mtb earlier than the road bike, it's geared different. Also, fat slick tires are still a lot less efficient on the road than skinnny slick tires.
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Old 03-28-09, 05:23 AM
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With the same rider/route, the roadie will be a third faster over a few miles for a number of reasons.
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Old 03-28-09, 05:33 AM
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I've heard nothing but mixed things about this topic.
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Old 03-28-09, 05:40 AM
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MB with Slicks -- About 15-20% Slower

Figure about a reduction of 15-20% on average.

So if your average on a flat is 18, on the whole, you'll probably be at 15. If you average is 20, figure about 16. If your average is 15, probably 13.5.
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Old 03-28-09, 05:48 AM
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Originally Posted by Pugsly View Post
Depends on the engine, but for me a lot. You are going to spin out a mtb earlier than the road bike, it's geared different. Also, fat slick tires are still a lot less efficient on the road than skinnny slick tires.
you can always change the gear range on MTB by going with a larger chainring.
since MTB can mean 26" or 29", 29" being the same thing as 700c, that and road has it's own smaller wheel variant of 650c, the gearing argument isn't valid.

for wheels, larger diameter = better rolling efficiency, so fatter slicks on 29'er/700c would give you even more rolling efficiency.
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Old 03-28-09, 05:50 AM
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recumbent, faster yet :
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Old 03-28-09, 06:06 AM
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Originally Posted by AEO View Post
you can always change the gear range on MTB by going with a larger chainring.
since MTB can mean 26" or 29", 29" being the same thing as 700c, that and road has it's own smaller wheel variant of 650c, the gearing argument isn't valid.

for wheels, larger diameter = better rolling efficiency, so fatter slicks on 29'er/700c would give you even more rolling efficiency.
Lol, way to take a general question with a good general answer and give one example of a configuration that nobody would use as a counterpoint. Bet you're great fun at parties!

Generally mtb = 26 and rb = 700c. But wait, it could also mean a fixie or a single speed. Road bike could also mean a track bike. Oh it's all so confusing.

btw, fast roadbike tires are all about rolling resistance. A fatter tire has much higher rolling resistance so will slow you down. That's why running your tires at lower pressure slow you down (it's not, as you would argue, the slightly reduced radius)
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Old 03-28-09, 06:40 AM
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I agree that, generally, a road bike is about a third faster than a MTB. My personal experience having ridden a century on a MTB with slicks and a Roadie later is that life was just way better on the road bike when riding on the road. Way better and faster. Then there is my commuter/tourer that is geared like my roadie but heavy like my MTB and I still manage to have fun on it and ride long distance without fear of being too light or too fast. It is wise to ask others about these things because there are so many variables and you have to be settled in your mind about what you really want. Best of luck to you.
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Old 03-28-09, 06:54 AM
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the reason why I ask is that where I cycle is mainly flat ( cycle path and road) and I already have a disc brake hardtail that weighs around 25lbs. It has some very smooth sun ringle hubs with some michelin 1.4 slicks.

Just weighing up if I should get a road bike as well. But road bike stuff seems to cost a lot more for decent gear.
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Old 03-28-09, 06:59 AM
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Generally, about a quarter faster for me; a whopping third if I have knobbies on the mtn bike.

It definitely depends on your mtn vs road bike build though - my mtn bike weighs 36lbs and has knobbies, whereas my roadie weighs <19lbs. I suspect that if I got on an ultralightweight 19 lbs mountain bike, the difference would be much smaller.

The gearing makes a difference as well - I max out my mtn bike gearing even on flats if I'm riding hard, whereas my tribike is geared aggressively enough for me to hammer even on downhills. For me, the gearing was actually a more limiting factor, as I could never get to a reasonable top speed before maxing out the mtn bike if I was riding hard.
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Old 03-28-09, 07:01 AM
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average speed 3.568790543 mph
top speed 11.123456789 mph


or depends
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Old 03-28-09, 07:17 AM
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The position makes more difference than anything else. The difference in tires is minimal, and will really depend more on the tire type and pressure. Gearing will only matter on descents, unless you're quite strong.
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Old 03-28-09, 07:21 AM
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I had a buddy who was a pro fat tire guy back in the 90s who could win PCad's fabled Nyack ride on a mountain bike with knobby tires.
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Old 03-28-09, 07:24 AM
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It's not just the gearing and wheels that make the difference. MTBs, by their nature, are designed for riding over rough surfaces so they have a lot of features intended to help absorb the bumps and jolts you encounter over typical MTB terrain. The trade-off is that those same features absorb some of the energy you put into the system by pedalling.

A road bike, by contrast, is designed specifically to minimize energy loss. You sacrifice comfort for the sake of a more efficient machine, which translates into a faster ride.

All things being equal (same rider, route, weather conditions, etc.), I suspect that a road bike would still be somewhat faster than an MTB, even if both bikes were using the same tires and gears. The road bike simply transfers energy better.
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Old 03-28-09, 07:25 AM
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Originally Posted by ssgg View Post
I've been wondering if anyone know how much faster is a RB over a MTB with slicks on the flat?

Both average speed and top speed.

Thanks for any input.
Use the Fredlich computation to calculate that : (M(2)*.45532/T)+(L/554.4) where M=mass of bike and rider, T=ambient temperature, and L=length of bibshort
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Old 03-28-09, 07:26 AM
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You don't really need to go faster on the bike path. MTB should be sufficient there.
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Old 03-28-09, 07:45 AM
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Duh, just plug your weight, your output at the crank, and IQ into this here formula and it will tell you exactly how much faster you'll be:

1/PI f^2(x) dx = a(0)^2 / 2 + (k=1..) (a(k)^2 + b(k)^2)
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Old 03-28-09, 07:50 AM
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Originally Posted by gsteinb View Post
depends.

/thread
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Old 03-28-09, 08:02 AM
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When I transitioned my 17 mile commute to work from a MTB with knobbys to slicks I gained about 2-3 MPH on average. Then, when I switched to riding a light carbon RB I gained another 1-2 MPH. So for me at least the biggest benefit was ditching the knobbys (~20% gain), compared to the difference of RB over MTB with slicks (~10%). Obviously there are a lot of variables, but this was my experience.
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Old 03-28-09, 08:02 AM
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Originally Posted by Pugsly View Post
A fatter tire has much higher rolling resistance so will slow you down. That's why running your tires at lower pressure slow you down (it's not, as you would argue, the slightly reduced radius)
If I'm reading you correctly, you have it mostly wrong. If there existed a 35mm tire that could hold the same pressure as a 23mm tire, the rolling resistance would make very little difference in speed. It's the lower pressures that result in the wider tires being slower.
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