Tire types?

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deronmoped
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Tire types?

I have read that they make low rolling resistance tires for cars, do they make them for bicycles? If they do, any idea what percentage increase they would give you over a standard set of tires.

One other thing, I noticed that E-bikes and Pedelecs do not use the skinny 10 speed type tires, has anyone rode a E-bike or Pedelec with them? If you did, what was the ride like?

Thanks, Deron.

fisher727
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Re: Tire types?

I have an electric car called a Force and it came with roll resistance tires. I drive the same 42 mile to work everyday. I wanted to see if I used the roll resistance tires on my gas powered car, with has the same size tire, would they give me better gas mileage. One thing I notice about the roll resistance tires was that the max pressure allowed was 45 psi compared to the 35 psi max on the non roll resistance tires. I used the tires for a month or longer with a tire pressure of 45 psi before I switch them back. They seemed to increase my gas mileage about 5%. I decided to pump the non roll resistance tires up to the 45 psi and try them that way. Not recommended this was exceeded the tire pressure by 10 psi. I ran it this way for a month and found that I was able to get a 5% increase in the gas mileage also. I did conclude that the pressure has more to do with the gas mileage than the type of tire. Maybe the only difference between non roll resistance tires and roll resistance tires is the max. allowed tire pressure?

Eric Fisher
www.Siliconebatteriesusa.com

cerewa
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Re: Tire types?

I would recommend against narrow tires for an e-bike unless you have suspension- you'll be putting extra stress on your rims and giving yourself a more uncomfortable ride for a minimal increase in efficiency.

I also think that for an on road e-bike that goes less than 30 mph, suspension is unnecessary if you have fat tires... and the weight saved by going without suspension plus the increase in pedaling efficiency ('cause your bike won't bob up and down) will benefit you more than having suspension.

deronmoped
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Re: Tire types?

Too bad the roads were not better, it's a shame that a road bike should need suspension. Here in San Diego, you almost need a full suspension mountain bike to be safe on the roads.

I do own a bike that is a cross between a mountain bike and a road bike, the tires are a little narrower then my Pedelec's tires. If I was to build a E-bike, I would definitely look for high pressure, fairly narrow tires. Could make a significant difference in range.

Deron.

pgarver
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Re: Tire types?

I actually created an account just to answer this question (finally, something I know!). I work with bikes and I can tell you that what you want for minimum rolling resistance is high pressure tires with no tread (unless you're riding off road). You'll notice I didn't mention skinny, and that's because the width doesn't make an appreciable difference in speed. Road racers ride skinny tires because they're lighter and have a smaller profile for drag, and every watt and every gram counts for racers.

I'm putting together an ebike right now, and I'm going to use Schwalbe Big Apple tires, because they're wide (2.0"/50mm), so they offer some built in suspension, slick so they won't waste energy bending tread every time they go around, and high pressure (70 psi, about 4.5 atm), so they will be efficient. There are many other suitable choices, some cheaper and some more expensive. If I were feeling more spendy, I would use the Schwalbe Marathon Supreme, but $70/tire is a bit much for this project. I wouldn't go skinny, because ebikes are often ridden at high speeds, and are generally made using low-end bikes, which are less able to withstand the abuse the additional vibration of skinnier tires.

If this seems unintuitive, check the calculator at kreuzotter.de. If you change tires from "narrow racing tire" to "wide high pressure slick", the rolling resistance figure actually goes down (the total power required to go a given speed goes up, but that's because the wide tires add to the frontal area and the wind drag).

A slick tire (or the least tread you can find - true slicks are hard to find for psychological reasons - people think they won't be stable in wet weather) is also the best tire to use on pavement in all situations; it seems rational that hydroplaning should be a problem, since it is with cars, but cars use very low pressure tires and very high speeds, which is why the problem occurs. The minimum speed for hydroplaning can be estimated as Vp = 9.0 * sqrt(pressure) (pressure in psi, speed in mph), so for a 50psi tire (not very high pressure), the minimum speed to hydroplane is 63mph or 100 km/h. For the Big Apples I'm going to use, the speed is 75mph. If you have to worry about that, you have other things to worry about as well. :)

However, that said, particularly at higher speeds, rolling resistance is not what's using up most of your energy. If you want more efficiency or speed (whichever is your goal), getting yourself into a more aerodynamic position somehow will pay much bigger dividends.

(Hydroplaning equation taken from http://yarchive.net/air/airliners/tire_prespin.html - hydroplaning is of course a big issue with landing planes, which is where this equation is from)

deronmoped
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Re: Tire types?

From what I remember, a bike with fat tires always seemed to pedal like a tank and when I jumped on a bike with skinny tires it always seemed to roll better. The pressures were quite a bit different, with low pressure (35 PSI) for the fat tires and high pressure (65-75 PSI) for the skinny ones. Now the fat tires always had a real aggressive tread and the skinny ones had almost no tread at all.

It does make sense though, if you go with no tread and high pressure the rolling resistance will be low.

Deron.

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