cyclocross ebike project

General Discussion about electric bicycles.
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chas58   10 kW

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Re: cyclocross ebike project

Post by chas58 » Mar 29 2017 4:47pm

Keep in mind your traction is not dependant on tire size. The basic physics is the traction is based on weight and coefficient of friction.
(Tour de France riders have no traction problems cornering hard down hill on tiny tires).
tire pressure will have some bearing on traction in that a lower PSI tire will stay in contact with a bumpy road more than a high pressure tire...

The ironic thing about burning fat calories is you burn more at moderate exercise. Once you start breathing harder you are burning sugar, not fat. So, for loosing weight, moderate exercise is best.
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flat tire   1 MW

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Re: cyclocross ebike project

Post by flat tire » Mar 30 2017 10:13pm

chas58 wrote:Keep in mind your traction is not dependant on tire size.
Ahh. I hear this a lot. It's a half truth. Yes, classical friction coefficient for a given material is independent of contact area... In reality, you are not limited to one material to make tires out of. You have a variety of different compounds possible and for a given load, increasing the contact area will lessen the relative demand on your contact patch, allowing a softer compound to be used. In other words, a bigger tire spreads things out so a soft compound doesn't just immediately get torn off.

Another thing to consider is tires don't get all their grip just from classical friction, there is actually mechanical interlock of the rubber with the riding surface. That's the kind of thing where more is better.

One other minor effect is a slight reduction in coefficient of friction the more you overload a given contact area. This effect is minor and I don't think it is important for something as light as a bicycle, but it is important for race cars.

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E-geezer   100 W

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Re: cyclocross ebike project

Post by E-geezer » Mar 31 2017 11:16am

My experience with commuting,especially with a motor is that you might want to go with wider tires down the road than most crossbikes are set up for. I prefer 35-40's now for the traction and cush.

Just to throw a monkey wrench in the works, I've got a buddy who uses a fully rigid chinese carbon 27.5mtb frame with 700c wheels as his cross/commuter, he loves it and there's no limit on tire size. I've converted a 26" HT frame to the road as well.
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atxmarmot   10 mW

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Re: cyclocross ebike project

Post by atxmarmot » Apr 22 2017 9:43pm

Just to throw some more experiences in to the mix. I have a BBSHD (48V) kit which I have mounted on 2 very different bikes and used for my 6 mile (each way) commute. My commute has one extremely steep hill and then around 15 lights/stop signs.

The first time around I mounted the BBSHD on a road bike with skinny tires. It was great, and my commute took about 25minytes with a fair amount of pedal input (by choice). I never once had any issues with loss of traction or being unable to stop the bike, even with rim brakes, but I live in a dry climate. The only reason I moved the kit to a different bike is that it was obvious that my other bike (a radwagon like RyanC) would be an even better match as it is a cargo bike and I use it to haul my kids around. Another thing that some people emphasize is the wear on the drive train. I have not found that to be issue over 800 miles, but I am pretty careful to use the appropriate gear and be progressive in the throttle application when I use it. I would not use an expensive drive train, but I don't think it is that much of an issue.

So, IMO go for it, it'll be a fun setup!

anth_85   10 mW

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Re: cyclocross ebike project

Post by anth_85 » Apr 23 2017 1:47pm

atxmarmot wrote:Just to throw some more experiences in to the mix. I have a BBSHD (48V) kit which I have mounted on 2 very different bikes and used for my 6 mile (each way) commute. My commute has one extremely steep hill and then around 15 lights/stop signs.

The first time around I mounted the BBSHD on a road bike with skinny tires. It was great, and my commute took about 25minytes with a fair amount of pedal input (by choice). I never once had any issues with loss of traction or being unable to stop the bike, even with rim brakes, but I live in a dry climate. The only reason I moved the kit to a different bike is that it was obvious that my other bike (a radwagon like RyanC) would be an even better match as it is a cargo bike and I use it to haul my kids around. Another thing that some people emphasize is the wear on the drive train. I have not found that to be issue over 800 miles, but I am pretty careful to use the appropriate gear and be progressive in the throttle application when I use it. I would not use an expensive drive train, but I don't think it is that much of an issue.

So, IMO go for it, it'll be a fun setup!
thanks that sounds brilliant.

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Re: cyclocross ebike project

Post by flat tire » Apr 23 2017 3:07pm

FWIW, those skinny road bike tires (good ones) have the best tarmac cornering grip and stopping grip available out of any type of bicycle tire. They have the most development, most exotic compounds and road bikes actually corner at speed on tarmac unlike basically any other type of bicycle around.

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Re: cyclocross ebike project

Post by Raged » Apr 26 2017 8:35am

flat tire wrote:FWIW, those skinny road bike tires (good ones) have the best tarmac cornering grip and stopping grip available out of any type of bicycle tire. They have the most development, most exotic compounds and road bikes actually corner at speed on tarmac unlike basically any other type of bicycle around.
Only when it's dry. Do a stop test at 40km/h on a 40+lb ebike with skinny tires and fat tires in the wet and you will soon appreciate balloon tires.
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anth_85   10 mW

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Re: cyclocross ebike project

Post by anth_85 » Apr 26 2017 9:21am

Raged wrote:
flat tire wrote:FWIW, those skinny road bike tires (good ones) have the best tarmac cornering grip and stopping grip available out of any type of bicycle tire. They have the most development, most exotic compounds and road bikes actually corner at speed on tarmac unlike basically any other type of bicycle around.
Only when it's dry. Do a stop test at 40km/h on a 40+lb ebike with skinny tires and fat tires in the wet and you will soon appreciate balloon tires.
That is true. But on a flat surface like tarmac, then the thread pattern is just there to clear standing water. The grip is created from the contact patch between the rubber and the road. Knobbly tyres just give you the contact on the knobbly bits so would give less grip. This is the order I'd say gives the best grip on wet tarmac.

Best - wide tyre for big contact patch, good standing water clearance
Image

Good - narrow tyre, smaller contact patch, good standing water clearance
Image

less -
narrow contact patch, slick tyre for poor water clearance
Image

Worst
Good for mud and trails but excessive water clearance for road gives less contact area.
Image

Off road is obviously very different

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