Wheel diameter and maximum speed

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CDinFrance
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Wheel diameter and maximum speed

Just got a new pedelec today - Villiger Levantina E with BionX - very nice bike. However the new software does not allow turning off the max speed - here in Europe it is limited at 25kph. I can change the wheel diameter though, so doesn't this have the same effect? For example a wheel circumference of 20% less will reach 25kph at a highr RPM. Of course this will throw off the speedometer, but who cares.

Am I missing something or will this work?

Thanks.

strawhistle
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Re: Wheel diameter and maximum speed

I think you got that backwards,
The limiter detects motor rpm if you use a larger wheel the motor turns to the same speed , you go faster

thank GOD I wake up above ground !!!!

sixpax2k9
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Re: Wheel diameter and maximum speed

I think you got that backwards,
The limiter detects motor rpm if you use a larger wheel the motor turns to the same speed , you go faster

I agree... you would need to put on a LARGER circumference wheel to get a higher maximum speed with the same motor rpm. This however, would make your acceleration a bit slower as well.

But what you wrote IS correct...

For example a wheel circumference of 20% less will reach 25kph at a highr RPM

... this is very correct, if the circ. is smaller, it will need higher rpms to reach the same speed. But if I understand correctly, You goal is to increase top speed from a motor that is set with a maximum speed. The only way to "TRICK" it into going faster would be to put a larger wheel on it.

Dave ; Tennessee
XB-600.

garygid
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Re: Wheel diameter and maximum speed

I think he wants to lower the bike's max speed to 25 to stay within his local laws.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

CDinFrance
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Re: Wheel diameter and maximum speed

Still confused. If the motor RPM is limited to a maximum, say 100 rpm, then a bigger wheel would go faster and a smaller wheel would go slower at 100 RPM.

But the motor is limited by bike speed not RPM right? If the bike has a large wheel and is turning at 100 RPM to get the max speed, then a smaller wheel would have to turn faster to get the same speed.

Programming a smaller circumference should tell the computer that the wheel should be turning faster to get to 25 kph.

Since the wheel is not smaller, but the computer thinks it is, the motor should max out at a higher RPM, and thus go faster, right?

garygid
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Re: Wheel diameter and maximum speed

Most motor-controllers are limited by rpm, not speed.
What are you trying to do, go faster, or go slower?

If you want to go slower, either use a smaller wheel,
or modify the controller's max RPM (reduce it).

If the controller calculates speed from RPM, and you can modify the calculation's "wheel size" parameter, increasing it should lower your max speed limit.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

antiscab
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Re: Wheel diameter and maximum speed

But the motor is limited by bike speed not RPM right? If the bike has a large wheel and is turning at 100 RPM to get the max speed, then a smaller wheel would have to turn faster to get the same speed.

Programming a smaller circumference should tell the computer that the wheel should be turning faster to get to 25 kph.

all BLDC controllers receive motor speed in RPM*poles. its how the software is setup that matters.

Some controllers do implement a speed limit by calculated speed rather than RPM.
If this is the case with yours, then yes, programming a smaller circumference will result in a lower top speed.
If this is not the case, then the reported speed will just be lower.

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

Alver
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Re: Wheel diameter and maximum speed

Today I tried on the Trek t500e (with Bionx firmware 3.8), but unfortunately no luck:
Code 3773 (Speed Limit) immediately returns to the main menu.
Code 3771 or 2005 (Wheel Size) allows no smaller diameter than 2109 (26").

Anybody knows other codes to improve speed?
Thanks

maxrevs
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Re: Wheel diameter and maximum speed

Won't do you any good mate, the max speed is RPM dependent and set at the factory.

Edbel
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Re: Wheel diameter and maximum speed

For me changing the wheel size did work, I set it half the factory default, which meant indicator where at half the real value, and I can reach 35 km/h without any problems in Europe, cheers,

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