Help! Larger profile tire or wheel?

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Heman B.
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Joined: 05/18/2012
Points: 102

Hey all,
It seems to me that after the initial rave of electric scooters died down in 2009-2010, this forum largely became inactive.
Nevertheless I hope to get some positive response;

I bought an X-treme XB-700Li, with LiPo4 battery. It's limited to 20MPH; but I live in Florida, where the law still allows these bikes to go upto 30MPH. I know many have commented that their bikes in reality do not surpass the 18MPH, so I wanted to know if I can equip my bike with a larger profile tire?
Here in Florida everything is basically flat, and few roads have sub 30MPH speeds. I have less use for torq, and realize if I can extend the wheel (make it larger),or put on a larger profile tire, I might be able to exchange some of that torq for speed and increased mileage per charge.

The only problem is, which wheel can I exchange it to, or which tire is best?

Thank you!

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PzlPete
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Joined: 06/22/2009
Points: 157
Re: Help! Larger profile tire or wheel?

Hi Heman,
So you believe me now that the 700li only goes 20mph? :) Your newer LIfePO4 batteries should last longer than my LiMn. What is your range on a charge? I swapped out the original tires for the Chen tires which fit the 13" rim, and they were definitely a little larger. Did I get more speed? No. According to my bicycle speedomter, I was still topping out around 19mph on level ground. I don't believe that 700 watt motor and 48 v system had the torque to push it beyond that. Just my 2 cents.

Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

thank you for your reply!
As to not believing about it driving 20mph, I don't know where I wrote that, as I've been all over the internet, seeking information for the past 3 days.
I know there are some users claiming it goes upto 18mph, others are happily saying it drives them 27mph! That's 9mph difference!

I've heard of people driving 350W motors,and seen many youtube vids of 500W motors. Both of them where accelerating fine, to tell you honestly, the vids of the 500W motor surprised me on how much acceleration it had; I had expected less.
The 700Li has a 700W motor, thus automatically it should accelerate better, at worst the same (due to slightly larger mass).

But that means once the mass is in movement, it will have more torq to make use of.
I also believe that even at 350W, with a better controller, these engines are able to go much faster than 20mph. Ive seen 'some' vids where some guy claims he has a 500W brushless motor, and is able to go as fast as 49MPH, though I take these numbers with a grain of salt.

Thanks for giving your opinion, however, if the tires are larger, and the speedometer (odometer) is not re-calibrated, it will show the incorrect speed. It shows the same speed, because the tires are doing the same rotations per second as before, meaning that it proves that the engine is powerful enough to rotate the wheels,even with larger tires.
(in fact the speedometer (odometer) may actually show more the correct speed now, because as I have read it shows you're driving faster than you really are)!
You will have to measure your speed with a handheld or portable GPS system to get the correct ratings. Best is if you have one nearby (steal it from your friend's car or something; and bring it back ofcourse) :o, then you can measure your real speed, and not rely on a bicycle or the internal odometer.

Can you please tell me where you bought the tires (link if possible)?
Thanks!

Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

Ow, btw, the bike is on backorder, supposed to be shipped in a week; so I bought one, but won't be seeing it until about 2 weeks from now!
In the mean time I just wanted to get as much info as possible to do an immediate mod on it, if possible!

Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

Ow, I just saw that the 700Li uses 16" tires, is that correct?

Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

I found some tires, but won't know if they'll fit, and if they will make the tire radius larger or not...

Pirelli tire $26

Shinko tire $33

mf70
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Joined: 12/01/2006
Points: 707
Re: Help! Larger profile tire or wheel?

I've got the XB600, which is about the same for power. I know what you mean about feeling limited in speed on the flats. My understanding is that the controller is rev-limited, and will reduce power as the rev limit approaches. With a high-grade calibrated bicycle speedo, I've found that that limit is almost precisely 20 MPH.

I would carefully measure the bead diameter of your present tires and have a "quality time" talk with the tire salesman to make sure you get the right size. The nominal size matters too, so don't neglect that.

I don't believe that the overall diameter would ever be more than a few percentage points greater that the stock tires, so the effect of top speed would be correspondingly minor. The most effective way I know to feel better about your speed is to give the scoot to a friend and try to keep up this him or her on a bike.

That said, I suspect that you will see better cornering and reduced rolling resistance from higher grade tires. You are running them at maximum pressure?

Mark

PzlPete
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Joined: 06/22/2009
Points: 157
Re: Help! Larger profile tire or wheel?

The Cheng Chen tires I put on my 700li were definitely larger. And I did recalibrate the bicycle speedometer for the larger diameter. I didn't get any higher top speed, as it still maxed out at almost exactly 20mph. I believe the factory speedometer read a little lower due to the larger front, which would make sense. It did ride much much nicer with the larger tires. I am 6'2" 225, so yours will do a little better. I was impressed with how well the 700li was able to climb hills. Anyone who says 27mph is either selling them, or has added extra cells to their battery pack.

Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

PzlPete wrote:

The Cheng Chen tires I put on my 700li were definitely larger. And I did recalibrate the bicycle speedometer for the larger diameter. I didn't get any higher top speed, as it still maxed out at almost exactly 20mph. I believe the factory speedometer read a little lower due to the larger front, ....

The meaning of larger tires is to put them on the rear wheel, where they would have effect, not on the front!
On the front you'd have a bike that's nose is a little higher, but nothing is done about speed and torq, and like you say, the speedometer would measure a lower speed, while maintaining the same speed.

It could be that the tire diameter is in order of millimeters larger. This would do almost no difference to speed.
Let's say tire 1 has a 16" outside diameter
Tire 2 has a 16,5" diameter.
1 tire rotation would be propelling you:
T1= 2 * Pi * R = 2 * 3.14 * 8 = 50.26 inch
T2= 51.83 inch.

If you would be driving 20MPH with the first tire, you'd be driving
20 * 51.83 / 50.26 = 20.625 MPH, or,
a difference of 1/2inch results in a speed increase of just over half a mile per hour faster.

If I would want to drive 25MPH, I'd need a rear tire of at least:
T3 = T1 * 25 / 20 = 62.83 inch
R = T3 / (2 * Pi) = 10 inch.

In other words I'd need a 20in tire to drive 25MPH. Something I won't find unless I change the rim.

PzlPete
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Joined: 06/22/2009
Points: 157
Re: Help! Larger profile tire or wheel?

Heman B. wrote:

The meaning of larger tires is to put them on the rear wheel, where they would have effect, not on the front!

Correct. I replaced both front and rear with the new larger tires. I actually did the rear one first and tested it for a couple hundred miles, and then replaced the front one later and recalibrated the speedo accordingly. My top speed was unchanged. But the improvement in ride quality was remarkable.

And just to give you another example, I actually replaced the rear tire on my 4000li with one that is considerably larger. The new tire is 2 inches taller in diameter. My top speed remains unchanged at around 55mph, but my accelaration from a dead stop is definitely a little slower, and of course my hub motor is turning less RPMs at higher speeds. But the higher gearing via larger rear tire didn't help there either, and my range actually suffered a little. But again, the ride is very nice on the larger tire.

Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

What you say is impossible, as the controller inside the bike does not know how fast you are driving (relative to your environment).
The speedometer get's it's results from the front tire, some people say it also reads from the back tire.
It does so by calculating tire's rotations per minute.
When you increase the diameter of the wheel, the bike will go faster, but the wheels will remain rotating at the same rotations per second.
In other words, the bike's speedometer does not read a speed increase, but if you could measure before and after with a GPS, you'd see the speed has increased.

I've heard of bikes that went in their 50mph's on a 500 - 800 motor. The 4000 has a pretty powerful motor, it should be able to go very fast.

Increase in mileage is only possible when you're driving long stretches. In city use, large tires are not beneficial, because it takes longer for the bike to accelerate to the right speed, and the engine needs to put more torque, but if you're mainly driving long, flat stretches, larger wheel diameter will improve mileage.

Another thing, larger tires usually mean softer tires (as the larger the tire, to keep the same hardness as smaller tires, you'd need to put a lot more air pressure in the tires). The softer the tires, the more resistance your bike will get from them.
If you somehow where able to increase rim size as well, you'd notice your ride will be harder, but mileage should improve somewhat.
You could improve it a little bit, by making sure the tires are inflated at their maximum rated pressure.

But an overall larger wheel diameter by selecting bigger tires MUST result in all of the below:
1- Higher max speed
2- Longer mileage on stretches
3- Shorter mileage on stop/go traffic
4- Lower torque
5- Higher wind resistance
6- Higher tire resistance

If your engine would not have enough power to pull this increase to a higher max speed I would have believed you, but the engine is clearly limited by the controller!

MEroller
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Joined: 09/26/2011
Points: 654
Re: Help! Larger profile tire or wheel?

Heman B. wrote:

What you say is impossible, as the controller inside the bike does not know how fast you are driving (relative to your environment).

If the motor happens to be of the brushless type, then of course the controller knows precisely at which RPM the motor is running, and if it is not slipping on ice or sand, the vehicle speed could easily be deducted by the controller.
Nevertheless, a larger tire on the driven wheel will only lead to higher max speed if there still is enough surplus torque in oder reach the same speed as before, but at lower motor RPM, AND even more surplus torque in order to overcome higher aerodynamic and/or friction forces due to the higher speed.

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Heman B.
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Joined: 05/18/2012
Points: 102
Re: Help! Larger profile tire or wheel?

MEroller wrote:

If the motor happens to be of the brushless type, then of course the controller knows precisely at which RPM the motor is running, and if it is not slipping on ice or sand, the vehicle speed could easily be deducted by the controller.
Nevertheless, a larger tire on the driven wheel will only lead to higher max speed if there still is enough surplus torque in oder reach the same speed as before, but at lower motor RPM, AND even more surplus torque in order to overcome higher aerodynamic and/or friction forces due to the higher speed.

Correct, the speed is deducted from the rpm's of the wheel. Make the wheel larger,and the controller does not sense the correct speed anymore.
In case of larger tires, perhaps the 0.5MPH gain is negated by the increase in tire resistance,and a bit more wind resistance for the 0.5" higher frame.

The motor is still limited by the controller; probably to prevent the motor for overheating, but also to stay within the speed limits.

Remove the limiter,and a 350/500/700W motor should reach upto 30/40/45mph the least!

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