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Discussion Starter #1
My Gen 1 Volt.
After buying some all season tires I lost 10milespercharge. I immediately went to the forums to learn why. After reading about so many losing milage afterms buying tires I cam up with to theory. The obvious that roll resistance kills and I believe the OEM tires are slightly too big, so new tread = larger wheel.

I've decided to fight roll resistance, I bought new 18"×8" wheels. The shorter side walls will support the weight better and the wider larger wheel has 18% more area so the same air pressure will support the weight of the car better and we know how much air pressure effects these cars.

The tire size chose is 225/45/18 which is slightly smaller than stockbut not much, its the same size as an OEM tire with no tread.

I thought hard about buying 215 50 17 for the stock wheels. I'm pretty sure that would also be an improvement over stock size. Its the same size that comes on the Gen2. I impulse bought the rims so I'm sticking to it but can't help but to wonder what improvement can be gained from a good 215 50 17 LRR tire.
 

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Tire pressure, tire diameter, tire width, tire construction, tire tread and other factors all have an effect on rolling resistance.On a completely smooth surface the following applies: The higher the inflation pressure, the inferior the tire deformation and thus rolling resistance.


Off road it is exactly the reverse: The lower the inflation pressure, the lower the rolling resistance. This applies equally on hard gravel roads and soft forest tracks. Explanation: A tire with low inflation pressure can adapt better to a rugged surface. It sinks into the ground less and the whole rotational mass is held back much less by the uneven surface.


Tires with a smaller diameter have a higher rolling resistance with the same inflation pressure, because tire deformation is proportionally greater. The tire is flattened more and is “less round”.


Wider tires roll better than narrower tires. This statement generally invokes skepticism, nevertheless, with tires at the same pressure a narrower tire deflects more and so deforms more.


Obviously, tire construction also has an effect on rolling resistance. By using less material, less material can be deformed. And the more flexible the material is, such as the rubber compound, the less energy is lost through deformation.


Generally, smooth treads roll better than coarse treads Tall lugs and wide gaps usually have a detrimental effect on rolling resistance.
https://www.schwalbetires.com/tech_info/rolling_resistance
 

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It may just be the new rubber compound being stickier until it wears off. I too lost range with my LRR Ecopia tires ... it took a few months to get it all back.
 

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10 miles of range per charge? That's a lot. I lost some negligible range switching to all season Continental Pure Contact, but it is worth it for improved performance in snow. Anyone else lose 10/ mile per charge switching to all seasons?
 

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Discussion Starter #5
I'll have the new wheels next week. I'll be posting the results, first run and break in.

I don't measure my millage based on dash reading but how far I can make it home before it switches to gas. This is a real world 100% accurate measurement.


In response to the link about roll resistance , the reason wide tires do not defect as much as narrow tires is because wider rims have more area or more square inches so the tire will have more total presure with the same pound per square inch of pressure. This is a big part of why I went to a larger rim.
 

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10 miles of range per charge? That's a lot. I lost some negligible range switching to all season Continental Pure Contact, but it is worth it for improved performance in snow. Anyone else lose 10/ mile per charge switching to all seasons?
I lose about 5 miles range putting on heavy knobby snow tires. 1o miles loss from one all season to the another seems like a lot. Perhaps the weather change is contributing an extra 5 mile or so loss?
 

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Discussion Starter #7
10 mile range lost. We did get them just as the weather was changing but last year below freezing temps we got better range.

In these 50° temps we would normally get 35-38mile range now seeing 28-30.

On gas we would get 44-48mpg, now 38 mpg. It's pretty bad.
 

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I would be very careful when changing to different size rims and tires. The car is designed for a tire of a certain circumference. If you change to a wheel with a larger overall circumference, the wheels will be turning slower, and the speed sensor won't be getting as many pulses. Your speedometer and odometer will be off, and your range will be off. Same thing with smaller wheels but in the other direction. One way to be sure is to use a GPS speed app on your phone and see if it matches the speedometer display.
 

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Discussion Starter #9
I'm already dedicated to the new rim tire setup and I'm sure it will be an improvement over stock. Im doing it just to see if I'm right.

I still really want to know how well the 215-50-17 from the gen 2 volt would preform on a gen 1. The shorter side wall will reduce roll resistance and the slightly smaller size will take load of the motor.

The math tells me the speedo will be off [email protected], [email protected] ect
This is a small change over all but from what I've read the primary drive motor for the Volt is small. Electric motors are not like gas where they have to maintain a mixture, lighten the load and extend the range. Lighten the load too much and lose top speed or fall out of effective range of the motor. Based on people losing range with new tires I believe the car is slightly over gear or over tired:)

I'm hoping somebody will be as curious as me and try it. I've even thought about buying new tires for the OEM wheels just to compare. My worn out OEM tires gave me 39-43 and 44-48MPG I beleave new 215-50-17 will match or beat those numbers.
 

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The wheel offset is also very important as it affects the scrub radius. If your wider wheels increase the track width even a little bit you will lose range because the tires will scrub when the wheels are turned and that increases rolling resistance by a LOT

The suspension geometry was carefully engineered for best performance and even small changes to it will result in a negative impact on range

You are making some pretty major changes - It will be very interesting to see how this works out for you

Don
 

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The wheel offset is also very important as it affects the scrub radius. If your wider wheels increase the track width even a little bit you will lose range because the tires will scrub when the wheels are turned and that increases rolling resistance by a LOT

The suspension geometry was carefully engineered for best performance and even small changes to it will result in a negative impact on range

You are making some pretty major changes - It will be very interesting to see how this works out for you

Don
It's surprising how many people think automotive engineers are straight out of grade school and that any tire/wheel/suspension modification will improve handling/ride/steering/mileage. On the other hand much is a compromise with pros and cons with the engineers goal aimed at the largest market segment might not be your goal. Nor being privy to the engineering realities one is restricted to generalities which might or might not work. You pays your money and you takes your chances.
 

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That's certainly true. When to comes to oversize wheels and tires, if the purchaser is in love with the 'look' then almost any of the negative attributes that come with them are usually overlooked - It doesn't matter if they make the car ride like a ten ton truck, reduce the tire life by half or knock 5 mpg off the gas mileage . . . . they're still GREAT!

Don
 

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Discussion Starter #13
Has nothing to do with looks. This is all about MPG and range. If bad tires can take that much away what is there to gain.

I believe the OEM wheels are slightly too big which explains why new in kind replacement tires lower MPG and range as noted by many people on this forum. New tires= taller tread.

Other believe this is do to new tire tread having more roll resistance and my new tires are not LRR.

My new wheel setup is very low roll resistance. Being an 18×8 has 18% more area to lift the car than a 17x7 so the side wall's will not flex as much and the side wall is smaller so it is stronger. The final thing I thought of was, oem tires work best woth little to no treadso my new tires are the same diameter as worn out OEM tires.

If I'm correct about OEM tires being too big than the 215 50 17 tires from the gen2 volt will work best on the gen 1 volt and only upset the speedo by roughly 2MPH.

My goal is to increase range and MPG. MY question is to find out which path is better. I took the expensive path buy going to a very low roll resistance setup and will have everything next week. I'm hoping somebody else will take the chance of buy the slightly smaller gen2 sized tire and let me know how it worked for them. I'm very confident it will be a total improvement over stock.
 

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Keep in mind that a smaller circumference will turn faster and chalk up more miles in the same distance as well as make your speedometer read faster than you are going, all of which makes it look as if you are getting better mileage. You will have to know the exact distance of a trip to equate your actual mileage compared to what is shown.
Your range will show an increase but you won't actually be getting it.
 

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My new wheel setup is very low roll resistance. Being an 18×8 has 18% more area to lift the car than a 17x7 so the side wall's will not flex as much and the side wall is smaller so it is stronger.
I understand your theory, truly I do - Actually, I believed it too . . . . until recently. Now, I firmly believe nothing beats true LRR tires

We've had two 2012 Mitsubishi iMiEV's now for more than 6 years - They are our daily drivers and we use them for more than 90% of all the miles we drive each year. The front tires on them are 145/65R15's mounted on a 4 inch wide wheel. The rears are 175/60R15's mounted on 5 inch wide wheels. OEM tires are Dunlop LRR's all around and for their size, replacement Dunlops are quite expensive

I never liked the 'look' of the car with the 145 front tires (they look like they belong on a Harley and not a car) but changing to anything else isn't easy. A 5 inch wide wheel will just barely clear the front struts (and 5 by 15 wheels are nearly non-existant) while a 5.5 inch wide wheel requires a spacer behind it *and* longer lug studs. A few members on our forum have switched using Mini wheels with spacers and longer studs all around and a variety of different tires - Everybody lost some EV range by switching to wider tires - Some lost as much as 10%

I didn't want to use spacers or longer studs, so I bought a set of brand new 15" BMW Mini wheels and had two of them narrowed from 5.5 inches to 5. This was done by cutting the wheels on a lathe and rewelding them once the half inch was taken out. For the front, I went from 145/65R15 to 175/55R15, which keeps the overall circumference nearly the same - You can't be off the stock size by more than 2% or so, or the cars computer disables regenerative braking and some other safety features. For the rear, I used 185/60R15's mounted on the stock 5.5 inch Mini wheels. The car drives GREAT (and looks better too) and is much more planted and stable, especially in the rain. New tires are Continentals which are advertised as being 'fuel savers' but are not true LRR tires

My result with the wider tires? Pretty much the same as everyone else's. I've lost 6 to 8% of my EV range just by switching to wider tires which have more square inches supporting the car's weight . . . . and that's no doubt in my mind due to the fact that the tires are not true LRR tires, which I can't find in 175/55R15

So my experience is . . . . true LRR tires are VERY important if you are going for maximum range and nothing else you can do will make non LRR tires behave like the real thing - If you want to change to a different size from stock, make sure you can buy true LRR tires in those sizes. Luckily, true LRR tires, which are often quite expensive, are still cheaper than new wheels and tires of another size, so for the Volt, when the time comes, it will be a new set of the best rated LRR's for me. I'm still happy with my switch on the iMiEV, but I just did it to my car and not hers - She can definitely drive farther than I can, but we always take my car when it's raining :p

Don
 

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It's surprising how many people think automotive engineers are straight out of grade school and that any tire/wheel/suspension modification will improve handling/ride/steering/mileage. On the other hand much is a compromise with pros and cons with the engineers goal aimed at the largest market segment might not be your goal. Nor being privy to the engineering realities one is restricted to generalities which might or might not work. You pays your money and you takes your chances.
Paying the money is a big difference. Individual owners often have very different cost targets to hit, than engineers that have to send reports to accountants, ESPECIALLY after the initial purchase has been absorbed into the financial stream.
 

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Discussion Starter #18
Don M thank you for the positive comments, this is all a learning experience for me. Sometime I make mistakes like when I said 18% more lift for the car. I've been rethinking it yeah my theory is correct but math was wrong so I'm not sure exactly what to expect now. The wider tires losing range surprises me. My whole theory is reducing the amount of tire flex which should reduce resistance.

The other theory is the car being over geared. I've read it uses two motors and primarily drives off the smallet motor. They said the gen2 can use both motors in combination for a varable gearing range so I'm not sure what the gen 1 does different. Either way the car shows symptoms of being over geared. They way they describe the gen 2 wheels size would have little effect.

People losing 5 mile range with new tires doesn't make sense to me. Maybe LRR do have a break in time.

Either way I'm still expecting better than stock results and no 5 mile loss with new tires or wait for break in time.

I'm hoping more people chime in with ideas and expirience. Thank you.
 

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Discussion Starter #19
Old stuff. It will only through the speed off 3% 1.5mph at50mph.

GF drives the car to work about 22 miles one way. She could sometime's come within 2 miles of our house round trip 1 charge. Car normally makes it the bridge in warm temps and Townsend area in the cold.

With the tires we just bought she makes it 5 miles away from her work, it's so so bad.
 

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You'll have a pretty good A to B comparison then

On our EV's, I run the tires at 45 psi and don't see hardly any sidewall flex. My 'theory' (and that's all it is) is that the tread flexes more than the sidewalls and that's where the energy in non LRR tires is lost - The tread. Wider tread, more energy lost to flexing. Your experiment will give more and better insight into what is actually going on, since you're making a big change in tread width. I do know from experience that LRR tires make a huge difference . . . . well, 5% or more anyway and overcoming the loss of not using them, and doing better without them, is going to be pretty difficult

But, we'll see!

Don
 
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