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Effect of wider tires on range

Ok.
4000 lbs car. (1000 lbs/tire)
40 psi.
1000lbs / 40psi = 25 sq inch.
305mm / 25.4mm/inch = 12.0 inch wide
25 sq inch / 12.0 inch = 2.08 inch length (front to rear)
205mm / 25.4mm/inch = 8.07 inch
25 sq inch / 8.07 inch = 3.10 inch length (front to rear)

It's out that inconceivable that a more narrow tire can't put 1 more inch front to rear on the ground?

That said, where in my post did I say a wider tire doesn't perform better? I think you made that argument up on your mind because you think that a bigger contact patch means more grip and extrapolated the argument on your own. I've only argued that the contact patch is about the same for a wide tire vs a narrow tire. Look at post #73. I even stated the condition "for a given pressure.". You're trying to argue a point that I am not...
Let's simplify things, since that's where I'm "off" compared to the balloon theorists. The argument this group is making is:

Contact Patch size is relatively the same, regardless of tire width. The argument is basically that a wider tire has a wider patch but it would "lift" to have less length. I think I understand the physics. But I do disagree. The reason is because tires aren't spheres. They're more like discs with nearly 90 degree corners and fairly stiff sidewalls (relative to the tread). I'm just arguing that the x-y of the contact patch isn't linear with a performance tire as it would be with a balloon. Based on that, I'm saying you'd have MORE RUBBER TOUCHING THE GROUND with a wider tire (like a 265/30/20 compared to a 205/40/20). If that were so, then it serves to reason that the 4000lb car's weight would be spread out more making it more nimble. Sorry that trying to argue the point took me sideways. I didn't mean that.
 
Let's simplify things, since that's where I'm "off" compared to the balloon theorists. The argument this group is making is:

Contact Patch size is relatively the same, regardless of tire width. The argument is basically that a wider tire has a wider patch but it would "lift" to have less length. I think I understand the physics. But I do disagree. The reason is because tires aren't spheres. They're more like discs with nearly 90 degree corners and fairly stiff sidewalls (relative to the tread). I'm just arguing that the x-y of the contact patch isn't linear with a performance tire as it would be with a balloon. Based on that, I'm saying you'd have MORE RUBBER TOUCHING THE GROUND with a wider tire (like a 265/30/20 compared to a 205/40/20). If that were so, then it serves to reason that the 4000lb car's weight would be spread out more making it more nimble. Sorry that trying to argue the point took me sideways. I didn't mean that.

At a given PSI, total contact patch with the ground is gonna be fairly constant and just change shape with different tire dimensions.

Conversely this is why raising tire pressure positively impacts efficiency because it actually makes the contact patch smaller (and maybe reduces sidewall flex)

What wider tires do impact is aero-concerns - a wider path in 4 different locations slicing thru the air, and possibly a less flush surface on the outer exposed wheel/tire area.
 
Let's simplify things, since that's where I'm "off" compared to the balloon theorists. The argument this group is making is:

Contact Patch size is relatively the same, regardless of tire width. The argument is basically that a wider tire has a wider patch but it would "lift" to have less length. I think I understand the physics. But I do disagree. The reason is because tires aren't spheres. They're more like discs with nearly 90 degree corners and fairly stiff sidewalls (relative to the tread). I'm just arguing that the x-y of the contact patch isn't linear with a performance tire as it would be with a balloon. Based on that, I'm saying you'd have MORE RUBBER TOUCHING THE GROUND with a wider tire (like a 265/30/20 compared to a 205/40/20). If that were so, then it serves to reason that the 4000lb car's weight would be spread out more making it more nimble. Sorry that trying to argue the point took me sideways. I didn't mean that.
I don't think anyone is saying the sidewall, tread rubber and belts have zero effect. But a huge portion of the contact patch size is going to be dependent on the air pressure vs load. And if you think about it, of the tire were stiffer overall, it would tend to make the contact patch smaller. Consider a solid rubber tire here.

The reason a wider tire grips better is because it's more stable. Much like a wider track on a car is more stable, so is the tire itself. Consider a block of wood that's square in it's cross-sectional shape vs a block of wood that is rectangular in it's cross sectional shape (long side horizontal). If you slide them along a high grip surface, the square block has a tendency to want to tip over much more than the rectangular block. Simply, it's just a more stable shape.
 
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I am surprised no one has done any experiments to prove/disprove this either way. Shouldn't be that hard...jack up car, coat bottom of whatever tire at x pressure with some dirt/dye/whatever, and then lower down onto a piece of paper...change pressure/tire and repeat.

Only two reasons for not doing the experiment, not having the capability/materials, or not wanting to find out you might be wrong....ok third reason...just lazy. :)

I don't have the materials(different width tires). I am also staying out of the theoretical discussion here cause there are many variables at play here that you really just need to do the experiment.
 
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I don't have the materials(different width tires). I am also staying out of the theoretical discussion here cause there are many variables at play here that you really just need to do the experiment.

I mean, road and track and Discount Tire both agree... This really isn't an argument.


 
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I am surprised no one has done any experiments to prove/disprove this either way. Shouldn't be that hard...jack up car, coat bottom of whatever tire at x pressure with some dirt/dye/whatever, and then lower down onto a piece of paper...change pressure/tire and repeat.

Only two reasons for not doing the experiment, not having the capability/materials, or not wanting to find out you might be wrong....ok third reason...just lazy. :)

I don't have the materials(different width tires). I am also staying out of the theoretical discussion here cause there are many variables at play here that you really just need to do the experiment.
For me, I don't have tires of a much different size I can use on this car, let alone the time.

The info is out there though. Google provides plenty of hits.

Here's one that talks about it. The editor is Mike Kojima. Former engineer at Nissan. Used to write for Turbocharger and Sport Compact Car magazines as a technical writer. Tons of track days. I've had a number of technical discussions with him at various meets. He's about as knowledgeable as they come. This article from good publication goes into some facts about wider tires down the page a bit.

 
Here's a great review of tires by Tire Rack, where they ran different sized tires on the same car. Like many of us keep saying... It's complex.
The key takeaways are that in the dry, a wider tire does not automatically mean faster lap times. Using a wheel width that properly supports the tire will provide faster laps than a wider tire with very little wheel support. We saw this in our testing - the 215/45R17 tire on the 9" wide wheel was noticeably faster than the much wider 245/40R17 tire on the 7" wide wheel. That's not to say tire width doesn't matter, though, as the 225/45R17 combinations were all faster than the 215/45R17s. The 245/40R17 on the 9" wide wheel was very close to the 225/45R17 on the same wheel. If we could fit a 10" wheel width on our test cars, the pattern seems to indicate a 245 on a 10" would have been the fastest combination of all.


Meanwhile... In the real world, when it rains sometimes, narrower tires are better...
 
I replaced the Continental Procontact RX tires 235/40R19 with Sumitomo tires of the same size. The Sumitomo tires have about 1/8" rim protection, where the Continental tires had zero. The Sumitomo tire sticks out about 1/8" more than the rim. I found a 3% increase in the WHM. My average WHM changed from 233 to 240. What I didn't really realize right away, and correct me if I am wrong, is essentially the battery range dropped 3% as well.
 

tm1v2

Active Member
Oct 18, 2021
2,431
2,125
USA
For me, I don't have tires of a much different size I can use on this car, let alone the time.

The info is out there though. Google provides plenty of hits.

Here's one that talks about it. The editor is Mike Kojima. Former engineer at Nissan. Used to write for Turbocharger and Sport Compact Car magazines as a technical writer. Tons of track days. I've had a number of technical discussions with him at various meets. He's about as knowledgeable as they come. This article from good publication goes into some facts about wider tires down the page a bit.

@CKwik240 This...THIS...is the holistic article that properly covers the topic. This is the one to read, by far, out of all the articles linked in this thread. Thank you.
 

remytennant

New Member
Oct 15, 2010
4
0
Currently running 265/35/19 +29 with Michelin Pilot Sport 4S. Getting about 290 wh/mi.

Before I had the OEM 19" V2 Wheels (235/40/19 +40) that had Continental Procontact RX and I had about 270 wh/mi
I just put this exact size PS4S tires on my M3P and am getting rubbing somewhere when I turn. 9" wheels (Martian Wheels, designed for Tesla, standard offset I think). Did you have this problem and what did you do? Thanks!!
 

dfwatt

Best Car Ever
Sep 24, 2018
3,732
5,892
FL
I just put this exact size PS4S tires on my M3P and am getting rubbing somewhere when I turn. 9" wheels (Martian Wheels, designed for Tesla, standard offset I think). Did you have this problem and what did you do? Thanks!!
That shouldn't be happening. When you say standard offset, the standard performance offset is actually 35 while the long range dual motor is 40 because of the thinner top hat on the performance rotor. Neither one should rub in a 9 inch width unless you were talking about a humongously wide tire? The wheel clears the inner control arm but it's pretty tight with the tire especially if you've got 40 mm. But if you've got the 265/30 that should be no issue as I have that on my car and there's no rubbing ever although the 19-in wheel moves the area of potential rubbing interference closer to the control arm.
 
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remytennant

New Member
Oct 15, 2010
4
0
That shouldn't be happening. When you say standard offset, the standard performance offset is actually 35 while the long range dual motor is 40 because of the thinner top hat on the performance rotor. Neither one should rub in a 9 inch width unless you were talking about a humongously wide tire? The wheel clears the inner control arm but it's pretty tight with the tire especially if you've got 40 mm. But if you've got the 265/30 that should be no issue as I have that on my car and there's no rubbing ever although the 19-in wheel moves the area of potential rubbing interference closer to the control arm.
Thanks for the prompt and thorough response!

Tires are 265/35/19's. 45 PSI right now. I am new to this but tried to do my homework and was pretty confident there would be no problems. So this is surprising. IDK if this helps at all but here are the wheels, which have +34 offset. 19x9.0

The rubbing is light but it's enough to be concerning.

Really hoping this can be fixed!
 

remytennant

New Member
Oct 15, 2010
4
0
I'm with @dfwatt - I run 275's with no rubbing, but with the right offset wheel. Nobody can tell you what's going on without knowing exactly the offset if the wheels.
I'm with @dfwatt - I run 275's with no rubbing, but with the right offset wheel. Nobody can tell you what's going on without knowing exactly the offset if the wheels.
Glad to hear you've got 275's without issues!

Offset is 34. Should be no rubbing, right? But there is!
 
I just put this exact size PS4S tires on my M3P and am getting rubbing somewhere when I turn. 9" wheels (Martian Wheels, designed for Tesla, standard offset I think). Did you have this problem and what did you do? Thanks!!
I do not have this issue :O
I have a M3 LR though, which has the LR brake rotors which means I'm pushed outwards 3-5mm compared to M3P I believe.
 

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