Effect of wider tires on range

[DrChaos]

Sure, deforming a thin flexible sidewall is less of a loss than the deforming of a thick stiff tread, but both a wide and a thin tire deform the tread and a thin tire would be deforming less total tread width but at a higher angle which is worse because the tire is losing more of it's shape.

Drag coefficient is still the biggest thing effected by tire width on a car overall and the main driving factor for using a thinner tire vs a wider tire and is why efficiency oriented cars use thinner tires.

I can see that it's complicated. Another aspect is that larger diameter tires at the same pressure have lower rolling resistance and that probably explains the BMW choice on the i3. The engieneering choice is higher diameter tires, thinner width versus lower diameter tires, thicker width, as those give the same area contact patch and hence weight at equal pressure. The diameter effect seems to be opposite of the width effect and it's probably something that requires specific experimental investigation.

When you say drag, do you mean aerodynamic drag even if the tire is covered in a tire well as it is for all normal cars (not F1)? The air being moved on the surface of the treads even in the wheel well?

 

[dfwatt]

One interesting note:

I recently purchased an identical wheel set to my race set, and mounted the same size tires but from the “Grand Touring” category. Anecdotally, I think I saw about a 10% increase in efficiency between daily-driving on 200-TreadWear race rubber and these 600-Treadwear highway tires.

They are 275/35R19 all around on very flush 19x9.5+22 (daily driving at race camber to make them fit). I am very happy to look back at this in every parking lot if it means a few extra minutes at every supercharger .

View attachment 861010

I'm kind of amazed that your front tires don't rub. It looks as though there is literally no clearance between the outer area of the tire and the inner area of the fender. Do you have super stiff shock settings? Is there some rubbing but it's not too bad? Rears look almost as tight for that matter.

 

[Lindenwood]

I'm kind of amazed that your front tires don't rub. It looks as though there is literally no clearance between the outer area of the tire and the inner area of the fender. Do you have super stiff shock settings? Is there some rubbing but it's not too bad? Rears look almost as tight for that matter.

Off topic, but that pic was before I went to ~3.2 degrees daily front camber, raised the front 5mm, moved closer to the middle of compression settings up front, and rolled/pulled the fenders to stop the rubbing.

 

[Huskyfan]

One interesting note:

I recently purchased an identical wheel set to my race set, and mounted the same size tires but from the “Grand Touring” category. Anecdotally, I think I saw about a 10% increase in efficiency between daily-driving on 200-TreadWear race rubber and these 600-Treadwear highway tires.

They are 275/35R19 all around on very flush 19x9.5+22 (daily driving at race camber to make them fit). I am very happy to look back at this in every parking lot if it means a few extra minutes at every supercharger .

View attachment 861010

Nice look tires/wheels. I have a M3P also. Just replaced my michelin PS4s at 16,000 miles. Thought about going with another tire/wheel set up but did not want to deal with increased road noise, etc. Have coil overs, sway bars, etc. Not super low. Front wheel camber is sitting at about negative 1.5.

What’s your average Wh/mile? I‘m right around 280, but i drive mostly conservatively, except on on/off ramps, etc.

How negative is your camber? What is your tire/wheel set up? Noise increase? Improvement in ride quality?

 

[Huskyfan]

Off topic, but that pic was before I went to ~3.2 degrees daily front camber, raised the front 5mm, moved closer to the middle of compression settings up front, and rolled/pulled the fenders to stop the rubbing.

Ouch, lots of work to get those tires on there. Never mind. Rolled/pulled is not a small amount of modification.

 

[dfwatt]

Off topic, but that pic was before I went to ~3.2 degrees daily front camber, raised the front 5mm, moved closer to the middle of compression settings up front, and rolled/pulled the fenders to stop the rubbing.

I suppose in a very literal sense it's off topic but it's all part of the downsides of super wide tires. And it's all trade-offs let's be clear. And this is coming from someone who has been addicted to super wide tires my whole Automotive career

 

[Sukhshanti]

I saw a drop of 10-15% range switching from stock 18 setup to 265/35/19 Falken FK510 with 19x9 flow forged Verde VFF02s, but it is SO worth it. Car feels way more planted!

 

[dfwatt]

I saw a drop of 10-15% range switching from stock 18 setup to 265/35/19 Falken FK510 with 19x9 flow forged Verde VFF02s, but it is SO worth it. Car feels way more planted!

That sounds about right. And the faster you go I would say the more punitive the penalty on Range of really wide tires and aftermarket wheels which as we've discussed are not terribly aerodynamic

 

[jackmott]

When you say drag, do you mean aerodynamic drag even if the tire is covered in a tire well as it is for all normal cars (not F1)? The air being moved on the surface of the treads even in the wheel well?

Yep, if you lay down and look at your car from the front, you can see the tires!

So can the air.

If you lower your car you may reduce the penalty of wide tires, as the air will see less of the tire. It may even reduce aero drag overall (CFD that Unplugged Performance did suggests this does happen, but it could be wrong)

There is also no doubt some penalty from the wider tire spinning through the air and all the turbulence and how that interacts in the fenders.

 

[DrChaos]

Sure, deforming a thin flexible sidewall is less of a loss than the deforming of a thick stiff tread, but both a wide and a thin tire deform the tread and a thin tire would be deforming less total tread width but at a higher angle which is worse because the tire is losing more of it's shape.

Yes, but for a constant diameter. That doesn't need to be constant.

On the i3, they went to unusually high diameter tires to lower that angle of deformation. With higher diameter the contact patch can be narrowed to support the same weight, and that helped with aero with skinnier tires.

Only problem was that the handling at highway speeds was poor and darty, and susceptible to flats all the time.

 

[Jangy]

Can you feel a lot of changes in the handling and softness comfort improvement?
Or did you made the change mostly for getting a nicer look?

The car is more agile because it spreads the weight over more area. I love the feel.

 

[mpgxsvcd]

Physics just doesn't allow this.
100wh/mi at 75 MPH means you used 7500wh more in one hour, which means it draws 7.5kW.
The heat pump in a Model 3 isn't anywhere near 7.5kW. Even the old resistive heater was way smaller than that. Most home AC units aren't 7.5kW.

I have in fact seen the air conditioning alone pull 7KW+ while the car is stationary and nothing else is drawing any power. I don’t know how accurate this reading is but I have seen it draw that much power in extreme circumstances. It won’t draw it for that long though. Just a few minutes until it doesn’t need to run full blast anymore.

 

[CKwik240]

The car is more agile because it spreads the weight over more area. I love the feel.

For a given tire pressure, the contact patch will be about the same for any sized tire (within reason). The shape of the patch will change, but the actual area will be roughly the same. Basically as weight is added to a tire, the contact patch will grow until the forces reach equilibrium. So a tire at 50 psi with 500 pounds on it will have 10 square inches of contact patch. Since there is no change on contact patch size thats not the reason the wider tire handles better...

 

[Jangy]

For a given tire pressure, the contact patch will be about the same for any sized tire (within reason). The shape of the patch will change, but the actual area will be roughly the same. Basically as weight is added to a tire, the contact patch will grow until the forces reach equilibrium. So a tire at 50 psi with 500 pounds on it will have 10 square inches of contact patch. Since there is no change on contact patch size thats not the reason the wider tire handles better...

How does increasing the width not increase contact patch area? I'm lost at your reasoning.

 

[gearchruncher]

How does increasing the width not increase contact patch area? I'm lost at your reasoning.

It's physics.
The car weighs a specific amount.
The tire has X PSI in it.
It only takes Y square inches to hold up the car. So that's all that touches the ground.

That doesn't mean you don't get more grip. There's a ton of other dynamics that matter. But it doesn't come from more total area touching the ground.

However, wider isn't always better either. If you actually care about going fast, it takes a lot more than just assuming wider tires will do it.

Point(s) of Contact: Wider isn't necessarily better

Wider tires put more rubber on the road, right? Wrong. Jason Cammisa explains why upsizing your tires may not be the path to improved performance.

www.roadandtrack.com

 

[CKwik240]

How does increasing the width not increase contact patch area? I'm lost at your reasoning.

If it helps to visualize this, think of a balloon with 10 psi of pressure in it. If you place 100 lbs of weight on the balloon, the bottom of the balloon will compress against the ground until 10 sq inches is in contact with the ground as this would provide 100 lbs of resistance force.

 

[tm1v2]

Isn't it normal to run lower pressure with wider tires (+ wheels) though, than you would with a skinny version of the same tire? Otherwise it does seem mostly pointless.

 

[gearchruncher]

Isn't it normal to run lower pressure with wider tires (+ wheels) though, than you would with a skinny version of the same tire? Otherwise it does seem mostly pointless.

It's not pointless, but it's also not always helpful. There are a ton of dynamics at play here. This is also a very simple model that ignores sidewall stiffness and other tire construction elements, and assumes that the only thing that matters for grip is total contact patch independent of shape.
Plus, if you think you're using all of your tire in a corner while having 0.8 degrees of camber....

 

[tm1v2]

Plus, if you think you're using all of your tire in a corner while having 0.8 degrees of camber....

You better believe I'm using the entire outside edge with my stock FUCA camber!

Though running lower pressure has helped I think. My 245 street tires grip better when 40-41 psi is warmed up temp, rather than 41psi cold / 44-45psi warm that I was using initially.

 

[Jangy]

There is a bunch of SCIENCE being spewed on this thread that is absolutely irrelevant to the topic at hand. INCREASING patch size (which is exactly what happens) makes the car more agile. ALWAYS. The "science" being spewed says that, too. For some reason theory is being thrown out and not applied here. Instead, it gets applied to a balloon in a vacuum. This group should run off experience some too.