-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
-
The final cut of TMC Podcast #34 is available now with topics timestamped. We covered Tesla's rollercoaster prices, Toyota pushing junk science, Mike's new Model 3, Optimizing track mode for snow driving, FSD V11 apparently coming by the end of this week, and more. You can watch and check out the chat replay on YouTube.
Effect of wider tires on range
- Thread starter Stefan Voinea
- Start date
Tell me you didn't read the link above without telling me you didn't read the link.
By your logic, a flat tire with no air in it makes the car more agile. ALWAYS. Because the contact patch of a flat tire is enormous. I'd imagine, what, about 4G's in a corner, given a stock tire can do about 1.3?
How is it irrelevant? Two posts have explained the physics behind why contact patch is largely dictated by load and pressure. You accuse us of throwing out theory without offering an explanation of why you believe contact patch size will change with the wider tire. All the while, throwing out a pretty simple physics theory that 2 people explained to you.
The balloon example was just to help visualize the concept we described. I'm well aware of some of the other factors such as sidewall, rubber, and belt stiffness that can contribute to the overall stiffness. But to varying degrees theses factors still exist on both tire sizes and the amount of load on them is small compared to the amount of stiffness added. How do we know this? If you delete the tire, it will crush the tire down flat. The exception will probably be run-flats.
I don't have a problem including experience. But you failed to offer any observation, data, analysis, or even a "theory" to substantiate your belief. And we're supposed to subscribe to your belief just because you say so? I'm so for having an productive discussion. But you're going to have to offer something more substantive than "because I said so."
I didn't make a blanket statement. I actually run the tires. Now, you change your theory to include things like "largely includes". This isn't a theoretical discussion. This is about running 265/30/20 on uberturbines. I'm happy to have a heads-up race to prove that the 265/30s are more agile. The difference in feel and ride isn't even close. The 235/35s are SLOPPY in comparison. That is FACTS and experience. Why it feels that way can be debated.
You're trying to make a point by connecting dots that were never there. Who runs no air? Why would no air increase contact patch on these rubber band tires? It wouldn't and we don't run on balloons, which is what your theory is based on.
Lindenwood
Member
Unfortunately, the actual area doesn’t change. The shape, yes, but not the area.
Think through the concept of pressure units “pounds per square inch.”
Where did I say that wider tires don't generally handle better? The reason it handles better is not because there is more contact patch. It's because the shape of the contact patch gets wider. It also gets more narrow from front to back. But the area is roughly the same.
And I never said largely includes. I said is largely dictated by.
psi is a choice. I ran 42 with the 235/35s. I run 38 with the 265/30s. Again that is a choice.
You're saying that a 205/55 has the same patch as a 305/50. again, PSI is a choice. We aren't taking a closed system and shifting it's dimensions. We are CONTROLLING PSI.
Same argument for a balloon the size of a tennis ball vs a basketball. It isn't about the 1lb weight on it when we CONTROL PSI and SHAPE of the structure. Tires are NOT round spheres. They are shaped. That doesn't matter?
Balloons are an analogy to help visualize the concept. Goodyear actually describes the concept using the same analogy.
"Picture an inflated balloon and lightly press that balloon against a wall. Notice how little of the rubber balloon makes actual contact against the wall? Now, press harder, and you’ll see the balloon conform to the wall, flattening a bit to put more rubber on the wall."
Tire Contact Patch | Goodyear Tires
A contact patch is your tire’s footprint on the road. Read more on maintaining the proper tire pressure and what impacts your tire’s performance.
www.goodyear.com
Understood. I get that. But we aren't having a hypothetical discussion. These tires have shape and much of the contact patch is established even without the weight of the car on them. A balloon would be round at that point. So what?Balloons are an analogy to help visualize the concept. Goodyear actually describes the concept using the same analogy.
"Picture an inflated balloon and lightly press that balloon against a wall. Notice how little of the rubber balloon makes actual contact against the wall? Now, press harder, and you’ll see the balloon conform to the wall, flattening a bit to put more rubber on the wall."
Tire Contact Patch | Goodyear Tires
A contact patch is your tire’s footprint on the road. Read more on maintaining the proper tire pressure and what impacts your tire’s performance.
And you are changing another variable. I can lower the pressure on a 205 tire and achieve a similar contact patch as your 305 tire running the same pressure. The 205 tire will have a more square profile. If you inflate a tire to 40 psi, then each square inch is going to put 40 pounds of pressure. If you have 400 lbs over the tire, 10 square inches will need to push up to hold the car up. If you change the pressure to 20 psi, then 20 square inches of your will need to hold up the car. How are you going to argue math and not consider a rudimentary equilibrium equation.
No it's not. Take a tire off the car and put it on the ground. Much less of the tire will be touching the ground. There is nothing hypothetical about that.
We wpould need to run the numbers. I do agree that you can use PSI to compensate in order to get a similar patch on different sizes. I disagree that a 205 can put the same amount of rubber as a 305. If that were true, all cars would run skinny tires and agility would be dictated purely by diameter. Life isn't that simple. I am not discounting theory; I'm simply pointing out that THEORY can't dictate truth because it may not apply. Like here. a 265/30 will simply outperform AND outlast a 235/35. I'm sorry that this is FACT and that your theory doesn't explain that. But facts are still facts.
Lindenwood
Member
Exactly. Imagine the audacity to speak facts. Sorry to upset your little group. Quite open minded of your group to be so aggressive against anyone not willing to blindly put faith into your rationale for running skinny tires and pretending it's performance oriented.
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...
Running no air is the easiest way to put more rubber on the ground. FACTS.
If 38 PSI is better than 42 PSI, why isn't 30 PSI? 20? 10? 0?
If you can't see how that demonstrates why you are clearly wrong that wider contact patches are ALWAYS more "agile," and that tires are complex. then you're just as biased then everyone else.
The hilarious thing is you're also not reading anything in this thread correctly. NOBODY said narrower tires increase grip. We said they decrease range, and that the increase in grip doesn't come from a larger contact patch. Which is totally different than saying narrower tires are better.
Similar threads
