[grovey]

I like the look of the 17 inch rims with wider tires. Does anyone have them and if so, how's your mileage?

 

[Joel]

45'ish - mostly highway - the wider tires are mostly to blame ( 205 vs. 185 ) cornering and breaking are greatly improved.

 

[john1701a]

cornering... greatly improved.

Sorry, I don't believe that.

I bet the improvement you experienced is from the higher quality tires, not the size.

Smaller tires have always been better for corning on bikes.

 

[priusenvy]

cornering... greatly improved.

Sorry, I don't believe that.

I bet the improvement you experienced is from the higher quality tires, not the size.

Smaller tires have always been better for corning on bikes.

Oh God, not more of this nonsense from john1701a again. Well, never let it be said that being completely uninformed ever kept you from posting a response.

Cars and bicycles are designed around completely different design parameters. Bicycles have maybe 1/3hp tops and a power to weight ratio at least twenty times less than that of a car. Cars don't lean into turns. Ultra light weight and ultra low rolling resistance aren't an issue in a car because a human being isn't providing the motive force. Car tire pressures are not 100+ psi. Ever seen the rear tire on a high performance motorcycle? They're wider than the Prius tires. Do I need to go on?

The tire contact patch on a wider tire (all other relevant variables held constant such as tire pressure and diameter) will be wider and shorter compared to a narrower tire. With a wider contact patch, the pressure will be more consistant across the face of the contact patch compared to a narrower, longer contact patch when cornering. This is why the wider tire can generate higher cornering forces at lower slip angles. Grossly simplified, a contact patch whose shape is longest in the direction it needs to resist force is better. Long and narrow is generally better for generating longitudinal acceleration (acceleration and braking), and short and wide is generally better for generating lateral acceleration.

 

[ehurtley]

Ever seen the rear tire on a high performance motorcycle? They're wider than the Prius tires. Do I need to go on?

Yes, and those bikes are all about acceleration, not cornering.

The tire contact patch on a wider tire (all other relevant variables held constant such as tire pressure and diameter) will be wider and shorter compared to a narrower tire. With a wider contact patch, the pressure will be more consistant across the face of the contact patch compared to a narrower, longer contact patch when cornering. This is why the wider tire can generate higher cornering forces at lower slip angles. Grossly simplified, a contact patch whose shape is longest in the direction it needs to resist force is better. Long and narrow is generally better for generating longitudinal acceleration (acceleration and braking), and short and wide is generally better for generating lateral acceleration.

You have it correct. The shape is longest in the direction it needs to RESIST force better. Long and narrow is good because it provides more SIDEWAYS resistance. Wide and short is better for acceleration because it provides more WIDTH of space to generate that force.

Example: Try pushing a snow shovel along concrete. Push it the 'normal' way, with the blade scraping along the wide direction in front of you. More resistance. More force needed. Now try pushing it side-to-side so it's narrow end is what is scraping. | -> vs. - -> It slides more easily. That's because even though the same surface area is sliding along the ground, you're making it slide differently. Now try 'turning' the shovel each way while sliding. The wide direction forward turns poorly, and tends to slip and slide as it does so. The narrow direction forward turns easily. (Like an ice skate, turning without slipping sideways.) A wide tire is like the shovel scraping the way it's meant to be used. Wide area providing lots of friction. A narrow tire is like the narrow end first. Turns on a dime, like an ice skate.

Conclusion: A wide tire is good for acceleration and braking, a narrow tire is good for cornering. Please note that this only counts for 'all other things equal' tires. As wider tires tend to be made to be higher performance, their sidewalls tend to be stiffer, and thus make them better suited for cornering than cheaper narrow tires. If you got high performance narrow tires, they would perform better than equal outside diameter wide tires. It really is all about the tire quality.

P.S. Please don't resort to personal attacks. It makes you look childish. I'm sorry, but John is one of the most informed posters on here.

P.P.S. I studied aerospace engineering in college, and know all about force and friction. (Didn't get my degree, got sidetracked; completed 3+ years, though.)

 

[ceric]

All else being the same, wider tires give your vehicles more roadholding. However, this does not equal "cornering" or "handling". To me, "cornering" also involves over/under-steering. Changing tire widths may disturb the balance of roadholding between front and rear if not done carefully. "Handling" is a more subjective term.

Just my two cents.

 

[priusenvy]

Yes, and those bikes are all about acceleration, not cornering.

Hardly. If that were the case, they would have square shoulders. Ever seen a MotoGP race from the viewpoint of a bike-mounted camera?

You have it correct. The shape is longest in the direction it needs to RESIST force better. Long and narrow is good because it provides more SIDEWAYS resistance. Wide and short is better for acceleration because it provides more WIDTH of space to generate that force.

You've got it backwards. Period. You know about as much about friction and tire dynamics as you do about the source of the technology in the Ford Escape's powertrain (you were proven completely wrong there too).

Example: Try pushing a snow shovel along concrete. Push it the 'normal' way, with the blade scraping along the wide direction in front of you. More resistance. More force needed. Now try pushing it side-to-side so it's narrow end is what is scraping. | -> vs. - -> It slides more easily. That's because even though the same surface area is sliding along the ground, you're making it slide differently. Now try 'turning' the shovel each way while sliding. The wide direction forward turns poorly, and tends to slip and slide as it does so. The narrow direction forward turns easily. (Like an ice skate, turning without slipping sideways.) A wide tire is like the shovel scraping the way it's meant to be used. Wide area providing lots of friction. A narrow tire is like the narrow end first. Turns on a dime, like an ice skate.

Wrong analogy - which is why it leads you to the wrong conclusion. Ice skates carve into the ice with their edge, it's not even an application of friction. Try your experiement with a rectangular brick.

Why do you think top-fuel dragsters have tall, narrow tires?

Conclusion: A wide tire is good for acceleration and braking, a narrow tire is good for cornering. Please note that this only counts for 'all other things equal' tires.

Again, that's completely backwards.

P.S. Please don't resort to personal attacks. It makes you look childish. I'm sorry, but John is one of the most informed posters on here.

That pretty much tells me and others everything I need to know about the technical content of anything you might post in the future, and your analytical abilities.

Read this, it might help: http://www.phule.net/mirrors/unskilled-and-unaware.html

P.P.S. I studied aerospace engineering in college, and know all about force and friction. (Didn't get my degree, got sidetracked; completed 3+ years, though.)

Whoop de doo. I did get my engineering degree, and it's from a school that would take about two minutes to reject your application.

 

[PriusByrds]

My wife and I each have a Prius, hers a 2004, mine a 2005. Mine came with the 17" EFPC wheels with 215/45WR17 Pirelli PZero tires (through SE Toyota Distributors), hers with the standard wheel/tire set-up. Mine has approx. 9,000 miles, hers approx. 9600 miles. My lifetime mileage is approx. 41.5, hers approx. 43.0. We both run air pressures at approx. 42/40 psi. We both do lots and lots of short trips of 2 miles or so, sometimes less (we live so close to everything), and both cars have done several long trips. When I drive her car, however, I seem to get higher mileage than when I drive mine, perhaps as much as 4-5 mpg more. This is a subjective observation. It also seems that the 17" wheels on mine have more road noise and they are not as smooth riding. I never tried measuring cornering or breaking performance between the two, but I imagine the PZeros would win hands down. They look cool, but I wouldn't choose them.

 

[john1701a]

Try driving on snow with wide tires. They float on top (think snowshoe), making corning more difficult.

With narrow tires, they dig in for a better grip.

 

[Jonnycat26]

Oh God, not more of this nonsense from john1701a again. Well, never let it be said that being completely uninformed ever kept you from posting a response.

Cars and bicycles are designed around completely different design parameters. Bicycles have maybe 1/3hp tops and a power to weight ratio at least twenty times less than that of a car. Cars don't lean into turns. Ultra light weight and ultra low rolling resistance aren't an issue in a car because a human being isn't providing the motive force. Car tire pressures are not 100+ psi. Ever seen the rear tire on a high performance motorcycle? They're wider than the Prius tires. Do I need to go on?

Yes, I'm afraid we're hearing more of this noise again.

But ya know, I remember how my old '87 Cavalier with 13" tires absolutely carved corners the way no Corvette with their 17" and larger tires could. I mean, wow, this thing was a demon.

Yes, Narrow and Skinny are great on bikes and rollerblades. They're not good on cars. With bikes and rollerblades, you have 2 wheels inline and a center of gravity that leans into turns. You also have a human providing the motive force and you need less rolling resistance for acceleration.

With cars, you've got a center of gravity that doesn't lean into turns (or plows into turns as does the Prius). Having a larger contact patch is a good thing.

Anyhow, if 15" tires are better than 17", then it stands to reason that 13" must be even better still. So please, for all the tire experts out there that think that way, go tire up with 13" tires and see what happens.

 

[Tideland Prius]

He's right about the snow hence rally cars have narrower tyres to dig into the snow but for dry, for god's sake, the wider tyres gives you a larger contact patch thus providing more grip on dry roads. Those with large tyres know that they'll have to switch to smaller winter tyres (mostly because there aren't any snow tyres for 18" and above (there's only a handful for 17") and that most of those larger tyres are summer performance rubber.

 

[Jonnycat26]

Here's a little snippet from the "Generic Auto Tire FAQ"...

3.A. Alternate Sizing - Why Do It?


Variations from the OEM tire size are usually done to improve a car's handling and performance. Except in the case of snow tires (see Section 5), a common goal is to get a wider tire and/or shorter sidewalls without changing the overall diameter of the tire. Wider tread width changes the tire's contact patch and can lead to a big improvement in handling. In general, more rubber on the road provides a better grip. A shorter sidewall (lower aspect ratio) provides less flex which can improve turn-in, responsiveness and stability. Keeping the overall tire height as close to stock as possible reduces the chance that changes will impact the accuracy of the car's speedometer and odometer, overall gearing, suspension dynamics and introduce potential clearance problems.



Couldn't have said it any better... more rubber on the road provides a better grip.

 

[priusenvy]

Just for clarification:

I'm not saying the contact patch of a wider tire is larger than that of a narrower tire - it could be larger or smaller, and largely depends on tire pressure. But the shape is different, wide and short (front to back) rather than narrow and long. It's the shape of the contact patch that allows the pressure across it to be more consistent during hard cornering. A narrow contact patch would have less even pressure across its face during hard cornering, much higher on the outer edge compared to the inner edge, compared to the wider tire. This more consistent pressure across the contact patch during cornering is what contributes to the ability to generate higher cornering forces at lower slip angles.

Very high performance tires also tend to be made out of softer, stickier compounds too, but don't last nearly as many miles.

 

[Joel]

Yes, the better quality tires, which are wider and lower profile, contribute to better cornering and breaking. I didn't spell it out that way because I figured it was obvious.

By the way, here is a link to the tire that I chose after much research. These only last 30k miles though and I'm newly on my second pair.

Falken Ziex-512 All Season Performance - Consumer Report's top choice

http://www.falkentire.com/tires_512.htm

cornering... greatly improved.

Sorry, I don't believe that.

I bet the improvement you experienced is from the higher quality tires, not the size.

Smaller tires have always been better for corning on bikes.

 

[john1701a]

So... what's the point of increasing traction on dry pavement at the expense of sacrificing wet traction?

With so many owners commenting about how great the cornering is improved with high-traction 15" tires, explain why the gain from the 17" is wanted.

 

[grovey]

Wider tires look better.

 

[john1701a]

By the way, that "better on dry" claim is not entirely accurate.

If a dry road is dirty (has sand on it, which is extremely common here), a narrower tire has better odds of being able to grip due to the greater weight each square-inch of tire is supporting.

 

[priusenvy]

You and ehurtley should write to the guys that are autocrossing the Prius and tell them they don't know anything about auto-x preparation, and that they need to put the stock 15" rims back on the car and go back down to the stock 185 width tires. Didn't I see where one or both of you wrote that "tall and narrow" was better for cornering?

 

[hyperion]

I have to hand it to you who have converted to any other size wheel to what Toyota designed and mounted.
That's got to be one darn smart ECM to recognise the wheel change and convert all inputs to the ECM to compensate for the change.
Maybe those tire engineers have got it all wrong with the "wider" tread concept used on the indy cars and also on the Corvette. Wider trires, more square inches on the pavement but at the sacrifice of milage. Toyota picked the best balance I would expect, and again nothing to be gained by change except looks and ride. (who said, "you can't have your cake and eat it too!)

 

[Jonnycat26]

With so many owners commenting about how great the cornering is improved with high-traction 15" tires, explain why the gain from the 17" is wanted.

Why does Toyota equip Euro Priuses with 16" tires?