I am doing a research paper on the performance changes by upgrading a car to bigger rims/tires. Specifically, I am looking at torque/horsepower measurements, fuel efficiency, ride quality, etc. Please reply with any information. Thanks!!!

A research paper huh? Sounds good to me. But note that the word "research" is dominated by the word "search" for which there is a rather large empty box on top of each page here. typing in key words might reveal a wealth of information. That would not only follow the "research" part of your paper but you would probably learn quite a bit more by searching rather than having someone basicly type the paper for you.

Oh and to answer your question, no bigger rims and tires don't mean better performance. It "depends".

The answer to your questions, from butt-dyno measurements, is yes and no.

Performance does improve in that your car can corner better.
The bigger tire/wheel combo gives more lateral suface area in the contact patch.

Performance also decreases b/c your quarter mile time is going to be better with the smaller tire/wheel combo.



Torque/horsepower measured at the wheel;
bigger tires and wheels will reduce your torque and probably not change your HP. This is due to a bigger wheel tire combo having more rotational inertia to overcome. The bigger wheel tire combo weighs more because the ratio of wheel/tire has gone up, so there's more metal, and less rubber, and metal weighs quite bit more than rubber, especially since the rubbber's hollow.

Fuel efficiency will go down because of the same reasons above.

Ride quality will get better . .and worse.
It will get better because your car will feel a whole lot more stable at hi speed with the bigger wheels.

Ride quality will get worse because your car will be more sensitive to irregularities (bumps) in the road with the bigger wheels at lower than highway speeds.

Hope this helps.

DW

He said bigger rims and tires. But didn't say larger diameter rims and same oem dia tires or larger rims and larger tires. And he didn't say larger and wider rims w/ oem dia tires or larger and wider rims and larger tires too. A superior set of 55 series tires might make the car perform better than cheap rate 45 series tires. (given the same oem dia.) Wider tires might make the car handle better but run slower due to the increased friction. Wider tires might handle better in some situations but actually handle worse than skinner tires in other situations.

Hope that helps too!

Bwahahahaha..

Also, if you increase the size of your wheel and keep to the stock diameter, the tire wall will thus decrease in size. this will result in your handling being more responsive since there is less flex in the tire wall.

We talk about this a few times a week in our physics class. NO! Wider tires DO NOT increase performance in anyway. I cant remember the specfics of it, but you can do some calclations and its the same.

You guys must remember that there is no way of increasing the contact patch on a car since it is directly related to the cars weight. Wider tires will increase your lateral contact patch, but the size of the contact patch will remain the same. Your car will handle better (to a point), but at near the limit, the tires can break loose with little warning. Wider tires will NOT improve straightline acceleration. Taller and narrower tires have a long contact patch which is good for drag racing.

I've run 17s with 235/45 hi-po tires and I am currently running 16s with 215/55 hi-po tires and my car handles nearly as good as the low profile tires. My straightline performance was dramatically improved with the narrower tires. BTW, my 16s are a extremely light which improved handling, acceleration, and braking.


Dave

True, he did say that. Since his question wans't too detailed, I figured, or assumed, he meant that the total diameter would stay the same, therefore if the wheel size increased, his tire aspect ratio would decrease etc. Its an OK assumption b/c increasing both tire and wheel size will just have your car sit taller, turning your car pretty much into a jeep if you take it too far. I really don't think he meant that. That would be understandable if he had a jeep and wanted more ground clearance, not on a Maxima.

DW

no bigger is not better, a popular myth though
only to a certain extent does bigger work, after that you will loose performance........

Are you guys enjoying writing this kid's paper for him? LOL. I don't quite understand how wider tires will NOT help? Fit a Porsche 911 Turbo w/ 400 horse power w/ 4 tires that run 175-75-17. Then run the same car w/ some 315-40-17. Which do you think will handle and accelerate better?

Then again to a point Dave B has some merit to his points. Hmmm I wonder who is right?? I guess some more "research" is needed.

Hey there...just to let you know, I have done plenty of research on this subject from magazines and books. I wrote this question on this forum to get some first hand experience from the auto enthusiasts who have tried to increase performance by increasing their rim size, and decreasing their tire size; or by decreasing rim size, and increasing tire size. The information and opinions posted are very helpful, and if anybody else has any experience with this...PLEASE REPLY. Your help would be greatly appreciated. I know I'll make an A. Thanks again!

OooOo cool.. in my physics class we learned rotation.. and so it depends on the style of rim you are running.. in one of the demo's the professor did, she took a metal ring.. and a solid round chunk of wood wieghing about the same, rolled both down the plank and u know wut? the solid chunk of wood went faster... she said that becase more weight has been directed towards the center of rotation thus, less force would be required to start wheel off. so that's hwy u see a bunch of road bikes with less spokes and a fat disk thinkgy closer to the center of the spindle... odd huh?? but i guess the one with more spokes (with the weight directed towards the outer rim) would spin longer.. so once u get those spinning u need less effort to keep them going than the solid circles..

You might want to pick up the Jan issue of Sport Compact Car. They have 7 pages dedicated to wheels, tires, and weight - how it translates into performance and ride quality on the track.