How will bigger wheels affect my car?

[deck]

I've got me a brand spanking new used 2003 Suzuki Aerio Fastback.

• It has 14 inch steel wheels.
  
• I need to replace the tires.
  
• I am considering replacing the wheels with 15 inch wheels (the car can take that size).
  

My question is;

Will bigger wheels affect the stability of my car? I find at 100 kph and faster the car gets a little wobbly and I need to make more corrections to keep my lane. I might also need to balance the wheels a bit or something (I'm not a car guy).

I'm also used to driving heavier cars with 15 and 17 inch wheels respectively, and I found my Aerio is less stable than them.

ALSO

Should I change the wheels to a bigger size, how will that affect how my speedometer reads the speed and how the odometer counts the mileage?

Thanks!!

[kombolcha]

http://www.miata.net/garage/tirecalc.html (Y)

it's got to be proportional, the bigger the rim the thinner the tire has to be to compensate, if you go too big you lose acceleration, but at high speeds you gain more speed and milage. the ratio is off and you'll be going faster than your speedometer reads. and if you have enough fat people in your car, it probably wont move because the gear can't turn it.

[tao muon]

Changing the wheels on a car is something many people do, for many different reasons. Besides the obvious 'it looks better' reason, better handling is the primary reason.

Given that you have 14" wheels on it already, there is a 'technique' known as 'plus sizing' that works well. Let's say you have 14" wheels and your tires are 195-60/14. 'Plus 1' sizing means you will increase the rim diameter from 14 to 15 inches. You will then decrease the aspect ratio of the tire accordingly. In this case, you will replace your 195-60/14 tires with 195-50/15 tires. What this basically means is that your tire will be (more-or-less) the same circumference and not affect your speedometer that much, but the sidewall will become smaller and the tread (where the tire contact the road) will get wider.

'Plus 2' sizing would mean going up two inches on the rim (from 14 to 16) and down two on the tire aspect ratio: from 60 to 40.

Usually, though, when you go 'plus 2', you will have to change the cross-section (the 195 part) down one size as well, from 195 to 185.

This is kind of like how you see people taking 16" wheels off of their truck and putting 20's or 22's on it: the original tire was probably a 70 or 75 (the second number in the tire size) and the new tire is probably a 35, 40 or maybe 50.

[Nose Nuggets]

the advantages or disadvantages from changing the wheel diameter is negligible. yes there are differences that occur regarding acceleration and top speed, but i think your question was more regarding handling, stability, etc. The direct answer to that question is no. increasing the diameter of the wheel by itself does nothing for you. unless you are saving weight. the tires are the biggest deciding factor in your cars ability to accelerate, turn, and brake (even more so then the brakes) and so, if you can increase the contact patch of the tire (the first number in the 295/70/15 tire sizing model) you will effectively increase all three of the above stated aspects. there is a limit to tire width based on wheel width. so, you might want to see how wide of wheels you can safely and effectively use with you vehicle. The reason Dodge vipers stop so incredibly well is not because they are light (they are not) and its not due to the large brakes, its because they have huge great big mammoth tires on it.

[MR_Candyman]

the advantages or disadvantages from changing the wheel diameter is negligible. yes there are differences that occur regarding acceleration and top speed, but i think your question was more regarding handling, stability, etc. The direct answer to that question is no. increasing the diameter of the wheel by itself does nothing for you. unless you are saving weight. the tires are the biggest deciding factor in your cars ability to accelerate, turn, and brake (even more so then the brakes) and so, if you can increase the contact patch of the tire (the first number in the 295/70/15 tire sizing model) you will effectively increase all three of the above stated aspects. there is a limit to tire width based on wheel width. so, you might want to see how wide of wheels you can safely and effectively use with you vehicle. The reason Dodge vipers stop so incredibly well is not because they are light (they are not) and its not due to the large brakes, its because they have huge great big mammoth tires on it.

well, I would also reckon the 14-inch brake rotors gripped by Brembo 44/40 dual opposing piston calipers in the front and Brembo 42/38 dual opposing calipers in the rear helps quite a bit in that viper reference. Can't entirely say that it's the tires because I know there's viper brake conservion kits for a lot of vehicles because they are such amazing brakes.

[Nose Nuggets]

well, I would also reckon the 14-inch brake rotors gripped by Brembo 44/40 dual opposing piston calipers in the front and Brembo 42/38 dual opposing calipers in the rear helps quite a bit in that viper reference. Can't entirely say that it's the tires because I know there's viper brake conservion kits for a lot of vehicles because they are such amazing brakes.

contrary to popular belief, brakes dont stop cars, tires do. Brakes are simply the mechanical component that allowes tires to do their job. the only benefit to having larger brake components is cooling, and most after market sets alowe you to adjust brake bias, but thats another discussion. so, if your doing hot laps around a race track you will eventually experience brake fade due to hot components not performing as well as cooler components. but, for daily driving it would take some extremely aggressive driving on public roads to get most factory brake systems into the brake fade region. i dont know if you have ever seen semi trucks race around a circuit track, but they have large containers of water at each wheel that spray onto the brakes when they are engaged.

heres a scenario to try to explain it. if you got into any conventional retail car from the last 12 years or so and switched off the ABS. Got that car up to 70MPH and put all your force into the brakes and littlerally stood on the brake pedal, you would instantly lock up the brakes. Honda civic to e55 AMG, does not matter. that being the case, how could larger brake components possibly slow the vehicle down quicker if the factory components have enough force to lock up the wheels.

i got this question it seems like every day while working at the track. i have heard almost all the theories and rationals for the contrary, i even have an article around here somewhere written by StopTech. if i can find it ill post the link.

EDIT:

well that was fast, here it is

“You can take this one to the bank. Regardless of your huge rotor diameter, brake pedal ratio, magic brake pad material, or number of pistons in your calipers, your maximum deceleration is limited every time by the tire to road interface. That is the point of this whole article. Your brakes do not stop your car. Your tires do stop the car. So while changes to different parts of the brake system may affect certain characteristics or traits of the system behavior, using stickier tires is ultimately the only sure-fire method of decreasing stopping distances.”

http://www.stoptech.com/tech_info/wp_brake...rformance.shtml

[wrench]

Changing the wheels on a car is something many people do, for many different reasons. Besides the obvious 'it looks better' reason, better handling is the primary reason.

Given that you have 14" wheels on it already, there is a 'technique' known as 'plus sizing' that works well. Let's say you have 14" wheels and your tires are 195-60/14. 'Plus 1' sizing means you will increase the rim diameter from 14 to 15 inches. You will then decrease the aspect ratio of the tire accordingly. In this case, you will replace your 195-60/14 tires with 195-50/15 tires. What this basically means is that your tire will be (more-or-less) the same circumference and not affect your speedometer that much, but the sidewall will become smaller and the tread (where the tire contact the road) will get wider.

'Plus 2' sizing would mean going up two inches on the rim (from 14 to 16) and down two on the tire aspect ratio: from 60 to 40.

Usually, though, when you go 'plus 2', you will have to change the cross-section (the 195 part) down one size as well, from 195 to 185.

This is kind of like how you see people taking 16" wheels off of their truck and putting 20's or 22's on it: the original tire was probably a 70 or 75 (the second number in the tire size) and the new tire is probably a 35, 40 or maybe 50.

You slipped up there a bit, tao. To maintain the overall diameter and circumferance as rim diameter increases and aspect ratio goes down, the cross-section should increase. This is illustrated in the calculator in the link in venezian's post. A 195/60-14, a 205/50-15 and a 225/40-16 all have approximatelly the same overall diameter.

[wrench]

contrary to popular belief, brakes dont stop cars, tires do. Brakes are simply the mechanical component that allowes tires to do their job. the only benefit to having larger brake components is cooling, and most after market sets alowe you to adjust brake bias, but thats another discussion. so, if your doing hot laps around a race track you will eventually experience brake fade due to hot components not performing as well as cooler components. but, for daily driving it would take some extremely aggressive driving on public roads to get most factory brake systems into the brake fade region. i dont know if you have ever seen semi trucks race around a circuit track, but they have large containers of water at each wheel that spray onto the brakes when they are engaged.

heres a scenario to try to explain it. if you got into any conventional retail car from the last 12 years or so and switched off the ABS. Got that car up to 70MPH and put all your force into the brakes and littlerally stood on the brake pedal, you would instantly lock up the brakes. Honda civic to e55 AMG, does not matter. that being the case, how could larger brake components possibly slow the vehicle down quicker if the factory components have enough force to lock up the wheels.

i got this question it seems like every day while working at the track. i have heard almost all the theories and rationals for the contrary, i even have an article around here somewhere written by StopTech. if i can find it ill post the link.

EDIT:

well that was fast, here it is

“You can take this one to the bank. Regardless of your huge rotor diameter, brake pedal ratio, magic brake pad material, or number of pistons in your calipers, your maximum deceleration is limited every time by the tire to road interface. That is the point of this whole article. Your brakes do not stop your car. Your tires do stop the car. So while changes to different parts of the brake system may affect certain characteristics or traits of the system behavior, using stickier tires is ultimately the only sure-fire method of decreasing stopping distances.”

http://www.stoptech.com/tech_info/wp_brake...rformance.shtml

Well, to say that brakes don't stop a car is kind of a matter of semantics. Brakes are where the kinetic energy of a moving vehicle is converted into heat, so you might say they do stop the car. Also, a car without brakes wouldn't stop very fast. It is true to say that more friction between the road and the tire allows for better braking but if you put Aerio brakes on that Viper, I'm not sure that you would be able to lock up the wheels.