18 inch vs 20 inch wheels: Performance Difference?

[Nathan Moreno]

Looking to get some replacements for my wheels.

Is there a performance gain/difference when going 18 inch wheels, vs. 20 inch wheels?

And if so, what is it exactly?

Thanks guys!

[Burnt_RS]

more tire slippage with the 20s from ppl drooling on the road, over how HOT they are. what are 18s btw hahaha j/k

[Don57]

It is my impression that lower profile tires feel less "spongy" and provide better handling. Bumps in the road are more noticeable, but low-profile tires can be wider at the road surface than high-profile ones, meaning you get more traction.

[usmc8411]

Ask yourself this, if 20s are better than why do all the race camaros use 18s? The zr1 comes with 20s, but the c6r team races on 18s. I would take pro racers word over regular posters on c5.

Anyways even for drag racing a 18" is better than a 20. Most likely a lighter wheel and tire, with more sidewall to allow for extra bite at launch.

[autobotaz]

Originally Posted by Don57

It is my impression that lower profile tires feel less "spongy" and provide better handling. Bumps in the road are more noticeable, but low-profile tires can be wider at the road surface than high-profile ones, meaning you get more traction.

The stock tires on the heritage wheels can handle 44psi max pressure when cold. I run mine at 40psi and it takes out most of the spongy feeling that you get with lower psi. It stiffended up the feel but still rides nice.

My wife's 08 scion xb has 245-30-20's on it and it makes for a pretty stiff ride and those tires love to follow ruts in the roads.

I'm really torn what to do with my wheels and tires. I like the heritage wheels as they really match my black LS but I have seen some sweet 20's.

[danhr]

18's are better for anything

less rotational mass
more sidewall
more tire selection

I can not see a single reason, performance wise, that a 20" wheel would be better than a 18" wheel

[Don57]

Originally Posted by usmc8411

Ask yourself this, if 20s are better than why do all the race camaros use 18s? The zr1 comes with 20s, but the c6r team races on 18s. I would take pro racers word over regular posters on c5.

Anyways even for drag racing a 18" is better than a 20. Most likely a lighter wheel and tire, with more sidewall to allow for extra bite at launch.

A drag racer is not going to need the improved resistance to side forces while cornering, so, obviously 20s are not better in that case.

But, unless I'm mistaken, I believe we were discussing normal street use.

[Don57]

Originally Posted by danhr

18's are better for anything

less rotational mass
more sidewall
more tire selection

I can not see a single reason, performance wise, that a 20" wheel would be better than a 18" wheel

Here are two performance reasons:

better traction
better cornering

[usmc8411]

Originally Posted by Don57

A drag racer is not going to need the improved resistance to side forces while cornering, so, obviously 20s are not better in that case.

But, unless I'm mistaken, I believe we were discussing normal street use.

Which is why I referenced the race Camaros using 18s and the c6r corvette team using 18s. 20"+ is for bling only.

[christianmotox]

Originally Posted by usmc8411

Which is why I referenced the race Camaros using 18s and the c6r corvette team using 18s. 20"+ is for bling only.

But those 18" wheels are using Racing tires, totally different compounds than what you can get on the street.

lower profile tires are better for cornering and they are wider as well for more grip.

So i guess it comes to the point of how wide the 18" will be and what compound tire are you planing on ruining.

[LoneStarCamaro]

If both size wheels are the same width, the main reason a 20" wheel would be better than an 18" wheel is because the lower profile tire allows for more rubber to contact the road. A smaller wheel has its mass closer to the center, so the 18" wheel will accelerate faster, in theory. The best way to go would be an 18" wheel that is also wide to have more contact between your car and the road.

[n116ebo]

Go from 20" to 18" and you will have to take your hand held GPS to see how fast you are driving. Speedometer will be off.

[danhr]

Originally Posted by Don57

Here are two performance reasons:

better traction
better cornering

explain how you get better traction and cornering with a 20" wheel, as opposed to a 18" wheel.

I wanna see how you can justify defying physics here.

Apparently all these prostock cars need to switch from the 15" wheels they have to some nice 22" or 24" wheels, because they need to get more traction

And I want to see more road race/auto cross people running 26"s, because they will corner better.....

[LoneStarCamaro]

Originally Posted by n116ebo

Go from 20" to 18" and you will have to take your hand held GPS to see how fast you are driving. Speedometer will be off.

Not if your overall wheel/tire height stays the same. The 20" wheels/tires are overall 28.7" tall, while the 18" wheels/tire combo is 28.6".

[danhr]

Originally Posted by LoneStarCamaro

If both size wheels are the same width, the main reason a 20" wheel would be better than an 18" wheel is because the lower profile tire allows for more rubber to contact the road. A smaller wheel has its mass closer to the center, so the 18" wheel will accelerate faster, in theory. The best way to go would be an 18" wheel that is also wide to have more contact between your car and the road.

Absolutely wrong. First off, we are comparing WHEELS, not tires... please tell me where the sidewall of a wheel is?

2nd off, we will assume that both tires are the same height and same width (thus meaning the 20" wheels has a lower profile). The 18" wheel will have a bigger contact patch because the lower profile tire will balloon the tire, causing the contact patch to narrow. So more of the vehicles weight is on the center of the tire, and less on the outside of the contact patch.

[christianmotox]

Originally Posted by LoneStarCamaro

Not if your overall wheel/tire height stays the same. The 20" wheels/tires are overall 28.7" tall, while the 18" wheels/tire combo is 28.6".

Right, my Camaro came with 18 heritage wheels, and i upgraded tho 21' and my spedo is correct, because the overall diameter is the same.

[rolnslo]

Originally Posted by danhr

Absolutely wrong. First off, we are comparing WHEELS, not tires... please tell me where the sidewall of a wheel is?

2nd off, we will assume that both tires are the same height and same width (thus meaning the 20" wheels has a lower profile). The 18" wheel will have a bigger contact patch because the lower profile tire will balloon the tire, causing the contact patch to narrow. So more of the vehicles weight is on the center of the tire, and less on the outside of the contact patch.

If the OP is talking about going from 20's to 18's on a brand new car, he's not going to run 26" tall tires on those 18" wheels. He'll correct us if I'm wrong but he's likely going to stay somewhat close to the stock height of 28.6" so sidewall height does come into play here with regards to handling/cornering. If he's drag racing only, then the approach to tire/wheel combos is completely different than for street use or auto-cross racing.

Besides, who buys a 5th Gen Camaro and puts tires/wheels on it that belong on a 4th gen? The fender to tire gap alone would look stupid without at least a 2" drop on the suspension.

The tires themselves are 3 inches taller than what you are used to seeing. 29" OEM tire vs a 26" 4th gen sized tire. This is an 18" CCW vs 20" 2010 wheel.

[Nine Ball]

Originally Posted by usmc8411

Ask yourself this, if 20s are better than why do all the race camaros use 18s? The zr1 comes with 20s, but the c6r team races on 18s. I would take pro racers word over regular posters on c5.

Anyways even for drag racing a 18" is better than a 20. Most likely a lighter wheel and tire, with more sidewall to allow for extra bite at launch.

Those are silly comparisons. First of all, the reason road-racing teams use 18s is because of the abundance of racing tires available in that size. Nobody makes 20" racing tires, but I'm sure it will happen eventually. Guys just like you used to rag on 18s about a decade ago, saying "16s are big enough, how come race teams all run 16s".

Wheels have continued to grow in diameter mostly due to brake rotor diameters and larger calipers being used. 18s won't fit properly on the ZR1 because the brake rotors and calipers are huge. These were driven by necessity.

But, to get back to the original point, there are a lot of variables to consider here.

1. Are you comparing 18s vs 20s with the same tire outer diameter?
2. Are you comparing identical construction wheels, with same widths?
3. What is your primary purpose for these wheels, street, drag, or road-racing?

You can't just base things simply on diameter. An 18" wheel with our 29" tall tire will likely handle very SUV-like since the sidewalls will be huge and floppy.

[LoneStarCamaro]

Originally Posted by danhr

Absolutely wrong. First off, we are comparing WHEELS, not tires... please tell me where the sidewall of a wheel is?

2nd off, we will assume that both tires are the same height and same width (thus meaning the 20" wheels has a lower profile). The 18" wheel will have a bigger contact patch because the lower profile tire will balloon the tire, causing the contact patch to narrow. So more of the vehicles weight is on the center of the tire, and less on the outside of the contact patch.

As far as I know, no one drives a car just on the wheels (maybe a train? maybe). So you have to factor in the wheel and tire.
2nd, I'm not sure you have seen wheel and tire combos of different sizes but with the same width. The tire with the lower profile ALWAYS has a bigger contact area, if the tires are inflated properly. Lower profile tires are constructed so that the treads are in contact with the ground all across the tire width. Thus, they have a more "square" shape than higher profile tires.

[Nine Ball]

Not sure what tire profile has to do with contact patch. Tires are simply round, and you can't make more of that circle touch the ground by changing what is inside the circle. Contact patch is dictated mostly by tire width and shoulder construction, not diameter.

[danhr]

Originally Posted by LoneStarCamaro

As far as I know, no one drives a car just on the wheels (maybe a train? maybe). So you have to factor in the wheel and tire.
2nd, I'm not sure you have seen wheel and tire combos of different sizes but with the same width. The tire with the lower profile ALWAYS has a bigger contact area, if the tires are inflated properly. Lower profile tires are constructed so that the treads are in contact with the ground all across the tire width. Thus, they have a more "square" shape than higher profile tires.

ok you win. you are, by far, the best engineer in history. Every drag racer that runs a 15" wheel obviously knows nothing compared to you. They should all switch to 22" wheels.

all autocross/road race engineers obviously dont have anything on you either, and need to switch out their 18/19's out for 24"s. Why? because the bigger wheel offers more traction and better cornering .

The rule of thumb for wheels, performance wise, was written a long time ago.... put the smallest wheel possible, that will clear the brakes.

[LoneStarCamaro]

Originally Posted by Nine Ball

Not sure what tire profile has to do with contact patch. Tires are simply round, and you can't make more of that circle touch the ground by changing what is inside the circle. Contact patch is dictated mostly by tire width and shoulder construction, not diameter.

Sorry. I was just going by experience of when I changed wheels on a previous vehicle. You know more about this than I do.

Originally Posted by danhr

ok you win. you are, by far, the best engineer in history. Every drag racer that runs a 15" wheel obviously knows nothing compared to you. They should all switch to 22" wheels.

all autocross/road race engineers obviously dont have anything on you either, and need to switch out their 18/19's out for 24"s. Why? because the bigger wheel offers more traction and better cornering .

The rule of thumb for wheels, performance wise, was written a long time ago.... put the smallest wheel possible, that will clear the brakes.

Ok, captain sarcasm. I made an observational mistake and admit that I am wrong.

[xpanda305x]

20's are more for looks i say.

heavier than a 18. more expensive tires. get me?

[600hp-lpe]

I have a set of 18's, 19's, and the stock 20's for my car.

The 18's are for autocross and road course racing. They have issues clearance wise because of the width (check my sig for sizes) . This set is almost 80 lbs lighter than stock.

I run 19's on the street. The car is lower, the tire profile is a shorter height by 1.8". The 285/35/19 tire size is awesome on this car. The smaller diameter is a speed increase. Feels like I did a gear change. They are 51 lbs lighter than stock.

I only put the 20's on when the car is going into the body shop, dealer, or other shops so the expensive CCW's don't get damaged or I pick up a piece of metal at one of the shops in a tire.

The smaller tires also let you get performance tires for drag, road coarse, or autocross. There are no good racing tires for 20" wheels. Hoosier doesn't make anything in a 20" tire.

[paul2010]

20s are great for looks but for drag racing you need at least 18s.