Debate: 17x7.5 or 17x7.0 - which ones better for performance?

[sush]

OK, so im looking to get rims for spring/summer, went to a few dealers, and they confused the hell out of me:


17x7.5
Advantage:
-wider tire, hence more area to grip

Disadvantage:
- wider tire = more mass, hence lower acceleration.
- wider tire, more area touches the ground. this is bad because, pressure = force/area, you increase the area, so the pressure on the ground is less, so lower grip...


17x7.0
Advantage:
- lower mass = better acceleration
- thinner tire, so on a turn, the tire will bend more, and the side wall will touch the road better. hence better on turns.
- thinner tire, less area touches the ground. this is better because: pressure = force/area, you reduce the area, hence the pressure on the tire increases, which will increase the grip.

Disadvantage:
-thinner tire, means less area touches the ground, hence less grip.
-thinner tire, with more pressure, means faster wear out.

I don't know what to get! Help?!?!
- does the thin tire, has better traction make no sense or what? but that argument does make a little sense.
- if thats the case...why do mustangs come with 18x9s? shouldn't they be...18x6.
- i thought thinner tires were only better in winter, because they cut through the snow.
- I'm just confused.

[SE2000]

That explanation does not make sense to me. Do you mean the exact same wheels? Different brands/models wheels and tires have different weights and mass.
Wheel width should be matched to the tires, the closer the rim to tread width, the better performance you'll see. Thats why the GA 16" 5 spoke wheels will better handle with 205/55 tire than the stock 225/50

[b2089]

Okay to keep it simple, I call foul with some of your explanations. I could be wrong, but I don't think so.

First - wider tires equals less pressure per square inch, not less grip or less total pressure. The mass of the car is the same. On ice they say it may be a factor but on dry pavement grip will be equal if other factors are equal.

next - bending and being on the side wall is bad, very bad. It damages the tire for one thing. Also you have to think, where is the tread? Taking the first thing I mentioned about pressure per area, why would you want to remove some pressure from the tread and spread it out on the sidewall, lowering grip considerably (this time it does lower because of friction on the sidewall being less)

After that I'd say make the decision not on grip but on what fits the car better.

[SE2000]

To keep it simple. The question is based on wheels. But thats only half a sandwich. Tires and tire size is the other half. And what is the purpose of the sandwich. To go fast, straight or around corners, to look good on the street or a compromise?

[sush]

well, im keeping the tires the same. Falken FK-452. the have some thread on the sidewall, so i was guessing, that would help on corners.

i need the car for everyday driving. but im usually the a$$hole that cuts in front of people and drives his car too hard. so i need tires to keep up with me, ive done several 180s coming off a ramp on the highway, and ... its not safe. :P

i spoke to one of my buddies in aerospace engineering, and he said that the grip would be the same. so b2089, is right.

he said the following:

- the horsepower of the car has to match the wheel. mustangs can have 18x9s, because they need it, they would tear apart 18x6s if you floored it.

- it works the other way as well, you can not put 18x9s on a civic. (i know they wont fit, i'm just giving an example), because the steering would not be able to turn such a tire on tight corners or the engine would not be able to accelerate as well, since the grip or increased friction would hold back the car.

-wider tires, will give a smoother ride, but they compromise on steering and acceleration if your car/engine is too weak.

THAT, made sense to me. :)

So the question now is... what is best for a Grand Am.
the mods i have made are:
- magnaflow exhaust
- CAI
- UDP

Can the Grand Am, handle 17x7.5s on tight corners without putting to much tension on the steering? and would a 7.5 hold back our cars acceleration? or is 7.5 safe, and perfectly handle-able by a GA SE?

i feel that people are over-killing tire thickness. for example: G6 GT, 224hp, still just uses a 7" tire thickness, is Pontiac just trying to save $$$ here? or is that actually the right size?

[coupe]

Your splitting hairs

[SE2000]

Mustangs certainly will not tear up 18x6 even if it has 600hp. The engineer is referring to tires and that is only partially true. What size tires are you looking at?
http://www.fk452.com/sizes.html

I would suggest 225 width for spirited driving

[sush]

i could go for: 225/45 17 or 245/45 17

225 would sit slightly more on the inside of a 17x7.5 right?

sorry if I'm confusing/irritating people. I'm spending about $1500, so i want to be careful about this and get the most i can for my money.

ps: "spirited driving" - lol. good one.

[bballr4567]

I personally have 18X7.5 and its an amazing upgrade from stock. The car handles sooo much better with the extra contact on the road.

Personally Id go with what you would look better on the car.

[SE2000]

Get the 7.5 rims as it will work with either tire. The rim width will not change drag on the road

[bandit307]

Your splitting hairs
:agree:

i need the car for everyday driving. but im usually the a$$hole that cuts in front of people and drives his car too hard. so i need tires to keep up with me, ive done several 180s coming off a ramp on the highway, and ... its not safe.

I dont really want to rag on you, but if your going to brag about being an http://www.gaownersclub.com/forum/images/smilies/icon_censored.gif when you drive. Well im going to try and nock you down a peg. Your the http://www.gaownersclub.com/forum/images/smilies/icon_censored.gif that turns me into an http://www.gaownersclub.com/forum/images/smilies/icon_censored.gif, good old road rage. Im not saying that makes me better then you. but what ever.

the horsepower of the car has to match the wheel. mustangs can have 18x9s, because they need it, they would tear apart 18x6s if you floored it.

I am really curious to see where you get your information from. I believe you have a lack of research going here and its really starting to confuse the heck out of me.


t works the other way as well, you can not put 18x9s on a civic. (i know they wont fit, i'm just giving an example), because the steering would not be able to turn such a tire on tight corners or the engine would not be able to accelerate as well, since the grip or increased friction would hold back the car.

It is not only grip and friction that hold back the car from accelerating. The total mass of your wheel and tire setup also plays a major role, So maybe thats something to look into as well.

I can keep ranting but i dont want to risk more warning points so i will leave it at that.

Listen to Ray and Josh, They have good suggestions there for you, I am going to agree with them. Look for what looks best on the car and fits. If your worried about performance that much maybe look into lite weight rims.

[sush]

o...k... bandit307,
sorry for not researching well enough to post a question?
and sorry for being a :censored: while driving.

i don't really care about the looks of the car, in fact i couldn't care less. id use pink and purple rims on my car if i got them cheap enough. i just wanted to know, i what size rims are ideal for the performance aspect of the car.

answering, with "get what looks good", is not the right answer for me. forget all my reasoning, it could be stupid. im just trying to get whats best for me. and if you dont want to help, or read what im saying, then please dont.

to keep it simple:
mountain bike = big wide tires, really suck on the road. you cant catch any speed with them.
racing bike = thin tires, good on the road, can reach high speed easily.

so why should i upgrade the tire thickness? whats the advantage? For more grip? We've agreed that the grip remains the same here.

I DONT GET IT. why have people upgraded tire thickness? i know a lot of people here have done so...whats the reason for it?

[Vampyrate]

if i were to get rims for my car, i would go with the rota slipstreams. they are next to nothing weight wise compared to other racing rims and are the lightest that ive ever seen:

http://www.machiii.net

[SE2000]

Originally posted by sush


to keep it simple:
mountain bike = big wide tires, really suck on the road. you cant catch any speed with them.
racing bike = thin tires, good on the road, can reach high speed easily.

so why should i upgrade the tire thickness? whats the advantage? For more grip? We've agreed that the grip remains the same here.

I DONT GET IT. why have people upgraded tire thickness? i know a lot of people here have done so...whats the reason for it?

I've replied several times that you asked about wheels. Your simple explanation is about tires. You do interchange the terms?

[bandit307]

Im with Ray, I am very confused here.

One post your talking about rim size now your talking about tire size.

While you debat about your wheel size maybe first you should figure out what size tire you are going to run. Go based on that.

By the way.
Mountain bike: yes the tires are wider, but they also have nobs for off-road traction. Which makes an uneven surface to ride on.

Racing bike: Tires are smooth which is a more efficient surface to ride on.

Maybe i am the only one not understanding this, but by upgrading the thickness do you mean the width? If so then hell get some 13" wheels, slap some 155 20 13 rubber on there and away you go. Good acceleration, next to nothing tire mass and who cares how wide they are they all handle the same right?

[sush]

ive just realized what SE2000 said, i didn't understand it before, the 225 will fit on both 7.5 and 7, to the area touching the ground will be equal (wheel size is irrelevant). I thought that the wheel size will relate to area of the tire touching the ground, and thats not right. < thats what ive been thinking all along, i can see why you guys are confused now.

and bandit, you got me again on the bike example, its the smoothness of the race bike that lets it go faster. i was thinking it was the fact that they are thinner.

my question should have been debating tire width: 225 vs 245.
...and 225 is better for me here?

[SE2000]

A 225 tire, regardless of the rim size will, give you optimum street driving. Anything wider will be more costly and give more rolling resistance, and more weight.
Going with the smallest rim for your taste will result in a cheaper tire. You can buy a better tire in a smaller size for the same price as a bigger/cheaper tire. That will give better performance and not hit the fenders under full suspension travel. wider tire are for looks and do not improve performance of a GA unless it's been heavily upgraded. A 205 tire is the best choice for a winter tire.

As to your original question, the 245 will wear out faster than a 225 because it will heat up more and actually shorten it's life plus the increas scrubbing when turning.

[sush]

Originally posted by SE2000
A 225 tire, regardless of the rim size will, give you optimum street driving. Anything wider will be more costly and give more rolling resistance, and more weight.
Going with the smallest rim for your taste will result in a cheaper tire. You can buy a better tire in a smaller size for the same price as a bigger/cheaper tire. That will give better performance and not hit the fenders under full suspension travel. wider tire are for looks and do not improve performance of a GA unless it's been heavily upgraded. A 205 tire is the best choice for a winter tire.

As to your original question, the 245 will wear out faster than a 225 because it will heat up more and actually shorten it's life plus the increas scrubbing when turning.


dude, that hit the spot. thats what i was looking for. an orgasmic answer. thank you.
:bow:

[bandit307]

There you go Sush. I was never trying to be a complete ass to you, But you just kept confusing the hell out of me with every post. Now that the question has been clarified you get the answer you need.

Good luck with getting your new setup.

[coupe]

I dont know why people worry so much about performance with these cars when chooseing a rim.
Your worried that it will slow you down, NEWS FLASH!!! Your car is already slow to begin with.

[bandit307]

I dont know why people worry so much about performance with these cars when chooseing a rim.

FTW :agree:

The GA is a sporty grocery getter. You can pick up milk in style.

Unless you plan on putting alot of money into your car, getting performance out of your rims should not really matter. If you do plan on putting money into the car, the power you make out of your done up GA should compensate for the minor choice effect in the rims you choose. If your looking for better handling you should also look into suspension as well. The tires are a big factor but so are the components that hold them on the ground. Brakes too while you at it.

[dandragonrage]

Yes, these cars are already slow, so making them even slower and even more importantly, putting more stress on the hub/bearing assemblies, is a BAD idea.

If you upgrade rims, make sure to get rims classified as light or ultra light.

[sush]

man people bad mouth grand ams a lot. :grrr:

i would like to ask something:

what other car (from 2002-2005) started at $22,000, had 175hp and 205ft-lb torque, or better?

-gave a smooth ride and could accelerate sufficiently even at 140km/h (80miles/hr), without the engine crying for help?

-impala and malibu are the only ones that i think compare, they are more expensive, and gulp way more gas.

- what car are u guys comparing it to, saying the GA is slow?

i love my GA! :)

[bandit307]

Alot of us Love are GA's as well. We are not necessarily bad mouthing GA's, Just stating the facts. Most of us have come to terms that we do not own 12 second race cars. Sure it has power, but it all depends on what you compare it too. Sure you can beat a sunfire. But you wouldn't want to pull up to a Trans Am and think your going to beat it.

So personally i think my car is slow, Wish it was alot faster. But with that comes lots of money. If your just looking for a performance application buy a different car. Lots of us on the forum try to make our GA's faster because we love the car, and are willing to spend the money to make it fast. But when all is said and done you probably could have taken the money you invested into your Ga, held onto it instead and sold the Grand Am. Then baught a faster car for cheaper.

You just have to keep in mind, the GA is not a sports car. Your looking at alot of money, time and fabrication to make it one. Thats all i have to say.

[sush]

i agree with that.

i could have got an older used car, with more miles on it, that would be faster, but then we have the remaining life of the car would reduce. and then u have problems like stiff door handles, older interiors, lights that need to be punched to work... blah blah.

...btw, whats a 'lot of money'? i wonder who's spent the most on their car here. hmmm....

[dandragonrage]

Well, before I got my Camaro, I was planning a 3.73 swap in my GA, plus potentially a 3400 swap w/ heads/cam/tune. I THINK I'm gonna sell the GA soon, it's been off the road anyway, but I'll do the 3.73 swap if not and leave it at that.

I like the GA for what it is. But it's not really "the" car for me. I don't like the newer GAs though (not including the G6 as a GA, and I've never been in one so I can't draw an opinion anyway)

[bandit307]

...btw, whats a 'lot of money'? i wonder who's spent the most on their car here. hmmm....

Alot of money well. It all depends on how fast you want to be.

I can give you a extimated idea.

MMS stage 2 package: $2700
Kit includes: -MMS Stage 2 heads -MMS Stage 2 cam -MMS Complete heads and cam install kit -MMS ported intake manifolds -MMS Stage 2 PCM -MMS 180 t-stat -MMS 36lb injector and harness kit -MMS chromemoly pushrods.

Turbo Kit: $3000 or up

No one offers a production kit as of yet. But there are two that i know of in the planning.

Milzy has a kit coming, Your looking around $3500

Turbochargedpower.com used to offer one, i just checked there site and it dosnt even list it anymore. So they may have given up on it.

Or you can get a custom turbo kit built aswell. But your prolly still looking over $3000 for sure.

Exhaust and intake:

S&S headers: $900
Catback Exhaust (custom): $100-300
CAI: $80-300

Plus the addition of forged internals to handle the added stress along with other misc upgrades an extra $1000-2000 to be safe.

so after aprox $7500-9000 you have a respectable power plant. But now your Trans is shot. So your looking at another $3000 or up for a HD trans to handle the power.

Then add suspension, wheels, tires, strut braces, brakes, and labour into that if you cant DIY.

So there you go $14,000 or more and you have yourself a fast GA. I say that is pretty expensive. There are cheaper alternatives to some of the products and i have more then likely over looked a few things to add in there. but all in all your looking over $10,000US.

[Pte Socks]

Ok, heres what I gotta say on this, 7 or 7.5" its not going to matter a whole lot mate. Your talking half an inch which is very minimal weight and you can still stuff a 235 on either a 7 or a 7.5" rim. IN some cases, adding a huge difference can add a headache to the person installing the tire ( like have a massive 275 fit on lets say an 8.5" so your sidewall is stretched to shit, thsi is just an example, I dont even know if it would fit ). So all in all, it doesnt really matter. What matters most is the weight of the rim ( keep them as low as possible ) and the wieght and fit of the tire ( Low pro tires tend to weigh more because they have a higher contact area ) whether or not to go with 225, 235 or 245, well that depends on the size of rim ( ie, 17" 18" 19" ) and go from there. I can tell you a 225/45R17 or in my case a 235/45/R17 works well on a lowered or stock GA. Go from there

[SE2000]

Originally posted by Pte Socks
Ok, heres what I gotta say on this, 7 or 7.5" its not going to matter a whole lot mate. Your talking half an inch which is very minimal weight and you can still stuff a 235 on either a 7 or a 7.5" rim. IN some cases, adding a huge difference can add a headache to the person installing the tire ( like have a massive 275 fit on lets say an 8.5" so your sidewall is stretched to shit, thsi is just an example, I dont even know if it would fit ). So all in all, it doesnt really matter. What matters most is the weight of the rim ( keep them as low as possible ) and the wieght and fit of the tire ( Low pro tires tend to weigh more because they have a higher contact area ) whether or not to go with 225, 235 or 245, well that depends on the size of rim ( ie, 17" 18" 19" ) and go from there. I can tell you a 225/45R17 or in my case a 235/45/R17 works well on a lowered or stock GA. Go from there

The extra width will make a bigger improvement gain than the small detriment of added weight.

[DontPassTheFence]

Id say 17x7 with a 225mm width tire, unless you autocross, you will not need more.

[sush]

Pte Socks: the way i'm looking at it, is that i have a stock tire of 6.5, adding 1 inch brings it to 7.5... thats a 15% increase in width, and i was worried about the increased width creating a frictional drag. we have that settled now. People do it for looks, not performance, skinny tires would be better with turning friction, and lower mass (only by a slight amount) and the wider tire... looks better.

the 17x7, with a 225 tire seems to be a good all rounder for my requirements for performance and looks, and thats what i'm going for.

you want looks: go bigger and wider
you want performance: keep it around 17x7, with 225s

thanks guys.

[Pte Socks]

but see sush, you dont really have to compare the 7.0 to the 7.5 because the main difference being made is the actual tires, not the rim. IMO, then, it really doesnt matter if your running a 7.0 or a 7.5" if you choose the same tire, in example, the 225/45/R17. A 225 width tire is going to have the same contact area on teh 7.0 as compared to the 7.5. Just a heads up on tires though. There is one important thing to learn about tire sizes, the tire width is measured at the WIDEST part of the tire, not necessarily at the tread. The reason I point this out is that I know on my tires, I have an extra lipe on them, on the inside and outside that extends the tread another 1/4 on each side for a total of .5" PAST the rim. I chose these tires specifically for this added advantage. This is important to realise beacuse many cheaper tires will actually skimp on the tread contact area. For an example, look at your lowest price tire you can find, like at a wallmart or something. Then compare and measure the tread width compared to the SAME sized tire, in a much more expensive brand. You will find that there is remarkably a huge difference in the tread width of the 2, even though they are the same size. I just felt like bringing that up because many people dont realise that. And on the topic of surface area, it can make a substancial difference in performance.