So the G8 GXP is going to be the poor-man's M5... so why does it come with such TINY Tires?

The tire size GM lists for the GXP is 245/40/R19, here is what the competition is wearing:

-2008 BMW M5
--255/40/R19 (FRONT)
---4% Wider
--285/35/R19 (REAR)
---16% Wider

-2008 Mercedes Benz E63 AMG
--245/40/R18 (FRONT)
---Same
--265/35/R18 (REAR)
---8% Wider

-2008 Audi S6
--265/35/R19 (FRONT & REAR)
---8% Wider


So what gives? Why can't we get a wider tire option? I'd at least like to see a 275 section rear tire as an option...?

~LSx

So the G8 GXP is going to be the poor-man's M5... so why does it come with such TINY Tires?

The tire size GM lists for the GXP is 245/40/R19, here is what the competition is wearing:

-2008 BMW M5
--255/40/R19 (FRONT)
---4% Wider
--285/35/R19 (REAR)
---16% Wider

-2008 Mercedes Benz E63 AMG
--245/40/R18 (FRONT)
---Same
--265/35/R18 (REAR)
---8% Wider

-2008 Audi S6
--265/35/R19 (FRONT & REAR)
---8% Wider


So what gives? Why can't we get a wider tire option? I'd at least like to see a 275 section rear tire as an option...?

~LSx

What should really make you mad is the GT has the same optional size as the GXP. Pontiac probably doesn't want to put out extra cost for the wider rear tires & any concerns over tire rub. Plus, GM's (cracked :nuts:) logic tells them that the GTO did just fine with only a 245mm wide set of rear tires, so should the GXP.

Gas Guzzler tax avoidance?

Gas Guzzler tax avoidance?

Tire size won't change the chances of landing in GGT territory. The revised EPA testing procedures would have a bigger impact than tire size.

What should really make you mad is the GT has the same optional size as the GXP. Pontiac probably doesn't want to put out extra cost for the wider rear tires & any concerns over tire rub. Plus, GM's (cracked :nuts:) logic tells them that the GTO did just fine with only a 245mm wide set of rear tires, so should the GXP.

EXACTLY! This is what caught my eye... everyone else (BMW, MERC, AUDI) bump the tire sizes on their performance models, but GM thinks the regular sizes will do? PULEASE!!! 400lb-ft of torque + 245 section tires only make SMOKE!

I'm hoping they offer a 265 option on these rims (or maybe on 20's).

This is just nuts.

~LSx

We have a lot of Cadillac CTS and owners call in and complain that they cannot rotate thier tires for better durability, maybe someone at GM had similar feedback ?

EXACTLY! This is what caught my eye... everyone else (BMW, MERC, AUDI) bump the tire sizes on their performance models, but GM thinks the regular sizes will do? PULEASE!!! 400lb-ft of torque + 245 section tires only make SMOKE!

I'm hoping they offer a 265 option on these rims (or maybe on 20's).

This is just nuts.

~LSx

Watch the rim width. Some Manufacturers go cheap and only put 8inch wide rims on the car (even on the performance model). Thanks for nothing!, since the widest tire that 8inches can support is 245s. A nice 9inch rim from the Mfg would be nice, supporting 275's and 285's.

I was REALLY hoping we would get the size/stagger from the new Camaro SS:

245/45ZR20 front
275/40ZR20 rear

These are the sizes that the Nurburgring test car was wearing when it was hot-lapping a few weeks ago. I was expecting this stagger for the GXP since it is meant to be a real sports sedan.

But then again, the new CTS-V is only running P245/45 R18 W-Rated Goodyear Eagle F1 EMT (run-flat)s and just set a lap record for Sedan's! Maybe they know what they're doing after all...


~LSx

Watch the rim width. Some Manufacturers go cheap and only put 8inch wide rims on the car (even on the performance model). Thanks for nothing!, since the widest tire that 8inches can support is 245s. A nice 9inch rim from the Mfg would be nice, supporting 275's and 285's.

my SRT4 was like that with a tiny 6" wide rim for a max width of 215 stock with 205! wtf my 92hp escort has 185 stock!

Don't you get it yet! I have owned Vets, Trans Ams and a Ford Mustang but this is a different car from GM. We are going to beat the imports at their own game. For years GM thought that adding massive tires was the best way for performance. Other cars did just as well on the skid pad with less fancy sneakers. We now have a ride from GM that thinks outside the box. A REAL suspension! Wait and look at the numbers, I hate to say it but size does not always matter. By the way, every millimeter smaller that they can make the tires and still keep it competitive in a slalom will make the ride better and in the event the car is caught in snow. Well I would not recommend this car in snow, but it is better in the snow with smaller tires. Go GM!

Don't you get it yet! I have owned Vets, Trans Ams and a Ford Mustang but this is a different car from GM. We are going to beat the imports at their own game. For years GM thought that adding massive tires was the best way for performance. Other cars did just as well on the skid pad with less fancy sneakers. We now have a ride from GM that thinks outside the box. A REAL suspension! Wait and look at the numbers, I hate to say it but size does not always matter. By the way, every millimeter smaller that they can make the tires and still keep it competitive in a slalom will make the ride better and in the event the car is caught in snow. Well I would not recommend this car in snow, but it is better in the snow with smaller tires. Go GM!

Agree about the ride comfort and the inclement weather. However, at the strip, 255's are just not enough meat to launch a 400+HP vehicle. Mine go up in smoke at 3/4 throttle. Big meats are American, too...:us_flag:

Again, wait for the results. If the suspension is set up as I suspect, just look at the numbers (times) don't worry about changing or upgrading a car that we have yet too touch or test.

Don't you get it yet! I have owned Vets, Trans Ams and a Ford Mustang but this is a ... I hate to say it but size does not always matter. By the way, every millimeter smaller that they can make the tires and still keep it competitive in a slalom will make the ride better and in the event the car is caught in snow. Well I would not recommend this car in snow, but it is better in the snow with smaller tires. Go GM!

OK, so you do have a good point. Too much tire and ride quality suffers, so to that end I hope they get it right. BUT, 400lb.ft and 245 section tires are not going to play nice...

Oh, and here in New England, you CANNOT use all season tires in the winter (FYI All season tires are not designed to run below 40°F). I'd be swapping for dedicated winter wheels anyway.

~LSx

Wait and look at the numbers, I hate to say it but size does not always matter.

In 1997, Pontiac tried to make us believe that "Wider is Better". :D

FYI All season tires are not designed to run below 40°F~LSx

Really? Then why are they all season tires? And why are they rated for their snow and ice traction? It's hard to get snow and ice to hang around above 40 degrees F last time I checked?!:dunno:

In 1997, Pontiac tried to make us believe that "Wider is Better". :D

My point exactly. Maybe the engineers at Pontiac have taken a page from the competition and come up with a great balance between ride/acceleration/handling. Again, my 1982 Trans Am was one of the fastest cars on the block. However cars like the BMW were starting to make a name for themselves. Smaller tires and more refined suspensions gave them ALMOST as good grip with a much better ride.

If I wanted to buy the fastest car available. I (as many others on this forum) could have stretched a little (money) and gotten something faster like a Vett. I chose this car because of many more factors including it's balance of power/ ride / 4 doors. I think the engineers are continuing with this thought, after all the Vett is not being discontinued. Yes maybe a fatter tire is right for you. Still the GXP is a 4 door sedan and it has a great suspension. Wait to see how it rides/ performs...

Not to mention, as has been discussed numerous times here, you can put wider tires on the G8. You just have to get after market rims, wider, to do much more than what is standard equipment. If that is your thing, go for it!:wink2:

Really? Then why are they all season tires? And why are they rated for their snow and ice traction? It's hard to get snow and ice to hang around above 40 degrees F last time I checked?!:dunno:

The rubber itself changes it's flexibility with temperature. Anyone who has done racing/autocross is aware of that. Rubber gets hotter, the rubber tends to "melt" (hence the funny wear pattern on the outside of street tires at the Auto-X). As all-season tires (not to mention summer performance tires) get exposed to cold temperatures, the rubber tends to "harden" (get less flexible). This causes a change in the handling of the car. Snow tires really don't exist anymore. Those tires have been redesigned into winter tires. Winter tire rubber compounds are different from all-seasons. They work best in the colder temps. Over ~45*, they wear out fast & lose grip easily.

Benny, tire selection is always a key for a happy customer. GM is leaning on the side of happy customers with good ride quality. As with any car, enthusiasts will wedge more tire in the available space (or add HP, bigger brakes, or other things). For enthusiasts, this is where doing your homework pays off. Grille your local tire salesperson, see tires, feel tires. A tire that will ride well will be able to have it's sidewall flexed (grab the bead w/ the tire off of a rim & pull & flex the bead) easily by the customer. Hi-performance tires will have those stiff sidewalls. Tire companies have to build a compromise set of tires. That's the reason that there are 2-4 different "performance" tires from each tire manufacturer.

The rubber itself changes it's flexibility with temperature. Anyone who has done racing/autocross is aware of that. Rubber gets hotter, the rubber tends to "melt" (hence the funny wear pattern on the outside of street tires at the Auto-X). As all-season tires (not to mention summer performance tires) get exposed to cold temperatures, the rubber tends to "harden" (get less flexible). This causes a change in the handling of the car. Snow tires really don't exist anymore. Those tires have been redesigned into winter tires. Winter tire rubber compounds are different from all-seasons. They work best in the colder temps. Over ~45*, they wear out fast & lose grip easily.

I think what you are trying to say is what a lot of us have known for a long time. There is no really great A/S tire. The best you can hope for is good in all categories, and better than summer only in wet and light snow conditions. Its tread design and type of compounds are better than the ones used for single season tires, but, rubber being rubber, it is not going to stick to cold wet surfaces. We should all know we're not talking velco here!:)

Really? Then why are they all season tires? And why are they rated for their snow and ice traction? It's hard to get snow and ice to hang around above 40 degrees F last time I checked?!:dunno:

From Tirerack.com

But Do I Really Need Winter Tires?
...
And while many of today's all-season tires (Original Equipment, touring and performance) address some of these issues, they still emphasize longer wear, a quieter ride or greater performance...not winter traction.

Only winter tires are designed to excel in the colder temperatures, slush, snow and ice that many parts of the country experience for three or more months a year.

...

Won't All-Season Tires Work Just Fine?
By design, All-Season tires are a compromise intended to provide acceptable traits under a wide variety of conditions. However, that compromised goal prevents them from being a master of any one of them. The All-Season tire tread designs and compounds that are engineered to provide extended mileages and durability under the summer's sun are less effective in winter's freezing temperatures, and through snow and on ice. Specific winter tires deliver much better snow and ice performance than All-Season tires because their tread designs and tread compounds are engineered to master those conditions, while summer tires are engineered to deliver better handling in the rain and on dry roads. Why not have the best tires for each of the conditions you'll encounter?

In short, All-Season tires are designed to run in snow and ice IN AN EMERGENCY... these tires are mean't for climates where snow and ice are NOT the usual conditions. They allow you to 'get thru' without being too dangerous, but they are NOT designed for climates where the temperature is regularly below freezing, and where snow and ice are VERY common.

~LSx

In short, All-Season tires are designed to run in snow and ice IN AN EMERGENCY... these tires are mean't for climates where snow and ice are NOT the usual conditions. They allow you to 'get thru' without being too dangerous, but they are NOT designed for climates where the temperature is regularly below freezing, and where snow and ice are VERY common.

~LSx

OK, but your original statement was A/S tires were not designed to run below 40*F. My point is, there is a lot of wet weather below 40*F that is not snow or ice. I know, I live through a lot of it every year, and have for the past 15 years here in the Pacific Northwest. I have run A/S tires around here all that time with great results, even the minimal amounts of snow are handled fairly easily. I have also driven with summer only tires that were OK in the rain, but sucked in anything frozen. I agree, for long term, Buffalo, NY type winter snow conditions, winter tires are the way to go. But, short of full blown winter conditions like that, and based on my 15 years and 100,000 miles of experience, you'd be hard pressed convincing me A/S tires were not designed for temps under 40*F.:nonono:

OK, but your original statement was A/S tires were not designed to run below 40*F. My point is, there is a lot of wet weather below 40*F that is not snow or ice. I know, I live through a lot of it every year, and have for the past 15 years here in the Pacific Northwest. I have run A/S tires around here all that time with great results, even the minimal amounts of snow are handled fairly easily. I have also driven with summer only tires that were OK in the rain, but sucked in anything frozen. I agree, for long term, Buffalo, NY type winter snow conditions, winter tires are the way to go. But, short of full blown winter conditions like that, and based on my 15 years and 100,000 miles of experience, you'd be hard pressed convincing me A/S tires were not designed for temps under 40*F.:nonono:

Ah, I seee... we are merely looking at things from two different directions. When YOU see 40*F its as cold as its going to get, and its probably wet on top of it. When I see 40*F I know that all that moisture will soon be ice, rendering A/S tires pretty much useless. Different perspectivs.

One other thing.. and this is just my hunch.. that your car would perform BETTER with a performance winter tire (Dunlop M3) under the conditions you listed. Why? I think a true winter tire would remain softer at those temperatures, giving you MORE traction.

But that's just my experience (which is also 15 years and 200K miles in cold climate conditions) telling me that.

~LSx

[QUOTE=BBBBGXP;55919]OK, but your original statement was A/S tires were not designed to run below 40*F. My point is, there is a lot of wet weather below 40*F that is not snow or ice.

I agree, for long term, Buffalo, NY type winter snow conditions, winter tires are the way to go. /QUOTE]

If you note, I said there is a lot of wet weather below 40*F that is not snow or ice. If the increase of traction between A/S and Winter tires is marginal for this type of conditions, why would I want to spend the money/time/effort to change tires and rims? If I'm looking at minimal snow and ice, with temps generally going right back over the freezing mark, what is the advantage?

Lastly, you will notice I agree with you on the areas with true winter conditions, that being a lot of snow and ice conditions. In these areas, winter tires would be a definite advantage.:wink2:

What should really make you mad is the GT has the same optional size as the GXP. Pontiac probably doesn't want to put out extra cost for the wider rear tires & any concerns over tire rub. Plus, GM's (cracked :nuts:) logic tells them that the GTO did just fine with only a 245mm wide set of rear tires, so should the GXP.


Definately "cracked logic."

The 245/40/17s (standard) and 235/40/18s (optional) that came on the GTOs were too skinny for a 400hp, 3700 lbs performance car.

Most the guys I know running wider tires on their GTO's have had their fenders rolled or trimmed to prevent rubbing.

This has been a major complaint from many GTO owners (the car not being designed to run a decent sized tire).

Definately "cracked logic."

The 245/45/17s (standard) and 235/40/18s (optional) that came on the GTOs were too skinny for a 400hp, 3700 lbs performance car.

This has been a major complaint from many GTO owners (the car not being designed to run a decent sized tire).

Fixed that for ya. A few days after having mine, I decided that bigger is better in this case. I used stiffer rear springs in order to fix the rub problem.

Fixed that for ya. A few days after having mine, I decided that bigger is better in this case. I used stiffer rear springs in order to fix the rub problem.


Thanks for the fix. I should know the right size because I had an 05 GTO with the 245s. Now I own a 06 GTO with the OEM 18s.. I'm currently running 255/40/18s KDW2's.
I'm still having some traction issues with the 255s. My 06 A4 is tuned with no torque management. I get quite a bit of wheel spin on the street if I go wide open leaving the line.

I came really close to getting new wheels and getting my fenders rolled so I could run a bigger tires, but I decided to wait. I'm still not sure if I want to go that route.

The car doesn't honestly compete with anything German. But it is priced and aimed directly at Chrysler's SRT8 cars. I would have thought we would at least get the same wheels and tire size as the HSV Clubsport which the GXP is based on.

Watch the rim width. Some Manufacturers go cheap and only put 8inch wide rims on the car (even on the performance model). Thanks for nothing!, since the widest tire that 8inches can support is 245s. A nice 9inch rim from the Mfg would be nice, supporting 275's and 285's.

Unless you have some different laws over there 8 inch rims will take a lot wider rubber than 245. I was running 265/50 BF Goodrich TA,s on 7 inch rims on my '73 HQ Holden. A mate of mine was running 295/50 on 8 inch on his '34 Ford rod.

Unless you have some different laws over there 8 inch rims will take a lot wider rubber than 245. I was running 265/50 BF Goodrich TA,s on 7 inch rims on my '73 HQ Holden. A mate of mine was running 295/50 on 8 inch on his '34 Ford rod.

Always check with the tire MFG on rim width tolerances, most will not suggest anything wider than 255 on a 8 inch rim. Sure, you can jury-rig 295's on, but that is an 11.5 inch tire on a 8 inch rim. Safe? I guess that would be OK following Darwin's law.

Always check with the tire MFG on rim width tolerances, most will not suggest anything wider than 255 on a 8 inch rim. Sure, you can jury-rig 295's on, but that is an 11.5 inch tire on a 8 inch rim. Safe? I guess that would be OK following Darwin's law.

Totally agree, go with the recommended tire size for rim width, very important.

Always check with the tire MFG on rim width tolerances, most will not suggest anything wider than 255 on a 8 inch rim. Sure, you can jury-rig 295's on, but that is an 11.5 inch tire on a 8 inch rim. Safe? I guess that would be OK following Darwin's law.

The tyre dealers wont fit them if they dont meet manufacturers specifications.They are liable if they do and I had them fitted by a national tyre chain.

The tyre dealers wont fit them if they dont meet manufacturers specifications.They are liable if they do and I had them fitted by a national tyre chain.

Could be that is a truck tire? Higher sidewall like 50 or 55? Smaller rim like 16in?

Always check with the tire MFG on rim width tolerances, most will not suggest anything wider than 255 on a 8 inch rim. Sure, you can jury-rig 295's on, but that is an 11.5 inch tire on a 8 inch rim. Safe? I guess that would be OK following Darwin's law.

This is the best thing someone has written on this forum in a while. When choosing the proper size, the manufacturers publish the approved rim widths for each size of tire. To counter Paul6t4, remember that the '00 Ford Mustang Cobra R came equipped with 265 wide tires, but the rims were measured out at 9.5" wide. Talk about getting short changed. Also, to add insult to injury, tire techs trying to squeeze 11" worth of tire onto 8" worth of wheel have a much better chance of scratching your wheels. Not that it's their fault, the sidewalls have tension when they are being installed.

The HSV's here have bigger rubber on the rears but they are pricey. The oem Bridgstone 20"s are $900 a corner.
I had 20's on mine but have gone back to genuine 19's and the car actually handles better than with aftermarket 20's on it.
I use 16' steel rims and DR's at the track.

cheers

Unless you have some different laws over there 8 inch rims will take a lot wider rubber than 245. I was running 265/50 BF Goodrich TA,s on 7 inch rims on my '73 HQ Holden. A mate of mine was running 295/50 on 8 inch on his '34 Ford rod.

Same laws here in OZ Paul just cos they fit doesn't make em legal. Insurance can and will wipe you in a prang.

cheers

Same laws here in OZ Paul just cos they fit doesn't make em legal. Insurance can and will wipe you in a prang.

cheers

Had the HQ over the pits due to a defect notice. They had no problems with the 265/50 on 7inch rims. My understanding of Western Australian laws are rim with plus 45%.
They wont fit them here out side manufacturers specs. I wanted to fit standard tyres to a VC Commodore and they said they wouldnt fit them because they were too narrow. Had to show them on the tyre placard that they were the correct size for that model before they would fit them.
The main reason for not fitting wider rims over here is that you are only allowed to increase the vehicles track by 25mm over standard so by increasing rim size by only 1 inch it is touch and go whether it would remain legal.