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Discussion Starter · #1 ·
Hey all...even though I didn't get my GT coupe in the driveway yet, I'm already shopping around for snow tires. It occured to me that the G6 4cyl and V6 have 16x7" steel wheels standard. So if I can get ahold of 4 of those, I don't even need to buy new snow tires, I can reuse my ones from last season and just have them remounted on the proper wheel.

My two questions are:

(A) the GT coupe and I4/V6 sedans and my GT coupe all use the same brake components right? In other words, will the 16x7 wheel fit properly on my car and leave sufficient clearance for the brakes?

(B) if so, where can I find CHEAP 16x7 steel wheels? tirerack and discount tire both have no steel wheels available. I suppose I could just order them from pontiac, but I'd pay out the arse (probably over $100 a wheel, which is insanity). I checked car-part.com to try and find a wrecked G6 with steels, but that too cannot be found...

Any thoughts?
 

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ragingfish said:
Hey all...even though I didn't get my GT coupe in the driveway yet, I'm already shopping around for snow tires. It occured to me that the G6 4cyl and V6 have 16x7" steel wheels standard. So if I can get ahold of 4 of those, I don't even need to buy new snow tires, I can reuse my ones from last season and just have them remounted on the proper wheel.

My two questions are:

(A) the GT coupe and I4/V6 sedans and my GT coupe all use the same brake components right? In other words, will the 16x7 wheel fit properly on my car and leave sufficient clearance for the brakes?

(B) if so, where can I find CHEAP 16x7 steel wheels? tirerack and discount tire both have no steel wheels available. I suppose I could just order them from pontiac, but I'd pay out the arse (probably over $100 a wheel, which is insanity). I checked car-part.com to try and find a wrecked G6 with steels, but that too cannot be found...

Any thoughts?
The non-GT/GTP cars have ~10.8" front brakes. The GT/GTPs have ~11.7" front brakes. So there are differences.

However, tirerack's winter package system indicates that 16" will fit on GT models.
 

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Discussion Starter · #5 · (Edited)
Unfortunately, I've been told by many that even though the 16x7's will attach to the hubs, I CANNOT safely use them on the GT because of the 3% difference in outer diameter between the 17 and 16 wheels. Supposedly anything more then 1% will F up the computers and cause systems such as ABS and traction control to either malfunction or function improperly.

I'm REALLY pissed to say the least, as I have practically brand new snow tires from last year that would easily fit the 16x7's, but now i can't use them. And there are no good snow tires available in 17".
 

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ragingfish said:
Unfortunately, I've been told by many that even though the 16x7's will attach to the hubs, I CANNOT safely use them on the GT because of the 3% difference in outer diameter between the 17 and 16 wheels. Supposedly anything more then 1% will F up the computers and cause systems such as ABS and traction control to either malfunction or function improperly.

I'm REALLY pissed to say the least, as I have practically brand new snow tires from last year that would easily fit the 16x7's, but now i can't use them. And there are no good snow tires available in 17".
You've been told wrong.

First, it's not the wheel size that matters, it's the tire size (rolling diameter). Find the appropriate tire size (probably 225/55R16) that is close to the same height, and you're good to go.

However, there are plenty of good snow tires in 17"...
 

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Discussion Starter · #7 ·
miscreant said:
You've been told wrong.

First, it's not the wheel size that matters, it's the tire size (rolling diameter). Find the appropriate tire size (probably 225/55R16) that is close to the same height, and you're good to go.

However, there are plenty of good snow tires in 17"...
They said nothing of the wheel size. The outer diameter of the tire has a 3% difference. My snows are 205-55-16.
 

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ragingfish said:
They said nothing of the wheel size. The outer diameter of the tire has a 3% difference. My snows are 205-55-16.
Gotcha. in the last post your said "wheel diameter". I now see in your first post "I can reuse my ones from last season and just have them remounted on the proper wheel."

You're right then there, those would be too small.

But there are good 17" snows.
 

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Discussion Starter · #9 ·
Here's the thing. My 16's I have from the Vibe are Green Diamond Tires. They have to be the MOST phenomenal winter tires I've ever driven on. They did amazing last winter...they're the only tire I'll buy. It's too late in the season, however, for me to get a new set of Green Diamonds...they're cleaned out...and besides, the only 17" tire they even make is 235/55/17. Not sure if that would be adequate.

Regardless. My question is this. I'm determined to get one more season out of the ones I have. Can they safely be put on the car if I discipline myself to keep to low speeds? The majority of my driving is stop and go anyway. Rarely do road trips in the winter months. I just have a long drive to work and can't even begin to imagine having to do it without snow tires. So how much of a risk IS it to use these tires for one season?
 

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ragingfish said:
Here's the thing. My 16's I have from the Vibe are Green Diamond Tires. They have to be the MOST phenomenal winter tires I've ever driven on. They did amazing last winter...they're the only tire I'll buy. It's too late in the season, however, for me to get a new set of Green Diamonds...they're cleaned out...and besides, the only 17" tire they even make is 235/55/17. Not sure if that would be adequate.

Regardless. My question is this. I'm determined to get one more season out of the ones I have. Can they safely be put on the car if I discipline myself to keep to low speeds? The majority of my driving is stop and go anyway. Rarely do road trips in the winter months. I just have a long drive to work and can't even begin to imagine having to do it without snow tires. So how much of a risk IS it to use these tires for one season?
There's no way to determine risk. But if 1" difference does cause problems, what it will do is "confuse" your abs and traction control system, which could cause you more harm than good. Those things acting up could actually induce problems.

IMHO, it's not worth it. If you are that worried that you need snow tires, you need to get the right size snow tires to be effective. Green Diamond or not, the wrong size of snow tires could make them utterly useless if your abs cycles when it's not needed or does not cycle at all when needed, etc.
 

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branderson said:
If you really need snow tires that badly maybe your next car should be AWD?
i don't believe that's a fair comment. Some people just like the added safety of being able to drive 50mph to work rather than drive 25mph, or to climb a hill rather than skid at it's base. The oem tires are not very good in the snow, so if you are going to replace them, why not replace them with snow tires, as he is trying to do.

Perhaps the question is, have you ever driven in snowy winter weather on good snow tires? If you had, you'd 1) not ask that question above, and 2) never gone back to all-season tires for winter again...
 

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At the risk of exposing my ignorance on the particulars of the G6 traction and ABS systems:
Every system I've ever seen for traction used the DIFFERENCE in wheel speed between two wheels rather than the absolute speed in determining whether or not to activate and compensate.
If that holds true for the G6, the wheel and tire combo size shouldn't affect the proper operation.
If a 23 inch diameter tire on the left side is spinning 600 rpm while a 23 inch diameter tire on the right side is spinning 250 rpm, it would seem the response by the TC system would be the same as if we were talking 24 inch tires PROVIDED the SAME SIZE TIRE on EACH SIDE.
Am I missing soemthing important here?
 

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RKH, I tend to agree with you. The speedo and odometer will not read correct, the display for oil change, fuel milage, miles to empty ect will all read wrong to some degree.
 

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RKH said:
At the risk of exposing my ignorance on the particulars of the G6 traction and ABS systems:
Every system I've ever seen for traction used the DIFFERENCE in wheel speed between two wheels rather than the absolute speed in determining whether or not to activate and compensate.
If that holds true for the G6, the wheel and tire combo size shouldn't affect the proper operation.
If a 23 inch diameter tire on the left side is spinning 600 rpm while a 23 inch diameter tire on the right side is spinning 250 rpm, it would seem the response by the TC system would be the same as if we were talking 24 inch tires PROVIDED the SAME SIZE TIRE on EACH SIDE.
Am I missing soemthing important here?
ABS systems, all the ones I know of, are calibrated to the vehicle tire size. They feature a speed sensor which measures the revolutions per mile. A larger tire will transmit a slower speed reading than true, where a smaller tire will do the opposite. From what I understand, this is what causes problems. I can't explain exactly why, as I do not know, but I can assure you that I know of people who have, and have encountered myself, the need to switch back to appropriate sized tires because of traction and abs problems with smaller or larger tires. Perhaps the wheel sensors are "compared" to other sensors, and if one sensor is correct and the other is not, that would turn on the traction or abs system prematurely, or too late, depending on the difference.

I do know that modern traction control systems no longer just compare one wheel to the other.
 

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ragingfish said:
Unfortunately, I've been told by many that even though the 16x7's will attach to the hubs, I CANNOT safely use them on the GT because of the 3% difference in outer diameter between the 17 and 16 wheels. Supposedly anything more then 1% will F up the computers and cause systems such as ABS and traction control to either malfunction or function improperly.

I'm REALLY pissed to say the least, as I have practically brand new snow tires from last year that would easily fit the 16x7's, but now i can't use them. And there are no good snow tires available in 17".
I don't know that this is true. Locally, there are but a few G6's on the road. One that I notice (and envy) is a silver one just like mine. It's the standard (non GT) with the regular moonroof just like mine, but it has the 17" chromed wheels. The owner said the dealer swapped them from another G on the lot for a nominal fee. I know, dealers have done stupid things before, but if swapping to a 17" wheel on a car that is "programmed" for 16's doesn't hurt anything, I have to wonder if going the other way (down to a 16) won't hurt anything either.

And if it indeed screws up so much, and can cause all the harm, how are aftermarket wheel manufacturers making so much $$$$?
 

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golf_n_motorcycles said:
I don't know that this is true. Locally, there are but a few G6's on the road. One that I notice (and envy) is a silver one just like mine. It's the standard (non GT) with the regular moonroof just like mine, but it has the 17" chromed wheels. The owner said the dealer swapped them from another G on the lot for a nominal fee. I know, dealers have done stupid things before, but if swapping to a 17" wheel on a car that is "programmed" for 16's doesn't hurt anything, I have to wonder if going the other way (down to a 16) won't hurt anything either.

And if it indeed screws up so much, and can cause all the harm, how are aftermarket wheel manufacturers making so much $$$$?
Again, it's NOT the wheels size that matters, it's the TIRE size. The 17" stock wheels have lower profile tires on them, so the overall height of the tire, and the subsequent revolutions per mile, are the same between the 16" wheels/tires and the 17" wheels/tires. The 4 cyl, 6cyl, and GT are programmed for ~26" tall tires. The GTP is programmed for ~27" tall tires. The tires he want's to put on are 25" tall tires. They're too short.
 

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Ok, I gotcha. I understood that, but didn't make it clear (and understand about his particular tire size).

For those that are interested, there are calculators available that with the right data, can tell you the speedo difference to expect with varying size tires.

I did a calculation to tell the difference in the Conti 17's that are on the chromed wheels and the Tiger Paws that are on the 16" painted steels (mine, anyway) and the difference is less than 1 mph. The Paws come in around 70.6 at 2000 rpm with the Contis at 69.9, I think it was.

Safe enough for me, and the chrome clads with the Contis should be here within a week :)
 

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Discussion Starter · #20 ·
miscreant said:
The tires he want's to put on are 25" tall tires. They're too short.
Let me ask you this then.

I can get green diamonds in a 215/60R16 size tire. According to one of the online tire size calculators I used, this is only a 1.2% difference in overall size (Speedo with non-stock tire is 1.2% too slow. When the speedo reads 60mph, I'm actually going 60.7mph.) Is that a small enough margin of error, or do I still need to try to find a size closer to stock?

EDIT: I just noticed that the G6 sedans with 16" tires from the factory come with 215/60/16 tires. So if I'm not an idiot here, then I should safely be able to do this, no?

BTW, this is a great tire-size calcualtor right here: http://www.miata.net/garage/tirecalc.html
 
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