18" Tires - Switch to Same Size All Around?

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18" Tires - Switch to Same Size All Around?

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Cadillac Forum >> Cadillac Models >> Cadillac STS >> 18" Tires - Switch to Same Size All Around?

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18" Tires - Switch to Same Size All Around? - 11/27/2006 11:18:10 AM

vballfan

Posts: 2
Joined: 11/11/2006
Status: offline

It's time to replace the tires on my 2005 STS. I have the 18" wheel option and they have different size front and rears. I've been told to switch them to same size all around to get longer tire life by being able to rotate front and back. Does anyone know if this is a good or bad idea? Also, what size would I switch to? Here are the sizes that are on it....255/45/18 and 235/50/18.

I could also use some advice on a good high mileage tire at a decent price. I drive about 30-35,000 per year so tread life/price is really important.

I appreciate any and all feedback!

Post #: 1

RE: 18" Tires - Switch to Same Size All Around? - 11/27/2006 11:48:22 AM

FLCaddytech

Posts: 507
Joined: 6/22/2006
Status: offline

Even if you change the tire sizes you still can't rotate because the wheels are different front to rear.
I like the larger tires in the rear, the more rubber to the road the better IMHO.

(in reply to vballfan)

Post #: 2

RE: 18" Tires - Switch to Same Size All Around? - 12/13/2006 8:05:39 PM

rchern

Posts: 5
Joined: 12/12/2006
Status: offline

quote:

ORIGINAL: vballfan

It's time to replace the tires on my 2005 STS. I have the 18" wheel option and they have different size front and rears. I've been told to switch them to same size all around to get longer tire life by being able to rotate front and back. Does anyone know if this is a good or bad idea? Also, what size would I switch to? Here are the sizes that are on it....255/45/18 and 235/50/18.

I could also use some advice on a good high mileage tire at a decent price. I drive about 30-35,000 per year so tread life/price is really important.

I appreciate any and all feedback!

I believe that there is about .22 inches difference between the 235 mm tire and the 255 mm tire. That might make a difference in the speedometer and odometer readings. I'm not sure how much of a difference it takes to through off the readings. Probably more than that. Could you tell me how many miles you got out of those tires. I just bought a car with the same tire combination.

(in reply to vballfan)

Post #: 3

RE: 18" Tires - Switch to Same Size All Around? - 12/13/2006 8:12:05 PM

rchern

Posts: 5
Joined: 12/12/2006
Status: offline

quote:

ORIGINAL: FLCaddytech

Even if you change the tire sizes you still can't rotate because the wheels are different front to rear.
I like the larger tires in the rear, the more rubber to the road the better IMHO.

I realize that the diameter of the tires is different but if the wheels are 18" wheels then what is different about them? The width? The offset?

(in reply to FLCaddytech)

Post #: 4

RE: 18" Tires - Switch to Same Size All Around? - 12/14/2006 5:45:32 AM

FLCaddytech

Posts: 507
Joined: 6/22/2006
Status: offline

I believe its the offset and width.
I know that they will fit in the wrong place and if you weren't looking for it you probably would not notice.

The diameter of the tire will be very close front to back.
Its the width that is larger in the rear.
235 mm wide vs 255 mm wide.

< Message edited by FLCaddytech -- 12/15/2006 5:28:27 AM >

(in reply to rchern)

Post #: 5

RE: 18" Tires - Switch to Same Size All Around? - 12/19/2006 2:29:09 PM

vballfan

Posts: 2
Joined: 11/11/2006
Status: offline

I checked with my caddy dealer (parts and service) and they said the rims are 100% identical front and back. The part number they order with is the same. Now, that doesn't mean the dealer is right, does it? Do you have any more specific info that says the front and rear rims are different for the 18" wheel package?

My thinking now is that it might be a little overkill to get same four tires all around. If I do a good job shopping for tires, it will alleviate most of my expense. Looks like I will need different brands for the front and the rear to take advantage of ride quality/pricing/treadlife/etc. Sizes seem uncommon.

In response to the post about the number of miles, I purchased the car with 30,000 miles. There's about another 5,000 left to go on the set. It's just that the fronts are cupped resulting in a loud "wubba wubba wubba" at low speeds. Dealer told me this going into the purchase and was told it was due to not being able to rotate front to back. I confirmed it thru a local tire shop and they seemed to confirm that this is common. Does this make sense to anyone?

(in reply to FLCaddytech)

Post #: 6

RE: 18" Tires - Switch to Same Size All Around? - 12/20/2006 9:49:18 AM

FLCaddytech

Posts: 507
Joined: 6/22/2006
Status: offline

05 STS Wheel RPO codes

quote:

QKP

Tire All P235/50R17-95S BW R/PE ST TL ALS

Q11

Tire All P235/50R17 Front and P255/45R17 Rear

Q12

Tire All P235/50R18 Front and P255/45R18 Rear

Q13

Wheel 17 x 7.5 Front and 17 x 8.0 Rear (Polished)

Q14

Wheel 17 x 7.5 Front and 17 x 8.0 Rear (Painted)

If your wheels have a different offset and width they will have "front" "rear" cast into the wheels under the center cap

(in reply to vballfan)

Post #: 7

RE: 18" Tires - Switch to Same Size All Around? - 7/30/2007 11:13:36 AM

larrygmoney

Posts: 4
Joined: 7/30/2007
Status: offline

My Caddy dealer rotated mine and the stupid tech went front to rear I did not notice untill i had a blow-out on the front i don't know if this was a factor in the blow out but you can put the rims on the fr or rear, I have went to after market now havethe wider rim and will put the same larger size all around , it won't be long i have 57,000 on these orig tires...

(in reply to FLCaddytech)

Post #: 8

RE: 18" Tires - Switch to Same Size All Around? - 8/10/2007 1:42:22 PM

rjonesco

Posts: 1
Joined: 8/10/2007
Status: offline

I just bought an 05 STS with 17 inch wheels. I am looking at a set of OEM 18 inch chrome
wheels. Will these fit with no problem? What about the speedometer problem mentioned above?
Was the dealer correct in stating the wheels have the same part number front and rear?
Is every factory wheel stamped "front" or "rear"?
Thanks guys.

(in reply to larrygmoney)

Post #: 9