: AWD Tire Replacement Sizing



Baldtop
09-21-06, 12:06 PM
Has anyone replaced tires using the same size front and back. I've noticed that my 2005 AWD6 has the same size wheels at all four corners. It seems to me that we could install 235/65/17 units all around and have the abilty then to rotate and increase tire life. The front tires on my vehicle are wearing noticebly faster than those in the rear. I've discovered that AWD6 STS's have the same size tires at all corners.

Smokin' SRX
09-25-06, 07:00 PM
Has anyone replaced tires using the same size front and back. I've noticed that my 2005 AWD6 has the same size wheels at all four corners. It seems to me that we could install 235/65/17 units all around and have the abilty then to rotate and increase tire life. The front tires on my vehicle are wearing noticebly faster than those in the rear. I've discovered that AWD6 STS's have the same size tires at all corners.

I have same front tire problem! (20 K miles ) Look at the active threads currently going on! Some guys have put 4 of-a-kind and swear it works! I haven't seen a single post saying that 4-of-a-kind caused a problem! Consensus seems to be that Caddy did it mostly for traction and balancing at full cornering/full launch concerns. I'll probably go with the OEM set-up as my lease is over in 18 months and it's not gonna bother me again! But I'd go 4-of-kind if I was gonna keep the car 30-70-K miles cause you can't rotate otherwise and I'll be buying tires again!! One guy went to 20" !!!!! Said he loves the look. Ride must suck! Good luck with 2 beautiful Caddy's!:bouncy:

wifescaddy
09-25-06, 07:12 PM
i had the same question,my fronts are worn and backs are fine i looked up sizes on both sizes .these are good year rsa also.this is from tire racks site

255/60 HR17
105H SL 260 A A
2039 lbs.
44 psi
11/32"
33 lbs. 7-9"
7.5"
10.2"
9.1" width
29.1" height
NA

235/65 HR17
103H SL 260 A A
1929 lbs.
44 psi
11/32"
29 lbs. 6.5-8.5"
7"
9.5"
9.1" width
29.1" height
NA

Smokin' SRX
09-27-06, 10:43 AM
i had the same question,my fronts are worn and backs are fine i looked up sizes on both sizes .these are good year rsa also.this is from tire racks site

255/60 HR17
105H SL 260 A A
2039 lbs.
44 psi
11/32"
33 lbs. 7-9"
7.5"
10.2"
9.1" width
29.1" height
NA



235/65 HR17
103H SL 260 A A
1929 lbs.
44 psi
11/32"
29 lbs. 6.5-8.5"
7"
9.5"
9.1" width
29.1" height
NA


More data on previous post ... "TIRE SIZES" .................
Be aware...less choice of tires with the V-8 AWD 18" tires! See dechief's results.........and "masking" problems...........

robhersch
09-27-06, 12:03 PM
SRX wheels - 17" or 18" (20" tbd?) - are reportedly the same all around; you can use a "tire calculator" at >> [url=http://www.miata.net]<< to compare tire sizes: sidewall, dia, circumf, revs per mi as well as speedometer reading. Since SRX are RWD or ALW, I assume the speedo reading is for rear wheel sizes.

Smokin' SRX
09-28-06, 09:59 AM
SRX wheels - 17" or 18" (20" tbd?) - are reportedly the same all around; you can use a "tire calculator" at >> [url=http://www.miata.net]<< to compare tire sizes: sidewall, dia, circumf, revs per mi as well as speedometer reading. Since SRX are RWD or ALW, I assume the speedo reading is for rear wheel sizes.


You're correct! The steel (or aluminum?) wheels (not tires) are same at all 4 compass points. But the ground 'contact patch" is different. Other post on this forum (just a few posts away)...... "TIRES", has much info on this!

Seems minor handling/balance/steering/warranty issues are in play, with GM's decision to stagger the tire sizes! I think MINOR steering or front tire wear issue will surface if all 4 same size (presumably the larger P255/55 size) are used. But I bet most drivers will never notice it!! On the other hand, get the DEALER to put the same size on , so if a front drive unit issue arises under warranty (AWD trucks only!)....you are safe!! See the other post for a wealth of info!:thumbsup:

robhersch
09-28-06, 12:51 PM
Ref the miata tire size calculator:
255/55-18: Circumference is 91.2", Revs/mile are 694.0, load factor 104v
235/60-18: Circumference is 91.4", Revs/mile are 693.0, load factor 102v

Speedo reading with 235/60-18 is 0.2% too slow
When speedo reads 60 MPH, you are actually traveling 60.1 MPH

If changing to same size all around, above indicates potentially fewer front-end-tire-rub, steering wear, and/or warranty problems by going to 235/60-18;
unless perhaps carrying 7 passengers, hauling or towing heavy loads where the extra 2% load is significant; or the added bite for drag-racing is needed.

Smokin' SRX
09-28-06, 03:56 PM
Thanks for the exc research! Seems circumference is about same. I'm gonna ask dealer to put 4 255/55-18" all around! The BFG tire sounds good, and I'll look at the Pirelli's also!(Scorpion Zero). Another poster had grat luck with them.
I'd like to be covered if the front drive axle has trouble later on! But I doubt it will. GM may have done the 2 diff sizes to avoid oversteer/weight issues? Based on your report and others, it appears to be ok!:)

robhersch
09-28-06, 06:00 PM
Thanks for the exc research! Seems circumference is about same. I'm gonna ask dealer to put 4 255/55-18" all around! The BFG tire sounds good, and I'll look at the Pirelli's also!(Scorpion Zero). Another poster had grat luck with them.
I'd like to be covered if the front drive axle has trouble later on! But I doubt it will. GM may have done the 2 diff sizes to avoid oversteer/weight issues? Based on your report and others, it appears to be ok!:)

Smokey - Please keep us informed. Thanks.

ryaus1
09-28-06, 10:25 PM
I wonder if the steering gets stiffer with 255s in the front?

Smokin' SRX
09-29-06, 09:36 AM
Smokey - Please keep us informed. Thanks.


Just visited the dealer! NO WAY...will they put same size 18" tires (P255/55-18 OE rear ) at all 4 compass points! (I have the AWD N*) Gave me song and dance about "rubbing and balance", and then looked dumbfounded when I told him that the '07 has a 20" tire option!!!! Stopped short however, of saying warranty would be voided!! (I think all dealers take as much warranty work as possible, only to bill GM, for a guaranteed paycheck! I'm told it's the lion's share of their profits!!!)

So hard to get a definitive answer. I must assume we are on our own if the front drive unit has problems after doing the swap! :rant2:

Thank God for the brave, and imaginative souls on this forum!!!

robhersch
09-29-06, 01:59 PM
Smokey - Thanks for the update; are the '07 20" same size all around?? Have yet to see any '07 SRXs at local dealers, but will try to check at GM on line.
Think I would (will when needed) opt for the 235/60-18 - 102v for all 4 wheels(vs 255/55-18 - 104v) at SRX RWD wt ~ 4393# (AWD a bit more#) ; can see no logical reason why these should not eliminate any GM excessive wear or warranty issues (unless you experience blow-outs - how likely for 102 vs 104 rating?? - or roll-overs ala Ford Explorer and try to collect damages from GM).
By the way, my 2 local dealers still push and have pushed Vogue tyres for years and frequently add them (at signif extra dealer installed $$$cost) to many new cars (not sure about them on SRXs) on their lots.
Also I would check out the new GY (if & when avail in the proper "V" speed rating) since the new models sound very good on paper; results are TBD.
My '99 DeVille Concours FWD wt ~ 4063# has the 225/60-16 - 97H GY RS/A rated with ~35k & ~ from 5 to 7 32nds tread left (looks like 45-50k mi possible). Good luck & keep us posted.

beekay
09-29-06, 05:56 PM
I wonder if the steering gets stiffer with 255s in the front?

We didn't notice anything significant with the tire change, my wife has no issues at all while driving it (which she does 99% of the time).

It will be interesting to see how all this sorts out at the dealers. has anyone been denied service yet due to same tires all around?

:confused:

stlgasman
09-30-06, 03:20 PM
Why not use the 235/65/17 all around? It seems like everyone wants to use the 255/60's.

BarryH_GEG
09-30-06, 10:23 PM
I'm running 255/45x20 tires on my V8 AWD. They have the same circumference as the 255/55x18 and are 2/10 of an inch smaller than the 235/60x18 which is statistically irrelevant. I bought them mounted and balanced on the Internet and had them shipped to my dealership who installed them. The wheels are 6x114.3 instead of the factory wheel size which is 6x115. Folks on this forum were sure that the larger wheels and slightly different bolt pattern would cause my wheels to fall off and create untold catastrophic problems. The car handles the same as it did before and the ride is the same also (I have MRC which I think makes a difference). Tires are wearing perfectly and tire balance is perfect also. The dealer has a new SRX on their lot that they've put aftermarket 20s on too. The same dealer installed my Corsa exhaust so I guess you can call them mod-friendly. These aren't space shuttles with zero degree tolerances - I think any tire with a similar circumference and width to either of the stock tires sizes will work just fine.

Smokin' SRX
10-01-06, 03:22 PM
THX to ROBHERSCH and other posters here.....I'm gonna go 255-55-18" all around, on my AWD N*! No one has had adverse effects in the 17" or 18" version. (17" was stock on the V-6, 18" stock on my N* V-8)

Also since the French rubber (Mich) is $210 per tire, and lasted only 19K miles :rant2: on the fronts, I'm gonna change to either a Pirelli, Goodyear , Cooper or Dunlap! I found all in 255-55-18" at TIRESAVINGS.com for $ 139, $164, $109 and $124 respectively! (good pix at site!) The Cooper's at $109 are a bargin! The Dunlap's @ $127, are an old favorite of mine. Note the Dunlap and Pirelli's are an "H" rating as opposed to a "V" rating. That's 130MPH vs. 150MPH! Guess I'll have to slow down a little!! :crybaby: Ride should be a hair softer if I go w/ the "H", handling about same.

Would like the bigger size at all 4 for a little better traction. Of course being able to rotate is desireable too!

As stated earlier post, my Delaer will not install, but will service afterward with no hard feelings!! Looking at late Oct. to do it. Will post results!