I am ready for new tires this spring. Any thought or Ideas about putting the same size on the front and rear? Will it do anything to the all wheel drive system? Currently the rears are the bigger size and I would put the same size as the rears on the front. Any techs have advice?

I have a 2005 STS4 1SG and changed the tires at 30k miles to the pilot sport A/S with the same size on all four corners. I like the handling better on both wet and dry roads. At 50 k miles the tires seem to be holding up well.

These are the tires I'm buying next... http://www.discounttiredirect.com/direct/findTireDetail.do?yr=2005&c=1&sw=false&cs=255&pc=38579&rd=18&vid=008914&ar=45

Are you going to run the same size on all 4 corners?

There's been quite a few posts on this subject and 99% of the replys have been favorable and no known problems with all four tires being the same size.

I highly suggest the Nexen N3000 255/45/18.
https://www.tiresavings.com/tireShop.php?action=findMan2&manufacturer=Nexen&tirename=N3000&season=
After 3K miles, I have been very pleased with how great these tires are. They are very very quite and grip well.
Due to the V tread, the wet traction is superior.
They are much less expensive than others, however, don't fall into the crowd of you get what you paid for. The bottom line is the expensive brands are making much more profit.

My 2005 STS was a lease vehicle and I didn't want to spend a lot on something I was going to trade in less than 9 months. So I put on Toyo Versado LX's, which is what they put on some BMW's and Lexus vehicles. Just Tires (Aka Goodyear) wanted over $1200 for 4 OEM Replacements which were Michelin's, and only $850 for the Versados which were the same exact size, larger in the rears, slightly smaller on the fronts. I couldn't tell any difference in either one regarding performance or road noise. I only got about 35K on the original tires and they got pretty noisy so I needed to do something. Here is the Versado LK link: http://www.toyo.com/docs/tires/tires.asp?lpid=29911&name=Versado%20LX&category=luxury

Thanks all

Do not rotate back to front if your rims are different widths.

Do not rotate back to front if your rims are different widths.

All four "rims" are the same size. Tires can be different.

I just checked my STS4 2007 and it came with all the same size tires. They are P235/50R17 S-rated and also says that on my sticker sheet. So somewhere along the line on the 4 WD STS's they must have changed it. So I see no problem in anyone going to the same size all the way around.

My service tech says that going to the same size tire on all fours could affect the stabilitrak and magnetice ride control systems along with the handling of the vehicle. Is there anyway this could be true?

This is for those who don't want to spend and arm and a leg. Take a look at this:
www.tires-easy.com has 235/50 x18 and 255/45x18 sunny 3800 tires to fit our hi-perf. needs for $365 and thats for all four tires. Wow you can't beat that.I will keep my eye on them and try them out when my tires call.

Jono