Upgrading Wheels and Tires

[Skotty]

Today I got my vehicle inspected and one of the tires has a bubble in the sidewall and needs replaced. Another tire leaks, so I was thinking of replacing it too. As long as I'm replacing two tires, I was thinking of replacing all four, as I don't really like the tires I have anyway. And as long as I'm replacing all four tires, I am considering replacing the wheels as well, and "plus sizing" it a little.

My car is a '97 STS with the stock wheels and tires. The tire size currently is 225/60R16. I want to bump it up only slightly, to perhaps 17 inch wheels. Was thinking maybe 245/50R17. I'm wanting wheels that are polished aluminum, probably a 5-spoke design. I'm going for a sort-of reserved performance look, sportier than stock but not all out. Will 245 be too wide for that? My 99 Mustang Cobra had 245/45R17s, so I'm wondering if 245/50R17 might look a little too fat for what I want.

The closest thing to what I'm looking for that I could find in the gallery were these, though none of them were right on (hopefully these links work):

http://www.cadillacforums.com/photop...o/4725/cat/507

http://www.cadillacforums.com/photop...to/752/cat/507

Anyone with experience changing wheels and tires on a '97 (or any from that generation), or just thoughts in general on any model, I'd be happy to here any comments or suggestions you have. For example, are there any clearance problems with the tires you used, and what size were they. What kind of offset did your wheels have? Did it look right? Did it change your driving experience? What would you have done differently?
And anything else I might should consider.

Another thing I was thinking of doing was just replacing the standard passenger tires with some high performance ones. Sometimes it makes a car look (and handle) a lot better just switching to high performance tires, as they simply look better, and the tread often looks wider than on a regular passenger tire. Some tires I was considering: Yokohama ADVAN S.4., Michelin Pilot XGT Z4, Michelin Pilot Sport A/S, Bridgestone Potenza RE750, and BFGoodrich Traction T/A.


Thanks,

Skotty
1997 Seville STS (dark green)

[Rick99STS]

I'm running 255/50-17's on my 1999 STS. No clearance problems whatsoever...installed Eibach springs that lowered it an inch or so and still no problems.

Although I haven't ran the Advan's I've had great luck with all the Yokohama's I've had. I'm currently running Kuhmo Ecsta SPT's and am very happy with them also.

One thing I would like to add is that our cars are capable of very fast speeds...I live in California and often travel to Vegas for fun, the open desert allows me the opportunity to stretch my STS legs. I often run above 100 mph for extended periods and would hate to put a wheel on my car that wasn't made for these speeds. For this reason I installed the 17" wheels from a 2001 STS. The wheels I wanted from HRE were about 5K and out of my price range at the time so the 17" option wheels were a cheap way for me to step up and still be certain they could handle the speed and power. Please believe me when I say there are MANY wheels out there that will fly apart when subjected to the weight, power and speed our cars produce. Don't go cheap here!

Good luck.

[Dadillac]

The first link is to my gallery. The wheels are Kazera KZ-T's, and the tires Kumho ASX. The tires are 235/50/18, and the wheels are obviously 18"ers. I have since sold them to another forum member (Jsmeloche). I have heard of folks going as wide as 255mm. I feel that the 235 is the perfect width for our cars. Just looks right.

Don

[Skotty]

What width rim is best for 235s? The stock 225s are on a 6.5" width rim aren't they? Maybe a 7" for 235s? Surprisingly hard to find info using Google on matching rims to tires (and related info).

[Dadillac]

I am pretty sure that most of the wheels for Caddy's are either 7" or 7.5" from the factory. Aftermarket wheels are mostly 7.5" and 8" wide. The biggest concern is offset. Factory offset is 40mm. You need a wheel that is between 35 and 45 mm offset. That will keep things where they need to be.

Don

[9BlackN*Black6]

I got 245/45R17zr nitto extremes, gave up a little of the "cush" but I really like to feel the road! The rims are also 8" wide, they give me alot more handling and steering response. No problems whatsoever.

[submariner409]

Whatever wheel/tire combo you go to, have the dealer calculate the new total diameter vs. the old diameter. Anything more than 2/10 of an inch + or - will show up as speedo error and maybe set some wheel rotation speed codes. Smaller section tires (large diameter wheels and thin section tires) will most likely look trick for a while, but handling suffers and they'll pound your fillings out. If, as posted above, you find a set of 17" GM upgrade wheels, that's the way to go. Don't make it look like a DC riceburner with a fart-can muffler...... (The optional 2002 17" GM rims are 7.5" wide for a 235-55-R17 98H tire))

[Rick99STS]

"...but handling suffers and they'll pound your fillings out."

Hate to disagree submariner but depending on your definition of handling I believe it will dramatically increase with lower profile tires. You'll have much less sidewall flex which will translate into much sharper turn in and a much more sporty feel.

As far as the "pound your fillings out" comment, I couldn't agree more.

[Skotty]

I found a set of wheels I like that I think should work. They are 17" x 7.5" with 40 offset and 5-4.5 bolt circle. I am thinking of using 235s on them. I did some calculations, and assuming I did them right, the correct profile to keep the same tire circumference would be about 52, meaning nothing will be perfect, but I can get away with using either 50s or 55s. Assuming this is all right, I would just need to decide between 235/50s and 235/55s.

[jadcock]

In 17" trim, a 245/50 would be ideal (their nominal diameter is 26.6" tall, exactly the same as a 225/60R16). I would prefer a 255/50 though (it's going to be about 27.0" tall).

The 2003 Cadillac Seville brochure lists the Cadillac's 17" wheel as 8.5" wide, but I believe that must be a typographical error, no? Can anyone confirm that it's that wide? You do need a wider wheel as you +1 and +2, as there's less sidewall flex to conform to a narrow wheel.

If you did want to go to a 255/50, a 17x8 wheel would probably be best. I'd seriously look at what GM has to offer...the quality will be better than aftermarket I'm sure...

Oh...and 4.5" bolt circle will NOT work. It has to be the FWD GM bolt pattern, 5x115 mm.

[Skotty]

Bear in mind my car is a 1997 model. What I've found online is that it has a 5x114.3, which is pretty much exactly 5x4.5", so I assume there is no signficant difference between 5x114.3 and 5x4.5". However, I'll go measure them myself later to find out for sure. Correct me if I'm wrong here -- bolt patterns measure the diameter of the circle that intersects the center points of each lug. So doing a little math with a pentagon inside of a circle, I came up with this equation: d = x / cos 54. In this equation, d is the diameter of the circle that defines the bolt pattern, x is the distance between two adjacent lugs (what I will measure), and 54 is in degrees. So take the distance between 2 adjacent lugs, divide that by cos 54 degrees, and you get your bolt pattern measurement.

I considered 245s, but I'm still leaning 235s. No decision yet on whether they would be 50 or 55 series.

[Skotty]

I'm kind of leaning towards 50 series now. Not too much price difference (55s are a little cheaper), the 50s will be less likely to have clearance issues, and I'm guessing the 50s will look a little better too. Looking at TireRack, my favorites right now are the Bridgestone Potenza RE960AS Pole Position tires. They are reasonably priced, have decent reviews, I like the tread, and they are listed as all-season. They are 400/AA/A W rated.

[2000 Seville SLS]

I went with the 18 X 8.5 in rims 235 50 18 BF Goodrich KDWS. The ride is the same. Handling is much improved and looks nice. I think 20's look better, but i did not want to lose ride quality for looks. After all it is a Cadillac.

[Shawn4.0]

Originally Posted by 2000 Seville SLS

I went with the 18 X 8.5 in rims 235 50 18 BF Goodrich KDWS. The ride is the same. Handling is much improved and looks nice. I think 20's look better, but i did not want to lose ride quality for looks. After all it is a Cadillac.

x2, I have almost the same setup, 18"x8" wheels (GXPs) with 255/45 KDWs. No loss in ride quality (I actually like the ride better), but massive upgrades in handling...

[jadcock]

Originally Posted by Skotty

Bear in mind my car is a 1997 model. What I've found online is that it has a 5x114.3, which is pretty much exactly 5x4.5", so I assume there is no signficant difference between 5x114.3 and 5x4.5".

Skotty, that is misinformation. Your car has a 5x115mm bolt pattern. Most places will say you have a 5x114.3mm bolt pattern (the metric equivalent to 5x4.5"), because they don't sell any 115mm wheels. They're close, but they're not the same. I would NOT mount any 114.3mm wheel on my FWD Cadillac. You will fatigue the studs and the wheel mounting holes and could cause BIG problems for yourself.

Do the right thing and insist on a 115mm wheel.