Changing tire size on a 9.5

The issue will be total tire width and total tire height

The meaning of the tire sizes is as follows (use your 215/55-16)

215 mm tread width 55 % of that width as sidewall height 16 is the wheel diameter

So, you can find the tread width of both tires easily. The issue here will be how they fit on the wheels that you have. Are they wide enough?

You can compute the height, got to convert mm to inches or back, but it's not that hard. You really shouldn't change the height of the tire all that much since it'll impact the speedo and can rub on things.

Thanks for the reply, Bill. There already are 205's on the front wheels, so the wheels will fit the tires. The way I figure it, using the "width divided by 25.4 x the %" formula I found on a tire site, the sidewall height of the stock tire is 4.66"; the height of the 205's would be 4.84", a difference of .18". Do you think that would work?

Thanks again,

Michaek

Size differences are negligible. Handling will be somewhat reduced, ride will slightly improve. Car might feel a little bouncier with the

60's.

I think your calcs are way off. Sidewall heights are 4.7 and 4.8 inches. It's a 5% aspect change against a 10mm cross-section change.

with the 205 60 16 when the speedo says 60 you will be actually going 60.9 MPH. The computer will adjust for the fuel differences which will be minimal. The ride will be more plush and car will ride 4/10" higher. The stock tire diameter is 25.3" and the 205's are 25.7"

The price is right too!!!!! They will work just fine

Norm

Norm:

25.7 and 25.3 are the *diameter*. The difference in radius (sidewall height) is .2"

i've heard of people putting tires as large as 215/40 17's on a saab with few rubbing problems.i am about to put 205/40 17's on my saab NG900SE. from people i've talked to, these are the largest that safely fit with no rubbing. your 205/60 16's should actually be SLIGHTLY smaller (we're talking less than half inch overall). if you have no suspension mods, there shouldn't be a problem.

be warned that your new 8 inch tires will be much more prone to hydroplaning than your old ones. there will be a distinct cornering benefit, as will your traction in general, especially braking. if you do a lot of bad-weather driving, be cautious with this change.

You are correct, I forgot to divide that by 2. Thanks for the help Sorry

Norm

All-

Thanks for the input. As I mentioned to Norm, I mispoke in my original post. The freebie tires are 225/60-16 and, according to the Saab dealership's parts guy that I called, the circumferencial difference between the free tires and the stock tire is too great and he directed me to the Discount Tire Direct Tire Calculator

to show me the way, as it were. He wasn'ttrying to sell me anything so I tended to agree with him, but then Normweighed back into the fray with further thoughts on diameter vs.circumference. I'm baffled, in other words, so I'll probably wind upbuying some Hancook Rad K 106 tires in the proper size for sixty-fiveclams per, delivered! Not free, no, but pretty damned cheap. This is what I get for not paying attention to my geometry teachers. Or do I mean algebra?

Thanks again for all of the give-and-take.

Michael

That's not much sidewall and a fairly large diameter change. I hope you drive on smooth roads.

A 215 is only 5mm wider on each side than a 205. Even a 225 is only

100 wider. Not that drastic.

The first common misconception is that there is some cornering benefit associated with wider tires. It's not true. The benefit comes from increasing the wheel size and causing a concurrent decrease in sidewall height. The lower sidewall increases stiffness and cornering response (or more accurately, reduces loss of response from sidewall bending).

Another common misconception is that a wider tire increases traction. It does not. The same amount of rubber is in contact with the road with a wide tire as with a narrow tire. The increase in handling (not traction) comes from what I mentioned above. There may be some advantages to a wider wheelbase in stability but at the same time, you are loading your suspension differently than designed and it may not help in any or all areas.

I've got Khumo 225/50/ZR16/92W on our Aero at the moment. They look good, with great grip in dry & wet, and not too noisy. Only problem is an occasional rub on the rear wheel arches over bumps when loaded up with the family & dog. But I use it mainly for commuting, so it's normally not a problem ;)

Just lease the dog to the bumper and let him run along. You know, like in "Vacation" with Chevy Chase.

LOL - Actually, I'll leave the dog in the put & make the kids run along behind... Is that the same one where they end up tying her dead grandmother in a rocking chair to the roof rack?? Hilarious.

How do you fix it so your posts melt away after a few days Bob? "This user has requested this post not be archived" etc??

Current sidewall height = 215*0.55 = 118.25mm New sidewall height = 205*0.60 = 123.0 mm --------------------------------------------- Sidewall increase = 4.75mm = 0.187 inches.

/Johannes

You have to have your newsreader/posting program insert the "X-no-archive" header in your messages. I'm not sure if you can do this with google but look around in the help for "x-no-archive".

A much better alternative is to use a real newsreader like Forte Free Agent or the paid version of Agent. It makes news reading much more pleasurable. Your ISP will have to have a newsserver though.

Cool - Cheers for that Bob. I'll look into it for my PC at home. I only started using the Google thing for when I'm supposed to be at work ;)

safety/handling/stability/ride and so forth of >the car.

First off, the Coopers are 1.7% smaller circumference than the Michelins. That will probably stuff up your front/rear balance at least marginally, so putting on a set of FOUR somethings all the same size is a good idea.

The 205/60-16s are only 1.5% bigger in circ than the 215s specified so you probably shouldn't notice any differences in ride/handling/speedo error. So it's all good so far.

Just make sure that what you're getting is worth putting on the car in the first place, regardless of price! Cheers