Full Size Spare

[SVT-COBRA]

I am getting new set of wider wheels and tires and I was thinking about using one of the stock 20" rear wheels as a full size spare. I want to swap out the tire so that the diameter will match the diameter of the new rear tires. This way I won't have mismatching tire sizes if I have to change a flat rear tire, preventing any damage to the rear. I found a thinner tire, 245/45/20, that will match the exact diameter of the new tire which is 315/35/20. The specs for the 245/45 tire say that it will fit up to a 9" wheel. Below are a few points/questions:

1.) I know that my speedo will be off slightly with the taller rear tires, but I want 315's and didn't want a drag radial like the R888's which are the only ones I can find in a 315/30.

2.) Anyone see any problems putting a 245 tire on a 9.5" wheel?

3.) I had to use the rear 20" wheels in order to find a tire that matches the exact diameter of the new tires. I couldn't find a combo using the front 19" wheels that would work. Are their any issues using the 20" wheels as a spare on the front with the Brembo's if I had a flat up there?

4.) If I put the spare on the front, It will be about an inch taller than the other front wheel. Would any issues/problems result?

5.) I know the new spare will be too tall to fit in the wheel well in the trunk, but I figured I would put the spare (along with a jack) in the trunk for long road trips.

Thanks in advance for any help and guidance!

 

[Devious_Snake]

Its not just the width but the height, I think the biggest wheel you can fit back there is a 19. I would take that measurement too in order to be sure

 

[SVT-COBRA]

Its not just the width but the height, I think the biggest wheel you can fit back there is a 19. I would take that measurement too in order to be sure

I know what I am trying to do will never fit in the spare wheel well in the trunk, but are you referring to the opening into the trunk and whether the actual tire can even get into it? I didn't think about that.

My goal here is to find a short-term solution for long road trips. I read some of the horror stories of having to wait to get towed and the associated waste of money and time. I want to avoid using the fix-a-flat and have a spare in the unfortunate event of a blow-out or some other irreparable damage to the tire.

 

[Devious_Snake]

I know what I am trying to do will never fit in the spare wheel well in the trunk, but are you referring to the opening into the trunk and whether the actual tire can even get into it? I didn't think about that.

My goal here is to find a short-term solution for long road trips. I read some of the horror stories of having to wait to get towed and the associated waste of money and time. I want to avoid using the fix-a-flat and have a spare in the unfortunate event of a blow-out or some other irreparable damage to the tire.

Both. 20 won't fit in the well and I doubt it will clear the trunk opening.

 

[7ONE7]

You should be able to fit a 20" in the trunk. When I had my Michelins mounted I had one of the 295's in the trunk. Somewhat tight fit though.

 

[lsp408]

20 inch svtpp wheel will not clear front brembo caliper. At least you will need spacer

 

[Devious_Snake]

You should be able to fit a 20" in the trunk. When I had my Michelins mounted I had one of the 295's in the trunk. Somewhat tight fit though.

interesting. It takes a certain way for me to just get the 18 DR's I have in there

 

[Iceman5000]

Your speedometer will be off more than "a little" with 315/35/20's. mine was off by 9 mph until I recalibrated the speedo.

 

[biminiLX]

Do you do a lot of long distance trips? I think it would be a tough fit for the 20" wheel and a taller tire to fit in there. I just drove one and was worried about 2 golf bags
-J

 

[SVT-COBRA]

20 inch svtpp wheel will not clear front brembo caliper. At least you will need spacer

That's what I was afraid of. I couldn't find an exact match using the 19" wheel, but maybe I can find a tire that is as close as possible.

Do you do a lot of long distance trips? I think it would be a tough fit for the 20" wheel and a taller tire to fit in there. I just drove one and was worried about 2 golf bags
-J

I don't do too many long distance trips, but that is why I am looking for a quick short-term solution. When I do, I don't want to worry about being stranded on the side of the road, waiting for a tow.

Your speedometer will be off more than "a little" with 315/35/20's. mine was off by 9 mph until I recalibrated the speedo.

What did you have to do to recalibrate it? Back in the day, I just needed to switch out the speedo gear on my '94 GT. I doubt it's that simple with these cars.

 

[Iceman5000]

What did you have to do to recalibrate it? Back in the day, I just needed to switch out the speedo gear on my '94 GT. I doubt it's that simple with these cars.

I used my SCT tuner to do it.