15" tires in 215/60 and 225/60

[myslateblue911]

Who makes 15" tires in 215/60 and 225/60?

[rswannabe]

Avon does. I have a set of their CR6ZZ in those sizes I'll sell you for $400 plus shipping. They have about 3k mikes in them and lots of life left. They are a very good, sticky modern tire compound with a vintage look.

[myslateblue911]

Originally Posted by rswannabe

Avon does. I have a set of their CR6ZZ in those sizes I'll sell you for $400 plus shipping. They have about 3k mikes in them and lots of life left. They are a very good, sticky modern tire compound with a vintage look.

I might be interested in this set you have. I know you said there are 3,000 miles on these tires.....how old are the tires?

[rswannabe]

I bought them in 2015.

[Bill Verburg]

Originally Posted by myslateblue911

Who makes 15" tires in 215/60 and 225/60?

why would you want those sizes?

the rear is 25.7" tire and will kill the acceleration of your car

If you want to raise the car a bit from what you have
195/65 215/60 on your 7 & 8 would be the way to go.

Pirelli P6000 is a great street tire in those sizes, Sumitomo HTR A/S P02 (H- or V-Speed Rated) would be a second choice

[myslateblue911]

Originally Posted by Bill Verburg

why would you want those sizes?

the rear is 25.7" tire and will kill the acceleration of your car

If you want to raise the car a bit from what you have
195/65 215/60 on your 7 & 8 would be the way to go.

Pirelli P6000 is a great street tire in those sizes, Sumitomo HTR A/S P02 (H- or V-Speed Rated) would be a second choice

Mr Verburg,

Mark White who runs Accumoto up in WI (0000 - "Dirk" — Accumoto Motorsport) said in an email that the white car he calls Dirk is an 80SC and he is running
a set of Avon 215/60 and 225/60 tires on 15" 7.5 and 8.5 wheels and thought that it would work running them on my 83SC. The only difference is I have 7 & 8" wheels.
What am I missing?.....I was previously running 205/50 & 225/50 on 16" Fuchs wheel

[racer]

The taller the overall wheel/tire height, the slower your acceleration.

A 215/60-15 has a shorter height than a 225/60-15.

Play around with tire sizes here to get an idea of how a change from your 225/50-16s to a 225/60-15 would impact your car. https://www.miata.net/garage/tirecalc.html


Taken from the link:

Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/50-16 4.4in 12.4in 24.9in 78.1in 811 0.0%
225/60-15 5.3in 12.8in 25.6in 80.5in 787 3.1%
215/60-15 5.1in 12.6in 25.2in 79.0in 802 1.2%

So the 225/60-15 will dull your acceleration by 3.1%. It will also impact your speedometer reading. The 215/60-15 is much closer in diameter.

[Bill Verburg]

Originally Posted by myslateblue911

Mr Verburg,

Mark White who runs Accumoto up in WI (0000 - "Dirk" — Accumoto Motorsport) said in an email that the white car he calls Dirk is an 80SC and he is running
a set of Avon 215/60 and 225/60 tires on 15" 7.5 and 8.5 wheels and thought that it would work running them on my 83SC. The only difference is I have 7 & 8" wheels.
What am I missing?.....I was previously running 205/50 & 225/50 on 16" Fuchs wheel

As Racer already noted drive tire Od can have a major effect on gearing and thus the feel of the car. Here's a comparison I had handy of 2 proposed rear tire options for an SC, the 275/35 x15 is 23" OD, the 255/40 x17 is 25" OD, the graph shows the acceleration potential for each.


Some people are willing to accept the loss of acceleration in return for cornering grip, others want the maximum acceleration that the car is capable of. When you originally proposed going to 15s from 16s I thought that you were in the latter category. The really dedicated will use the taller tires but also change the motor and trans characteristics, for most this is not a viable option.

[myslateblue911]

Originally Posted by Bill Verburg

As Racer already noted drive tire Od can have a major effect on gearing and thus the feel of the car. Here's a comparison I had handy of 2 proposed rear tire options for an SC, the 275/35 x15 is 23" OD, the 255/40 x17 is 25" OD, the graph shows the acceleration potential for each.


Some people are willing to accept the loss of acceleration in return for cornering grip, others want the maximum acceleration that the car is capable of. When you originally proposed going to 15s from 16s I thought that you were in the latter category. The really dedicated will use the taller tires but also change the motor and trans characteristics, for most this is not a viable option.

Yes, you are correct. I do prefer acceleration to handling, if one must decide between the two. I guess when the tire is more narrow, then the aspect ratio relative to that width is not as tall, right? So the relationship is, the taller the tire the more this diminishes acceleration "power"?

A follow up question is...I currently am running Toyo R1R 205/50 & 225/45 on 15" 7 & 8 wheels.

If I switch to the 195/65 & 215/60 as suggested, how much height do I gain AND how much acceleration do I lose?

[darrin]

this should help with your first question -- https://tiresize.com/height-calculator/ -- suspect the second one's a LOT harder to quantify.

[Bill Verburg]

Originally Posted by myslateblue911

Yes, you are correct. I do prefer acceleration to handling, if one must decide between the two. I guess when the tire is more narrow, then the aspect ratio relative to that width is not as tall, right? So the relationship is, the taller the tire the more this diminishes acceleration "power"?

A follow up question is...I currently am running Toyo R1R 205/50 & 225/45 on 15" 7 & 8 wheels.

If I switch to the 195/65 & 215/60 as suggested, how much height do I gain AND how much acceleration do I lose?

It's not either or
you start w/ the rear tires, the more hp/torque the wider they will need to be, for best acceleration the tires need to be as short as possible

for better handling you want lower profile tires on wider wheels, for ride comfort you want taller side walls on narrower wheels

the wheels have to fit over the brakes, the faster and heavier the car the bigger the wheels need to be because the brakes are bigger.

last you do the fronts, you just want these to match and balance the rears.

for an SC/Carrera w/ 7 & 8 x15
205/50 & 225/50 is a great short excellent handling setup, it allows the car to run very low ride height which can lead to issues w/ the spoiler hitting things,
205/50 & 225/45 adds a little more grip in back, but otherwise similar to above, it is shorter and will accelerate ~4% better
195/65 & 215/60 raises the car ~2" in front & ~1.2" in back from 225/50 ~2" from 225/45. This will still handle well just won't have the ultimate 10/10 grip of the above. Ride comfort and pothole resistance will be noticeably better. Acceleration will drop ~11% across the rev range in all gears and will, be more or less comparable to what it was with 225/50 x16, maybe a smidge less but it depends on the idiosyncrasies of the tires selected.