Tires for 15" wheels?

[Driven97]

Don't forget there's no free lunch. You're not actually getting more torque out of your engine, you are just re-gearing your car.

With my rev limit and an OE tire, my car will go 67 in 2nd. On the stubby 15s it'll do 62 mph. That works out to just about perfect for 98% of AX courses. Flip side is driving on the freeway sucks as I rev to the moon to keep up with traffic. For track people, it may put you in different gears around your local track, which may be good or may be bad.

[Litle brother]

Originally Posted by Driven97

Don't forget there's no free lunch. You're not actually getting more torque out of your engine, you are just re-gearing your car.

With my rev limit and an OE tire, my car will go 67 in 2nd. On the stubby 15s it'll do 62 mph. That works out to just about perfect for 98% of AX courses. Flip side is driving on the freeway sucks as I rev to the moon to keep up with traffic. For track people, it may put you in different gears around your local track, which may be good or may be bad.

Hi.
I know that my engine is not getting more torque, I just want more usable torque delivered to the ground thats why I am thinking of smaller tires.
My car also has a gear box ratio that with my RSR engine gives a real top speed of 171mph. I really do not need all that speed here in Norway and I do not drive much on Norwegian highway or freeway. So a rim size that could give me 20-25ft lbf more torque to the ground would be way better than the classic 911 freeway rocket ship it is now.

Cheers
Eskild


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[Bill Verburg]

Originally Posted by darrin

Bill: in your chart above, it looks like you're using a 225/45-16 rear tire as your baseline for your torque calculations -- wouldn't the torque difference be greater if you used the stock 225/50-16 tire size generally used on 16x7 or 16x8 rear wheels?

I just posted what I had on file, the difference between 225/45 & 225/50 is small, <1lb-ft
Both are good choices for an 8x15

[darrin]

thanks bill! --

Group -- looks like the tire options for a 7x15 and 8x15 fuchs wheel set that will be used on my '86 targa for summer-only spirited summer road, ax and DE purposes (205/50-15 front 225/50-15 rear) would include

Yokohama Advan ao52
Pirelli Trofero R
???

From prior comments, I'm leaning toward the yoko advance ao52

Would use the 15" wheel set in conjunction with my current fuchs 16x7 front 16x8 rear wheel set running Michelin AS3+ tires (which would likely be preferable for road trips and my primary cold weather setup)

Any other thoughts/suggestions?

[Bill Verburg]

Originally Posted by Driven97

Don't forget there's no free lunch. You're not actually getting more torque out of your engine, you are just re-gearing your car.

With my rev limit and an OE tire, my car will go 67 in 2nd. On the stubby 15s it'll do 62 mph. That works out to just about perfect for 98% of AX courses. Flip side is driving on the freeway sucks as I rev to the moon to keep up with traffic. For track people, it may put you in different gears around your local track, which may be good or may be bad.

Actually if you look at the data i've broken the inertial and gearing cost into separate slots, in the above the front axle is all inertial and the cost is ~3.69lb-ft in back the inertial cost is ~1.5lb-ft for a total of ~5.2lb-ft inertial the other ~12.2lb-ft is gearing

[Driven97]

Oh no way I never noticed you calculate for that. Sweet.

[Litle brother]

Originally Posted by Bill Verburg

Actually if you look at the data i've broken the inertial and gearing cost into separate slots, in the above the front axle is all inertial and the cost is ~3.69lb-ft in back the inertial cost is ~1.5lb-ft for a total of ~5.2lb-ft inertial the other ~12.2lb-ft is gearing

Hi again Bill.

I have been looking at a tire calculator. It shows that the difference between the 225/50-16" and a 225/45-16" tire is .9"

The difference between 225/50-16 and 225/50-15 is 1.0"
This means that it is only a .1" difference between the 225/50-15 and the 225/45-16.

SO, can I assume approx 12ft lbf more torque with the gearing from 225/50-16 to 225/45-16" ?

Cheers
Eskild


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[Bill Verburg]

Originally Posted by Litle brother

Hi again Bill.

I have been looking at a tire calculator. It shows that the difference between the 225/50-16" and a 225/45-16" tire is .9"

The difference between 225/50-16 and 225/50-15 is 1.0"
This means that it is only a .1" difference between the 225/50-15 and the 225/45-16.

SO, can I assume approx 12ft lbf more torque with the gearing from 225/50-16 to 225/45-16" ?

Cheers
Eskild


Sent from my iPad using Tapatalk

Here's the closest I could come up w/, I had to use different tires because no one line has all the relevant sizes
205/50 & 225/50 compared to 205/50 & 225/45


205/50 & 225/50 compared to 205/50 & 245/40, I don't like this one because of the staggered widths and heights


205/50 & 2225/50 compared to 225/45 & 245/40, only thing here is that the wheels would be wider for best results

[JCGMS]

Originally Posted by darrin

thanks bill! --

Group -- looks like the tire options for a 7x15 and 8x15 fuchs wheel set that will be used on my '86 targa for summer-only spirited summer road, ax and DE purposes (205/50-15 front 225/50-15 rear) would include

Yokohama Advan ao52
Pirelli Trofero R
???

From prior comments, I'm leaning toward the yoko advance ao52

Any other thoughts/suggestions?

Consider federal rsr-r 205/50 and 225/45. Cheap 200 treadwear streetable sticky tire. At approx $450 for four corners they're worth a try.

Edit: actually they were actually <$400. Only autocrossed them once so far but I was impressed. I usually run re71r.




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[geoff_68s]

There are a good selection of 200-treadwear tires in 205/50-15, because it's the spec Miata tire size. (And 200-TW is the lower limit for street classes) RE-71R is super popular among autocrossers, and the Falken RT-615K+ is a fair bit cheaper if you don't mind being a second slower.

The sidewalls on a 205-50 not as tall as one would think "looks right", you'll see some air between the tire and fender, but hey, they're light and the lower gearing is helpful on short tracks.

[022spa]

Bridgestone re760
Part number 10347006
In 205/60-r15
Available in Mexico. I live near boarder. One day I might go down and pick up a set.
Anyone else see these state side?

[PRE-H20]

225-45-15 Rear

205-50-15 Font

[darrin]

pre-h2o, looks NICE -- what tires are those? 15x7 and 15x8 rims?

thx

[PRE-H20]

Thanks Darrin......

they are Hankooks......

225-45-15 REARS

205-50-15 FRONTS

YES...... REARS are 15x8
FRONTS are 15x7