Smaller Diameter Tires to Boost Final Ratio

[RBGT]

Looking at the MT82 vs Tremec ratios, its unfortunate that the gears are taller in with MT-82.

Ordered the manual non-PP GT with 3.55 gears with the Brembos.

Besides the fender gap (that can be lowered and speedo) would it be a bad idea to get smaller diameter tires?

Stock = 255-40 with 3.55 gears

275-35 Final ratio = 3.61
285-30 Final ratio = 3.73

Sponsored

 

[RBGT]

The PP tires is actually larger than the stock rear tire and lowers the final ratio a bit.

PP rear tire
275 40
PP effective ratio is = 3.65 compared to stock

 

[RBGT]

The dark horse on the other hand with shorter 315 30 tires and 3.73

Has an effective ratio of 3.81

 

[RBGT]

Swapping out the rear axle is a pain and a couple of local mechanics said they wont touch it as it will void the warranty and they don't want to be liable.

I would want the warranty myself.

 

[RBGT]

 

[Zig]

Does that show about a half foot less per rotation?

 

[RBGT]

Drove the 3.73 Mach1 and it didn't feel snappy.
Below 3500 rpm, it could be any regular car and really comes to life 4500 and up.


I see folks with the S550 switching to 4.09 gears.

 

[RBGT]

Does that show about a half foot less per rotation?

4.5 inches less per roation.

 

[agreywolfe]

Does that show about a half foot less per rotation?

Yes, about 4.1 inches less, which equates to about .05 mile less for ever 1 mile on the odometer or about 5 miles every 100 as can be seen with the speed chart under the tire images

 

[RBGT]

Car is lowered 0.6 inches.

Braking should be better.

Rotational inertia decreased in tires.

Smaller sidewall will feel bumps a bit more.

Fuel economy will suffer.

 

[RBGT]

Yes, about 4.1 inches less, which equates to about .05 mile less for ever 1 mile on the odometer or about 5 miles every 100 as can be seen with the speed chart under the tire images

Speedo will be off by a few MPH, not the end of the world.

70mph on the speedo will be 67mph in reality.

Acceleration should be more aggressive in all gear instead.

 

[agreywolfe]

Speedo will be off by a few MPH, not the end of the world.

70mph on the speedo will be 67mph in reality.

Acceleration should be more aggressive in all gear instead.

Yeah I worded that badly, the point I was trying to get across was for every 1 miles worth of rotation the larger tire does, the smaller one only completes .95 miles, so you'll need to push the tire that 5% longer to achieve the goal of the larger tire.

 

[RBGT]

Why not just get the PP?

$5000
Tries supplied are not really "performance"
Wheels not very nice, quite skinny, and heavy
"Drift" brake is a gimmick (to me)
Don't want a rear wing - prefer the clean look
Missing out on the front springs + K-brace (don't seem expensive to add)

Already got the brake + AE

 

[RBGT]

Yeah I worded that badly, the point I was trying to get across was for every 1 miles worth of rotation the larger tire does, the smaller one only completes .95 miles, so you'll need to push the tire that 5% longer to achieve the goal of the larger tire.

Yes, main reason would be to increase the force to the ground and up the effective torque.
Ideally, the Tremec + 3.73 would be better but then its the Dark Hor$e

Sponsored