35's - by the numbers

[Casey]

Just added a set of Cooper 315/75 STT's last friday. Here's a by the numbers review.

67 - approximate weight of the tire (stock =56, Toyo 315 =76) one of the deciding factors Cooper > Toyo

34.47 - tire diameter / 11.92 width (vs 35.9/12.9 for toyo 315's - I was looking for a "small" 35 - again another deciding factor)

92.2 - miles indicated vs 100 actual miles traveled - calibration for factory 32's - checked this over two separate 100 mile intervals

1.084 - calibration factor for mileage vs factory 32's based on above actual miles traveled (40 psi)

15.99, 16.33, 16.45 - first three tanks of gas corrected MPG average, mostly highway miles. These trips would normally net at least 17.5 with the 33's

960 - dollars for 4/mb - on the high end of all of the pricing I have heard. Tire was 209 + tax + fees + mb / ea

825 - dollars additional gas cost over standard tires over 50,000 miles @ 10% MPG reduction and $2.75 gas (about 12-14 months for me )

[H3slate]

Great info Casey!! i am looking to get a set of Coopers next year. Would love to see some pics of your rig with the new tires!

[marin8703]

Originally Posted by Casey

Just added a set of Cooper 315/75 STT's last friday. Here's a by the numbers review.

67 - approximate weight of the tire (stock =56, Toyo 315 =76) one of the deciding factors Cooper > Toyo

34.47 - tire diameter / 11.92 width (vs 35.9/12.9 for toyo 315's - I was looking for a "small" 35 - again another deciding factor)

92.2 - miles indicated vs 100 actual miles traveled - calibration for factory 32's - checked this over two separate 100 mile intervals

1.084 - calibration factor for mileage vs factory 32's based on above actual miles traveled (40 psi)

15.99, 16.33, 16.45 - first three tanks of gas corrected MPG average, mostly highway miles. These trips would normally net at least 17.5 with the 33's

960 - dollars for 4/mb - on the high end of all of the pricing I have heard. Tire was 209 + tax + fees + mb / ea

825 - dollars additional gas cost over standard tires over 50,000 miles @ 10% MPG reduction and $2.75 gas (about 12-14 months for me )

geezz, someones been busy.

[wannabeH3]

show me some pics of your rig with them on. ill be ordering mine after the 15th

[stagger_lee]

Now thats the kind of info we need around here. Your the man. Thanks!

[SnakeH2]

Originally Posted by marin8703

geezz, someones been busy.

Or not "busy."

[Desert Dan]

How is your acceleration now?

[Casey]

First a correction, the toyo diameter should be 34.9 not 35.9 as stated.

More numbers:

2.5 - turns on the torsion bar

23.25" - hub to fender on the front

Only one rub spot on the right front swaybar, but I think it's barely touching since I can't even hear it.

Two additional tanks of gas, 15.61 MPG with about 100 miles hwy, 200 city/mixed and another 15.99 highway trip.

The acceleration difference is noticable, but not horriffic. The biggest thing that I see is really the shift points on the auto tranny. I have tried keeping it in 3rd at points where I see I won't be over 45 mph indicated. The factory shift points were sluggish (early) even with stock tires and the taller tires seem to make it a bit worse. The worst seems to be 3-4 where that kicks in under 45mph indicated and rev's down to 1600 rpm and there is not enough torque. One thing I have noticed and am starting to play with is there seems to be more inertia carried after letting off the gas, so you can let off of the gas earlier coming to a pending stop and forward momentum is carried before having to get on the brake. Overall braking response was essentially unchanged surprisingly as I expected some slight differences with the increased inertia.

I don't know if a 0-60 would give any real information since I rarely go wide open throttle acceleration anyway. I would like to know if anyone has played with shift points which I know hptuners can do, and I think PCM for less can do also.

Also a noticable difference with these tires at 40 psi, much more suspension compression is felt in the cabin when going over speed bumps and the like, even at slower speeds. I kept the 33's at 38 psi and would often take speed bumps faster than you think you should normally without much harshness in the cabin. I may take a little air out and see if mileage numbers are affected much.

Oh yea, got a wheelin trip planned next weekend, so I'll take some good pics of the tires before I head out, and hopefully some good before and after pics on the trails.