Final drive is too steep
Thread Starter
|
Mountain Pass
Joined: Oct 2011
Posts: 218
Likes: 0
Final drive is too steep
I'm turning a little over 2300 going 70mph with a 4.30 rear gear and 31.5" overall tire height. Since I'm seeing about 16mpg city and 16mpg highway I feel like i'm spinning the motor past it's "happy spot" on the highway.
I'm wondering what rpm is the best to be at and if a tire change can get me there?
I would swap the gear but it's a 4x4 so that a little expensive changing 2 sets and I need rubber anyways.
2000 Excursion, E99 7.3L, 2000 4r100, 4x4
I'm wondering what rpm is the best to be at and if a tire change can get me there?
I would swap the gear but it's a 4x4 so that a little expensive changing 2 sets and I need rubber anyways.
2000 Excursion, E99 7.3L, 2000 4r100, 4x4
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
Somebody changed it to 4.30s as PSD Excursion were only available with 3.73.
IMO you should be around 2000rpm at 70mph...unless you tow heavy. A tire change could put you there but you'll be running 35s.
Some 295/75R16s would split the difference with a calculated RPM at 70 of 2180. And they should fit on your stock rims without too much effort.
IMO you should be around 2000rpm at 70mph...unless you tow heavy. A tire change could put you there but you'll be running 35s.
Some 295/75R16s would split the difference with a calculated RPM at 70 of 2180. And they should fit on your stock rims without too much effort.
MMNC (SS)(Ret)
Joined: Mar 2004
Posts: 11,604
Likes: 149
From: SE Georgia
you sure you have 4.30's?
could someone have thrown v-10 axles under there?
I'd shoot for a 33" or 34" diameter. that'd slow down the tire speed and lower the highway RPMs. not to mention look better
could someone have thrown v-10 axles under there?
I'd shoot for a 33" or 34" diameter. that'd slow down the tire speed and lower the highway RPMs. not to mention look better
Thread Starter
|
Mountain Pass
Joined: Oct 2011
Posts: 218
Likes: 0
I forgot about having a couple of mustang buddies from back in the day and they regularly swap out gears/tires and use online calculators to figure out where they're at. I got a link to a calculator:
Tire Size Calculator
I plugged in my numbers into the very bottom calculator and it was pretty close: it said I have a 30.8 inch tire now and it's 31.25. I know my speedo under-reports a little anyways cause I just drove to N carolina and watched the mile markers.
After I put in the same 2330 rpm but moved the speed up to 80 instead of 70 it said I'd need a 35.2 inch tire. I have 18x10" rims but that's still a lot of sidewall for a highway vehicle. Do any of the new trucks come with tires that big?
Tire Size Calculator
I plugged in my numbers into the very bottom calculator and it was pretty close: it said I have a 30.8 inch tire now and it's 31.25. I know my speedo under-reports a little anyways cause I just drove to N carolina and watched the mile markers.
After I put in the same 2330 rpm but moved the speed up to 80 instead of 70 it said I'd need a 35.2 inch tire. I have 18x10" rims but that's still a lot of sidewall for a highway vehicle. Do any of the new trucks come with tires that big?
Thread
Thread Starter
Forum
Replies
Last Post
