quick tire and gear question

[scottyg]

i'm new. I've been searching and searching and reading threads from beginning to end and just need a definite answer if its possible:
97xlt SOHC: i would like to do a 2" torsion twist with aal's and shackles in the back. my question is this...will this fit 31x12.50's? or will it only fit 31x10.50's?
Also, will i need to mess with the gears any?
I would like to keep it simple. Is there anything else i would need to do besides a 2"TT, AAL, and shackles, get rancho shocks (<-- optional right?) to fit 31x12.50's or 31x10.50s?
thanks alot for any help. this forum kicks ass!

 

[Alec]

31x12.50s will not fit very well with only 2" of lift. In my experience you need 3 or 4" and trimming to clear them.

Use stock or 15(16)x8 rims for the 31x10.50s, 15(16)x10 rims for the 31x12.50s (another reason they're harder to fit, wider rims are necessary).

As for gearing, it depends on what gears you have stock. What's the axle code on your driver's door sticker? With 3.73s or 4.10s stock you'll be fine. Higher gears and you'll want more power off the line.

 

[scottyg]

3.73 or 4.10's. all right. so 31x10.50's is what i have to work with. thanks! what is the difference in gears? you said higher # the more power off the line? so 4.10 gears are quicker?

 

[Alec]

The higher the number, the lower the ratio: the higher the rpms at any given tire speed > better acceleration but higher highway RPMs.

 

[scottyg]

excellent. thanks!
what makes these gear ratios ideal?

 

[Alec]

Multiple factors such as tranny ratios, tire size, weight of vehicle, power curves of motor, and efficiency range of motor.

When talking just about the Explorer, tire size is the main factor. You want to have decent power off the line and RPMs of 2200-2800 on the highway depending on motor and mods. My OHV is most efficient cruising at about 2700 RPMs, but that is high for an OHV.

 

[scottyg]

will gas mileage be affected any?
do the bigger tires lower the rpm's per gear due to the wheels turning fewer times?
like i know i go 2100 rpms at 60 mph...with 31's would it be something like 1900 rpms at 60 because of the wheels' larger radius?
BTW i just wanna say that you are the man. your black truck is inspiration!!

 

[Alec]

Of course you're gonna affect mileage. The weight and rolling resistance of the tires won't help, and then you're changing the RPMs vs speed of the vehicle.

As for the geometry, you've got it.

 

[ExplSport02]

Scotty why dont you go with 32x11.5's??

 

[brendan]

I was thinking about going 32x11.50s recently. But when I had my 95 w/TT warrior shackles I had 31" Swamper SSRs and they were actually 31.6" OD. Most 32s are 31.7" OD but they then have the extra inch of width.

The width was my biggest concern. I had to trim a bit of my plastic to get the tires to turn (BTW I had 15x8 rims) and when wheeling sometimes they would rub on bumps. So I was really concerned about the extra inch width when I actually do make the purchase. I think I just might wait 2yrs till school's over and then do TT/shackles and 4" superlift on my 2000. That way I can do 33's and not worry about anything. Although every time I look at the thing it's crying back, "Please buy me real tires and a little lift!!!)

If my dad didn't give me new tires when I bought it, I'd already have 31x10.50 BFG ATs. Damn the bad (or good I suppose) luck