As a relative novice when it comes to tires and such in regards to my truck (2001 4x4 Ext. Cab ORP) I have a few questions.

I've been following the thread on the 315's on the super crew, but how about the Super Cab. Will they fit with some trimming and a tortion bar lift?

And is this something I can expect my local tire shop to do for me? I would be nervous about venturing down this road.

And what's this I'm seeing about changing out gears? Is that something that one would NEED to do?

Thanks,
David

 

From what I've seen on the "net", the "315" is a 35" tall tire. I have seen it suggested that a 3" body lift was needed to clear the tires w/o rubbing. "Tweaking" the torsion bars will raise the front somewhat, but I don't know if it would be enough. As far as gears go, going to a tire that tall you will definately see a loss in power w/o a gear change. I am sure you'll get some better info' from some of the folks with experiance in this area, so good luck!

 

I have had the 315/70/71's for 4 months and love them. I have a screw with the FX4. They should fit on the supercab. I had the front T-bars adjusted 1", minor trimming on the valance and mudd flap, adn trimming on the rear mud flap. I love them and they look great clean or dirty

 

So to confirm you DID NOT change out any gears? Have you noticed any loss of power?

Thanks,
David

 

I ahve the 3.73 LS and have noticed slight power loss. I can still turn them over sometimes. I have the 5.4 and no engine mods yet

 

10-4, thanks.

Taka care,
David

 

I have a 2000 Super Cab and I have the 285/70/17's. I still have some space in the fenders for some more tire, but I think 305 would be about the most. The major reason I went with the 285 is that I like to take my truck off road and with the larger size tires I am affraid they will bottom out when I hit some big ruts and things. I think it comes down to what you want to do with your truck and I also wonder if the new FX4 is alittle taller than the Off Road packages that came before them.

 

Gearing is a matter of feel for most people. With 3.73' s and the 5.4 I don't think that gears are needed with 35's. I have a 4.6 and 3.55 in the rear and want need gears bad. the power loss was bad and the engine downshifted a lot. It also stayed in a lower gear way to much going up small inclines. I'm putting 4.56's in my truck which is about 2 gear sets above my stock config but want the extra somethin-somethin. With more info on your truck I could probably give you a pretty good idea of if you would probably want new gears or not. Maybe even give you advice on what gear to put in.

 

I have 35s as well but with a 3" body lift. I don't see how you can get those big meats on their without a lift, but if you guys say they fit then I believe you. Are you running aftermarket rims though?

I have the 3.73:1 GR with 35s and I am happy with it. Same experience as what was mentioned, yes a noticeable decrease in performance but not enough to even care. I have 'inadvertantly' roasted my 35" mudders on more than one occasion. (Nothing like burning up $800 worth of tires )

kev

 

I just added some 315's recently and (without the MicroTuner) did notice some power loss. The truck could still get up and go, just wasn't quite as responsive. However, with the MicroTuner program in, it seems to have returned to stock, at least. Last night driving around I was getting on it and loved the response. Now I know why nobody *ever* gets better MPG with the Tuner!!!

Mike

 

A microtuner may get you back to stock but the only way you can lessen the impact on your drivetrain is by re-gearing. Re-gearing will give you your power back and in a sence make the impact on your drivetrain non-existant. Just got 4.56's with my 35's and have only had them a couple of days but am already liking it. I know when I make it through the "break-in" period I will have more get up and go than I could want(like was mentioned before, nothing like burning through $750 worth of tires ). The place I took my truck charged me $460 but my bearings were going bad and needed them replaced so that cost me another $160. Grand total $636.

 

Correct me if I'm wrong, but doesn't the "315" stand for the width of the tire and not the height? I had some 315/35/17s on my Trans Am and they surely weren't 35" tall. I believe the second number is the measurement for the height. The tires I had on my TA were very low profile, whereas the 315/70/17's I have seen have much bigger sidewalls.

 

1st Number = width in millimeters
2nd Number = aspect ratio, basically a % of the width
3rd number = Rim diameter, in inches

So, to get the rough tire diameter:
((Width/25.4)*Aspect Ratio*2)+Rim = Diameter

The 25.4 converts mm to inches. Diameter is in inches.

Thus a 315/70/17 is:

((315/10/25.4)*.7*2)+17 = 34.4"

A 315/35/17 is:

((315/10/25.4)*.35*2)+17 = 25.7"


So the short answer is changing thw width does have an affect on height if the aspect ratio is not changed.

 

I have 285/70/17 BFG AT's on my 01' supercab. If you tweak your torsion bar at all it could affect your steering when you tow, so the biggest you can go with no trimming at all is the 285. It fits nice and the BFG's make it look alot better....Pictures to come soon.....