Got an opportunity to get my hands on a set of 33x12.50R17 Mickey Thompson Baja Radial MTZ's for a screamin deal. BUT, my truck has the puny 4.2L V6 under the hood. It's a 2WD as well.

I don't think the motor has enough ***** to run tires that big and gnarly.

I presently have 265/70R17 Dunlop Rover AT's on the truck, which are already plus sized from the OE 235/70R17's that came on the truck from the factory.

Thoughts?

 

On a 2wd, you are about as big as you can go. No way that a 33x12.50 will fit.

 

What he said^. You'll need to at least get a leveling kit up front first, and 12.50's are a little too wide to go on stock wheels too. But as for the motor size, gears will make all the difference.

 

4.56 gearing????

 

4.10's would probably be good for 33's but don't take my word for it. I'm new to this. They would be better than the 3.55's that are probably in there now though.

 

4.10's would match 33's if he had a v8, but 4.56's would be better with the v6.

 

I think that 4.56 would be nice for acceleration, but the engine would be screaming at 70mph with 33's. I would not go lower than 4.10s.

 

Screaming? Hardly. With an automatic in locked up overdrive, it will be at 2275 rpm. The IMRC's aren't even near ready to open. With 4.10's it will be at 2050.

 

Since he's 2wd, 4.30s are an option and are what I'd go with

But, since he didn't ask to spend $800 re-gearing his pumpkin, just get the tires anyway (with a level of course). The truck is slow as dirt already, so who cares if it's a little bit slower?

 

Which is really too high. His stock gears and tires are probably around 18-1900 at 70. 33s would lower that further. Anything over 2000 is just too high at that speed. It will do nothing but waste gas on the highway.

 

Oh really? My 4.2 is turning 2300 rpm at 70, the gas mileage isn't bad. The gas mileage doesn't start to tank till it gets over 2500 rpm when the IMRC's start to open. If I keep it to 70 and under, I get 20 mpg unless I'm fighting a headwind.

 

And my 5.4 turns 18-1900 at 70 with a 3.73. I see no reason why yours should turn that high. It is basically the same engine with less cylinders. Yours is even a 3.55 which should be less rpms. Or your 2250 number for 4.56 is way low. That would be an increase of almost 25% on the rear, but a less than 10% on tire diameter. Stock being 30-31" going to 33". In that case the rpm would be a good bit higher than your 2300 rpm.

 

I have a manual transmission, 5th is 0.8:1. The auto is 0.7:1 in overdrive.

Correction, I used the wrong tire size. I'm turning 2225 at 70. I thought they were 29's, they are actually 30's.

 

When I run the numbers through an RPM calculator, The RPMs with a 30" tire and 3.55s only hit above 2000 RPM (actually 2275) when it is basically a non OD vehicle, or a 1 to 1 final trannie ratio. In all cases, the 33" with 4.56 rear are at least 300+ RPM over a 30" with 3.55. To me that is a waste of fuel. On your vehicle, with 33" tires and a 4.56, you would be turning 2600 rpm, over 300 higher than current setup. The 33" with a 4.10 rear is much closer to what is the current setup, both for you and the OP. It would only be an increase of 50-100 rpm.


Here is a good place to check out the numbers. Put in any size tire and gear ratio you want.

http://www.csgnetwork.com/multirpmcalc.html