TheSamba.com :: View topic - Is a 30" diameter tire doable on a lifted 2wd?

Fri Nov 06, 2009 7:25 am

Just curious if I could stuff them under the fenders on my GL 2wd I have 19" from fender lip to center of the hub in the front and 19.5" in the rear. Any thoughts?

Fri Nov 06, 2009 7:34 am

I would think you would get real tired of 1st gear.

Fri Nov 06, 2009 7:38 am

Still brand new, my 225/75r16s spec says 29.1" and when I measured them they looked close to 29-3/8" inflated at 45psi (65psi max.)

30" is doable from my observation.. spring lift or not.. but you will most likely have to modify the fender lips in front and you will most definitely need to space out the rears and grind the corner of the control arm, removing a good chunk of that flange. Still leaving only millimetes of clearance. (No room for chains)

Spring lift buys you a little more wiggle room in the front, but only until you compress the springs.. Potential for contact is still there in travel, regardless the spring lift.

At 30" in the rear you are VERY close to the limit of what you can do with that swing arm without modifications like Burley makes to thiers.

You are also getting closer to the tops of the wheels wells (inside) on full spring compression.. I don't have a real good measurment for that clearance yet. Mine clear, but I couldn't tell by how much.

My observations, YMMV.

Fri Nov 06, 2009 7:58 am

Well with my 1.9td im not sure how first gear would be an issue. maybe im wrong though. I need to get my rpm's down a tad on the highway. Im thinking this will do it. I am thinking of running a 255/70/16 my other choice is a 215/85/16 These are based on overall diameter. a Revs per mile. The first one is 704 rpm's the second is 686.

Fri Nov 06, 2009 8:15 am

A true 30" tire would not fit on my lifted syncro so I don't think they'd fit on yours. I have 30x9.5 15 on now and I have about 1/2" clearance between the tire and control arm with the lip ground off. The tire actually measures 28" and change. With the stock springs they rubbed on the rear of the front fender when turning and compression happened at the same time.

I went from a 215/75 15 to the 30x9.5 to reduce RPMs and the effect was barely noticeable, maybe 200 rpms.

Fri Nov 06, 2009 9:23 am

allsierra123 wrote: I am thinking of running a 255/70/16

Be very, very careful running this wide of a tire. You will have to contend with clearance issues at the front upper control arm, the rear control arm and the sliding door.

On the front, I think that your biggest hurdle will be gaining enough clearance between the tire's bulge and the area of the upper control arm that is curled up along its length. This will be the area where the tire makes contact at full steering lock (or just before full lock). Clearance at the upper ball joint will also be an issue, but I think that with the correct offset and maybe a little metal persuasion, that can be worked around. As others have already said, the front and rear lower fender lips would have to be trimmed back for clearance as well.

On the rear, and only considering the tire at it's widest point, not the tread width, you would only have a couple of millimeters either way before the tire fouled the control arm or the door. This means that the offset of the wheel would have to be right on the money to pull it off. That only deals with the tire at it's widest point, but the rear control arm curves outward as it goes forward so you would have to make room for the wider tread area by trimming it back.

Fri Nov 06, 2009 9:25 am

what size tire would be doable to get me the most drop in rpm's. Or is the most I will be able to attain a 2-300 rpm drop?

Fri Nov 06, 2009 10:31 am

There is a gear/tire calculator on this page that should tell you what you can drop.
http://www.syncro.org/Tires.shtml

Here's another:
http://users.rcn.com/derekdrew/syncrotireandgearratios.xls

Fri Nov 06, 2009 12:17 pm

That tire is to large for your motor we are talking hit on performance not only that your springs and shocks will not take to kindly to the higher ride
19 is not enough maybe 21 if you are not around this high you will need some serous fender trimming

Fri Nov 06, 2009 12:53 pm

this is really getting to be an issue. My mileage is killing me right now. I can only achieve the low 20's and From what I here that is kind of low for a turbo diesel.

Fri Nov 06, 2009 1:46 pm

What do you have for gearing now and what is your tire size?
How much HP and torque of your motor?

Fri Nov 06, 2009 2:46 pm

Won't your mileage drop with bigger tires? Any time I put bigger tires on a vehicle my mileage suffered.

Bigger tires = more mass = more energy to turn them.

Fri Nov 06, 2009 3:24 pm

I have 19" to the fender lip and am running 215 75 15 which are spec'd at 27.6" and I can hit the fender lip on the passenger side turning into a driveway.

So it will take work to make them fit if they will.

Heavy tires take more torque to turn so if there is not extra torque it will make MPG go down. It's not the height it more the weight and surface area and drag come into play.

Fri Nov 06, 2009 3:35 pm

Not sure on the toque or HP of this motor. Ita a 1.9 TD (aaz) and its mated to and auto tranny.

Fri Nov 06, 2009 4:35 pm

With the diesel you will want to do everything you can to lower the rpm's.

For tires use the tirerack site to compare spec's. I tired to find the longest wearing, tallest, lightest, high load rated tire.

BFG's look awesome but are way heavy, and I don't "offroad" that much.

Fri Nov 06, 2009 5:31 pm

Its worth a try I have 27" swampers on there now on the stock alloys. I would like to get the rpms down and I dont want to commit to a tranny swap just yet. Would like to drive it a bit after the year long conversion.

Fri Nov 06, 2009 5:40 pm

PDXWesty wrote: Won't your mileage drop with bigger tires? Any time I put bigger tires on a vehicle my mileage suffered.

Bigger tires = more mass = more energy to turn them.

Kinda sorta. There's generally two aspects to consider: acceleration (in town), and maintaining speed (highway).
Peak torque is where you find the most efficient mpg, so in town with gas motors your equation works very well.
The diesel hits peak torque is maybe 1500-1800 rpm, so getting the revs down gets the best return on the highway.

Fri Nov 06, 2009 5:55 pm

I've been looking for a taller skinnier tire for my rig as well but am limited by the 15" rim. This is the kinda thing that I would like to try but I would call them first to get an actual measurement.
http://www.pacificcustoms.com/TIRE29X700.html
If it came in a radial with a quiet tread I'd have em.

Fri Nov 06, 2009 6:10 pm

fairweather wrote: I've been looking for a taller skinnier tire for my rig as well but am limited by the 15" rim. This is the kinda thing that I would like to try but I would call them first to get an actual measurement.
http://www.pacificcustoms.com/TIRE29X700.html
If it came in a radial with a quiet tread I'd have em.

If you do go that tall and thin stay with a load range E

Fri Nov 06, 2009 6:15 pm

They are bias ply so I'm guessing they are pretty stout, not good for airing down. Just got an email back from them and the off the rim actual is 29".