Leif Pihl's Jeep TJ, Tires, Speedometer Gear & Rims upgrade:

 

Contents:

• Tires Upgrade
• Speedo Gear
• Rims Wheels
• Picture(s)
• Diff

Tires upgrade (done):

At about 22K miles, I was told that I have another 20 thousand miles left of the tread on my factory Goodyear Wrangler RT/S P215/75R15 tires. Once these tires were worn, I was willing to spend money on replacing them with larger size tires, but my ego or enthuseasm for off-roading meant that I ended up replacing them early.
(At 23K miles, or around July 5 '98, I was also told the original tires had 22K miles left.)

31x10.50R15 BF Goodrich Radial AT TA mounted on my original 15x7" steel rims was my choice in new tires (with the Trail TA coming in at second place). Since I did not purchase new rims with a larger backspacing, this meant that I had to add machine washers at the steering stops. Since I purchased my tires, The AT TA has been replaced by the AT TA KO.

Steering Stops & Washers (58.3K & 168.4K)

The B. F. Goodrich A/T TAs seem to perform well in Minnesota's winters; including ICE (as well as snow). They seem to have some ability on the trails as well as being good-mannered on the road.

NOTE: There is 1.0" to 1.25" of additional (radius) space for larger tires to still fit on the stock spare tire mount. I may or may not actually purchase a fifth (Phase I) tire, but what ever choice I do make should be able to fit onto the factory spare tire mount. This means that the new tires may be UP TO 2 & 1/2 inches taller than Goodyear Wrangler RT/S P215/75R15, but no more. (See "Future Plans" for an expected new tire carrier/bumper.)

{(30.5 - 27.5 = 3) / 2 = 1.5 inch radius of additional height from just the tires.} + 1.25 from the spring spacers = 2.75 inches of total lift to my TJ.

FLOTATION/METRIC CONVERSION This table is from page 70 of the December, 1996 edition of Four Wheeler Magazine.
FLOTATION	DIAMETER (INCHES)	METRIC SIZE
27x 8.50R14	26.5	225/75R14
	27.5	215/75R15 This is the size tire I originally had.
	?	225/75R15 This is the 1st optional size tire I have could have factory ordered.
29x 9.50R15	28.5	235/75R15
30x 9.50R15 This is the 2nd optional size tire I have could have factory ordered.	29.5	245/75R15
31x10.50R15 (The size tire I did get.)	30.5	265/75R15
32x11.50R15	31.5	295/75R15
33x12.50R15	32.5	315/75R15
33x12.50R16	32.8	285/75-16

Tires:
Q: What size tire can I fit on my Jeep without rubbing?
A: As a rule Rubicon recommends the following: TJ 4.5"= 33x12.5, TJ 3"=33x10.50

(Although I did not choose it, Brian Hassing reccomended I look into the Goodyear 31x10.50R15 Wrangler AT/S tires, now in production. Check out the following link: http://www.goodyear.com/nat/pclt_cat/products/wrangler_ats_specs.html.)

Speedo-gear tech data:

Because of my 31" BFG AT TAs, I probably should have already installed a different Speedometer Gear (Mopar #52067633?) regardless of if and when I re-gear.

I was once told that Daimler/Chrysler sends all TJs out the door with the 52067627 Speedometer gear, but I find it difficult to beleive that this is true. I've also been told that the original "215/75R15" tires I had on my Jeep came with the "33" speedo gear... the same gear that would me necessary if I used 31" tires and 3:73 gears, again I find this difficult to beleive.

8/18/99: I finally got around to removing my Spedometer gear and inspecting it: My TJ has a 30-tooth Speedo gear. Problem: I don't think that a 27-tooth gear is available from Daimler-Chrysler. I'll probably have to go aftermarket. Anyone know what 30 vrs. 27 teeth has been doing to my Odometer/Speedometer and/or engine computer's programming?

Once I get around to actually removing and examinging my existing speedo gear (i.e.: now), I'll make a decision as to which one to replace it with... OK, I admit it, I should have done so a long time ago.

The below data is another way of presenting the above chart. It's data is derived from a print out from a Bell & Howell terminal at a Jeep Dealer's Parts Department.

52067625:	25 teeth		My Jeep Dealer's parts dept. says that 52067625- & lower are not valid part numbers. (SG25 also may not be a valid Teraflex number.)
52067626:	26 teeth		My Jeep Dealer's parts dept. says this is not a valid part number. (But, SG26 may be a valid Teraflex number!)
52067627:	27 teeth		My Jeep Dealer's parts dept. says this is not a valid part number. (But, SG27 may be a valid Teraflex number!)
52067628:	28 teeth	3.07 Axle Ratio	30x9.5R15 Wrangler OWL
52067629:	29 teeth	3.07 Axle Ratio	All 225 / 245 Tires
52067630:	30 teeth	3.07 Axle Ratio	All 215 Tires
52067631:	31 teeth	3.07 Axle Ratio	All 205 Tires
52067632:	32 teeth		My Jeep Dealer's parts dept. says this is not a valid part number. (But, SG32 may be a valid Teraflex number!)
52067633:	33 teeth	3.55 Axle Ratio	30x9.5R15Wrangler OWL Tires
52067634:	34 teeth	3.55 Axle Ratio	P225/75R15 OWL Wrangler Tires, 3.73 axle ratio
		3.73 Axle Ratio	30x9.5R15 Wrangler OWL Goodyear Tires
52067635:	35 teeth	3.55 Axle Ratio	P215/75R15 OWL All Terrain, P215/75R15 RBL Wrangler, All 205 Tires.
52067636:	36 teeth	3.73 Axle Ratio	P225/75R15 OWL Wrangler, P215/75R15 RBL Wrangler, P215/75R15 OWL All Terrain, Goodyear
52067637:	37 teeth	3.73 Axle Ratio	P205/75R15 Wrangler RT Goodyear Tires
52067638:	38 teeth		My Jeep Dealer's parts dept. says this is not a valid part number. (But, SG38 may be a valid Teraflex number!)
52067639:	39 teeth	4.11 Axle Ratio	All 255/245 Tires
52067640:	40 teeth	4.11 Axle Ratio	All 215 Tires
52067641:	41 teeth	4.11 Axle Ratio	All 205 Tires
52067642+:	42+ teeth		My Jeep Dealer's parts dept. says that 52067642 & higher are not valid part numbers. (SG42 also may not be a valid Teraflex number.)

Rims (Wheels):

At some point in the future, I will probably replace the stock rims with aftermarket rims that have a larger backspacing. As of this writing, my favorite is the American Racing "Gambler". Thi is partly because I like the looks, and partly because it looks similar to the factory Gamblers. I was once told that my TJ needs a "5-4&1/2 Bolt Circle" pattern.

Below are listed four of the possible options (lugs not included).
I'll probably want to get part no. 52-5865.

The Diff:

I am very interested in the Power Trax No-Slip Diff. My plans are to wait several months after the inital release...
THEN I will replace both stock Open-Differentials with the NSD.

At the same time that I upgrade to the NSD, I HAD planed to also change my gearing. My stock gears are 3.07s. I thought that this was totally inappropriate for my 31" BFG AT TAs tires. I had planed on installing 3.73 gears at the same time that I have the No-Slip Diff installed in the front and back.

• Gears NOT changed from 3.07 to 3.73.