Tires, lift & gear ratio

What tire fits each lift and what gears to run — the XJ guide

When you fit bigger tires to a Cherokee, everything changes: acceleration, fuel economy, transmission temperature and, above all, that feeling that it's "gutless". That's why, after a decent lift, you almost always need to change the ring-and-pinion gears (what enthusiasts call a "regear").

Why you need to regear

A taller tire is effectively like fitting a "longer" gear: the engine spins slower for the same road speed. That's nice for highway economy but poison off-road, because you lose the torque multiplication exactly when you need it most to crawl.

The whole point of regearing is to keep the effective drive ratio close to stock. Stray too far and, besides going gutless, you can overheat and punish the automatic. Rule of thumb: new ratio = stock tire height × stock ratio ÷ new tire size.

What tire fits each lift

Before you think about ring-and-pinion comes the physical question: how much tire actually fits? On the XJ that depends on lift height and how much fender and bumper trimming you're willing to do. Treat it as a guide —wheel offset, tire brand and body condition all shift the result.

Tire size by lift height (XJ guide)
Lift	28"	29"	30"	31"	32"	33"	35"	37"
Stock	OK	OK	±	++	—	—	—	—
2"	OK	OK	OK	±	++	—	—	—
3–4"	OK	OK	OK	OK	±	++	—	—
6"+	OK	OK	OK	OK	OK	±	++	—

OK No modifications ± Minor trimming / bumpstops ++ Major trimming or body lift — Not recommended without more lift

Recommended gears by tire size

Quick guide for the 4.0. Most automatic XJs come with 3.55, so gearing up with used axles is often cheap. Note: the AW-4 automatic and the AX-15 manual want different ratios.

Suggested ratio (4.0 engine)
Tire	AW-4 (auto)	AX-15 (manual)	Notes
Up to 31"	3.55 (stock)	3.55	Stock ratio is fine
33"	4.10 – 4.56	3.55	4.56 is better for acceleration and crawling
35"	4.56 – 4.88	4.10	Upgrade the rear axle (Ford 8.8 or Dana 44)
37"	4.88 – 5.13	4.56	Consider full-size axles
40"	5.29 – 6.17	4.88 – 5.13	Basically undriveable on the street

The full chart

And here's the full map: reference RPM at 65 mph (~105 km/h) in direct drive, for every tire-and-ratio combination. Find your tire on the row and see which ratio puts you in the green zone.

Big tires mean stronger axles

From 35" up, the XJ rear axle (Dana 35 or Chrysler 8.25) starts to run out of margin. That's when the community swaps in a Ford 8.8 or Dana 44. At 37"+ people move to full-size axles. Buy your gears for the axle you'll actually run.

Reference RPM at 65 mph (~105 km/h) in direct drive (1:1) — tire size vs. axle gear ratio
Tire	3.31	3.42	3.55	3.73	3.91	4.11	4.27	4.56	4.88	5.13	5.29	5.38	5.71	6.17	7.17
27"	2677	2766	2872	3017	3163	3325	3454	3689	3947	4150	4279	4352	4619	4991	5800
28"	2582	2668	2769	2909	3050	3206	3331	3557	3806	4001	4126	4196	4454	4813	5593
29"	2493	2576	2674	2809	2945	3095	3216	3434	3675	3863	3984	4052	4300	4647	5400
30"	2410	2490	2584	2715	2846	2992	3109	3320	3553	3735	3851	3917	4157	4492	5220
31"	2332	2409	2501	2628	2755	2896	3008	3213	3438	3614	3727	3790	4023	4347	5051
32"	2259	2334	2423	2546	2669	2805	2914	3112	3331	3501	3610	3672	3897	4211	4894
33"	2191	2263	2349	2469	2588	2720	2826	3018	3230	3395	3501	3561	3779	4083	4745
34"	2126	2197	2280	2396	2512	2640	2743	2929	3135	3295	3398	3456	3668	3963	4606
35"	2065	2134	2215	2328	2440	2565	2664	2845	3045	3201	3301	3357	3563	3850	4474
36"	2008	2075	2154	2263	2372	2493	2590	2766	2961	3112	3209	3264	3464	3743	4350
37"	1954	2019	2095	2202	2308	2426	2520	2692	2881	3028	3123	3176	3370	3642	4232
38"	1902	1966	2040	2144	2247	2362	2454	2621	2805	2948	3040	3092	3282	3546	4121
39"	1854	1915	1988	2089	2190	2302	2391	2554	2733	2873	2962	3013	3198	3455	4015
40"	1807	1867	1938	2037	2135	2244	2331	2490	2664	2801	2888	2937	3118	3369	3915
41"	1763	1822	1891	1987	2083	2189	2275	2429	2599	2733	2818	2866	3042	3287	3819
42"	1721	1778	1846	1940	2033	2137	2220	2371	2538	2668	2751	2798	2969	3208	3728
43"	1681	1737	1803	1894	1986	2087	2169	2316	2479	2606	2687	2733	2900	3134	3642
44"	1643	1698	1762	1851	1941	2040	2119	2263	2422	2546	2626	2670	2834	3063	3559

Economy / highway Ideal / balanced High / aggressive off-road

Where it was used: Jeep Cherokee XJ