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Tire Size (Downsizing?)

Old 09-17-2015, 06:13 PM
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Default Tire Size (Downsizing?)

I bought the Cherokee with 33" Super Swampers on it. Unfortunately, they are cracked bad and I wanted to replace them any way.

I checked the manual and for the 76 wide track the 33 12.5 R15 is the original tire. I will do more town driving than off-road and have heard 31" tires are better in the snow than 33" tires and offer better gas mileage.

My question for the community would be, can I change to a 31 10.5 R15 tire without issues? Pros/Cons?

Thanks in advance.
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Old 09-18-2015, 07:32 AM
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It's not so much that 31" are better in snow than 33", I think it's more the 10.5 and 12.5 difference. I've read that a narrower tire cuts through snow better than a wider tire, but I live in Cali so I don't have much experience there. Narrower tire also cuts rolling resistance, thus improving MPG. But honestly, you have a '76 full size, don't know if it will make any noticeable change. Pretty sure some companies make a 33x10.50x15 tire. Might be an option?
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Old 09-18-2015, 07:55 AM
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There is a big weight difference between 33's and 31's. In addition to weight difference there is a section width difference 12.5 vs 10.5. What gear ratio are you running? i think wide tracks were 4.10's if i remember correctly. That will play a big difference. It really comes down to what type of snow. Wide tires do best in Powder and Narrow tires do best in wet slush. You will see an increase in mpg's from less rolling resistance by switching to 31's. I have no qualms running them in our snow here. Sure i lose some ground clearance, but snow wheeling takes more than just spinning the tires as fast as you can. On my 67 F250 i ran 33 12.5 16.5's for a long time and averaged around 8 mpg. Switched to 235/85/16's (roughly a 32 tire but a 9.5" section width) and bumped up to around 11. Running 4.10 gears.
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Old 09-18-2015, 10:14 AM
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With respect to weight difference, I don't understand the concern. The rig weighs 6K pounds.

Thank you for the info, that makes perfect sense. I believe it is a 4.10 ratio, but the previous owners have made 'enhancements' that will likely be removed systematically with time.

The intention for this Cherokee is to bring her back to her former glory and become a daily driver for me.
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Old 09-18-2015, 11:00 AM
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It is the rolling mass and ground resistance that kill you. your engine has to work harder to spin a heavier weight. think of it as rolling a socker ball vs rolling a medicine ball. it takes allot more muscle to roll a medicine ball.
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Old 09-18-2015, 11:27 AM
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Thank you, that makes sense now.

So would i be better off buying a seperate set of smaller/studded winter tires and keep the 33's for the rest of the year?
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Old 09-18-2015, 12:36 PM
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Originally Posted by Spinich View Post
With respect to weight difference, I don't understand the concern. The rig weighs 6K pounds.
holy **** what is it made of lead?? your jeep can't possibly weight more than 4500lbs... it's probably less than that

x2 on what WyoCherokee said
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Old 09-18-2015, 12:54 PM
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Originally Posted by Atmos View Post
holy **** what is it made of lead?? your jeep can't possibly weight more than 4500lbs... it's probably less than that

x2 on what WyoCherokee said
Thats what the specs say. Gross weight, 6,025 lbs. Am I reading that wrong?

1976 Jeep Cherokee 401 V-8 Quadra-Trac Hydra-Matic (S)

Jeep Cherokee 401 V-8 Quadra-Trac Hydra-Matic (S), model year 1976, version for North America U.S.
3-door wagon body type
4x4 full-time (all-wheel drive permanent Borg Warner Quadra-Trac 1305/1339 with center differential), automatic 3-speed gearbox
petrol (gasoline) engine with displacement: 6573 cm3 / 401.1 cui, advertised power: 153 kW / 205 hp / 208 PS ( SAE net ), Torque net: 435 Nm / 321 lb-ft
characteristic dimensions: outside length: 4661 mm / 183.5 in, wheelbase: 2761 mm / 108.7 in
reference weights: estimated curb weight: 1940 kg / 4280 lbs, gross weight GVWR: 2733 kg / 6025 lbs
how fast is this car ? top speed: 166 km/h (103 mph) (theoretical);
accelerations: 0- 60 mph 10.6 s; 0- 100 km/h 11.2 s (a-c simulation); 1/4 mile drag time (402 m) 17.8 s (a-c simulation)
fuel consumption and mileage: average estimated by a-c: 21.5 l/100km / 13.2 mpg (imp.) / 11 mpg (U.S.) / 4.7 km/l
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Old 09-18-2015, 01:00 PM
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Curb weight is what you want 4280 lbs. GVWR is what you can "legally" weigh with full cargo and trailer tongue weight
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Old 09-18-2015, 01:34 PM
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Originally Posted by Spinich View Post
Thats what the specs say. Gross weight, 6,025 lbs. Am I reading that wrong?
you have a 1976 wagoneer?
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