2 quick questions

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frankrizzo

NAXJA Forum User

Location

illinois

• Jan 6, 2013

• #1

1. I got new 31x10.50 15s. At what psi should they be inflated for regular street use. I heard that on bigger tires it shouldn't be 35psi. Is that true?
2. I have a 99 4.0, when I start the Jeep, for the first 20 minutes the battery gauge will read between 14.2 and 14.5 volts. (I have a digital gauge in my cigarette lighter socket). But after twenty minutes or so it'll go down to 13.6 and 13.8. Is it normal to fluctuate like that?

 

in4aride

NAXJA Forum User

Location

Montrose

• Jan 6, 2013

• #2

1 - what size rim, as in width. what is load rating on the tire? pressure rating?

 

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Digger87xj

NAXJA Forum User

Location

Buffalo Creek/Lakewood CO

• Jan 6, 2013

• #3

2. perfectly normal. The alternator is re-charging the battery after the start-up.

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Jan 6, 2013

• #4

2. Yes.

1. Use the tread face/chalk method to determine the "correct" pressure for your vehicle when using non-standard tires. http://www.jpmagazine.com/techarticles/wheels/154_0704_tire_pressure_science/ (note: vehicle should be loaded as "normally" driven)

 

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WB9YZU

NAXJA Forum User

Location

Madison, WI

• Jan 7, 2013

• #5

1) Yes, it is normal for the voltage to fluctuate after starting. "Normal" is 13.8V.

2) The tire patch method is the best. With a OEM rim and a the tire size you are using, I would start at 32psl.

Remember that if under inflated, the sides will wear before the inside, and visa versa.

 

Ecomike

NAXJA# 2091

NAXJA Member

Location

MilkyWay Galaxy

• Jan 7, 2013

• #6

frankrizzo said:

2. I have a 99 4.0, when I start the Jeep, for the first 20 minutes the battery gauge will read between 14.2 and 14.5 volts. (I have a digital gauge in my cigarette lighter socket). But after twenty minutes or so it'll go down to 13.6 and 13.8. Is it normal to fluctuate like that?

Click to expand...

That all sounds normal to me, but my jeeps are older. Mine drop with the head lights and AC blower on Max too. I thin the voltage regulators drop the voltage after the battery is fully recharged. It also drops when you turn every power hungry appliance on at idle.

 

Last edited: Jan 7, 2013

F

frankrizzo

NAXJA Forum User

Location

illinois

• Jan 7, 2013

• #7

in4aride said:

1 - what size rim, as in width. what is load rating on the tire? pressure rating?

Click to expand...

theyre 15x8s. not sure what the load rating is but the tires are goodyear duratracs

 

5-90

NAXJA Forum User

Location

Hammerspace

• Jan 7, 2013

• #8

Chalk the tyres and play with the pressure - it's the best way to find out. Take you an hour or so, usually.

And bear in mind that the starter motor on our 6-242 engines is usually good for anywhere from 160-185A to crank the engine, PLUS all the loads involved in actually RUNNING the engine. Yeah, the battery's going to have to "top up" after that, it's something of a workout. If the voltage DOES NOT drop, then it's time to start worrying...