The Mysterious Fifth Shock

[MNgopher]

Zombie thread - but for what its worth the poster with the Load Range C tires was underinlflated by about 5 psi. LT tires run a substanially different pressure to carry the equivalent load due to tire construction than P-series tires like what came stock on the Explorer. They are a not "straight" substituion despite the same size.

 

[grant00]

I have 32" BFG allTerrains and Im running them at 30psi... they look a little underinflated and ive been asked a few times if my tires are low :scratch: and i get around 12-14 mpg if i drive easier and slower. so i guess ill try running them at 35 and see if theres any visible and mpg difference..?? any thoughts?

 

[Mbrooks420]

Get some chalk and run some lines across the tires. Drive a few feet. If the center of the chalk wears away decrease pressure. If the outsides rub away increase pressure. As for the 5th shock removal making no difference, it probably doesn't make ANY difference if the shock you remove is BLOWN.

 

[Hevyg]

Zombies just wont die! LOL, too true. I got snarked at for asking questions about stuff that was already posted ;o(
So, im browsing the older stuff, after all its all new to me ;o)

As ive said many times, I friggin love it here

 

[Electrohacker]

I like the chalk idea, too bad its all wet from the snow, maybe grease chalk...

anyway the BFG all terrain's I have (stock size) are rated at 50psi max preassure, and I run them there in the summer, in the winter I run them lower, between 32-40 psi to have better traction

on of my old professors tld me that for ever 10lbs of air pressure added you gain 1mpg or something like that, so if you're rated at 35 and you get 12mpg then it follows that you MIGHT get 13mpg at 45psi, but there's so many other factors involved that its really up to preference

also the more PSI the harder the ride

 

[MNgopher]

What size rims on the 32" tires? If they are on 8" rims, they would tend to look more underinflated. The loading tables would seem to suggest the 30psi would be reasonable for that tire size on an Explorer.

As others mentioned, the chalk idea can help dial things in too to minimize tire wear issues.

 

[grant00]

yeah theyre 15x8 wheels. i put them at 35 at the shop tonight so ill try that. if not, out comes the chalk :

 

[Awsum97]

any more come of this? i am looking into whether i have to get the "5th shock" my car DOES infact shimmy at 67mph-ish as one of the above posters said would happen w/out or with a shot 5th shock. so that is very interesting. the poster said usually people think is is the wheels in need of balancing etc. my wheels were balanced and it still shimmys at 678mph-ish on the highway. only caveat is one of my rear tires has worn pretty horribly. i could believe how uneven the circumference of the tread was when the guy at the tire shop showed me it on the wheel balancer. so i am still thinking that the tire is causing some issues w shimmying. but maybe this 5th shock too.

one thing to think about is that my car is old (1997) there is a lot of rusting underneath in various housings. i know that sometimes it is better to leave stuff alone unless it is a difference maker. i am afraid that stuff will break as i am trying to get this old 5th shock free. this 5th shock is hard to get to as well.

as always your feedback is much appreciated!!

 

[yavapaires]

Why do you say 30 PSI is too low? Are you like my dad was, and go by the max pressure on the tire? Then wear only the center of the tread. I have experimented with my 96, and find 30 in front 28 in the rear. Two people, Two small dogs, no cargo, combination of highway/city driving. P235/75/R15 all season tires.

 

[CDW6212R]

any more come of this? i am looking into whether i have to get the "5th shock" my car DOES infact shimmy at 67mph-ish as one of the above posters said would happen w/out or with a shot 5th shock. so that is very interesting. the poster said usually people think is is the wheels in need of balancing etc. my wheels were balanced and it still shimmys at 678mph-ish on the highway. only caveat is one of my rear tires has worn pretty horribly. i could believe how uneven the circumference of the tread was when the guy at the tire shop showed me it on the wheel balancer. so i am still thinking that the tire is causing some issues w shimmying. but maybe this 5th shock too.

one thing to think about is that my car is old (1997) there is a lot of rusting underneath in various housings. i know that sometimes it is better to leave stuff alone unless it is a difference maker. i am afraid that stuff will break as i am trying to get this old 5th shock free. this 5th shock is hard to get to as well.

as always your feedback is much appreciated!!

The fifth shock is basically for side to side control of the rearend. I doubt you have any vibration or tire wear from that one shock. They are difficult to install, if the new one has any pressure in it.

 

[CDW6212R]

Why do you say 30 PSI is too low? Are you like my dad was, and go by the max pressure on the tire? Then wear only the center of the tread. I have experimented with my 96, and find 30 in front 28 in the rear. Two people, Two small dogs, no cargo, combination of highway/city driving. P235/75/R15 all season tires.

All tires are different, your tires require different air pressures than my tires, because of the tire.

Each new tire needs a constant monitoring of the air pressures, and adjustments as needed.

The people who selected the OEM tires have no clue about what tires each person will change to next. Thus the pressures recommended on any door jamb sticker are useless except for the one OEM tire.

The tire failures years ago were greatly due to low air pressures, it wasn't just the tires. Any tire will fail if the pressures are too low, almost no tire will fail with too high of pressures. So it's smarter to have too much air pressure, than too little.

I suggest beginning with the tire's MAX rating, put in just under that on the heavy end, 2-4psi less on the light end. Drive the vehicle, if it truly feels too harsh, lower the pressures slightly. Drive it again, give it some time, if after a few days it still feels too rough, carefully change it some more.

Don't go too low, the edges will wear out faster. If the edges show more wear than the rest, you have too little air in the tires.

 

[SoNic67]

On-topic:
I just replaced the fifth shock and it made a difference at hard acceleration. The way is mounted, it supposed to attenuate the rear axle wrap at maximum torque. The new Monroe shock SC2958 is doing a better job at that than the worn-out, 10 year old OE shock.


Off-topic:

The tire failures years ago were greatly due to low air pressures, it wasn't just the tires.

No, it wasn't the pressure. Same pressure in Goodyear tires didn't lead to separation. The ONLY affected tires where from the Firestone Decatur plant that had the workers on strike during that period. One in ten of their tires failed, while one in 1000 of the others fialed. That plant was eventually closed.

http://www.highbeam.com/doc/1P3-583568461.html
http://abcnews.go.com/US/story?id=95685&page=1

 

[CDW6212R]

On-topic:
I just replaced the fifth shock and it made a difference at hard acceleration. The way is mounted, it supposed to attenuate the rear axle wrap at maximum torque. The new Monroe shock SC2958 is doing a better job at that than the worn-out, 10 year old OE shock.


Off-topic:


No, it wasn't the pressure. Same pressure in Goodyear tires didn't lead to separation. The ONLY affected tires where from the Firestone Decatur plant that had the workers on strike during that period. One in ten of their tires failed, while one in 1000 of the others fialed. That plant was eventually closed.

http://www.highbeam.com/doc/1P3-583568461.html
http://abcnews.go.com/US/story?id=95685&page=1

The OEM specs for those tires was about 28psi, which if actually followed is not enough air pressure for any tire used on a loaded SUV.

How often do people actually have the intended pressure installed, even when they intend to have too little(door jamb specs) air in the tires? We all know that most tires have less air in them then people intended. That means that the failures likely all occurred with much less air in them than 28psi.

You go drive on a long vacation with 25psi in the tires, or 20psi, and see what happens. Most times with good tires nothing will happen, but when thousands of people do the same thing, any tire not very well built will fail. If you flirt with disaster by purposely using too little air pressure, some day the right(poor) tire with less air than you thought was in it, it will blow.

Put more air in the tires(any tires), and that adds a safety margin. Too much air gives the tire more capacity to lose some and not become way too low. There are good and bad reasons to run extra air pressure, and more bad reasons to run less.

 

[gavin]

i could believe how uneven the circumference of the tread was when the guy at the tire shop showed me it on the wheel balancer.

if it was noticeably out-of-round due to uneven wear, then 99% chance that is the cause of your shimmy.

 

[Awsum97]

i think u are right....

 

[SoNic67]

The OEM specs for those tires was about 28psi, which if actually followed is not enough air pressure for any tire used on a loaded SUV.

You keek insisting to ignore the data. The fact that 99.9% of the tire separations where from the same lot and factory.

Your suggestion to inflate the tire to the "maximum" value stamped on wall is irresponsable in my oppinion. The tires that had stamped value as a worse case scenario of the tire, it has nothing to do with vehicle stability - that is beyound tire manufacturer control. Only Ford test the Explorer, so their recommadation is the only one that can be realistic.
Original Expl had 28psi recommended with 35psi tires. My Explorer says 30psi with 45psi tires.
If it was to low originally, it was with some 2 psi, not 17 psi like you suggest!