Lower tire pressures, effects on front suspension and pressure specific alignment ?

[verk]

Hi folks. I've been inflating fronts tires to 55-60 psi and rears to 35-40 psi for the last 50k or so miles. I appreciate the difference it makes in ride comfort. Looks like I'm getting about 50-70% of normal tread life using outside treads (which wear faster) as indicators. Does this accelerate wear on front suspension as well and if so what components ? Do tire pressure specific alignments exist and is this right thing to do at least for the front that has camber adjustment ?

 

[EDankievitch]

Heavy wear on the outer edges of the tire is due to too much Toe In. Not so much tire pressure. I run 65-75 Psi on my fronts I don't find them wearing out any faster since I re set the Toe In. The old days before the computer alignment machines the factory manual called for mesuring the Toe In at the bead of the rim (inside to inside) as high up on the tire as you could get and still be able to mesure the same location on the beads in front of the axel and behind it. The Toe in should be between 1/16 -1/8" any more and you'll kill the tires fast. I set my trucks around 1/16".

 

[phantomusa]

First off you should never under inflation of any tire ask any tire manufacturer they will tell you to inflation to the pressure on the sidewall and I know on 18 wheelers 10 psi less then sidewall psi is considered a flat tire and either inflat to spec's or repair the tire
Low tire pressure causes heat and delamination of the tire ply's so why risk your safety or others just to have a comfortable ride
You want to ride like a country Cadillac you should have bought a country Cadillac

 

[lpennock]

no reason to inflate tire on a unload truck to sidewall pressure. TRA defines load vs pressure for every tire made. As long as you meet load tables you are not under inflated. 35 psi on a LT295x70-18 is minimum pressure specified for the tire and still provides load margin on rear of an unloaded truck.

 

[phantomusa]

And you suddenly need to put a load into the bed of your truck in the middle of boonsville with no compressed air around ....your now driving unsafety
Besides the fact most people wouldn't remember to reinflat their tires after loading the bed

 

[lpennock]

You are free to run your tires at sidewall pressure to protect yourself from forgetting to properly inflate them. Being caught out with a sudden load isn't as big an issue as you want to believe. Keeping the speed below 45 will keep a severely under inflated tire from overheating long enough (20-30 miles) for you got get to someplace to air up. I will normally recommend people run 10psi over the TRA load tables to handle cold temp changes and less than religious pressure checking.

Now for some real numbers the example LT295/70-18E129 35psi rating will give about 1000 lb of load without going over weight. Rear axle weight is 3200-3500 empty where the 295 gives over 4500 of capacity at 35psi, air up to 45psi and you hit 5400 lb. And at 80 psi you have over 8000 lb capacity. Airing this tire to full 80psi is doing nothing but giving you a rough ride unless you are well over GVW rating. (Some of us run over 7000 axle weights but even then 75psi is usually plenty for this tire.

Now a smaller tire will use higher pressures so for another example the LT275/70-18E125 would also give 4000@35psi so you would still be able to put a 500lb load without an issue. Add my 10psi recommended margin and it becomes 4900 for 1000-1500 load margin which should handle most surprise situations

Bottom line running a LT at full side wall pressure is only necessary when you are running heavy and need the full tire capacity.

FYI: When feds mandated that TPMS had to be set to pressure required for maximum load rating, GM and Dodge both submitted briefs that the stopping distance is increase by the over inflated tires but feds was more worried about blowouts because people didn't understand proper inflation. Around 2014 the ram lost the light/heavy load switch due to the fed mandate.

 

[Bob4x4]

For the op.you are not that far off on pressures.IIRC the front as per door sticker should be at 60psi and the rears at 45psi for light load,Check your sticker to be sure.Shoulder wear can also be caused by cornering speeds or just lots of cornering ie city driving or lots of driving on curvy roads.The straight axle you have doesn;t have any camber adjustment

 

[GrantP]

I've run 50 psi in the front and 35 in the rear for many, many years on 35" tires. It has never caused a wear problem. I do keep a portable air compressor onboard but I've never needed it for my truck, usually for a trailer or my quad....or someone else's rig.

 

[AH64ID]

Sidewall pressure is max load at max pressure and not run all the time pressure.

If your load doesn't change much, or you're willing to adjust as necessary, there are load/inflation tables published so the proper pressure can be ran for the load.

My normal weight is 5200/3400 and based on the load/inflation tables I should run 55/35. I find the fronts need a little more air to be stable while cornering and run 60-65 most the time.


One of the drawbacks to running 19.5's, which I do in the summer, is that they have a minimum pressure regardless of weight. I only need about 50 psi in them, when empty, but can't go below 70 for sidewall flex and bead issues.


Back to the original question, no I don't feel lower tire pressure will negatively effect suspension components and I actually think it will increase the life of them since they don't have as harsh of a ride.

Everyone always talks about the impacts of running under-inflated but very few talk about the issues of running over-inflated. Over-inflated tires causes a harsher ride, increased susceptibility to road hazards, decreased traction (acceleration/braking/lateral), and improper tire wear.

 

[KPotter]

no cure for stupid

 

[DaveHess]

I ran my original factory rubber at the pressure stated on the door post and got over 60K out my tires. I continue to do so and do this all year long whether towing or not. The pickup has been sitting since just after Thanksgiving so I will be checking tire pressures here soon before I move it. IIRC: 70 PSI front and 60 PSI rears, I continue to run the OEM size and rated tires on factory rims. I will say this though; during my "towing" season (May through October), I run all four tires to include the spare at 70 PSI. I do this for tire rotation and in an emergency purposes where I do not have an available compressor that can handle these pressures. I also carry a calibrated torque wrench and 10-ton bottle jack in the event a tire needs to be moved or replaced.

 

[verk]

Thanks for the informative replies, the wealth of knowledge on this forum is amazing. I should have mentioned that I never have a load. Those that said toe-in/alignment issue are correct as confirmed by local tire shop. I tried taking a photo to show the difference between treads on inside and outside of tire, but nothing showed the difference well.

 

[verk]

For those looking for their curb weights to match tire inflation charts: http://dodgeram.info/ lists curb weights for front and rear axles of assorted Ram truck from 1994-2005. Along with tire inflation chart from Michelin I was able to do set tire pressures to load for perhaps the first time since having the truck Don't forget to include passengers, cargo and accessories.

 

[Killer223]

i say alignment as well. only outside tire wear is tow OUT not in as stated before.
i don't listen to the na-sayers that state you must run yada yada tire pressure. i run 55F 40R and leave it alone. it rides great. however my 08 has the darn TPMS and i have to run 65F and 45R, or it yells at me.
the softer tires will help the balljoints last longer.
run what ever you fell is correct for YOUR truck.

 

[Regcabguy]

no reason to inflate tire on a unload truck to sidewall pressure. TRA defines load vs pressure for every tire made. As long as you meet load tables you are not under inflated. 35 psi on a LT295x70-18 is minimum pressure specified for the tire and still provides load margin on rear of an unloaded truck.

I run 55 psi in my 285-75-17 Toyo AT2's. front axle weight is 4K#,rear 4.5K# This extremely strong tire yields a very rough ride if I inflate them to 65 psi and causes the center to wear prematurely. I have no drift issues at this psi and carry my 1800# camper around always.