Suspension lowering question.....

[05 GRAND DADDY]

Make sense Fred Thx


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Dan & Wendy
"05 GRAND DADDY"

 

[Phrede]

Copied from Tire Rack

Disadvantages of Underinflation
An underinflated tire can't maintain its shape and becomes flatter than intended while in contact with the road. If a vehicle’s tires are underinflated by only 6 psi it could lead to tire failure. Additionally, the tire’s tread life could be reduced by as much as 25%. Lower inflation pressure will allow the tire to deflect (bend) more as it rolls. This will build up internal heat, increase rolling resistance and cause a reduction in fuel economy of up to 5%. You would experience a significant loss of steering precision and cornering stability. While 6 psi doesn’t seem excessively low, remember, it usually represents about 20% of the tire’s recommended pressure.
Disadvantages of Overinflation
An overinflated tire is stiff and unyielding and the size of its footprint in contact with the road is reduced. If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when running over potholes or debris in the road. Higher inflated tires cannot isolate road irregularities well, causing them to ride harsher. However, higher inflation pressures usually provide an improvement in steering response and cornering stability up to a point. This is why participants who use street tires in autocrosses, track events and road races run higher than normal inflation pressures. The pressure must be checked with a quality air gauge as the inflation pressure cannot be accurately estimated through visual inspection.

Advantages of Correct Tire Inflation
Maintaining correct tire inflation pressure helps optimize tire performance and fuel economy. Correct tire inflation pressure allows drivers to experience tire comfort, durability and performance designed to match the needs of their vehicles. Tire deflection (the tread and sidewall flexing where the tread comes into contact with the road) will remain as originally designed and excessive sidewall flexing and tread squirm will be avoided. Heat buildup will be managed and rolling resistance will be appropriate. Proper tire inflation pressure also stabilizes the tire's structure, blending the tire's responsiveness, traction and handling.




I'll add that, in my opinion, an under inflated tire is at a greater risk of catastrophic failure due to a road hazard (blowout).

HTH

 

[Stella]

I have never run a tire at the pressure printed on the tire (MAX safe pressure) I run my current tire at 34 psi and 50psi is printed on the tire. Even on my truck with load range E tires I run 10 psi less than the MAX of 80psi.

I guess you just didn't read my response thoroughly. I said" I start with the tire recommendation printed on the tire, then adjust from there. My question is what does Cadillacs recommendation mean if you've changed their tire. Which 80% of the people on here have done. Just about every passenger car has a operating pressure between 35-42psi. I think tire manufacturers have alittle more experience with their tires than any of us.

 

[Phrede]

I guess you just didn't read my response thoroughly. I said" I start with the tire recommendation printed on the tire, then adjust from there. My question is what does Cadillacs recommendation mean if you've changed their tire. Which 80% of the people on here have done. Just about every passenger car has a operating pressure between 35-42psi. I think tire manufacturers have alittle more experience with their tires than any of us.

I think you may not understand the meaning of the pressure printed on the tire. That is NOT a recommended pressure as I have read in my thorough review of your comments.

The correct tire pressure depends on many things that the tire manufacturer has no idea about when they make the tire. They have no clue how much the vehicle weighs that the tires are ultimately installed on. They DO know what the maximum safe pressure for their tire is, and THAT is what is printed on the tire. It has nothing to do with the correct pressure for the application.

I disagree with your statement that every passenger car tire is correctly inflated at between 35-42 psi, and so do the car makers. That is why the tire pressure placard reads what it does. Why would Cadillac say 30 psi when 42 is OK? That is a 40% increase over their recommendation.

 

[ald42]

The inside of the door show 30psi on all tires so is that wrong for a tires that not a run flats?



Sent from my iPhone using Tapatalk
Dan & Wendy
"05 GRAND DADDY"

original size tires,run or non run flats,go by the door jamb sticker. not max press. on side of tire.

 

[ald42]

I think you may not understand the meaning of the pressure printed on the tire. That is NOT a recommended pressure as I have read in my thorough review of your comments.

The correct tire pressure depends on many things that the tire manufacturer has no idea about when they make the tire. They have no clue how much the vehicle weighs that the tires are ultimately installed on. They DO know what the maximum safe pressure for their tire is, and THAT is what is printed on the tire. It has nothing to do with the correct pressure for the application.

I disagree with your statement that every passenger car tire is correctly inflated at between 35-42 psi, and so do the car makers. That is why the tire pressure placard reads what it does. Why would Cadillac say 30 psi when 42 is OK? That is a 40% increase over their recommendation.

I agree, Al

 

[Stella]

If you look at the tire it gives a max load rating and a max tire pressure. Which means that the tire will handle a max load of specified value and also the pressure. I did not say go by the max reading. I said once again start with that value and adjust from there.
What do the tire engineers go off of then. They design tires, they test tires and pretty much know there limits. All cadillac does is look for a tire with their preferred supplier that meets their specs.
Cadillac knows nothing about tires and the performance of tires that's why I would always recommend the manufacturer specs. Like you had said it's only a recommendation their are many variables.
Tires with little side wall need more pressure or tires with a higher load rating. Now run flats I can see running at 30psi. It has a thick side wall, and cadillac wants a nice plush ride. Go and put 30 pounds in a non run flat and look at the tread contact to the road surface. Bet it looks under inflated. Then take a high speed turn and watch the deflection of the tire.

I've been a mechanic for almost twenty yrs. I've been racing shifter karts,dirt bikes for over 15 years,and been drag racing for over 10. Put many tires to there limits always gone off manufacturer specs have never had a problem. I'm not just reading some articles in consumer reports.

 

[Phrede]

Cadillac knows nothing about tires and the performance of tires....

I'm sure the design engineers would like your number so they can get some help from you. Maybe the racing team as well??

 

[Stella]

I'm sure the design engineers would like your number so they can get some help from you. Maybe the racing team as well??

What would the design engineers for a car have to do with tires. Now they might call a tire rep for specs on what their dealing with.
Do you think the cadillac race team uses factory tires and they look in the manual for their pressure ratings. Pretty funny I called my guy at discount tire and empire tire and they both stated that they would go off the tire spec unless specified by customer? Hmmmmm
I'm not claiming I know all their is to know about tires,but your crazy if you think the car designer dictates what tire goes on the car. That would mean that tires are made for specific cars.
Just like those crazy 26's and even 30's. They couldn't make a rim that large till the tire manufacturers got up to the same level.
Either way I'm just trying to inform I really don't care what you think because your not giving much of an argument other than something you read or some smart ass remarks.
Why don't you ask gizmo if he runs 30psi in his tires.

 

[fcarga]

I would imagine GizmoQ runs different pressures front to back and side-to-side depending on what he's doing
with the car and a whole bunch of variables like temp, surface condition etc. The question under consideration
was/is something wrong with my car because it doesn't "ride" as expected. A little civility would be nice.....

 

[Phrede]

What would the design engineers for a car have to do with tires. Now they might call a tire rep for specs on what their dealing with.
Do you think the cadillac race team uses factory tires and they look in the manual for their pressure ratings. Pretty funny I called my guy at discount tire and empire tire and they both stated that they would go off the tire spec unless specified by customer? Hmmmmm
I'm not claiming I know all their is to know about tires,but your crazy if you think the car designer dictates what tire goes on the car. That would mean that tires are made for specific cars.
Just like those crazy 26's and even 30's. They couldn't make a rim that large till the tire manufacturers got up to the same level.
Either way I'm just trying to inform I really don't care what you think because your not giving much of an argument other than something you read or some smart ass remarks.
Why don't you ask gizmo if he runs 30psi in his tires.

One final post on this and then I'm done:

• You do not know me or my expertise level or engineering credentials, to assume my information is solely based on "something I read somewhere" is far from accurate. I'm also not relying on what some salesman at some discount tire store says.
• Tire and auto manufactures work closely together on tire specifications. On occasion, tires have been developed for specific vehicles. Auto designers may not posses the depth of knowledge about creating the desired characteristics but DO have comprehensive knowledge on the performance aspects of tires, including variables like load, temperature and pressure.
• Tire manufacturers DO NOT make recommendations on pressure settings, they rely on the auto builder to do that, as they have the final data.
• Tire manufactures DO create specifications on every model tire as far as MAX pressure, MAX load, tread wear, temperature and traction ratings. These are NOT recommended pressures or loads, but are not to exceed maximums.
• Pressures used during competition ARE NOT the same as what would be used in a normal street environment. It is a different application with different results desired.
• To instruct someone to inflate their tires to the max pressure listed on the tire is bad advise and could be very dangerous. That pressure could result in an overpressure situation as the tire heats up.

I'm not picking a fight, just taking exception to false claims and bad advice.

 

[MarkSki]

That is factory recommended pressure for the OEM tire. Everything is a compromise and it is no different here. I have found that best performance (over dozens of different car/tire combos, not just and XLR) is usually a few psi above the sticker, but not the best ride. On some cars, not my XLR, front and rear pressures differ. I always adjust then drive to see how things are handling, then repeat. If you are more concerned with ride over performance then you will most likely end up nearer the recommended pressures.

IMHO, I would start at about 33 psi on your tire and go from there. If you like it better at 30psi there is certainly nothing wrong with that pressure. Maybe someone else here is running Pilot SS tires and can chime in. I would try and go for a ride in a different car and compare the rides.

I seem to settle with 32psig all the way around. If I want a little more stopping power Ill go to 33/34 with 34 about the max for the street. Autocross its 40 in the front and 38 in the rear.

Like you said, you have to play with it for your car and prefered ride and handeling.

 

[Phrede]

I seem to settle with 32psig all the way around. If I want a little more stopping power Ill go to 33/34 with 34 about the max for the street. Autocross its 40 in the front and 38 in the rear.

Like you said, you have to play with it for your car and prefered ride and handeling.

What tires are you running, Markski?

 

[MarkSki]

What tires are you running, Markski?

The non-run flat Mich. tires of the same oem size that came on this car when I bought it last July. I'm going to change to a Bridgestone brand when it's time for new tires. I like the grip and non noise of that brands tire. Personnel preference.

 

[HOMEGAMEROOM]

The runflat Michelins, IMHO, are a quieter ride than the runflat Goodyears. I'm waiting for the Bridgestones as well. We'll see what they are like!

 

[airmike]

I emailed a Goodyear help site and got a reply the next day from a lady named Barbara. Asked, if I change tire size from original is there a chart some where to use for air pressure. She was very nice and helpful and said when the time comes to call her and she will take all info, including original size, and pressure recommendations. And then she has a chart to apply new tire size, to weight of car etc...if anyone is interested her number is
330-796-9298.. she seemed to like her job and wanted to help and seemed very knowledgeable.

 

[GizmoQ]

Why don't you ask gizmo if he runs 30psi in his tires.

I would imagine GizmoQ runs different pressures front to back and side-to-side depending on what he's doing with the car and a whole bunch of variables like temp, surface condition etc.

My street tires are 255/40/18 (8.5w) front and 275/40/18 (9.5w) rears. I run 34 up front and 36 in rear for highway use. My race tires are 265/35 front 285/30 rear all 9.5w and yes the pressures are all over the place, as high as 40 or as low as 28, lefts and rights also differ based on track layout.

 

[zeek]

And all this relates to lowering the vehicle how??? Nice hijack guys.....next time start your own pizzing contest about tire freekin pressure....

 

[Phrede]

Also, I know about penetrating oils, but what specific brand does "PB" stand for?

and what does this have to do with suspension lowering??

 

[Stella]

and what does this have to do with suspension lowering??

I'm the one that recommended the pb blaster. It had everything to do with suspension lowering. He asked about the adjustable bolts on the traverse spring and I recommended using some before he attempted turning them.