Air Pressure Used with the KDWSs?

[WhatsUpDOHC]

Hi -

I've tried to search for a thread on this but haven't found anything.

Just wondering where you run your tires.

Do you keep them at 32PSI as specified or do you pump them up a bit higher?

Mark

[justbob]

From research in the past I heard 40 PSI. I tried that this go around and nope, just the same as usual.

[DOOM]

I run 40psi!

[1stMerc]

I run mine at 40 psi

Don't believe there was ever a definitive answer.

[Mr. Man]

Run ours at 36 front 37-8 rear.

[Bluerauder]

35 PSI front and 38 PSI rear. I average 36K miles on the front KDWS and about 21K miles on the rear KDWS. Have never experienced the inside wear on the fronts. Only got 15K out of one set of GoodYear Eagle F1's so I'm back to the OEM. I like 'em for handling and ride despite the general negative comments from many on MM.Net.

Door stickers on the 2003 MM said 32 PSI all around. This was changed in 2004 to 35 PSI all around. Even 35 PSI rear did not stop the excessive center wear on the rears --- this was discussed almost continuously in the early days of MM.Net. Our tires act exactly opposite to conventional wisdom on tire inflation. More pressure in the rears reduces the center wear problem. There's a thread in here somewhere from a tire expert that explains that this is a common trait on performance tires with stiff sidewalls. When I have more time, I'll go find it. :D

Posted in a thread from April 2007 >>>> http://www.mercurymarauder.net/forums/showthread.php?t=35011&highlight=tire+expert



*RE: RE: ???Center wear on rear KDWS's
by TireNerd2
February 23, 2005 8:28PM


Nope. The KDWS does not have a softer compound in the middle of the tread. The KDWS uses a single tread compound accross the entire face of the tread. Center rib tread wear can be caused by many things. However, take it from me as a Tire Designer (6 years) and Ex-Test Driver for BFG (6 years), rear wheel drive, high horsepower, and high torque applications that exhibit accelerated center rib wear usually benefit from INCREASING cold inflation pressures. Now I know absolutely everyone in the public domain will tell you accelerated center rib wear is caused by over inflation, but believe me it's also caused by under inflation on the 'driven axle'. So in a sense both situations lead to center rib wear depending on whether the axle is being driven or not i.e. whether the tire experiences an engine driving torque or not. Adding some air to the rear axle of the Marauder in this example will stabilize the contact patch and help it maintain its shape better by keeping more rubber on the road under a driving torque. Essentially, if a driven axle tire is under inflated when it experiences a high driving torque, the leading edge of the contact patch is forced into the road and the trailing edge of the contact pathch is 'pealed' up (you can watch dragster tires do this when they stage at the line). When this happens the unit contact pressures increase at the leading edge of the contact patch, which increases contact stresses and accelerates wear. The centerline of the contact patch just happens to be the location of highest contact pressures and so exhibits the highest wear rate. I know this may sound odd - and I know maybe counter to what you've heard BUT adding air reduces center rib wear in higher horsepower applications by stabilizing the contact patch shape. Keep in mind O.E. inflation pressures are a comprise by the manufacturer for ride and handling and not optimized for tire wear life. So add at least 5 to 7 psi cold to the rear axle tires and the KDWS wear life should increase.

[justbob]

I never once experienced the inside wear either until I lowered it. Can't even get it close to carfixers specs. Now she eats up the inside very fast.:mad:

[FordNut]

36-38 front, 38-40 rear

[breeze]

30 front 32 back. Im probably the only person likes the bfgs

[RF Overlord]

Ford changed the tire pressure from 32F-32R in '03 to 35F-35R in '04. Since nothing else in the suspension changed, I figure there was a good reason for upping the pressure, like reducing wear or improving handling.

I run 35F-38R as that was the general consensus back when it was discovered that the rears were wearing the centres abnormally and that increasing the pressure helped.

And before one of the new people chimes in with "but that's backwards", normally you would be right, but even BFG engineers stated that for the OEM rear tire size on an 8" rim, increasing the pressure reduced "ballooning" and improved the centre tread wear.

[Comin' in Hot]

I never once experienced the inside wear either until I lowered it. Can't even get it close to carfixers specs. Now she eats up the inside very fast.:mad:

My blue was that way, so I installed SPC camber bolts, now I have car fixers specs with lots of adjustment to spare

[tbone]

35 all around. Fronts wear perfectly. Rears, same as everyone else. Got 25k out of the last set, but I don't do burnouts. I'm perfectly happy with the BFG's and will never switch.

[guspech750]

I have Generals and I believe I have them at 44psi.


---
- Sent from my iPhone
Eaton Swap + 4.10's = Wreeeeeeeeeedom!!

[Bluerauder]

I have Generals and I believe I have them at 44psi.


You may want to check your MAX pressure rating on your tires. It is printed on the sidewall. At 44 psi, you may be above 90% of MAX and be into questionable inflation territory.

MAX Pressure in the OEM KDWS is 45 psi. Tire manufacturers recommend never going above 90% of the MAX rating ... so 40-41 psi is recommended tops for the OEM KDWS from a safety perspective. This also provides a buffer for increasing pressures as the tire heats up in use.

[Paul T. Casey]

Im probably the only person likes the bfgs

Nope, I love 'em. Back on topic, I run 32 front, 34 rear, seems to work. 42 front, 23 rear at the track.

[WhatsUpDOHC]

35 PSI front and 38 PSI rear. I average 36K miles on the front KDWS and about 21K miles on the rear KDWS. Have never experienced the inside wear on the fronts. Only got 15K out of one set of GoodYear Eagle F1's so I'm back to the OEM. I like 'em for handling and ride despite the general negative comments from many on MM.Net.

Door stickers on the 2003 MM said 32 PSI all around. This was changed in 2004 to 35 PSI all around. Even 35 PSI rear did not stop the excessive center wear on the rears --- this was discussed almost continuously in the early days of MM.Net. Our tires act exactly opposite to conventional wisdom on tire inflation. More pressure in the rears reduces the center wear problem. There's a thread in here somewhere from a tire expert that explains that this is a common trait on performance tires with stiff sidewalls. When I have more time, I'll go find it. :D

Posted in a thread from April 2007 >>>> http://www.mercurymarauder.net/forums/showthread.php?t=35011&highlight=tire+expert

Thanks Charlie/Everyone!

I've been wanting to ask this question for a while - 32F/32R sounded soft to me.

I'll play with all suggestions - Mileage has to improve, regardless.

Thanks again,

Mark

[screamn]

35 psi all around! Nice ride & good traction IMO.

No exceesive wear in the middle of the rear tires but they are Riken's with about 28k miles. Might have to up the pressure to 36-38 when I put on the Nittos.

Fronts have Nittos and seem just fine with 35 psi.

[1stMerc]

30 front 32 back. Im probably the only person likes the bfgs

I like the BFG's. Just to hard to find at a a good price, when time comes to replace.

[1stMerc]

35 psi all around! Nice ride & good traction IMO.

No exceesive wear in the middle of the rear tires but they are Riken's with about 28k miles. Might have to up the pressure to 36-38 when I put on the Nittos.

Fronts have Nittos and seem just fine with 35 psi.

I ran my rear Nitto 420s at 40 psi 20k and they wore nice and even. Still plenty of tread. Just not enough to risk if get caught in snow. Probably put them back on when snow season ends.

[Bluerauder]

Thanks Charlie/Everyone!

I've been wanting to ask this question for a while - 32F/32R sounded soft to me.

I'll play with all suggestions - Mileage has to improve, regardless.

Thanks again,

Mark

I guess that I should have also said that I replace my tires at or before they enter the "Red" zone .... somewhere around 4 mms. The 36K fronts and 21K rears still had ~ 4 mm tread on them at replacement using the 35F/38R scheme. I don't like running without good tread on the tires and never run them down too far. :D Brakes and tires are 2 things that I won't cut corners on.

[WhatsUpDOHC]

I guess that I should have also said that I replace my tires at or before they enter the "Red" zone .... somewhere around 4 mms. The 36K fronts and 21K rears still had ~ 4 mm tread on them at replacement using the 35F/38R scheme. I don't like running without good tread on the tires and never run them down too far. :D Brakes and tires are 2 things that I won't cut corners on.


You should sell them to DOOM for futher "baking".........

[screamn]

I ran my rear Nitto 420s at 40 psi 20k and they wore nice and even.

I'll keep it in mind when I put on my 420s which is in the next 2-3 weeks.

Thanks!!

[BirchMarauder]

30 all the way around...using nitrogen. No pressure fluctuations. Perfect wear, front and rear.

[WhatsUpDOHC]

Hi -

I've tried to search for a thread on this but haven't found anything.

Just wondering where you run your tires.

Do you keep them at 32PSI as specified or do you pump them up a bit higher?

Mark


Houston, we have 35F and 38R with a full tank of gas (Checking mileage change).

Thanks again,

Mark

[Zim Hosein]

Do you keep them at 32PSI as specified or do you pump them up a bit higher?

Mark

I drive an '04 and all four tires are running at the recommended T/P according to the sticker on the fuel filler door, hope this helps Mark. :)

[Bluerauder]

I drive an '04 and all four tires are running at the recommended T/P according to the sticker on the fuel filler door, hope this helps Mark. :)

I bet that I have opened and closed that gas door nearly 350 times in 8 years and really never noticed that ^^^^^ little sticker until this post. :rofl: It even has tires sizes F&R, recommended tire pressure, and the VIN on it.

[kirk]

When I was at Ford's Dearborn Proving Grounds for the panther event in 2004 the Ford engineers were running 38 psi on all 4 corners of the Marauders running the track. Actually had stickers at each wheel well with the pressure. Gotta believe they knew what they were doing and had a reason.

[Svashtar]

I have had the stock tires, the KDW2's, and now the Nitto 555 extreme Z-rated tires. I really like the Nitto's best overall. The KDW 2's cost me $1000 for the set, but it could be argued they were slightly better in the wet. I like the Nitto's because they wear like iron, and that they cost $250 less is a bonus, and I've never had any control problems with them. Noticed some bad wear on the outside of one front and inside of another, but had the front end realigned using specs from this site and the problem went away. I should just make 30K on the fronts.

The fronts are the stock size of our MM's and state a max PSI of 50 lbs, while I went the same overall sidewall height in the rear, but with a slightly wider tire, which looks better and has a max PSI stated of 44. I've just been running 40 PSI all around, which is 80% of max for the front and 90% for the rear. After 25K I'll bet there is still 4mm left on the sides of the rears, but the center rib is showing the tread flush with the wear indicators, which sucks a bit, as I don't quite think they'll make 30K unless I push it.

I think I would have done better but ran the rears at 35 psi. until just a few months ago when I went to 40 all around.

[Rkammer]

I run 38-40 PSI cold pressure in all 4 tires. I've been using the forum recommended front end specs since after the first set of KDWS came off and my front end man has had no trouble setting those specs. No irregular tire wear front or back. I'm currently running the newer Cooper RS3-A factory replacement sizes front and back and love them.

[Zim Hosein]

I run 38-40 PSI cold pressure in all 4 tires. I've been using the forum recommended front end specs since after the first set of KDWS came off and my front end man has had no trouble setting those specs. No irregular tire wear front or back. I'm currently running the newer Cooper RS3-A factory replacement sizes front and back and love them.

Out of curiosity, I wonder how much of an increase there is between "cold" pressure and "at temp" pressure. I know ambient temps play a big role, but IIRC, the MAX T/P on the sidewall of the KDWS' are 44 PSI... :confused:

[Rkammer]

Out of curiosity, I wonder how much of an increase there is between "cold" pressure and "at temp" pressure. I know ambient temps play a big role, but IIRC, the MAX T/P on the sidewall of the KDWS' are 44 PSI... :confused:

Here is Florida, the difference between cold pressure and hot (at temp) pressure can be as much as 4 or 5 PSI. I believe that is taken into consideration when manuf. specify max pressure. In other words, 44 PSI max means as measured when cold and it would be OK for pressure to get to max when they are heated up.