As stated by those who know, it depends om your driving habits and a few other things .

Back in the 1960's & 1970's is was fairly common to use twenty year old tires and not have failures although they didn't have very good traction .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Well, in the sixties some cars were lucky to get 10,000 miles on a set of tires. The grip was much much less too.
Tires are so much better now it is not funny.

Those old bias ply tires could be long lived too. When I got my old 59 Ferrari it had 20 year old dunlops on it. I had them over 100 mph numerous times before putting new tires on it. The old tires were like rocks.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I'm not going to claim I'm a tire engineer but now you've opened a whole new can of worms with ultra-low aspect ratio tires.

I suspect higher pressures are mainly for fuel economy numbers, as someone mentioned, along with style. They are supposed to then take up the lack of compliance with the suspension, which is not always successful. This gives the feel and impression of better handling and is one of the easiest ways to do that (lack of engineering slight of hand).

The cost of this trend is pretty high but many people dont understand that. Any loss of pressure (flat) results in a total loss of the tire (no more limping along slowly to the next turn off) and I am hearing about alot of catastrophic wheel failures (cast wheels are garbage, but cheap).

I used to run my tires at 5-10 PSI above the factory recommendations and I would constantly have people tell me that my tires were flat, or that I needed to do a better job of inflating them. I'd tell them that the pressure wasn't low, in fact, they were overinflated. But then the edges of the tires would wear out like they were underinflated, despite being inflated to a higher PSI than recommended.

No more! Modern tires (which have changed even since the radials these cars were made with) really do seem to be required to be inflated much higher than the factory recommendations. 40+ PSI in tires when the factory only called for about 28 seems like the correct thing to do, even if it seems insane.

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Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

Tires are load rated at standard pressures, which maintains the specified sectional width. They may also specify a higher pressure for higher loads to restore the correct width and load. All of these specs are agreed by the carmaker and OEM tire mfg. Your results may vary, but changing specs shifts the liability.

I’ve not heard of any problems recently, but some of you with retentive memories may recall the Ford/Firestone snafu. Let me review. Ford built an ugly, clumsy SUV which inexplicably became the best selling POS murican car in history. In developing the car, it was discovered that the static stability factor was unacceptable. SSF is the ratio of the roll center height to the width, and is a contributing factor in rollover accidents. Think tall and top heavy. To make things worse, the horrible suspension geometry caused the roll center to rise as weight shifted over bumps (so called ‘tripped’ rollover.) Ford should have tossed the design and come back with a wider track, lowered the engine and gone with an SLA front end. Of course, too expensive, and the marketing department had spent a decade establishing the twin I beam as technical marvel. So they did a few things like lightening the roof and upper structure, which lowered roll center and improved fuel economy. And when finally out of options, they lowered tire pressure. These changes made the car somewhat less likely to roll. But lower pressure makes tires run hotter, So they went back to Firestone and had them make a cooler running tire. The way this is done is to reduce mass, which is to say, thinner construction. These weak tires tended to fail in hot weather, perhaps because people weren’t checking that pressure often enough, or maybe because they were just too weak. And minor rubber defects which meant little with normal tires proved critical when construction was thinner. This caused rollovers. Increasing pressure prevented tire failure, but raised the roll center height, causing rollovers. The only thing that maybe worked was keeping the pressure exactly spot on. That’s why we have TPMS today. The rest of the story was the rollover catastrophe, with hundreds of deaths and injuries and millions in legal settlements. Engineers don’t always get it right, but the companies have liability when they get it wrong. You can relieve them of that responsibility if you want to, but you probably can’t fix the engineering.

I thought the problem with the ford suvs was that Ford ignored the tire mfgr advice and recommended lower tire pressures to improve ride. Then the underinflated tires would roll off the rim if the car slid sideways causing it to roll over.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

No, the explanation I gave is a pretty good synopsis. It’s all in the court records.

Car and driver did a test where they rigged tires to deflate while driving, the Explorer didn't roll over. https://www.caranddriver.com/features/a15139397/why-are-ford-explorers-crashing/

Why are Ford Explorers Crashing? CSABA CSERE Jan 1, 2001

I recall that in the roll over crashes related to tread separation, the tire was still fully inflated and only lost the tread cap. Also, the vehicle only rolled after it left the road way. ( driver panic )

At the time our cars were made (1970s and 1980s) the tire pressures recommended by Mercedes may have been spot-on (maybe--it's possible they may have been on the low side to give a softer ride), but tires seem to be different these days, and seem to require higher pressures (since the tires seem to look like they are flat and wear like they are underinflated).

While it seems good practice to use the tire pressures recommended by the automobile manufacturer, it may not apply to today's tires. I don't think there is a possible situation where I could sue Mercedes for something related to tires since my car is so old and the tires are not original, so there is really no liability on their part that I'm giving up by running higher pressures. I'm sure this would be different if I had a recently-made Mercedes, however, the tire pressures would have been calculated for the technology of the tires that were on it.

__________________
Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

I'm still interested in finding what the original tires weight / max PSI rating is. Someone has to have an original tire floating around somewhere.

On my 84 300SD the GVWR is 2315 lbs for the front and 2435 for the rear.
I have the original Data Card and it lists the tires as Continental 09/4 ??



Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Here is an excerpt from the Wiki article about the subject:

Investigation and Possible Causes
On March 6, 2000 NHTSA began a preliminary inquiry[17] and on May 2, NHTSA began an investigation (PE00-020)[2] concerning the high incidence of tire failures and accidents of Ford Explorers and other light trucks and SUV's fitted with Firestone Radial ATX, ATX II, and Wilderness tires.[2] On August 9 Firestone recalled all ATX and ATX II tires and all Wilderness AT tires manufactured in Decatur, IL. On August 31, 2000 the Office of Defect Investigation (ODI) upgraded the investigation to an Engineering Analysis (EA00-023) to determine whether Firestone's recall covered all the defective tires.[2]

Ford and Firestone both issued root cause analyses to NHTSA.[2] Firestone argued that vehicle weight, tire design, low recommended inflation pressure, and lower tire adhesion for tires manufactured at the Decatur, IL factory contributed to the tire failures. Ford argued that the tire design led to higher operating temperatures compared to similar tires manufactured by Goodyear and that differences in manufacturing at Decatur led to weaker tires that were more prone to failure. Ford also argued that the size of the wedge, a strip of rubber between the first and second belts, is smaller in Firestone tires than Michelin tires making them weaker than comparable Michelin tires.

Publicly Firestone argued that Ford's recommended 26 psi inflation pressure was too low and should have been 30 psi.[7] In addition Firestone argued that the Explorer was abnormally dangerous and prone to rollovers in the event of a tire failure, leading to more injuries and fatalities. In the words of Firestone CEO John Lampe, "When a driver of a vehicle has something happen such as a tread separation, they should be able to pull over not rollover."[18]

Ford argued that the Explorer was no more dangerous than any other SUV[19] and that the accident rate for Explorers with Goodyear tires was far lower than for Explorers with Firestone tires.[20] Ford also argued that there was something wrong with the design of Firestone tires and with the manufacturing of those tires at the Decatur, IL factory.

Some outside observers speculated that both parties were to blame suggesting that[14] Firestone's tires being prone to tread separation and failure, and the Explorer was especially prone to rolling over if a tire fails at speed compared to other vehicles.[21]

Ford Explorer

'91-'94 Ford Explorer

95-98 Ford Explorer
The Ford Explorer was first offered for sale in March 1990.[22] The Explorer was originally designed by taking an SUV cabin and attaching it to a Ford Ranger undercarriage. This cut the cost of producing the new Explorer because Ford could use existing facilities, parts, and robots and wouldn't have to design everything from scratch.[23] This created problems though. Because the Explorer was taller like a pickup truck, it had a higher center of gravity and was more likely to roll over in the event of accident. It was also more likely to sway during sharp turns because it used the same leaf spring suspension that is found on the Ranger.[23] The likelihood of a crash and likelihood of injuries and fatalities from a crash were greater in an SUV experiencing a tread separation than on a pickup truck.[2]

Ford came up with three options for correcting this problem; use shorter suspension springs to lower the vehicle half an inch in the front and 1 inch in the back, lower the tire pressure to give the Explorer a more car-like ride, or widen the wheel base by two inches which would involve a substantial redesign.[23] After the Explorer rolled over in company tests prior to production Ford decided to lower the suspension and remove air from the tires to 26 psi compared to 35 psi for the same tires on the Ranger.[14][24] They did not widen the wheel base.

Sorry but I think the wiki article supports my statement.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yup, exactly.

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CENSORED due to not family friendly words

It does support your statement, and the article also agrees with the recall letter we received. We had a '96 Exploder as our family car that we bought new. My dad always kept the car serviced "by the book" and wondered about the low tire pressure, but maintained it anyway. Our first tire came apart 7000 miles into ownership, the second, a couple thousand miles later. Had the tires changed to Michelins (that outlived the car) and kept them inflated to 30PSI. Part of the recall was to affix a new door sticker with tire pressures at 30PSI.

The laughable part is that the recall letter that came out in late 2000 offered a free replacement set of tires if the original Firestone turds were still fitted, or something like $50 towards the replacement cost if the owner had already replaced them. Yeah, sure, like those crappy tires would still be installed 5+ years later. LOL!

Don't forget about the multiple recalls on the '95/96 Exploders with their torsion bar front suspension. During cold weather and hard cornering, they were known to snap. Only in northern climates would they replace them, so we were stuck with the stock ones that sagged to the point the front wheels splayed out, even with the adjusters at full rotation. POS turd of a car only made it 71,800 miles before the garbage tranny died and we finally unloaded that nightmare of a vehicle.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thanks

Crunching the data:

The OP's modern tire is Michelin Defender in 195/70R14 is rated at 1,356 lbs when inflated to 44 psi

The OP's and your 84 300 SD has a per wheel max weight of Front 1,158 LB and Rear 1,218 lb

The factory inflation for full load is Front 30 PSI and Rear 34 PSI

I'd need to see a load Vs inflation chart but on the surface, the factory specs seem woefully low for a modern tire.

Data I still need:

Factory tire load rating / max inflation.

84 300SD empty front / rear weights ( or payload rating )