I don't keep cars long enough to worry about tread wear. ha ha

 

Tire pressures have always been a mystery. The heavy part of any car (Engine forward) is the front, sooooo, why is it, most all tire pressure placards have the rear tires with the highest pressure?

Just wondering. Anyone know?

 

biases handling towards understeer == keep amateurs out of trouble and away from
personal injury lawyers.

 

Hi Guys. Others have thrown the BS Flag when I've reported this before, but it's true. I am just now replacing the rear tires I bought in 2012. Kitty is my daily driver and long distance GT. Highway speeds are usually 80 mph, but she sees 100+ every once in a while as a treat. I don't push the car handling-wise much, but I do enjoy dropping a gear or two and nailing it for back roads passing. I've always run 43-45 psi in all four tires. The rears have worn unbelievably even. "All" the wear bars are just about to breach the surface. If there's any asymmetry in the wear, it is the inner side of the tires wearing infinitesimally more than the outer; not center vs. outer.


They have just over 80, 000 miles on them. I am not kidding.


I've never had a set of tires last this long, let alone wear so evenly. To be honest, they're a bit slippery on wet roads, but are not prone to hydroplaning (good tread pattern). The car is an absolute dream to drive at 90 mph.


For those of you interested in a quiet, long wearing tire, try the Falken Azenis PT-722, if you can find them. I couldn't this time, so I'm replacing them with a very affordable experimental alternative: Ohtsu FP7000 255/45R18 99W. They cost just over $100 each (delivered!). I'll be running the same high pressures. We'll see how they work-out.

 

Registed to this forum to answer.
Live and was born in Holland ( Europe) and once got hold of the formula officially used to calculate pressure for a sertain load on tire with all the extras for speed and camber angle.
Went running with it and learned myself Excell to make spreadsheets for it.
Made a mission of it and google dayly on tire/tyre-pressure to see if I can give advice.
Call myself nowadays "Duch Pigheaded Self-declared tirepressure-specialist.
Because I dont own a Jaguar and only react to tire-related questions, I dont think its usefull to introduce myself in a seperate topic, but if wanted, I will do so.

first thing that is not totally correct is the 50 and 51 psi maximum pressure.
A standard load P-tire always have a pressure needed for the maximum load , up to 160km/99m/h of 35 psi ( EUR tyre 36 psi with exeptions to lower).
A XL/reinforced/Extraload P-tire this AT-pressure( as I will call it furtheron) is 41 psi ( EUR 42 psi with exeptions). On sidewall is given for those tires maximum allowed cold pressure , and difference is used to highen up the AT-pressure for higher speed.

LT tires only give AT-pressure on sidewall, if its given , and so maximum allowed cold is higher. Most American tiremakers allow 10 psi higher then AT-P. Seen in Eur document 1.4 times AT as max allowed cold.

Then second is your calculation, havent checked it , but probably lineair calculation. Not that bad but if you would use the ideal formula to laws of nature, wich I determined in time, it can be lower pressure for same load.
So forget all the pressure/loadcapacity lists and only go from maximum load, AT-pressure and speed you drive and wont go over for even a minute, in relation to the maximum speed ( or speedcode) of tire.

Then looking back in old american lists you will get higher loads , because up to 2006 the calculation was different in America. and still is now for LT and TRuck tires. Leads to higher loads for the pressure, or other way around, higher pressure for same load.

Added a picture I made to show what acording to the EUR system I got hold of , the AT pressure has to be highened up for speed, different system for different speedcodes, and even maximum load lowering for speeds from 30 km/h below max for V,W,Y tires.

I am also known for my long story's, so to make it short, mail me at my hotmail.com adress with same username as here ( combine yourselfes, spamm machines cant this way...I hope) and I can give you many documents and spreadsheets and info and always willing to discuss.

Greatings from this Dutch Pigheaded Selfdeclared tirepressure-specialist.
( ja dat is ) Peter ( from a duch namesong , translates as yeah thats Peter ).

 

I have extreme contact continentals on my detroit wheels. After having the car sit for awhile, two tires developed dry rot & cracking. I replaced them at some point last year and today I managed to hit a pothole with my newly refurbished wheels...Isnt that how it always goes?. Wheel seems ok except for a little tweek in one of the trim rings..THE BRAND NEW ONES....ANYWAY... I have a few questions.

1) Why is the front tire taller than the rear when you can get a 295/30/20 which is the same diameter as a 255/35/20
2) Can a 295/30/20 fit in the rear?

A little more sidewall and width would be ok in my books if it will fit.

Thanks guys...Totally disgusted at the moment