Recommended tire pressure is calculated by tire rating and load... I'm not sure how its calculated but sometimes stock psi isn't the right pressure for after market tires unless you got the same spec tires as stock.

I would go with what the specialist told ya.

 

^^ I agree. But the load factor in the report varies by <1%, but the recommended tire pressure differs by >8%.

Also the message dada received from Falken Tire Corporation states the fronts have a load rating that is less than stock, and rears have a load rating greater than stock.

42 psi is pretty high. Imagine starting a road trip on the expressway driving at high speed in hot weather. The psi will increase (creeping towards the maximum 50 psi limit for the tire).

If Falken is advising such a high psi, it must have something to do with the tire’s construction and the low profile on a 20” wheel. This seems odd to me, but apparently Falken tires (or at least this specific Falken tire) needs a very high psi to compensate for whatever.

Like dada, I am also confused.

--Spike

 

For what it's worth, Saturday I got 245/35-19 and 275/35-19 Falken 452's and the installer said the proper pressure was 38, not 35 psi as recommended.

 

So… Apparently you do this with Falken tires and the Z?

• 18” wheels with Falken tires and the Z you fill to 36 psi?
• 19” wheels with Falken tires and the Z you fill to 38 psi?
• 20” wheels with Falken tires and the Z you fill to 42 psi?

And, with any other tire brand (the exception being Falken) on the Z, you fill to 35-36 psi no matter the tire or wheel size?

So why is Falken different in this requirement?

--Spike

 

[QUOTE=Spike100;6994704]So… Apparently you do this with Falken tires and the Z?

• 18” wheels with Falken tires and the Z you fill to 36 psi?
• 19” wheels with Falken tires and the Z you fill to 38 psi?
• 20” wheels with Falken tires and the Z you fill to 42 psi?

And, with any other tire brand (the exception being Falken) on the Z, you fill to 35-36 psi no matter the tire or wheel size?

So why is Falken different in this requirement?


The reinforced tire seems to have a Extra Load tire making the tire carry a greater maximum load at a higher inflation pressure than the Standard Load tire and will have a higher maximum inflation pressure.

It seems therefore, that at 35 psi our standard stock tire can carry a load of X. When upgrading to a different tire size this is our target number. Also our OEM tires have a load index of 91 for front and 96 for rear but the new tires have 90 in front and 97 in rear.

At 35 psi our standard tire can only carry a load of X. and the Extra Load Falken can carry a load that is actually slightly worse at Y! This explains why the Falken dude said what he did. Quite literally if I were to fill the Falkens with 35 psi this is about the same as running my stock at about 15 psi!!!!!! In fact if I put less PSI in the Falkens, it would seem that the tire will possibly overheat, fail and blow out.

In order for the load rating to match ,it seems my Reinforced Tire as an Extra Load version will match the load rating if only I pump them up to 42 psi where you will get a load capacity of equal to X, the original load capacity of the car. To compensate for Y, I have to increase the air pressure which a reinforced tire can take?

Anyway thats how I am now making sense of it.

 

It isn't necessarily Falken. It's just the tire load rating with that specific tire. dada explains it perfectly above. (if still confused look @ yahoo link from dada... Mark F knows what he's talking about if you go through his answers he explains it in more detail but its still a little difficult to understand the calculation)

42psi isn't dangerous unless you have long trips and/or driving hard (But also don't forget max tire pressure rating is also at cold temp). The most my psi has gone up after an hour drive would be 3-4 psi. But to dada, i would watch your pressure closely and adjust accordingly to temperature change just incase... or fill up on nitrogen

 

also spike 42 out of 50 isn't that bad compared to 35 out of 40.... (stock tires)

 

ill let you know how it works out, for the first 2-3 days i was driving with 45 psi because the technician who installed the rims didnt want to reduce the psi, i am now at 38 and it doesnt drive as well as it did with 45 so im going to go now to 42 and report back

 

It appears that I’m wrong here, and you are right.

I’m also on a Mazda RX forum (I like the Mazda, but still prefer the Z), and members here recommend running the Falken 452 tire at 6 psi over the stock psi (psi recommended for the car with OEM tires) as you suggest So… on the Z that would in fact be what you suggest (36+6=42 psi).

I still don’t get the relevance of the “load rate” since it seems to be the same. But, apparently the Falken has additional reinforcement that requires a higher psi. If you run with too low a pressure (the Mazda RX forum members also recommend 42 psi), the reinforced Falken tire flexes excessively, and warms to a potentially high psi level. I believe that was also the point Voboy makes.

I think the concept and reality is that the Falkens’ reinforced tire-structure maintains psi more consistently than “other/normal tires,” and you never need to worry about the tire heating and the psi increasing excessively if you run at the suggested psi (which is higher than what you might choose if basing your thinking in what other tires use for “normal” psi on the Z car). Keeping the psi relatively high (by Z standards for the majority of tire brands) on the Falken in fact prevents excessive pressure gains in even the most demanding situations (high speed driving in hot weather).

Is that correct? ...I’m not sure. My message here might be completely bogus.

--Spike

 

Yes thats is absolutely correct. Can you send me the link on the mazda forum would like to see what they say.

 

Better than that: If you “Google” Falken 452 + psi (also do “Falken + pressure”), you see many different opinions on various forums, not unlike what you see on your thread here. There’s some interesting reading and opinions on these links. One thing I notice reading these links/threads is that some (many?) Falken owners backed the psi down from an initially high value to the car’s recommended “stock” psi.

Here’s a link to Falken’s warranty page that has charts for psi related load index.
http://www.falkentire.com/xhtml/technical_warranty.php

Notice that 42 is the maximum value on the chart for a reinforced Falken tire. It seems odd that the Z would require the maximum psi, but as you point out, Falken technical services provided this recommendation to your inquiry for the Z. You have 20” wheels (not exactly a common size), so that might be a factor that sends the value “off the chart.”

I’m not sure what to think since 42 psi is so high, but you do have a definitive answer directly from Falken, and that is hard to dispute.

--Spike

 

i have falken 452, w/245/40/18 front, 275/40/18 rear.....what is proper tire pressure i need to set? 35 all around?

 

I hate to dig up an old thread but something is not adding up. I have tires that are rated 93 up front and 100 in the rear. I haven't been able to find a definitive answer for finding the 'right' psi for that load. This thread was the closest thing I could find.

I could be completely missing something and I probably am, but using the formula as provided earlier (http://www.vanagonauts.com/Tire-Pressure4.htm) gives me inconsistent results with what Falken recommends.

Assuming the wheel size has nothing to do with anything and all we're looking at is equating the stock calculated load to the new tires. This also assuming the load scales the same way for each tire as pressure increases. (This assumption may be completely wrong and why the equation doesn't work, or perhaps the equation provided is wrong?)

Stock load index: 91 (1356lbs)F, 96 (1565lbs)R @ 35psi for both ends where 51psi is the max on RE050a.

That comes out to:
1356 * (35/51) = 930 lbs*psi up front
1565 * (35/51) = 1074 lbs*psi rear

New tire load for Falkens and max pressure: 90 (1323lbs), 97 (1609lbs)

930 = (x/50)*1323
x = 35.147psi Front

1074 = (x/50)*1609
x = 33.37psi Rear

Those values are far from 42 all around. Whats going on here? After running the same exercise with my tires, I get 32psi up front and 30psi in the rear, which seem really low. Are 'tougher' tires suppose to run lower psi? Seems counter intuitive from what Falken claims.

 

just put 35 psi in them and call it a day.

 

I don't know where the hell they got that equation but if you look in a different recent thread about tire pressures (have to search), I have described how to correctly calculate what pressures you need and there's a link to a table also.

 

Email Falken they will do the math and give you the right answer thats what I did

 

There's a fundamental problem in what Falken and some people are doing here. Yes, manufacturers have tables of max load data for given tire size, rating, inflation pressure.

For example, the OEM rears 245/45/18" XL @ 35 psi have a max load of 1521 lbs. That is the maximum that tire can safely carry at 35psi. What Falken is doing is going to the chart and looking up 275/30/20" XL and finding the corresponding pressure that matches 1521 lbs and is coming up with 42 psi (on my chart I read 39 psi). What that means is that you can inflate that tire up to 42 (or 39) psi and safely carry 1521 lbs, just like the OEM tire did.

What you are failing to see is that this is the LIMIT of load carrying capability. The Z doesn't weight 6000 lbs so the tires are never going to see that much loading. 42 psi has nothing to do with the NORMAL psi that the should go in the tire. Notice that tires aren't stamped with inflation pressure, they are stamped with MAX inflation pressure. The tire manufacturer knows nothing about the car the tire is going on so there's no way they can recommend a pressure. All they can do is calculate the max load.

The car manufacturer comes up with a recommended pressure based on the car weight, suspension, handling characteristics, acceptable wear, and other factors. As long as that pressure in combination with the actual load on the tire (weight of the car) and tire rating are below what the charts say, there is no problem.

Sure 42 psi handles great. I ran 40psi in my Falken Azenis for autocrossing. I bet on the street it's "teeth rattling" hard and eventually the bulging centerline will wear out prematurely. I'd guess for almost any tire we can fit on a Z, the real world, practical inflation pressure is 35 ± 3psi.

One thing I find interesting about Falken's reasoning that XL tires can hold more pressure is that their logic seems backwards. On soft sidewall tires, we normally run a few PSI higher than normal to stiffen them up. If you have reinforced sidewall tires, you don't need the extra PSI to get good handling, that's what the stiffer sidewall does for you.

 

I highly recommend everyone who doesn't understand this stuff to read this document - it spells everything out:
http://www.tiresafety.com/images/Tir...t%20Manual.pdf

For example, if you had read this Dave you would have known that the load rating corresponds to the maximum speed rating of the tire, and that reinforced or XL tires require more pressure to attain the higher load capacity, and that some XL tires may actually offer less load capacity at some or all inflation pressures... I know it seems complicated but if you stop trying to poke holes in it and just follow the ratings it's very easy.

 

Actually, that's the manual that I'm using.

You refer to "reinforced or XL tires require more pressure to attain the higher load capacity". Load capacity is a limit, not the everyday setting. Yes, if you want to carry more, use higher pressures. We're talking about 6000 pounds of load capacity and the Z weighs half that, so nobody will be near the load capacity of their tires.

Note that the heading on every page of those charts says "Tire Load Limits in Pounds (lbs.) at Various Cold Inflation Pressures in Pounds Per Square Inch (psi)" - it's doesn't say anything about normal operating pressure. You're supposed to be an engineer, you know about normal operating conditions vs max operating conditions, right? Virtually no one operates their car at the limits of it load capacity on a daily basis.

I'm still trying to find a car that the manufacturer recommends a pressure in the 40 psi range. If what you say is true, surely there would be factory recommendations in that range (short of some big truck tires).

Apparently owners/managers/shop foremen at tire shops are unaware of this information too, none of them has ever recommended such a high pressure or warned me that my pressure are too low.

 

I cannot find an automobile manufacturer producing a 2-door performance car that recommends running 42 psi in its OEM summer performance tires (please correct me if I’m wrong here).

The OEM recommendation (for a lot of different OEM tires) for this type of car is always around 36 psi (plus or minus 3 psi).

Of course, I’m referring to a moderately light car (a “sport car”) equipped with summer performance tires. An SUV or heavy sedan has very different specifications depending upon its load factor. For example, I ran 40+ psi on my Montero, equipped with 33” Michelin Mud/Snow tires, when I loaded the vehicle with lots of gear and people.

--Spike