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Split/Different Front and Rear Cold Tire Pressures
Split Cold Tire Pressures: Front-to-Rear
I understand the technical reasons for why some car makers specify different cold tire pressures for the front and rear axles of certain models. My question concerns those vehicles (except for the obvious: large SUVs and work vans) for which different pressures are specified, vs vehicles for which a single cold pressure is recommended all around(all four wheels): IE: Makes and models with less of a Front/Rear GAWR(Gross Axle Weight Rating ie: less than 55/45) - Audi, BMW, Mercedes, Subaru, etc., might specify up to a 5psi difference for the Front vs Rear axle pressures, where as makes with a significantly higher Front/Rear weight split(60/40) - Chevrolet, Ford, Honda, Hyundai, Toyota, etc., recommend a single pressure value for front and rear Axle - in particular front-wheel drive models. Typical late-model European sports sedan or wagon recommended cold tire pressures: F/R: 32/36psi Typical late-model domestic or import front-wheel drive sedan or wagon cold pressures: F/R: 30 to 36psi, all tires. My theory: The former are built for a more discriminating, enthusiast driving demographic whom will pay more attention to such things as different front/rear axle tire pressures, while the latter are built for the blue-collar masses, whose main priority is economical transportation in reasonably well equipped, reliably built vehicles, and live a busy lifestyle where it is easier to remember one PSI number - a compromise I'm sure - to set all of their tires to. What's your feeling behind this difference? |
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Split/Different Front and Rear Cold Tire Pressures
On 8/18/20 12:26 PM, Chris K-Man wrote:
> Split Cold Tire Pressures: Front-to-Rear > > I understand the technical reasons for why some car makers specify different cold tire pressures for the front and rear axles of certain models. My question concerns those vehicles (except for the obvious: large SUVs and work vans) for which different pressures are specified, vs vehicles for which a single cold pressure is recommended all around(all four wheels): > > IE: Makes and models with less of a Front/Rear GAWR(Gross Axle Weight Rating ie: less than 55/45) - Audi, BMW, Mercedes, Subaru, etc., might specify up to a 5psi difference for the Front vs Rear axle pressures, where as makes with a significantly higher Front/Rear weight split(60/40) - Chevrolet, Ford, Honda, Hyundai, Toyota, etc., recommend a single pressure > value for front and rear Axle - in particular front-wheel drive models. > > > Typical late-model European sports sedan or wagon recommended cold tire pressures: F/R: 32/36psi > > Typical late-model domestic or import front-wheel drive sedan or wagon cold pressures: F/R: 30 to 36psi, all tires. > > > My theory: The former are built for a more discriminating, enthusiast driving demographic whom will pay more attention to such things as different front/rear axle tire pressures, while the latter are built for the blue-collar masses, whose main priority is economical transportation in reasonably well equipped, reliably built vehicles, and live a busy lifestyle where it is easier to remember one PSI number - a compromise I'm sure - to set all of their tires to. > > What's your feeling behind this difference? > Ya' got way too much time on your hands, dude ;-) -- Why is it that the people who want more government control over your life are the same ones who want you to be disarmed? |
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Split/Different Front and Rear Cold Tire Pressures
On 8/18/2020 11:26 AM, Chris K-Man wrote:
> Split Cold Tire Pressures: Front-to-Rear > > I understand the technical reasons for why some car makers specify different cold tire pressures for the front and rear axles of certain models. My question concerns those vehicles (except for the obvious: large SUVs and work vans) for which different pressures are specified, vs vehicles for which a single cold pressure is recommended all around(all four wheels): > > IE: Makes and models with less of a Front/Rear GAWR(Gross Axle Weight Rating ie: less than 55/45) - Audi, BMW, Mercedes, Subaru, etc., might specify up to a 5psi difference for the Front vs Rear axle pressures, where as makes with a significantly higher Front/Rear weight split(60/40) - Chevrolet, Ford, Honda, Hyundai, Toyota, etc., recommend a single pressure > value for front and rear Axle - in particular front-wheel drive models. > > > Typical late-model European sports sedan or wagon recommended cold tire pressures: F/R: 32/36psi > > Typical late-model domestic or import front-wheel drive sedan or wagon cold pressures: F/R: 30 to 36psi, all tires. > > > My theory: The former are built for a more discriminating, enthusiast driving demographic whom will pay more attention to such things as different front/rear axle tire pressures, while the latter are built for the blue-collar masses, whose main priority is economical transportation in reasonably well equipped, reliably built vehicles, and live a busy lifestyle where it is easier to remember one PSI number - a compromise I'm sure - to set all of their tires to. > > What's your feeling behind this difference? > Feeling?? Engineers actually know something about this. Try running a Corvair with same F/R pressure some time. Just don't try cornering! -- Andrew Muzi <www.yellowjersey.org/> Open every day since 1 April, 1971 |
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Split/Different Front and Rear Cold Tire Pressures
On 8/18/2020 6:02 PM, AMuzi wrote:
> On 8/18/2020 11:26 AM, Chris K-Man wrote: >> Split Cold Tire Pressures: Front-to-Rear >> >> I understand the technical reasons for why some car makers specify >> different cold tire pressures for the front and rear axles of certain >> models. My question concerns those vehicles (except for the obvious: >> large SUVs and work vans) for which different pressures are specified, >> vs vehicles for which a single cold pressure is recommended all >> around(all four wheels): >> >> IE: Makes and models with less of a Front/Rear GAWR(Gross Axle Weight >> Rating ie: less than 55/45) - Audi, BMW, Mercedes, Subaru, etc., might >> specify up to a 5psi difference for the Front vs Rear axle pressures, >> where as makes with a significantly higher Front/Rear weight >> split(60/40) - Chevrolet, Ford, Honda, Hyundai, Toyota, etc., >> recommend a single pressure >> value for front and rear Axle - in particular front-wheel drive models. >> >> >> Typical late-model European sports sedan or wagon recommended cold >> tire pressures: F/R: 32/36psi >> >> Typical late-model domestic or import front-wheel drive sedan or wagon >> cold pressures: F/R: 30 to 36psi, all tires. >> >> >> My theory: The former are built for a more discriminating, enthusiast >> driving demographic whom will pay more attention to such things as >> different front/rear axle tire pressures, while the latter are built >> for the blue-collar masses, whose main priority is economical >> transportation in reasonably well equipped, reliably built vehicles, >> and live a busy lifestyle where it is easier to remember one PSI >> number - a compromise I'm sure - to set all of their tires to. >> >> What's your feeling behind this difference? > > > Feeling?? Engineers actually know something about this. > > Try running a Corvair with same F/R pressure some time. Just don't try > cornering! Don't try cornering in a swing axle Corvair, period. |
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Split/Different Front and Rear Cold Tire Pressures
AMuzi:
Corvair The Corvair had a Front/Rear weight difference that definitely warranted the big difference between recommended front and rear cold tire pressures. The cars I'm talking about are somewhere in between that extreme, and the other: rear- and all-wheel drive sports sedans with almost no(less than 55/45) front-rear weight bias. The last time I checked, a typical BMW F/R weight split is like 51/49%. Yet recommended front/rear pressures differ by 5psi. My Honda Accord, for example, is F/R: 54/46% axle weight split. Some 'econoboxes' venture toward 60/40, yet for the Accord and those cars, a single pressure figure, for all tires, is specified on the door frame placard. |
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Split/Different Front and Rear Cold Tire Pressures
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Split/Different Front and Rear Cold Tire Pressures
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Split/Different Front and Rear Cold Tire Pressures
On 19/8/20 10:23 am, AMuzi wrote:
> On 8/18/2020 6:43 PM, wrote: >> AMuzi: >> >> Corvair >> >> The Corvair had a Front/Rear weight difference that >> definitely warranted the big difference between >> recommended front and rear cold tire pressures. >> >> The cars I'm talking about are somewhere in between >> that extreme, and the other: rear- and all-wheel drive >> sports sedans with almost no(less than 55/45) front-rear >> weight bias.Â* The last time I checked, a typical BMW >> F/R weight split is like 51/49%. Yet recommended >> front/rear pressures differ by 5psi. >> >> My Honda Accord, for example, is F/R: 54/46% axle >> weight split.Â* Some 'econoboxes' venture toward 60/40, >> yet for the Accord and those cars, a single pressure >> figure, for all tires, is specified on the door frame placard. >> > > And all those have different suspension designs, rates, tire sizes, > front end geometry, body roll or lack thereof and so on. > > You're isolating one very small aspect of 'auto handling' which is a > very large area. > Yep, way too complex an issue to be isolated to one specific aspect. You need to look at the car as an entity - and that would, of necessity, be from an engineering perspective. -- Xeno Nothing astonishes Noddy so much as common sense and plain dealing. (with apologies to Ralph Waldo Emerson) |
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Split/Different Front and Rear Cold Tire Pressures
Xeno:
My particular mid-size front-wheel drive specifies 32psi, front and rear. It already has 'light'(easy) steering due to its wide, 50-series low profile tires. So for a while, I took it upon myself to experiment with adding 2psi to the heavier axle(the engine) and removing 1-2psi from the lighter rear axle. So I had a set up of 34front, 31rear. While the back end seemed more planted, the steering actually became more 'dartier' than ever on the highway, and I found I had to make more corrections thn ever to stay in a lane! During the third week, I reset all tires back to 32psi cold, and the car calmed down, and actually drive as intended. I'm actually running 33psi cold all around now, because the weather here is starting to get cooler, and handling is still fine. So for my specific car, a 56/44 split weight front wheel driver, using the same front/rear pressure - as specified - actually works! Can BMW and Audi do different front/back pressures simoly because their models' axle weights are closer to 50/50? |
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