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2010 2.4EX
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Discussion Starter · #1 ·
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?

Mods/Admins:

Please move this thread to a subforum - such as Tires & Wheels - where it will get more attention than it ever will in the Pit.

I reposted it there earlier - sorry about duplicating! - because DriveAccord does not presently have a Delete Thread option for posters.

Thanks!

Well, I guess my question is either too complex or too esoteric to garner attention no matter where it resides! smh..

But I did gain some knowledge on the subject of front/rear tire pressure differential here:

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PS: Ignore what the link above says! Clicking will take you to the conversation. Google just revamped their whole GoogleGroups Usenet interface, and it's a complete cluster🦆.

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(See, ^^this^^ is what's wrong with society today - we're a buncha wusses! Afraid of a couple of course words. I was raised on so-called "foul" language. And you know what they say about people who cuss a lot?)

They won't end up as a mass shooter or domestic violence case. Their blood pressures below average. So I say, don't be a wimp... swear with flair! :D (just don't name-call!)
 

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2010 2.4EX
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402 Posts
Discussion Starter · #2 · (Edited)
Today I went out to my car and found out why I might not need to increase the cold tire pressure in front and decrease same, in the rear: Honda already took that into consideration!

I measured my front and rear coil springs: Front = 14mm, Rear: (approx)12.5mm - or, a slightly loose 13mm hand wrench. In other words, Honda already considered the additional weight up front, where all the propulsion takes place, and speced front and rear coils accordingly(no pun!).

Upon calculating my front to rear weight offset a month ago, I ended up with the following front to rear pressure offset: Front tires: 34.5psi cold, Rears: 29.5psi cold. Rounded to nearest half-psi.

I've been running those pressures now for almost a month, and my observations are:

1) Steering: Slightly more responsive than I'd prefer, but, can take turns at higher speeds but still in control. Back end not 'wishy-washy', despite lowered tire pressures there.

2) Ride: About as smooth as before, with 32psi recommended in all four tires.

3)...and this is the biggest one!... Rolling: This thing ROLLLLLLLLS with the tire pressure offset I calculated! Which leads to..

4) Braking: No difference in brake feel, but because of what I noticed in item 3), I am using them a lot more - at least as much as I use the right pedal!

5): Gas economy: Didn't really notice any difference. Probably the same, since more air in the front tires and less in back lends a slightly nose-up stance, aerodynamically.

Will I go back to 32 or 33psi all around? It depends!
 

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To tip the balance towards understeer rather than oversteer. Sounds counterintuitive if you think about it, but the logic behind it is not that straightforward.
 

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2010 2.4EX
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Discussion Starter · #4 ·
To tip the balance towards understeer rather than
oversteer. Sounds counterintuitive if you think about it,
but the logic behind it is not that straightforward.
With the different spring diameters?

There is much debate over which causes which, but which setup do you think promotes understeer, and which creates over, assuming the same daily driver front-wheel-drive-only car...

More pressure in front tires, or more pressure in rears? Being as simple-minded as I am, I always assumed more pressure in front tires leads to oversteer, being as they're doing the steering, in most cars I know of.

I only reported my calculations and driving observations, others' experiences may differ.
 
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