Quote:
Originally Posted by qx4dude
Also,
3) Assuming higher PSI = better FE, why do most auto makers choose a door sticker PSI number approximately 30% less of max sidewall pressure.
-snip-
And don't say "it's a conspiracy".
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Door stickers have been rising for years.
Unfortunately, as others have said, and has been shown, advantages level off after a certain inflation pressure.
Manufacturers aren't going to spend extra money on better shock damping to make up for extra-hard tires just to claim another half-mpg on the EPA.
Quote:
Originally Posted by qx4dude
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Nothing to do with inflation pressures (space savers are supposed to be inflated to between 60-90 psi).
And it's only partly to do with contact patch size and mostly to do with tire construction and compound. Space savers don't have the same gummy compound and stiff sidewalls as your typical low-profile sports sedan tire.
Hell... motorcycle tires would have been better.
Quote:
Originally Posted by qx4dude
Perhaps MPG isn't the #1 consideration, but it's easily in the top 3.
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Truck sales are booming. Honda Fit sales spiked briefly during the 08 spike, then crashed again.
Most people who are silly enough to buy new typically aren't concerned enough about gas prices to sacrifice (perceived) comfort for another few mpg.
We are. But then, we're not "most people".
Quote:
Originally Posted by qx4dude
On a mass-produced vehicle like that, how much would it really cost on a per-unit basis to make the suspension a little softer so that an extra 10 PSI goes unnoticed by the new car buyer? Manufacturers tweak suspension / ride setups all the time.
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That's actually the wrong way around. cbaber had it right.
A suspension designed around stiffer tires is more expensive. A softer suspension would just destroy wheel control and make the tires bounce, To run an extra 10 psi "comfortably", you will need more expensive, beefier shocks with stronger damping. Perhaps even two-way valving to better control wheel motion if you don't want to go with stiffer springs. (yes, stiffer, not softer)
Then you need firmer bushings, rubber isolated suspension subframes, etcetera. That builds up cost quickly. All simply to ensure people don't complain about the ride.
Just ask BMW about it... as they've had to do all of that to deal with their stupid runflats.