My theory is the higher than Toyota recomended tire pressure I am using (40/38) is improving my mpg but could cause traction control issues on snow covered or wet roads. Any thoughts?
Sure. Higher pressure can reduce traction. I don't think it is a major issue, but it could contribute. Tom
Doubt it. Think about how a tire wears down. Wear on the sidewall parts of the tread is a sign of traction right? If there was no wear, there wouldn't be any traction (meh, sorta). Now, we know for a fact that an "factory recommended" psi wears way more heavily on the edges and barely any on the center... What your doing with higher psi is redistributing the traction so it is more even across the tire. Now, the question then becomes: does the shape of the traction footprint change the traction characteristics on snowy/wet roads.
That's my impression too. More energy from the bumps get transferred to the suspension with higher pressure. Lower tire pressure tire would absorb some of those and pass less energy to the shocks to absorb. The end result I believe is more contact with the road. When you ride a bicycle with higher tire pressure, you feel more vibration. The chains shake more. The same concept.
The traction problems I've experienced were due to poor tires, not air pressure. I think maybe at 60psi you'd notice a difference, but not 40.
I run 52/50 and have not experienced traction issues. I spent a year at 35/33 and then went to 42/40 for a year before pumping up to 52/50 for the last three years. I replaced my OEM tires after almost exactly four years and roughly 48,000 miles and they were evenly worn. Anecdotally, I can not corroborate any decrease in traction caused by increased tire pressure.
If anything, higher pressure lets tires bite down into the snow better than letting it squash out more. High for ice/snow, low for sand/gravel/mud where you *want* a big squashy footprint. That's about the only place lower pressure makes any sense. . _H*
