Tire Pressure and tire life expectancy

[wiztecy]

Curious, but doesn't running the pressures low down to 26-27lbs offer higher risk in damaging the rim when it contacts a pothole? Meaning that the tires will collapse under the hit where then the rim connects on the impact zone directly. I've been running my tires at 42 front and 44 rear. I'm not pushing the car around corners hard and would like to preserve the tread life over the life of the tires. I can see how lowering the pressure up front can help prevent understeer as well as give a softer ride. The road on my commute, highway 17, isn't all that bad, so the higher pressure isn't beating me up. I'll try to search, but wondering if anyone has data on the rolling efficiency with the tires at max 44 PSI vs the lower 26f/36r combo.

 

[slcasner]

Tesla's recommended settings are 30/40.

 

[jory]

or 25/36 for "comfort mode"

Tesla's recommended settings are 30/40.

 

[wiztecy]

Thank you. But curious if this risks damaging the rim in the worse case scenario? Possibly since the front end is really light that the risk is low... just a theory. Secondly I hear the numbers Tesla came up with, the PSI #'s, are the best for rolling resistance, cornering, and balance with comfort. Are there metrics Tesla has published and can share on this Test and the efficiency curves that led to these figures?

 

[frequencydip]

The tire pressure would have to be very low 20PSI or lower for a normal pot hole, if you hit a curb or massive pot hole yes you can damage the rim at any tire pressure.

 

[jerry33]

That's only if you hit the pothole square. If you hit the edge or at an angle it takes a lot more pressure to save the tire and wheel.

 

[wiztecy]

Thanks, good to know the rims are not all that vulnerable at a lower PSI.

 

[wiztecy]

"I recently did a skid pad test with A048's and the standard 35/45 tire pressures appear to be pretty good. "

I think this is the key and I now understand Tesla's low PSI #'s! Stopping!! A possible reason why so many roadsters are rear ending cars is that the car's weight is focused over the rear wheels. Secondly the suspension is really stiff. Cars with ICE engines up front typically have more weight over the front wheels and a softer setup of the suspension. When these cars brake, the rear lifts and the front compresses over the front wheels focusing the majority of the cars weight on the front wheels. The front is where the majority of the braking comes from! Just talk to a motorcycle rider, I'm one, and I don't use my rear brake at all... no real weight or downward force there.

So when the roadsters try to stop with an ICE car up front, the roadster is now traveling faster and now engages its brakes. The weight of the roadster is focused from the back to the forward direction of the car, not down, which the tight suspension contributes to. Lowering down the front tire PSI will help the roadster compress some of this force downward not just in a strait forward plane across the pavement. Lower pressure will also yield a wider track which will improve the track pad #'s as reported in this thread.

Makes sense now

Time to lower my front tire PSI now that I know I won't damage the front rims! Thanks All.

 

[wycolo]

> Time to lower my front tire PSI [wiztecy]

65 Chevy Corvair 4door with soft brake pads (grabby). One night locked up the wheels stopping for a deer.
Next morning looked at the skidmarks: all were exactly the same density (on old concrete). All 4 tires had the same force against
pavement, as per GM's design(!!). With radials ran 35+lbs rear & like only 18 or 20 front.
--

 

[znino]

I presume all the tire pressures discussed here at ambient temperature right? Before driving?

 

[wiztecy]

Tires typically are checked when "cold" and cold is at current ambient temperature before driving-- be it 20 or 100 degrees F (with tires out of direct sunlight). So yes, that's correct. You just have to watch your rear pressure and possibly lower it due to the tire pressure sensors. At 45psi checked at 70 degrees F cold my rear sensors went off on a 95 degree F day on a heated road so I needed to drop them down to get my traction control back.

 

[Lloyd]

I had to replace one tire yesterday on my Model S. One kept losing pressure, about 3 lbs per day. For everyone's information the warning of pressure low comes on about 33 lbs. 1750 miles, the tire had a small cut in the sidewall. Not sure how it happened. The tire shop seemed to think that I ran over something pretty sharp, or it was vandalized. No rim damage whatsoever. Tesla sent a ranger out with a new tire which I took to a local shop for mounting. $15. Because this was a 'road hazard' there is no warrenty coverage, and I will have to pay for the new tire. Tesla will send me a bill for the tire.

 

[jerry33]

1750 miles, the tire had a small cut in the sidewall. Not sure how it happened.

It's hard to tell just from the description. I don't suppose you took a picture?

 

[djp]

I have found that with the non sport suspension and AD07 tire the front tires perform best at about 27lb and rears at 38lb, if you want to decrease understeer further leave the rears at the recommended 40 but this will increase wheel spin when accelerating hard out of corners.

I think frequencydip is right that 27/38 is the ideal pressure for the AD07s. I've been running mine at 30/40 and found the centre has been wearing faster than the edges which would indicate overinflation. It's possible that Tesla's recommended settings of 25/36 and 30/40 bracket the ideal pressure, with slight underinflation for comfort and slight overinflation for range.