Tire Pressure and tire life expectancy

[Lloyd]

Yes, I run a small airline and it is required in aircraft tires for that reason. Tires get hot on landing and taxi, then to -50C at altitude. Racing teams will always use Nitrogen because they can set their tire pressure prior to race and not have it adjust as the tires heat up. Race teams will see increases of 10 to 15 lbs + during race conditions, if nitrogen is not used, that affects the handling of the car.

If you drive your car hard and heat the tires up you will see and feel the difference. Other claimed benefits of less oxidation of the tire and wheel and less leakage through the tire are bogus. If you are just motoring on the roadway it is likely not worth the cost.

 

[SByer]

I don't have anything like the power of a roadster, and we don't have many concrete highways, but all the fuel savings from EVs are going to be spent on tyres if they don't last longer than that...

I'm pretty much a small car mid-engined kind of guy (MR2, 911). The tire life on my Roadster is not out of line. The 911 I had needed new rears once a year as well. Well, at least the way I drive.

The annoying thing is that the wear bars are tuned for gas burners, where they have to kick in earlier and be much more (waay too much more) obvious to get noticed. Sigh.

 

[tennis_trs]

...

The annoying thing is that the wear bars are tuned for gas burners, where they have to kick in earlier and be much more (waay too much more) obvious to get noticed. Sigh.

What difference(s) do you think there should be for tires for an EV?

 

[vfx]

how do you fill a tire with 100% gas?

Fill them in a vacuum?

 

[Talkredius]

I was also surprised about the short life time of the rear tires (Yokohama). First time (after 3 months, 13.000 km ) when I checked them, the wear bar was already gone
I got them exchanged on the same day.
Taking in account my driving style so far (everyone wants a test drive, I want to impress them => pedal to the metal) I came to the conclusion that the Yokohama tires may be the best for the performance but not for the life time. And you can't switch between front and rear as I can do on my FWD ICE.

I'm thinking about to use two different rear tire sets, mounted on rims, in the summer, one with the Yokohama one with Michelin. So I can compare them more easily, e.g. making a longer business trip with one set and then make the same trip with the other set. If I really do so I'll report. My guess is that Michelin will have the lowest roll resistance and the longer life time.:wink:

What difference(s) do you think there should be for tires for an EV?

A LED ring which lights up when wear bar is gone ?:smile:

 

[Lloyd]

how do you fill a tire with 100% gas?

Fill them in a vacuum?

Its all a matter of percentages. I guess if you wanted close to 100% you could fill and purge, then refill.

 

[vfx]

Right,

Rinse and repeat

 

[SByer]

What difference(s) do you think there should be for tires for an EV?

I'd be all down for an LED warning, sure. The wear bars just don't need to be so deep or so strong - they don't have to compete with an engine for attention, it was pretty darned obvious that I was starting to hit them (again...), and it really sucked to know that I still had a couple of months left on them, and I have to put up with the buzz until then. Shoot, I could deal with 200mi worth of wear bar, not what seems to be about 900mi.

In the 911, yeah, it was subtle, sub-conscious - crept in over the couse of a month or so until I finally realized what it was (oh, yeah, it's that time of year!). 900mi (just a SWAG) and overly firm was needed.

 

[tennis_trs]

...I was starting to hit them (again...), and it really sucked to know that I still had a couple of months left on them, and I have to put up with the buzz until then. Shoot, I could deal with 200mi worth of wear bar, not what seems to be about 900mi.
...

Everything I've read indicates that you're supposed to replace your tires once, or a little before, any of the wear bars reach the surface. Do they cause any/much noise before they hit the surface?

 

[Talkredius]

Everything I've read indicates that you're supposed to replace your tires once, or a little before, any of the wear bars reach the surface. Do they cause any/much noise before they hit the surface?

oh yes ! But because it doesn't switch to loudness when the wear bar is touched but is increased bit by bit you might not notice it until you get a new tire set or the wear bar is totally gone and the tire gets an uneven surface.

 

[bolosky]

If you inflate with Nitrogen you will get much less variation with temperature. I keep a bottle for my cars and motorcycles.

This doesn't sound right to me. The basic physics of gasses is the Combined Gas Law: pV = nRT. That is, pressure times volume = count of molecules times a constant times the temperature. It doesn't depend on the type of gas, it's for all gasses. In a tire, for the most part the volume and amount of gas are fixed, so pressure rises proportionally to temp, period.

Maybe nitrogen has some other advantage (say, lack of oxygen and water vapor holding down corrosion or something), but its pressure will vary with temp the same way that air or any other gas will.

See, high school physics is actually good for something, if you only wait a couple of decades!

 

[mpt]

Maybe nitrogen has some other advantage (say, lack of oxygen and water vapor holding down corrosion or something), but its pressure will vary with temp the same way that air or any other gas will.

Nitrogen molecules are bigger; nitrogen filed tires don't leak.

These guys have a lot to say on the subject: Nitrogen in Tires : Information about Nitrogen Tire Inflation News, Benefits, Generator Dealers, Location Finder & More

 

[TEG]

The Straight Dope: Is it better to fill your tires with nitrogen instead of air?

Nitrogen vs Air In Tires - Why Nitrogen in Tires - Popular Mechanics

 

[zack]

Nitrogen schmitrogen.

 

[MelTyree]

RE: Tires for Roadster 1.5

:smile::smile:

I got my 2008 Roadster used with 5500 miles on it and I have put an additional 1500 miles on it in the 2 months I have had it. The tires do not look worn to me at this time and I would like to maximize their remaining life. Having been the owner of some very underpowered EVs, the Solectria Force (0-60 in about 20 seconds), I have no trouble driving the Roadster sedately most of the time so I am already doing that to maximize my tire life.

When I got the car, the tires were 36 front and 46 back, is that slightly overinflated or way overinflated? What are you running them at?

RE: Tires for Roadster 1.5

I bought a used 2008 Roadster 1.5 with 4000 miles on it and am now up to 9000 three months later. I was disappointed with the high wear on the original Yoko's when I mounted Pirelli winter tires. The tread on the rear Yoko's were more than half gone but the wear on the fronts was less. The Tesla store in NY City had very few tire options recommended for the Roadster 1.5 series because of the different traction control system, which can't 'learn' different tire sizes. They did however sell me Pirelli snows and said they were recently approved for the Roadster 1.5. The front tires are different from the Yoko's:
Original Front Yoko's 175/55 R16
Pirelli Front 195/50 R16
The Pirelli fronts translates into a tire that is 1.3 mm more in diameter and is probably okay because treads usually start out at 7 yo 8 mm high and wear unevently and the tranction control seems to deal with that okay.
HOWEVER, after 4000 miles the rear Pirelli were again half worn off!! So I called some local sports car dealers to ask what kinds of summer tires wear well. Based on this advice I bought and installed summer Dunlops:
Front: RZ101 195/50 R16
Rear: RZ101 225/45 R17
Since these sizes are identical to the Pirellis, the traction control was happy (no problems so far) and the speed and load ratings were identical between the Dunlops and Pirellis. I bought myslef a dial caliper to measure tread thickness to within +/- 0.2 mm. I will let this group know how much wear I get after 4000 miles. The Dunlops were about half the price of the Pirellis (< $400 for a set of 4).

Does anyone else have experience with different tires on a Roadster 1.5??

Thanks,
Mel

 

[ChargeIt!]

Based on this advice I bought and installed summer Dunlops:
Front: RZ101 195/50 R16
Rear: RZ101 225/45 R17
Thanks,
Mel

Do you mean DZ101 ?

 

[tdevince]

This doesn't sound right to me. The basic physics of gasses is the Combined Gas Law: pV = nRT. That is, pressure times volume = count of molecules times a constant times the temperature. It doesn't depend on the type of gas, it's for all gasses. In a tire, for the most part the volume and amount of gas are fixed, so pressure rises proportionally to temp, period.

Maybe nitrogen has some other advantage (say, lack of oxygen and water vapor holding down corrosion or something), but its pressure will vary with temp the same way that air or any other gas will.

See, high school physics is actually good for something, if you only wait a couple of decades!

I think the key is that the Nitrogen is dry, so that you don't get pressure variations as the water vapor in the air condenses when the tires cool, or add to the partial pressure when condensed water goes to vapor. Most air stations during the summer will fill your tires with warm moist air.

 

[MelTyree]

Do you mean DZ101 ?

YES DZ101; thanks for catching that error. I hope the Dunlops work for you; I have had mine for only a week. My Pirelli show tires have 0.24" on the rears, which is just about enough for another winter. In comparison the rear Yokos have 0.18", which is maybe enough for another 4000 miles whereas the front Yokos are 0.26" The minimum legal tread is 0.063" (about 1/16").

 

[frequencydip]

Just adjusting tire pressures will help though. To reduce the bumpy ride, you need lower tire pressures but to reduce understeer you need to increase the front tire pressure so to an extent you can not have both grip and comfort.

Reducing rear tire pressure will be a win/win for you as it will lower understeer and improve the bumpy ride. I assume the lowest rear pressure you can have without the tire pressure monitoring getting upset is going to be 36psi (as above) so try that with say 30 at the front.

You can drop the front pressure a bit more for a softer ride (and perhaps a better feel through the steering) but this reduces front end grip a bit so understeer will increase.

Having owned several Lotus over the years, I have always found that the suspension settings / tire pressures are very sensitive to changes and it seems the same on the Tesla. A few psi change in tire pressure can make a big difference to how the car feels.

This is not necessarily correct. It depends on the car, and the spring rate of the wheel where tire pressures are bing changed if that will increase or decrease understeer. For the Tesla without sport suspension, decreasing front tire pressure 2-5 lb will decrease understeer. When adjusting tire pressures you are changing multiple dynamics of the vehicle at the same time.
Changing size of contact patch
Changing stiffness of sidewall
Changing overall spring rate of that wheel

The Tesla has a very stiff suspension and increasing tire pressure from 30psi increases wheel spring rate and reduces contact patch size, this increases understeer. Now if you reduce tire pressure to much you will also increase understeer. under inflation also decreases contact patch and causes the sidewall to roll and change the roll angle of the tire again increasing understeer. Every combination of tire and suspension has an optimal tire inflation for maximum traction. 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.

 

[Doug_G]

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