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Do you ever worry about a blow out at 45psi?
- Thread starter acarney
- Start date
artsci
Sponsor
Agree, I’ve been driving for over 50 years and have never had a blow out, including 6 plus years of driving Teslas.
TomT
Technical Maven
Atari2600
Active Member
I would say operational limit. Of course the safety limit is going to be higher than that.
SammichLover
Banned
When I was a teenager, so I'm not sure about what sense of "modern" that covers.
It was a tubeless radial, so design wise modern albeit with materials short of what we have now. But it wasn't the side blowing out. It was the tire tread unfurling, at a speed that shall remain unnamed, and it beat the living crap out of my rear passenger quarter panel as it kicked a huge rooster tail of rubber bits up into the air behind me. At first I thought the hole rear end had blown up or something, until I noticed the rooster tail was to one side. I may have run that tire a little past the time it should be changed.
Plus tire material was generally more susceptible to dry rot back then, and before I inherented this extended-family owned vehicle (well, bought for $350) it had done a bit of sitting so the tires had time to age.As mentioned above, these days your tire only "blows out" if you have run it really low on air (and ignored your pressure warnings) or you clip large, and sharp road debris that cuts the tire. edit: Or potentially if you run it down to the cords being exposed and then keep driving.
Tire pressure is always referenced vs. atmospheric so 45psi period, BUT if we drive to different elevations the pressure in the tire will "change" just because the atmospheric reference has changed.
Set it where you do most of your driving, don't worry about the variation unless spending weeks at a drastically different elevation.
SammichLover
Banned
That's why I wouldn't normally set to 50 PSI cold locally here. The hot, direct sun days could easily push that up to 55 PSI without even driving hard. That's getting a bit much, and those high pressures just murder the middle of my treads even at 45 PSI cold.
SageBrush
REJECT Fascism
And plenty of others spec high pressures. Of the cars I own:
2010 BMW 535i M-Sport - 42 PSI
2014 Audi Q7 - 44 PSI Front, 49 PSI rear
2007 Dodge Ram 2500 - 50 PSI front, 70 PSI rear
ucmndd
Well-Known Member
You don’t. 45 psi is 45 psi and you should set the pressure to read what you want it to in your typical environmental conditions.
That said if you take a tire inflated to 45 psi at 5,000 feet elevation and bring it down to sea level, that tire will register a lower pressure by a few psi.
https://m.tirerack.com/tires/tiretech/techpage.jsp?techid=167
Maybe they drive down to lower altitudes regularly? Or they don't know what gauge pressure is.
You can't compare a Q7 or a Ram, those have completely different tire dimensions and weights. Trucks are always going to have high PSI numbers.
The 535i is comparable, it uses 42 PSI, which is lower than the typical 45 PSI recommendation for RWD Teslas. It's also in a very similar weight class as a Model 3 and has similar tire dimensions. That seems a more reasonable number for our 18" tires.
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SammichLover
Banned
Last week my Tech asked me if I wanted my tires checked and I say yeah, but I didn't want the standard 45PSI. He had expected my door said 42, and was going to set them at 42. Some Model 3s come with that door sticker instead (seems linked to having 19" rims?).
He was cool with setting them to my preference of 40 PSI. That's different than the past where Rangers have insisted on 45 PSI and then I'd bleed them out myself later.
One thing that's probably driving the 45 PSI is that the tires are fairly narrow for the 2 ton curb weight of the AWD models, they are narrow for the RWD weight frankly, and so with the smaller patch contact area and also wanting it to not deform as much for range reasons they have it run at a bit higher PSI.
The max 50psi cold will take extreme use into account, the extra heat of the sun or driving won't cause a failure, there is plenty of safety margin.
Now treadwear will most definitely suffer if at 10psi over recommended.
May be dating myself a bit but I suspect most of us here are middle-aged or beyond. Remember the Ford Explorer/Firestone fiasco? That was Ford's fault for recommending excessively low tire pressure to improve ride quality. Low pressure creates a lot of problems
SammichLover
Banned
Yeah, it is mostly treadwear I'm thinking about. Plus you lose some lateral grip, which I regularly use most of. The harder, more "jumpy" ride doesn't bother me, but it could be a factor for some. Very clear trade-off for the range enhancement of driving very firm tires.
100% agreed here.
The door sticker on my AWD with 19” wheels shows 42psi recommended. Tires of course say 51psi. I prefer a cold tire pressure of 48-50psi in cool weather, which is most of the year where I live. (Edit: apologies, don’t know why these photos display upside down, they look correct when viewed on my iPad)
SammichLover
Banned
The PSI rating stamped on the tire is just the maximum for the tire itself, not an actual "recommended pressure" for the vehicle they are on. Once upon a time you basically never wanted to be close to the tire rating max as handling would be atrocious and it would even impact acceleration characteristics because of poor contact with the road. Modern suspension design has made that much less the case but if you ask a lot of your tires in handling performance then it still matters some to keep lower (but not so low that you run into heating your sidewalls, having the tire roll over on the shoulder when turning, risk popping the seal on the bead, etc).
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