Trouble Averted

I've been driving my C4 with 45 front and 43 rear with no problem since the first week I bought my car in June. And I'm checking to have them at those psi every first week of the month. I'm driving 50/50 highway and city. I've read people put more than 50 psi here but couldn't find the post.

 

The tires are NOT "rated" for 35 PSI. Toyota recommends 35 PSI. Their recommendation is a compromise for safety, comfort, economy, tire life, etc. Tires are NOT unsafe at the maximum cold inflation pressure. In fact, that is the minimum pressure at which the tire meets its load rating. At a few pounds more than the recommended pressure, you will be rewarded with better gas mileage, longer tire life, and crisper handling. In my book, you, any passengers, and the public will be safer.

 

They are Bridgestone like most of us in CA and the door recommended PSI is the same as yours if not all of vehicles in the US.

 

One thing to remember: PSI reading in "cool" condition like sitting in the garage for few hours. Driving to the station to fill up will raise the PSI and that's why when I'm pumping them up about 1 psi more at 46/44 while I'm at Costco Tires.

 

Only "trouble" averted is not getting good gas mileage.. You can go above 50psi with no issue if road conditions allow it.. The rougher the road the lower the psi and the smoother the ride. The more you experiment with different pressures the more aware of car traction you'll be, and thus the more conscious you'll be when avoiding an accident when traction matters most. It's also drastically changes mpg.

 

No, they won't 'hand grenade' on you anywhere near that pressure. The 35/33 label on your door frame doesn't know what tire model was originally installed on your car (a survey of our 2010's here found 3 different models for 15" wheels, and three more for 17"), nor what model you use as replacements when the originals wear out. So it doesn't know if the tire is labeled for 44 (like mine) or 51 or 55 psi.

My 2010 arrived with the same door label you have, but at delivery the tires actually had 40/40/40/39 psi. More discussion here found that Toyota loads them up to 40 psi to avoid flat spots during their Pacific boat cruise. The dealer is then supposed to lower the pressure before delivery to the customer. Mine and many others were not, but we had no grenade reports. Some owners did have the correct pressure, while some had too-low pressure, likely a dealer trick to make a softer ride.

I never lowered mine, in fact bumped them up slightly. The selling dealer never lowered the pressure during service (yes, they did check the pressures). But the one service at a different dealership while traveling caused a run-in with a so-called 'tire professional'. That shop was above 6000 feet elevation, and I arrived straight from a long highway run, so the tires were highway hot and nearly 50 psi. The tech insisted this was dangerous, and wouldn't let the car out with more than 40 psi. After the tires cooled overnight, and I returned to sea level, the tires were actually under-inflated (fronts were 33). The 'professional' didn't know about pressure rising as tires warm during operation, nor the approximately 1 psi per 2000 feet of elevation change that his customers experience as they head to Sacramento, less than two hours away.

Have you ever seen warnings at high elevation, e.g. 10k-12k feet in Colorado, telling drivers to lower their tire pressure to prevent grenading? No, neither have I.

 

Why would Big O Tire want tp at 35psi? A soft tire runs hotter and wears faster and on the edges. That means owner will be in the tire shop sooner rather than later to buy new tires & maybe get an alignment. Go into an empty parking lot & practice some evasive maneuvers at 25mph or turn a corner at 25mph. If your tires squeal they are underinflated and may aggravate an unpleasant situation.

Do you remember the Ford/Firestone fiasco? Ford strong armed Firestone into agreeing to 28psi on the door placard. What happened during an evasive maneuver? The hot tire failed causing a roll over.

 

If you google "over-inflating tyres" you may find some interesting reading, like the following link.

Dangers of Over Inflating Tires | Hybrid Cars

The sticker pressure is both a recommendation and a minimum, as you don't want your tyres under-inflated. I suggest you try a small increase, say 2 psi to see what the effect is, perhaps then a little more. I have always run my tyres 2 psi over; as tyres always lose air, +2 psi keeps pressures from going under the sticker pressure (with regular checks), and also tightens up the handling and cornering noticeably. I also inspect tread depth, and look for any uneven wear regularly.
No-one knows how your car handles like you do; you be the judge!
P.S. Invest in a good pump and a gauge and do your own tyres - I have an excellent high pressure push-bike pump that stands vertical with a tee-handle you push down; it does car tyres easily (make sure it has a valve for car tyres).

 

RocMills,
If you drive on decent roads, inflate up to max PSI as written on the sidewall without a worrry. If you bounce from pothole to pothole then be more circumspect.

I top off my tyre pressures with a bicyle pump.

 

Our tyres are different and have different recommended pressures but I find it interesting that the stickers here migrated a long time ago from the door pillar to the glove box. Funny that it would be located differently... wonder what on earth the motivation for that was.

 

I still have trouble grasping how you folks manage, wandering around upside down all the time.

 

First of all, there is some sort of safety factor built into everything, including tires. So over inflating by a mere 20% isn't going to be an issue, especially if the max psi is higher. I'm sure even the max psi has some sort of safety factor built into it.

When I went for my 15K service early in the morning before work, I brought along my pancake compressor, because I knew that Toyota would reset the pressure in the tires back down to about 36 psi. So, when I left Toyota, I just pulled into a nearby parking lot and inflated my tires back to 42F/40R, because I have a 70 mile round trip to work.

 

Lots of good comments here. The door jamb sticker indeed is a minimum cold PSI recommendation to handle the indicated gross vehicle weight [aka loaded with people & stuff]. There are sometimes several recommendations on those stickers for various loads [e.g. 2 vs. 4 people], and various OEM tire sizes. It's all a legal disclaimer to keep the OEM's from being sued.

For what it's worth, driving on the street doesn't heat up tires all that much, so after a long road trip you can expect 1 or 2 PSI increase from the tire being warm. Of course a bad alignment will heat up a tire more, as will aggressive cornering.

The maximum inflation pressure molded into the tire sidewall is of course the maximum the tire manufacturer is willing to rate the tire at.

So Toyota's sticker says something like 38 front 36 rear cold to handle the weight of the car + load, and Bridgestone says 55 psi max. These are your logical bookends. Now we get into things like fuel economy, comfort, tire wear, and handling. All of those aspects will dictate varying tire pressures for maximum performance in each category. It's up to the owner to determine what pressure they find optimal, be it based on a hunch or a full-blown data set. Most of us aren't taking tire temp readings across the tread width after a drive to determine how to tweak our pressures [and alignment], but that's just an easy example of the next step needed after simply guessing or seeing what happens.

Long story short, unless you're willing to do some investigation, stick to the Toyota sticker recommendations based on how you load the car, or perhaps bump them up a couple PSI just to give yourself some leakage room. Tires after all don't seal perfectly; this is why you should check them literally every fuel-up.

Cheers,
Ryan

 

I wish this article had some technical backup, in particular on these two items:

His traction claim violates my understanding of classical friction. His hydroplaning claim flat out contradicts the NASA and aviation industry articles that has been discussed here in the past.

Absent some technical backup, I can't believe him.