Auto Rain Closing Sunroof/Windows?

[enigma-2]

Well, since you asked- I'm at least as smart as them. Got my PE stamp right here.

In what field?

 

As most of us know, a PE stamp only covers the discipline you tested in. In all other areas you may not know shit. (I'm not trying to be mean, but stating that you "at least as smart", is somewhat a rediculuous statement. Unless you work for an automotive company, or in a related field, your just a layman like the rest of us). A license does not make anyone an expert. Experience does. A license simply means one has demonstrated the minimum qualifying expertise in a particular field.

 

The reason we trust the engineers at Ford, is for their expertise in automotive engineering. They have to consider hundreds of varables and have knowledge of the history of their particular area.

 

Unrelated, I worked with an automotive engineer who worked for Bendix Automotive. (He was also one of the engineers who had a hand in the Lunar Lander). The experience I gained from him could fill a book. There are so many small points of knowledge concerning each individual part, making up the whole. For example, we spent two hours talking about one screw, the forces affecting it, the shear stress on the thread tips, etc.

 

We don't run your tires underinflated, not JUST because Ford tells you not to; we do it to maintain stability in turns, to prevent overheating around the chords (and subsquently failure), to prevent short life of the treads, to improve braking distance, etc. etc.

 

There is simply no good reason to run tires on low pressure. The soft, squishy ride you get is detromential to the tire, to the suspension and to the car's ability to recover from high speed cornering. It's one of the reasons the feds mandated in the FMVSS to have low tire pressure warning indicators. Lower gas milage certainly, but for all the others reasons as well.

 

BTW, your the first Professional Engender I've met that bragged he was an expert in Automotive Engeering. Every other PE I've ever known in the field were always quiet as to how much they knew. I would guess it's because it's such a large, complicated field.

 

Question: would you, as a Professional Engeneer, feel comfortable stamping a design for running 36 psi on an auto designed to run at 44 psi? Would you be willing to take the professional responsibility for underflated tires?

Edited August 23, 2017 by enigma-2

[IWRBB]

You guys are right, my truck will roll over in turns and the tires will catch fire and explode. I'll go put them all back at 44 PSI right away.

[IWRBB]

BTW, your the first Professional Engender I've met that bragged he was an expert in Automotive Engeering.

 

Never said anything of the sort did I? You asked if I was as smart as Ford's engineers. I said I am.

 

 

Question: would you, as a Professional Engeneer, feel comfortable stamping a design for running 36 psi on an auto designed to run at 44 psi? Would you be willing to take the professional responsibility for underflated tires?

 

The wheels and tires on the truck are not OEM. Therefore, they were never "designed" to run at 44 PSI. I am confident it is not unsafe in any way, despite all the nay-sayers here. I don't consider them to be under inflated. With how I use the truck, I consider 44 PSI over inflated- as evidenced by a chalk test and by the wear pattern on the previous set of tires.

 

I have checked the tread wear on the new tires at the lower pressure, both with the chalk method and over the long term.

 

I have checked tire temps and tire pressures after driving at high speeds, and for long distances. It doesn't heat up any more than the OEM tires at the OEM pressures did. Maybe a degree or so, but nothing that is truly a measurable difference. The hot pressures are only 2-3 PSI higher than the cold pressures which is normal.

 

In the engineering field- the correct answer to any questions is always "it depends". The door sticker pressure is based on OEM tires and wheels, which are both long gone. What is an acceptable pressure for different wheels and tires? It depends. It depends on load, speeds, and temperatures.

 

So back to your original question- would I stamp it at 36 PSI? No way in hell. Ford has to use a number that works for a truck that is running at it's top speed, non-stop until the fuel tank is empty, fully loaded, and in the hottest possible conditions. Absolute worst possible scenario for the tires. If I was to use my truck like that- you can be damn sure I'd not be running less than the door sticker. Ford cannot count on a customer to adjust their air pressures as needed, so they have to assume the worst case scenario to cover their ass.

 

If you remember, some car user manuals used to actually recommend different tire pressure for different loads and speeds. That's all gone due to the inability of people to use their brains anymore. Lawyers have driven us to the point where you are all berating me for running less then the "balls-out" pressure when the truck is unloaded. Sad times.

Edited August 23, 2017 by IWRBB

[Waldo]

There is simply no good reason to run tires on low pressure. The soft, squishy ride you get is detromential to the tire, to the suspension and to the car's ability to recover from high speed cornering. It's one of the reasons the feds mandated in the FMVSS to have low tire pressure warning indicators. Lower gas milage certainly, but for all the others reasons as well.

 

 

There are many good reasons to run tires on lower pressures. As I was trying to allude to in my post above, you just have to know the reasons not to and be comfortable that you won't be concerned with those conditions. Lower pressures almost always result in shorter stopping distances for example.

[clegg78]

Having done a good bit of AutoX in the past - a tires optimal pressure for grip is not the same as the optimal pressure for longevity on the road. Same on motorcycles. 2 of the biggest names in motorcycle handling courses and training (Keith Code and Lee Parks) recommend ~4 PSI under factory recommendations on motorcycle tires for street riding and track use because it increases grip by a good margin and keeps the tires in optimal temperatures easier in inclement weather.

 

But it does all depend on the tire. If you use more performance focused tires with higher temps for their optimal window you run lower pressures to keep them there. If you are going for efficiency and longevity you put higher pressure in. Higher pressure (than factory recommended) will virtually always cost you traction and wet weather braking capabilities.

 

This is very similar to the fact that bigger rims will almost always cost peak traction in exchange for high response on inputs.

Edited August 24, 2017 by clegg78

[omar302]

By the way, Toyota (at least in region, and maybe Nissan, don't remember) specify to increase the tire pressures for continuous high speed trips (~120+ Km/h). Here is also an article from TireRack on the subject, which I believe IWRBB is kind of applying but going lower since his speeds & loads are less.

Edited August 24, 2017 by omar302

[clegg78]

Makes sense, for road trips I tend to increase the pressure as well.