R-1150 / Gary:
Whoa, buddy, slow down there on the attitude. If you are going to take offense or get a bit testy when other members either ask you questions to define, explain, or ask you for clarification, it's gonna be a bumpy road. Fred's is well known for its civility, humor, technical knowledge, but also for the good natured but fairly zealous commitment to challenge posts that make, let's say, unreasonable or hyperbolic claims.
I have responded with explanations of what I meant by my comments.
All of which support my position. Yet you still label them as 'unreasonable or hyperbolic'.
That characterization would have a thread of credibility if you had actually refuted any of my claims.
You seem to confuse your 'challenge' with something that approaches a 'refutation'.
You have not done that yet.
The statement "over-inflated tires are a formula for disaster" is, for me, a bit too vague, if not an exaggeration, so I asked you to define, explain, and clarify. In fact, I asked you to please do so, and you'll find from a search that I am rarely impolite. I apologize if you took my humor the wrong way- it was certainly not sarcasm. I did have to chuckle at the "recipe for disaster," but gave you lots of room to clarify, amplify, and qualify your statement, lest I was misunderstanding.
Tires that have had their traction reduced to the point where braking distances are increased or their ability to hold a corner lessened, are also more likely to be involved in a collision.
I acknowledge only that the expression 'formula for disaster' is subjective.
The degree of the 'disaster' is dependent on how serious any resultant accident is.....
As for my being "obviously not well informed," I hope that remains to be determined. I do hope, though, that when members lacking information (in your view, at least) ask questions, your answers will be void of poor attitude towards their post.
The previous post of mine that you originally responded to reflects what I believe to be the basic principles of tire performance.
When you chose to challenge my post it appeared to be less a sincere request for clarification, but rather a characterization of the claims as being in your words 'subjective (and odd)'.
Yet, you have yet to provide anything that actually refutes what I have said, other than point to many others who have "got millions of miles, lots of tests, (and hundreds of posts), that reveal higher PSI's producing notable % gains in FE."
Again, I never denied higher tire pressures result in fuel saving.
I only pointed to the reality that reduced rolling resistance caused by harder tires also brings with it a reduction in traction and uneven tread wear.
Yet there still are members here who advocate running tires at pressures above 40-psi when VW recommends pressures closer to 33-psi.
It is irresponsible and incompetent to promote pressures so much higher than recommended without addressing the effects on tire traction, and safety, that also results from such practices.
Yet your response neither denies nor refutes my claim that traction reduction is a by-product of that practice.......
Lastly, (for now at least), my hope was to have you provide some more exacting parameters so your strong caution to others could be better understood. That did not happen. IMO, and not to offend you, you crafted a carefully worded statement that largely says something akin to "your tires are dangerously overinflated at the point at which they are dangerously overinflated." In that case, I agree.
Sorry to hear that you would misinterpret my statement that "Typically the larger the difference (in pressure) above what is rated by the manufacturer as optimal the greater the reduction (in traction).......
I thought the concept was clearly stated and explained for exactly what it is.
I did not supply support documentation for the simple reason that every tire manufacturer I have seen recommends that you follow the manufacturer's recommendations for tire inflation to get the maximum traction and tread life from their tires.
You have yet to demonstrate how they are ALL wrong.......
My point, which was made previously, but may have been incomplete, is not that drivers should exceed the max sidewall to improve FE, but that TDIClub members interested in these topics, have for the past 13 years, been testing/observing their tires under a variety of real-world conditions, and documenting their results in threads here. We have many ardent proponents of "sticking to what the door jam/fuel door says," (thinking of you many years back, Joe_Meehan) but we also have -literally- hundreds of posts, in over 300 threads, with millions of miles, where drivers have seen a notable increased % in FE, without crashing or other mishap caused by tires being run above what "the sticker" says.
First: - There is typically a large difference in the max pressure rating on a tire, and the pressure recommended by the manufacturer. (Tires on most vehicles are 'over rated' for the typical use and load they are intended for. If the same tire was on a heavier vehicle the recommended pressure would be closer to the maximum rated pressure on the sidewall.)
Second: - There certainly are many posts by members on this topic. There are many who even have documented the effect of the change on fuel economy. You also acknowledged that there are differing opinions on which approach is best.
My response is that none of these are controlled scientific studies that conclude anything different from what the tests conducted by the manufacturers have found.
Third: - Your statement "where drivers have seen a notable increased % in FE, without crashing or other mishap caused by tires being run above what "the sticker" says." is one that you will have difficulty supporting.
There have been many posts on this forum by members who have been in accidents. Who here can say with any certainty that at least some of them might have been avoided or the damage minimized by tires with better traction by not being over-inflated?
Without a proper controlled study that analyses the contributing factors of accidents with members tires that were run at various pressures above what is recommended, vs those at the recommended pressures, you are merely guessing that none of the many accidents mentioned have resulted from the reduced traction higher pressures provide.........
Tire companies have invested much research, and multi-millions in testing, to get the significant knowledge they have about optimum tire construction and how to get the best performance out of them.......
But again, if you actually have anything that approaches a study that refutes their findings lets see it......
For others reading, there are numerous outstanding threads on FE, tires, PSI, etc., which are not only fun to read, but full of great information, and spirited give and take. Most of these are from the years prior to the Mark VI, but are likely applicable. The focus in not racing, autox, or rally, but simply how members have charted their FE and handling with a variety of tires and PSI variations. Search is your friend.
Not to denigrate anyone here, but I remind you of the limits inherent to an enthusiasts' site.
You can pick a side to support that reflects your opinion, but unless you can back that with something better than anecdotal experience, that is as good as it gets.....
The main reason I challenged the practice of raising tire pressures to increase FE in the first place is because it ignored the universal recommendations of the tire and vehicle manufacturers.
The results of over-inflation are widely recognized throughout the industry as adversely affecting traction.
To promote such a practice without acknowledging this potentially significant safety risk is either ignorance or incompetence.
Members should have the knowledge of the risks involved before making their choice.
Gary