Barry,

I hope you will forgive me for hijacking this thread for a moment. This deals with your excellent treatise on nitrogen vs. air in tires. You suggest adding 460 to the degrees Fahrenheit to convert to Kelvins. It would actually be degrees Rankine. I thought that The Old Wrench would be a better forum to make this suggestion since it would not detract from the professional nature of your presentation.

JT

I'm a liitle confused about one point.

Wouldn't a difference in wheel base result in a rear toe and thrust angle problem?

"Proofreading is not my strong suit!"

Engineers! I blame it on my poor typing skills. BTW, I'm an engineer, too, if that wasn't clear before.

What I would have done is gotten a calibrated level and show the service manager that is wasn't right.

But back to the original subject:

I am of the opinion that if a vehicle comes into an alignment shop, one of 3 things ought to happen:

1) The vehicle leaves in spec.

2) The operator of the vehicle is told the vehicle is not in spec and needs an eccentric bolt / camber plate / etc, and refuses to pay for the installation (I would hope this would be covered BEFORE the vehicle hits the alignment rack!)

3) The operator of the vehicle is informed that the vehicle is not in spec and that he needs to take it to a frame shop to get straightened.

What should not happen is the vehicle leaves the shop out of spec AND:

1) The customer doesn't know it

- OR -

2) The customer doesn't know what he needs to do to fix the problem.

My reason for starting this thread is to address how to respond to posts - whether or not we know enough to make a determination as to which situation we have.

OK,

I had forgotten about the disconnect between the service writers and the tech's - and I'm pretty sure we've seen posts where "the mechanic" was really the service writer.

And about those eccentric bolts? This was just an example of what MIGHT be possible. I realize that there are some situations where the alignment truly isn't adjustable without bending things - and I'm not advoating that should SOP.

Nevertheless, there is the other side of the coin - some customers only hear what they want to hear. When I read posts, I always try to remember that the post may not have accurate and complete facts.

I just had a lengthy conversation with a former quality engineer at a vehicle assembly plant. He came to work a couple of years ago for the tire manufacturer I work for - again, as a quality engineer.

I asked him if in his plant he was certain that vehicles leave the plant out of alignment. He said a definite "Yes!". He said they measure every vehicle going out on the same equipment they use to adjust the alignment. During ride evaluations, they will, from time to time, find some that have pull issues. Every time this happens, all the vehicles with pull come from the same alignment booth - and that one always proves to be faulty and giving bad readings - so they adjust it. The problem is that their data would not show bad alignments leaving the plant because the vehicle is leaving the booth "within spec". The only way they can pick it up is to drive the vehicle. Another way to put it is that they do not randomly check the vehicles for alignment on a calibrated jig.

I am sure that not all vehicle manufacturers use the same set up - machines, procedures, suspension designs, etc. - but this leaves me pretty cold that we can depend on new vehicles ALWAYS being properly alignment when they are delivered to buyers. (And I didn't even mention shipping damage!)

After following this discussion, it reinforces the lesson I learned with my Impala when I had to replace tires at only 14k miles due to a severely out of alignment rear end from the factory. Next time I buy a car it gets a four point alignment as part of the purchase agreement or immediately afterwards. I'll also keep alignments as part of regular maintenance on a 12 to 24 month schedule from now on rather than wait until I think I detect a problem. In fact, just had that done this week along with an oil change.

I bet what my old car needed (among other things) was to have the rear end aligned as I don't recall ever having that done. Dad only ever had front end alignments when he thought there was a problem and that's what I had learned. With respect to my father, I've learned some things about good maintenance of a car from y'all that he apparently didn't know.

---

Marnet
...still reading, still learning!

I've been to some dealerships - as part of something else - where they do next to nothing. Some don't even install the parts that come in the bag!!



I think the problem here is what to tell folks when they ask the question: "Is it necessary?". If folks are willing to sacrifice a tire or 2, then they only need to do when they detect a problem.

But a lot of folks don't pay attention to anything, and while they would probably not ask the question to begin with, if they hear "Not Needed!", they interpret that to mean "Don't ask, don't look, don't tell, nothing bad will happen!", but will complain loudly when they have to pay to replace DANGEROUS tires.

- but I digress! -



1) If you remember bias ply tires, you also remember that cars were "body on frame". They had a huge rubber isolator between the frame and the body. The wad of rubber does wonders to reduce the amount of vibration that gets transmitted to the driver. Pickup trucks are still built this way - and if you look under the body, you'll still find them - and they work just as well. Pickup trucks are pretty insensitive to wheel end vibrations.

2) In addition to more unibody cars, the use of computers has allowed car designs to be stiffer - moving the resonant frequencies of the body closer to the resonant frequencies of the suspension. This makes the car more sensitive.

3) The actual manufacturing processes have improved and the cars are just tighter - again, making the car more sensitive.

4) Old recirculating ball steering mechanisms were more isolated that the rack and pinion system used today.


When you add all these things up, the general movement has been towards making cars more sensitive. Interestingly, you'd think that the use of alloy wheels would greatly reduce the amount of weight of the tire / wheel assembly - but it is not as much as you would think.

One of the interesting aspects to all this - at least from an engineering philosphy point of view - is that it is much easier to make a car twice as sensitive than it is to make the tire's variation half what it used to be.

PLUS - radial tires are much more sensitive to toe in, making them more prone to generating offending vibrations - and frankly, the tolerances for toe-in having changed since the bias tire days - and they should have!

Besides, if you got a set of bias tires to last 30K, you were doing good. Nowadays, it is expected that radial tires will last 30K - and that's about where these vibrations start to show up.

So when someone say cars were better built in the good old days - I say " Your memory isn't as good as in the good old days!"

And as a followup:

Does anyone have access to alignment specs? Are they available on-line somewhere?