On page 183 in the book 'Corvette Restoration Guide by Richard Prince he posts a tire sticker that says:
Max load F=28 R=32
Reduced load F=20 R=26
Tire size255-60-R15

 

Huh. I can't read them. Is the stated lower pressures for the 1978 sticker?

 

The defense rests it's case.

 

As a matter of interest I have owned my '82 for 27 years and got used to how well it handled on twisty mountain roads. After I bought my big block '71 I immediately noticed how BAD it handled because of the additional 250 pounds of front end weight. That's why I run a whopping 24 psi in it's front tires for safety reasons..

 

You guys just don t get it do you? Toobroke rattles your cage and you all bark in unison ... Wake up and smell the coffee

 

That's just plain obnoxious.

 

No one is interested in anything except ensuring others don't fall for your ill-conceived advice....

 

No, they have rattled their OWN cage by failing to understand some simple laws of physics. In their lifetime they have gotten so accustomed to pumping 30+ psi into the tires of all of their other vehicles they never stopped to realize their C3's with their huge 255X60R15's don't need nearly that much pressure.

 

The modern "low profile" tires need a lot more pressure to prevent rim contact with the highway when hitting ruts or bumps in the road. The much larger 255X60R15's can operate at 2/3 the pressure as the distance from the rim to the road is about 2/3 more. Although weighing more the larger tires do offer a softer ride because of the amount of "give" in them.

 

Even more BS....

The stock low profile tires on a C5 take the same pressure as the high profile tires that shipped on a 82 Corvette.

 

Looks like ALL the specs for a '78, from another thread:http://api.viglink.com/api/click?for...fications.html


Front 28 PSI, Rear 32 PSI.

 

NO...I honestly by now I think WE ALL get it.

Has nothing to do with 'rattling your cages'. He posts a thought that he feels he has all the answers to and this allows many of us to either agree with it or not agree with it. Good, bad or indifferent...it is a forum.

I can always count on him coming up with some crazy stuff to discuss. And after working all day on these Corvettes.....sometimes I need a laugh or just shake my head in total amazement of 'some people.' Especially when the evidence is right in from of them...they still can not see it or acknowledge it.

And honestly...in my opinion....not everything that he writes is incorrect.

DUB

 

This is what I thought before actually doing it. It makes sense to someone who reads a lot but when you actually do it like I did you get completely different results. I changed my BFG 255/60/15's to 255/45/17 and 285/40/18's on the back and was anticipating a tooth jarring ride.

What I found was nothing short of amazing, the new lower profile tires had a much smoother ride on every type of road than the BFG's. Just more proof to me that you don't WTF you're talking about. I mean I already knew you full of it but now I know you post things that make sense to you instead of real world experience.

Please if you are going to post try to post about things you actually have experience with that way you won't pizz every body off. But somehow I know that ain't gonna happen.

 

The "bump and rut friendly" nature of the bigger 255X60R15's does give them an advantage on rough roads and their larger air volume would allow the car to sink slightly slower when driven off a pier...............

 

Please let us know how that works out for you.

 

 

 

AAAAHHHRRRRGH! Why am I still trying to fly out of this black hole?

Why am I left shaking my head? It's all I can do...shake my head.

IT'S ALL ABOUT THE CONTACT PATCH!!!

Yes, I concede that "taller" tires have more sidewall and are, therefore, more forgiving to under-inflation than are, for example, a 40 series tire. This is, in part, due to the increased potential for the tire to get pinched between the ground and the rim.

I'm confused though...there have been REPEATED arguments made about the lower pressure due to the increased WIDTH of the tire being a factor in running lower pressures...some examples of said argument:

So. Using this path of logic, the P275/40ZR-17 tires utilized on the 1991 Corvette really should require LESS pressure. Probably closer to 15 PSI, right? And those awesome 345/30ZR19 tires on the Dodge Viper...those suckers probably only take, like, 8 PSI.

But now the discussion takes a turn...now it's NOT about the cross-section, but rather it's about some other factor. It's about some 'factor' of the distance of the road from the rim. That's a new one.

I'll let you in on a secret: IT'S ABOUT WHAT IT TAKES FOR THE TIRE TO KEEP ITS SHAPE!!! ANY TIRE!!! NOT JUST 'LOW PROFILE' TIRES!!!

I will go ahead and concede the point that the centers of your tires may wear when properly inflated. Blame BFG for that...something about the tires must not be shaped right. But OH MY GOODNESS, 20 PSI? It's just not worth it.

For no reason other than knowing, I went out to my car this evening and decreased the pressure of the tires to 24 PSI front and 20 PSI and compared my impressions of "feel" to my 30 PSI to 32 PSI normal.

Yes, it was smoother. No question. It should be.

Yes, there was more traction. There should be. There's more tire touching the ground.

The problems I noticed were two-fold.

First was the dramatic increase in rolling resistance. This translates DIRECTLY into heat introduced into the tire carcass. That's bad.

Second was the "wallowing" feeling that just didn't seem to go away. The car 'rolled' into turns. I could feel the rear tires taking a set instead of the car just, you know, TURNING. It felt like the tires would roll off the rim.

And heaven forbid I saw at the steering wheel right-left-right-left. It was COMICAL. Every bit of the car's motion was soaked up by sidewall flex! Not very confidence inspiring, to be sure.

My feeling? It felt like I was driving around on under-inflated tires.

Just like there's no amount of evidence we can provide to convince you there is no merit to running tires at 20 PSI, there is absolutely no way the flawed logic and story-changing will convince the rest of the world that running 20 PSI is a brilliant idea.

Lord knows...I would give anything for a "Hmmm...maybe there's something to your arguments" response. It would make me feel so much better inside.

 

About a dozen posts back I admitted I made an error in referring to the tire's "cross section" and corrected it to volume. So yes, I did use a wrong term and I'm sorry for making that error. But then this thread was about why G.M. specs said 20 psi was okay. In the past 27 years I have experimented with different pressures in my 6-7 sets of 255X60R15's: 30 psi wore the centers out in about 15,000 miles, 25 psi wore the centers out in about 20,000 miles, and 20 psi wear almost perfectly even. The centers still wear faster by a little bit which means a lower 17-18 psi would be more suitable for maximum tread life.

At 68 I really don't care about the " sports car feel" of my C3 any more but rather care about the harshness of it's ride. My C3 is my daily transportation from point A to point B and it rides about as smooth as a Cadillac. If running high pressures make you happy then by all means do so but in the meantime I'll run my lower pressures and really enjoy my trips.


Kiethinspace, I'd like to make a suggestion: Lower your pressures to 24/20 psi (again) and then drive it for an entire month instead of 5 minutes with your already biased negative opinion. After a whole month of city and freeway driving come back to this thread and give us your honest opinion. You'll quickly discover your C3 can ride as smooth as your family car and still retain most of it's sports car feel and all of it's visual appeal.

 

You self screwed up alignment is most likely out because you should not be wearing out any part of the tread by 15k miles.