I have a 72 skylark with a 350 in it. She has 215 60 15 Cooper Cobras on the front and 235 60 15 Cooper Cobras on the rear. The fronts are 29psi and still look soft? Any ideas as what is correct pressure?o No:
I set my tire pressures to the maximum recommended pressure cold, printed on the sidewall on the tire. Usually, around 35PSI foy my size/brand of tires. See what yours say, and try that. ElectraJim
28 is soft and what most say on the door jam, [what my wagon door sticker says to use] but that is for ride comfort. And why them SUV's were rolling over. Forget that n use whats on the side wall of the tires. I run 40psi but my tires are rated 35-52psi on the side wall with no deformation.
I dont want to put too much air in them due to the heat factor when rolling. Apparently they can gain 10 psi just through that, dont want to exceed the safety limits.
This is not accurate. Tires will heat up, and the pressure will change more from _underinflation_. The sidewall flexes more causing heat, and the pressure rise. http://www.richmond.com/automotive/4617 http://www.aaanewsroom.net/main/Def...rchEnginePageSize=&CategoryID=4&ArticleID=490 http://www.betiresmart.org/tire_safety/tire_maintenance_and_safety/how_to_take_care_of_your_tires/ That's why you check tire pressures cold (as printed on the tire sidewall), and NEVER under inflate. Dangerous practice to underinflate tires to "compensate" for a tire problem or for "safety limit". Reade the sidewall, set to that pressure, cold. ElectraJim
Ok, I'm out. Anybody else care to field this one to clarify to Buick Bloke about underinflation of tires and the potential dangers?!? ElectraJim
I'm afraid following old OEM instructions will mislead you as well, unless you are running bias ply tires like the originals. Switching to radials can mean different requirements. Maybe some of these will help? Air Pressure - Correct, Underinflated and Overinflated Air Pressure vs. Dry Performance Air Pressure vs. Wet Performance Air Pressure, Temperature Fluctuations Air Pressure/Load Adjustment for High Speed Driving Air Pressure: When and How to Set Devon
IGNORE THE OWNERS MANUAL They give a psi to use for the best ride for their end to sell a car. What the tire makers prints on the tires is the right one to follow as they made the tires to run at that psi and no less. Why them SUVs were rolling over. Folks running 28 or less for a nice ride like Ford wanted but in a panic manuver your F'ed as they are under inflated. Even though firestone took all the flack, it was Fords fault for telling folks to underinflate their tires so they could claim a smooth ride over panic manuver safety. Buy the right tires to get a bigger psi rating. On the side wall of my tires it says 35-52PSI which means I can run anywhere in that zone and the tires will not deform in shape. I like 40 cold. Though most tires only say 35, better brands have a bigger range. More psi you can run makes for less rolling resistance. But they must be rated for more, are tires not made for it will ballon which is just as bad as underinflated.
In a nutshell, underinflation causes tire sidewalls to flex more than they are designed for, which can cause catastrophic failure. You've all seen those truck tire treads and casings on highway shoulders. Probably 90% or more of those were directly caused by underinflation. For an easy example of what happens to a tire with less than correct inflation, just take a paper clip, and bend it back and forth until it breaks. That's essentailly what happens to tire sidewalls. Now to answer the original question about correct tire pressure, my guide has always been the information on the tire itself. However, one must also consider the weight load each tire carries. Here's some more information from the Uniroyal Tire site: http://www.uniroyal.ca/care/expertadvice/index.html?id=6
Though their are a few time I have under inflated my tire on purpose, like on a bad winter day with bad snow and ice, ill drop to 30 for some more grip but putit back to 40 soon as the roads are clear.
No way. It's a max rating and that is just plain bad advice. I have no idea who told you that but you need to listen to some more opinions. Given a light load application, running a tire at max is the same as "overinflation". You can wear the center of the tire's tread right down to zero in no time. Devon
Firstly like to thank everyone for their 2 cents. But i do feel some have missd my point! I actually sell tyres and car parts for a living!!!! So i didnt step off a boat yesterday. But there is no chart, or literature for the weight and load of my Skylark on modern tyres. I could tell you the correct tyre size and psi for every car on the road, except mine!!! My car does not have the tyres it left the factory with, nor does it have any information on correct tyre inflation. Obviously it has new tyres on her, how would the new tyre size correspond with the old to give the correct ps? Now with tyre sizes open to interpretation due to the large wheel arches the cars can vary from quite skinny to fat! There is no set in stone chart of tyre pressures for the corresponding tyre. This is my problem??? 215 60 15 front with the weight of 350 motor is going to differ from 215 60 15 front with the weight of a 462 motor, the pressure aint gonna be the same. The info on the tyre states "max loads" not what the car should be running at. Other wise every car would be the "same".
There is another method that I used to use, which was simply do a burnout or three, and check the resulting rubber marks. :laugh: :laugh:
Are these tires retreads by chance? IF so, they may have ground off the information that was on the sidewall. If not, maybe the recommended pressure is on the other side of the tire. Is it common for Cooper not to print this on the sidewall? Maybe a call to the tire manufacturer is in order. They should have a tech number specifically for a tire/part vendor like yourself. I'd be curious to hear what they say. I think I understand what you are getting at...sort of... PS, running REAL low tire pressures may have worn off any print on the side of the tire, right at the wheel rim. I've seen that before PPS, exactly how much of a weight difference are you expecting will you have with the engine swap? Good luck, ElectraJim
No they aint re-treads but it is all a bit vague as you can see. Heres another piece of advice ive had " if your tyre pressure is too high the wheel will easily lock and skid in stead of stopping" ( drum brakes):shock: :Smarty: Perhaps we should get a buick guide on tyre application going on this forum as nobody else has!:grin: From normal street to strip tyres!! Where's the guys with the all knowledge?? This would benefit everyone as well as the safty aspect too.
Maybe your tires look a bit fat because they're a little too wide for the rim? My tires look a bit squashed, but that's kind of the look you get with these rims/tires, even at 30-40 psi. I'm usually at 35 psi, then I know I'm not killing it in either direction. What's written in the manual seems to apply to a different era somehow. Every time I have any shop do anything to a tire, it comes back at around 40 psi.
She's got Buick Rally rims 7"x15" I did'nt think 215/60/15 & 235/60/15 was too wide for the rim? I know exactly where your coming from with tyre shops. How about the guys going crazy with the air guns!! Whoaa!!! steady on the the torque buddy your gonna brake something!!
