Wide Oval Radial - Recommended Pressure
#1
Wide Oval Radial - Recommended Pressure
I've recently bought a set of the Coker produced Firestone Wide Oval GR70-14 Radials for my '70 442 and I'm struggling to find any recommended tire pressures for them anywhere (surprisingly nothing on the Coker website that I could find). Just wondering what pressure others are using for these tires - typically unloaded and maybe 2 passengers. Thanks in advance
#3
I've recently bought a set of the Coker produced Firestone Wide Oval GR70-14 Radials for my '70 442 and I'm struggling to find any recommended tire pressures for them anywhere (surprisingly nothing on the Coker website that I could find). Just wondering what pressure others are using for these tires - typically unloaded and maybe 2 passengers. Thanks in advance
#4
I will offer my thoughts. Since you didn't mention what width rim you are using, that is a factor.
I think that if you have "Anti-Spin", inflate the rear tires to 30 PSI and do a burnout for 20 feet or so.
Examine the "black marks". Are they uniformly black across the "black marks". If they are lighter in the center, increase pressure 2 PSI and burn out again.
When they are uniformly black across the "black marks, you are done.
You'll likely get lighter black marks on the pavement on the left rear tire.
As far as front tires, I would inflate them 2-4 PSI more than the rear. Don't exceed max tire pressure listed on the sidewalls.
.....Just my two cents worth.
I think that if you have "Anti-Spin", inflate the rear tires to 30 PSI and do a burnout for 20 feet or so.
Examine the "black marks". Are they uniformly black across the "black marks". If they are lighter in the center, increase pressure 2 PSI and burn out again.
When they are uniformly black across the "black marks, you are done.
You'll likely get lighter black marks on the pavement on the left rear tire.
As far as front tires, I would inflate them 2-4 PSI more than the rear. Don't exceed max tire pressure listed on the sidewalls.
.....Just my two cents worth.
#5
I can make you a pressure/loadcapacity list with maximum reserve at wich comfort and gripp is still acceptable.
Then you " ONLY" have to determine the axleloads 99% acurate, the most tricky part, and your responcibility.
I dont know your tires, but you can give me the data. I assume its a radial cartire.
Need next, can be read from sidewall.
1. Maximum load or loadindex
2. Kind if tire to determine the referencepressure.
3. Speedcode, less important, shall be Q or higher.
Then you " ONLY" have to determine the axleloads 99% acurate, the most tricky part, and your responcibility.
I dont know your tires, but you can give me the data. I assume its a radial cartire.
Need next, can be read from sidewall.
1. Maximum load or loadindex
2. Kind if tire to determine the referencepressure.
3. Speedcode, less important, shall be Q or higher.
#6
Thanks you all for your feedback I really appreciate it. I'm going to start off at 30 PSI and see what the ride & handling is like and will tweak from there. I've replaced my upper ball joints with the UMI tall ball joints so it will be interesting to see how this combination hopefully improves the ride & handling.
#7
But then again, I remember the Olds dealer back in about 1970 or so telling my grandmother, who had asked him about proper tire pressure, to go to an empty parking lot, do a few burnouts, and then come back and tell him the results. She did scratch her head about this, but she did it!
#8
It's more of an old drag racer's trick to figure out what PSI is going to give you the best bite off the line with any given tire. As noted, sort of overkill for a street-only vehicle and leaves you guessing as to what pressure is best for the fronts. Unless you have AWD.
#11
The tall ball joints are one of the best things I've done to the 67 to date. That, and dial in as much caster as it will take. The difference is night and day at cruise altitude.
As far as tire pressure goes, 30 psi is a safe bet, then adjust for personal preference.
As far as tire pressure goes, 30 psi is a safe bet, then adjust for personal preference.
#12
#13
Holy crap. This is a hell of thing to do just to figure out a good tire pressure! What do you do to clean the windshield? Fire a nuclear missile at it and examine the pieces to see how clean they are?
But then again, I remember the Olds dealer back in about 1970 or so telling my grandmother, who had asked him about proper tire pressure, to go to an empty parking lot, do a few burnouts, and then come back and tell him the results. She did scratch her head about this, but she did it!
But then again, I remember the Olds dealer back in about 1970 or so telling my grandmother, who had asked him about proper tire pressure, to go to an empty parking lot, do a few burnouts, and then come back and tell him the results. She did scratch her head about this, but she did it!
It's more of an old drag racer's trick to figure out what PSI is going to give you the best bite off the line with any given tire. As noted, sort of overkill for a street-only vehicle and leaves you guessing as to what pressure is best for the fronts. Unless you have AWD.
Damage ? You'll have plenty of rubber left over. You really only need to do a few short burnouts to see if the tread is making uniform contact.
Many, many years ago there was an article written in Hot Rod magazine about "Tire footprints". It could have been written by Roger Huntington or some other well versed person. I am sure it included pictures and diagrams to illustrate things. Perhaps Professor Joe P remembers it.
Technically its not even a "trick".
Last edited by OLDSter Ralph; April 26th, 2024 at 05:04 PM.
#14
Yes thats what I've read on other GM forums too - huge improvement. I've only changed the top ball joints at this stage and will see what level of improvement it gives. Did you change both upper & lower on your '67 or just 1 ??
#15
i did both because I wanted to lower it a little.
#16
Tall Ball Joints
Thanks, good to know. I'm taking my '70 to the Oldsmobile Club of Australia National Meet next weekend but on return I think I'll be doing the lower ball joints too. My car has the stock ride height but it's a tad too high at the front so changing the lower ball joints will give the bonus of dropping it almost a 3/4" win - win.
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