What tire pressure do you run in G78-15 tires?

[BobinBC]

I have a 48 special deluxe club coupe, but I know very little about them really. First car was a 57 Dodge but been mostly GM products since then. I want to learn so feel free to EDUCATE ME!

Edited April 29 by BobinBC

[Doug&Deb]

If you are running bias ply tires I recommend the pressure stated in the owners manual. For radials I run 35 psi.

[Ivan_B]

+1 for the manual. And I would recommend considering the pressure stated on the tires themselves, as well

[DJK]

40 minutes ago, Ivan_B said:

+1 for the manual. And I would recommend considering the pressure stated on the tires themselves, as well

The pressure indicated on the tire is for maximum allowed pressure for inflating the tire, not operating pressure, on modern cars the pressure is listed on the door frame, check your owners manual.

[Sam Buchanan]

4 hours ago, BobinBC said:

I have a 48 special deluxe club coupe, but I know very little about them really. First car was a 57 Dodge but been mostly GM products since then. I want to learn so feel free to EDUCATE ME!

 

 

Beautiful car!

 

According to the manual 6.70x15 bias-ply tires are to be inflated to 24 psi. This may sound low for those accustomed to running radials, but keep in mind the P15 is not a heavy car, about 3200 lbs, the same as an old Chevy S-10 pickup.

 

You do have a service manual, right? Well, in case you don't:

 

https://www.rockauto.com/en/moreinfo.php?pk=10593924&cc=1486874&pt=10335&jsn=385

Edited April 29 by Sam Buchanan

[Ivan_B]

Am I looking at the wrong manual? I am reading 6.5x16 at 28 psi.

[Plymouthy Adams]

quit guessing, contact the tire company/online site visit and get the real deal.  If you got the tires locally, check with them,  they the ones standing behind your tires.

[Sam Buchanan]

9 minutes ago, Ivan_B said:

Am I looking at the wrong manual? I am reading 6.5x16 at 28 psi.

 

The '48 P15 has 15" tires. But without knowing for sure if the OP is running bias or radial tires on the stock rims we are kinda in the dark.

[Plymouthy Adams]

per my manual they do not list a 6.5x16 but a 6.0x16 was stock with early production.  page 17 section 10 of front suspension

[Ivan_B]

The title actually says that the TS is using Coker G78-15 tires 😅 Coker rates them as 1620lbs@32 psi. I would probably inflate to 28-30 and call it a day. Running BP tires too low creates a risk of overheating. I am running similarly rated 16 tires at 28 (per user's manual, no highways), and did check them for overheating... Doing good.

Edited April 29 by Ivan_B

[Plymouthy Adams]

Posted 5 hours ago (edited)

I have a 48 special deluxe club coupe, but I know very little about them really. First car was a 57 Dodge but been mostly GM products since then. I want to learn so feel free to EDUCATE ME! 

 

the thread does not mention Coker tires as the brand he is running

Edited April 29 by Plymouthy Adams

[greg g]

In the alfa coded tire sizes  A was equivalent to a 600 bias ply or a 155 radial. The 78 is a reference to aspect ratio where tread with is 78% of sidewall height.  Your Gs are probably comparable to a 215/225 mm tread width radial. I don't like a floaty, leany ride.  I usually knock 5 to7 psi off the tires max,  or split the difference between the frame sticker and the max on the tire.

 

 

[BobinBC]

Thanks for all the replies, what an active board and a great surprise when I checked my messages this morning!

 

The tires are Remington, I haven't found a date code on them and they are bias ply not radial. 

 

Unfortunately I don't have any manuals but would like to get some. Thanks for the links Sam Buchanan and Ivan_B!

 

The tires had not been checked for who knows how long as the car just came into my care very recently. Front left was at 24 and the rest were less than 20! I filled them all to 30 as a starting point but I believe they are a little oversized for this car (almost 28" diameter) soo was wondering what others used for a reference?

 

Car seems to ride great at 30psi due to the soft springs and shocks but I'd read of people running 36 or 38 which seems very high!

[Sam Buchanan]

Bob, I have Coker H78-15 bias ply on my '48 P15 which is oversize compared to the original tires. However the speedometer is spot on so the diameter must be very close to original. The tires work fine at 26-28 psi, these large tires would probably be happy with less pressure but lower pressure would require a bit more effort when parking.

[Ivan_B]

44 minutes ago, BobinBC said:

The tires are Remington,

Oh, sorry, I just googled G78-15 and Coker came up... I thought it was a brand-model. In this case, something between the max rating (on the tire) and what the manual suggest (for this same size) should work for you. Also, here are more links you might find useful:

Previous model years Plymouth service manual (goes up to P14, but plenty of things are the same or very similar)

P15 introductory update

It looks like the 46-54 service manual covering your specific car is not available online (or at least I could not easily find it) but there are plenty of inexpensive books on eBay.