Tire Pressure on Vintage Goodyears

[mj_duell]

Hello Everyone,
just got a set of vintage style Goodyear’s (#D2546 & #D2547) mounted. They fit the wells perfect and I am not getting much in the way of "Hunting". The tire shop pressurized them to 32 pounds. After a quick drive I saw that the rears had too much pressure do to the wear in the center only, so I lowered them down to 29 pounds. The fronts seem to wear fine at about 31 pounds. Can anyone give me some insight into what seems to be the best pressure for regular "Around town driving" ?



--Mike

[mj_duell]

Anyone, Anyone, .......... Bueller?



--Mike

[Allan A]

I have 24 all the way around.

Allan

[Rick Parker]

25-30 seems to be the range, with the upper end for track use.

Rick

[mj_duell]

Thanks Guys,
I thought 32 was high. I am going to leave them at 30 front and 28 rear for now. As far as alignment specs, did you have to change the toe or camber settings to make the tires feel and perform better on the street?



--Mike

[Excaliber]

These are BIG tires and fairly light weight cars, the normal tire pressure rules simply don't apply with this application. 24 sounds good, I'm running closer to 20-22 myself and that seems to be working fine.

[mj_duell]

Excaliber,
what does your car weigh in at? I think I am around 2500 lbs without a driver, but with a full tank. Maybe I will try lower pressure settings. The wheel feels a little light at 30 lbs. Do you think I should run additional toe out or in? What about high speed stability, should I run less positive caster with these tires?
My current settings are:

Front:
-1* Camber
2.5* Caster
1/16 Toe in

Solid rear axle.



--Mike

[Excaliber]

I'm 2700 with 1/2 tank, no driver and an iron big block. I'm sure Allans car (running 24 psi) is lighter than mine.

I couldn't even make a guess on your alignement settings, just "rule of thumb" stuff as it varies so much from one replica to another. High speed stability you want some "toe in", 1/16 is good. Toe out or zero WILL make the car wander badly at speed, but can work great for SCCA "cone racing" events where your doing a lot of quick right/left stuff.

Again, SCCA cone racing you want negative camber (outside edge top of the tire leaning in, bottom edge out). But that will eat up the edges of your tires pretty quick on the street.

Best thing to do is try different pressures and see how it feels. The steering is "light", well that could be good or bad!

Keep an eye on the tire wear to see if your low or high "over time". To low will wear the edges and leave the center tread untouched. To high will wear the center and leave the edges untouched EXCEPT for where a large camber number is being used. Alignment is an "art" and there are no "magic numbers", just some better than others.

[mj_duell]

I have drivers school at Watkins Glen coming up. So I will take your advice on the toe in. I guess I will keep playing with the toe and caster to see what feels better and handles better at the track. I like the look and feel of -1* of camber, so I think I will keep it there for now, but keep a close eye on the tire wear. It seems to be harder to nail down the aligment with these tires. The adhesion is great, but the set-up is difficult.



--Mike

[RACER X #99]

Mike,
What driving school are you attending at WGI? I instruct for 4 different schools at WGI, usually in Cobras.
I run the Goodyear Bias ply slicks on my Cobra and I usually start out at around 20lbs all the way around. After taking tire temps sometimes I might wind up with only running 18 lbs. You really have to take tire temps to find out what the correct pressures should be. Forget about what you might be running in Radials. entirely different .
If I should see you at the Glen I can help you out with the tire temps.

Phoenix CMR June 6,7
Apex August 3,4
Phoenix CMR August 22,23
PDA October 7.8.9

Instructor Cranky
Roger Davis

[mj_duell]

RACER X #99,
Sweet! I will be at Phoenix CMR June 6,7! Now I'm really happy. I've done a little Auto-x, but never any track time. I'm glad to know a CC member will be instructing at WGI. I only have a single hoop, so I was told I will be playing lead/follow. I would love it if you can help me out with the tire pressures at the track. See ya there! Let me know of any other open - Cobra freindly events between now and June 6th.

Thanks!



--Mike

[RACER X #99]

Mike,
I did not know that Joe was going to do lead follow instruction but that's OK by me. I'll be glad to help you out anyway I can. Here is a photo of some of the cars/guys who run the Glen.

[mj_duell]

Joe had said that instructors would not like to ride in single hoop Cobras so he would have them do lead follow. Either is fine by me, I'm there to learn. I'm glad to see all the Cobras that run at WGI. June is coming fast and I am trying to get the car ready for both street and track driving. I also have to find a trailer, perferably enclosed. Heres a question; Joe said long pants and shirts are fine, but I think I would feel better in a fire suit. Do you think it is worth the money or should I just wear a long shirt and pants? Are there things I should bring that most people forget or don't know to bring?



--Mike

[RACER X #99]

Mike,
Most if us all wear fire suits but one of the most important safety items you need are arm restraints.
Bring plenty of spare parts and you will not need any of them. If you leave it home you will need it.
I always bring spare tires, brake pads, brake fluid, belts, hoses, fuel pump, carburetor, water pump......blah blah blah... you never have enough spares.

[mj_duell]

Thanks Racer X #99,
O.K. what vendor do you like for safety clothes? I have a current Snell rated helmet, but I need a suit, arm restraints, socks, shoes, gloves etc. Sorry for all of the questions, new at this.



--Mike

[REDSC400]

Originally posted by mj_duell


Hello Everyone,
Can anyone give me some insight into what seems to be the best pressure for regular "Around town driving" ?



--Mike

Well Mike, If you get yourself some "soft" chalk and mark a chalk band about 1" wide on a front and rear tire tread, this will provide a nice quickly deployable and wearable visual guide patch size and to tire wear. Then with your current inflation you can drive a few miles, trying to keep your turns at a minimim and then scrutinize the wear on the chalk. Even wear is good. Center wear means over inflated and edge wear means under inflated OR corner wear. (all assuming your alignment is not exhagerated). So try to perform this test and like I said, attempt to keep your turns at a minimum during the test. This should tell you alot.

FWIW, I run about 22 Lbs in my large tires for normal street use.
265-50-15 front and 305-50-15 rear. Any more air than that and the ride is bone jarring and I get pretty severe center tread wear patterns.

[mj_duell]

Thanks REDSC400,
I use to do the chalk test with my Vette at SCCA meets. Sounds like a good idea. I think I'm having a hard time adjusting to the thought of low tire pressures. I have a fear that low tire pressure at sustained highway speeds maybe dangerous. However, I've never had Bias Ply race tires before only Radials. I know what you mean about the hrash ride. I'm running 350# rear springs and with the tires up at 30# pressure it feels very jarring.



--Mike

[rdorman]

As has already been touched on...... the bias plys don't run as much pressure as radials. BFG had a formula for calculating a pressure but I will be darned if I can find it now. With me and fuel my car is 45/55 split, 2730 pounds. Seem to me the formula said 24 front 26 rear. I run more in the 20-22 pound range in the front and 22-24 in the rear. For competition, need a tire pyrometer (not the infrared type). Most of the buys busting tires are to young to even remember passenger car bias plys!
Rick

[coyled]

Roger, I start mine at 18 in front, 17 in back. I wind up at 24 in front and 25 in back hot. Tire temps this weekend were 200 in back and 185 in front, pretty even across the tire, on an 80 degree day, on a short technical track. Where do you wind up hot as far as temps and pressure? Scott

[RACER X #99]

Scott,
I have been running about + 4-5 lbs and temps of 175 but WGI is not technical and has a lot of long straights to cool the tires. Still searching for the "perfect setup".

Roger