Weather beaten '68 Charger 4-speed Hurst

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 2:33 pm

Definately Clivey

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 3:03 pm

My car has a squidgillion psi in the rears at the mo.

Dave-R · Post by **Dave-R** » Mon Aug 17, 09 3:04 pm

Clivey wrote:My car has a squidgillion psi in the rears at the mo.

Yeah. Another one with no power to plant.

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 3:07 pm

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 6:08 pm

If the motor bogged with 22psi tyre pressures then you got issues , possibly fuel & timing , if the motor was set up properly then it would of spun the tyres with 30psi tyre pressure , i'm with Gareth , the car hooked better with the lower pressures & the motor fell flat on it's face , this proved the point the car faired better with the lower pressures , or more to the point it will do when set up , tis all a learning curve.

Anyone getting decent 60fts with tyre pressures @ 28/30psi?

GTXJim · Post by **GTXJim** » Mon Aug 17, 09 6:44 pm

Hi Jonny, What was your mph on your runs, it's a good indication on what times you should run.

Dave-R · Post by **Dave-R** » Mon Aug 17, 09 6:52 pm

So the guy that develops tyres for GoodYear talks Bananarama! does he?

Adam. I am told it is in the side walls. They are very rigid on normal radials. So as the tyre pressure drops the center of the tread pattern applies less pressure to the road and the edges of the tread apply more.

Over inflation is bad as well of course because then the center of the tread pattern is taking most of the load. It is a matter of finding what pressure applies the load evenly across the tread width. It will be somewhere between 26-34 psi depending on the tyre and thw weight applied.

Slicks and drag radial do not have the same side walls and respond well to low pressures as in their case the footprint of the tyre is not effected and a soft sidewall has advantages with storing energy.

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 7:05 pm

Maybe we've gone off topic here , a motor that won't pull the skin off a rice puddin will be ok with higher pressures (not refering to Patina but generally speaking) , when i had the old 440 motor the tyres would spin , lowered the pressure to 20 psi & picked up on the 60ft , this is fact Dave , what pressure does everyone else run? , i'm not arguing with the tyre man but the time slips don't lie , also if yer gonna run the 1/4mile & heat the tyres you ain't gonna be too bothered about havin to buy another set.

Maybe we should get a poll goin , "what tyre pressure does everyone run" , might learn something from it.

Jon · Post by **Jon** » Mon Aug 17, 09 7:17 pm

If you underinflate an ordinary street radial it will only grip at the outside edges..I'm with dave on this one...having tried it ...with a 493 that might just have managed to get that rice puddin skin off skin off

street legal drag tyres are a different kettle of fish

latil · Post by **latil** » Mon Aug 17, 09 7:42 pm

http://www.hankooktyre.com.au/Serv/Infl ... ChildNum=3

Much less rolling resistance with a tyre at the correct pressure,let it down a little and there is more rubber on the road which will take more power to spin up and lose traction.So instead of spinning the power is transmitted to the tarmac.Lower the pressure too far and the tyre runs on it's outer edges only,with no grip in the centre section but requiring more effort to turn because of the deformed sidewalls.

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 7:43 pm

Clivey must be outta sight by now!!!

Philth · Post by **Philth** » Mon Aug 17, 09 7:44 pm

Good stuff Jonny!

Bet you loved every second of it!

Sounds like it would have been a good match between you and Woody

I know too well about bogging issues, and I ain't talking toilet! Pretty much sorted now after the Nats

Best I ran at this years Nats was 15.5 @ 95.9 (first was 15.7 @ 96.3). PB a few years ago, when it was a four speed and had an old .509 MP cam, was 14.2 @ 98mph. All with a 'whoopsee' 2.76 open diff!

As for tyre pressures, I reccon 25 psi is a safe bet for streer treads, but I guess it's all about what you find the best through trials. Jem has treads on the Ratster but you could see that all of the tread width was not being used, even at 19 PSI. I think they are the special sort of street treads, if you know what I mean...

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 7:52 pm

The way it worked for me was to spin the tyres (locker) till the tyre patch was heaviest , i think this was around 22psi , i can see how reduced pressure can cause the tyres to deform , maybe different weight cars will be different , it did get worse (unstable) & loose traction below 20psi , an open diff would be another kettle of fish.

Anonymous · Post by **Anonymous** » Mon Aug 17, 09 8:04 pm

Jon wrote:If you underinflate an ordinary street radial it will only grip at the outside edges..I'm with dave on this one...having tried it ...with a 493 that might just have managed to get that rice puddin skin off skin off

street legal drag tyres are a different kettle of fish

Jon how far did you get on street tyres with the 493"?

Jon · Post by **Jon** » Mon Aug 17, 09 8:26 pm

just about to the end of the track in one piece

anywhere from high 12s to 14s at around 113mph... 60 fts were around 2-2.5 seconds

letting them down on the advice of others just made it worse