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Discussion Starter #1
Hey guys! I've read all sorts of stuff from a few years ago on what pressure to run in a 275/60r15 ET street radial and this shit ain't working for me. I have run my last 2 sets at 13.25 or 13.5 psi in the staging lanes. Ends up at 14.5 psi after a run. This is about 3-5 psi less than anyone recommends. Has been working great for me but I keep getting told by guys that it's way too damn low. I go up to 15 cold and blow the tires off like frig all. What are your thoughts? I can't get anymore tire under it without moving shit.
The car is a 3450lb big block '71 Challenger with superstock springs
Roughly 520 torque and HP.

Thanks.
Don.
 

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My car is 3825 lbs with about 475-500 hp. 19 lbs. works great for me. I think if you are having troubles with higher pressures you have other suspension issues. JMO.
 

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How wide is your wheel? We run a 10" wheel and a 275 Pro. @ 17# our tire footprint is 100%. At 18#'s it's about 90%. We discovered this after making a pass and driving the car to the trailer thru some short grass, there was no grass sticking to 1" of tire footprint on the inside on both tires. We blew the tires off on the 18# pass also. Lowered the pressure back to 17#'s and back up on the bumper.
 

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Discussion Starter #9
Thanks guys! I'm gonna say F'it next time out and run em at 18. I'll give it another go like that. I do run them on an 8" draglite. A 10" wheel pulls the sidewalls out a little more and gets into the 1/4 panel if the suspension compresses.
Thanks for the responses!
Don.
 

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I am running the 275/60-15 on 8" wheels on my Chevelle. Car weighs 3800lbs with me in the car. I run 18PSI and most runs it hooks, occationally it will spin bad but not often. I usually have around a 1.47 60' time and run mid 10's.
 

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I have 305/45/18 and run at 17#'s. Radials are hit and miss. It takes a lot of tweaking to get them to hook correctly on a not so great track. If the track is prepped well, you should hook with no problems at 17#. You really need to get the weight ratio right and work on the suspension.

In my car, I have no issues on good track. Will hook every time. If the track is average, I'll spin. I had to add weight to my trunk to get the car to hook consistently on an average track. I'm replacing my springs next and hoping that helps on the average to bad tracks.

But I had the same exact results as bigdaddyb1. I noticed a considerable difference in the tires spinning and hooking between 18 and 17#'s.
 

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Discussion Starter #15
Have you matched your tire gauge with anyone else? It could be anywhere.
Doug
Yes Doug, my gauge is within a needle width of two others I've compared with. Could be a lot to do with it being a big block Challenger with horrible weight transfer. I've got 90/10's on the front and adjustables on the rear set full stiff to reduce chassis separation on launch. Dodges don't seem to have the best weight transfer anyway. I will start at 17lbs and try again.
Don.
 

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Yes Doug, my gauge is within a needle width of two others I've compared with. Could be a lot to do with it being a big block Challenger with horrible weight transfer. I've got 90/10's on the front and adjustables on the rear set full stiff to reduce chassis separation on launch. Dodges don't seem to have the best weight transfer anyway. I will start at 17lbs and try again.
Don.
First thing that jumps out in what you said is you have the shocks set at fulltight to reduce chassis seperation, this is exactly the opposite of what you want, you want the chassis to seperate to drive the tire into the ground... With that said...

How fast is your car? Do you have a power adder?
How much does your car weigh?
What kind of traction device do you have?
What rear shocks do you have? Is it a double adjustable?
Is your front suspension stock? How much front end travel do you have?
 

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Discussion Starter #17
Front has over 5" of upward travel from ride height. Rear shocks are cheap Comp Eng 3 positions. Set on 50/50. I've tried the other settings and it just hits and unloads. I know a good set of IMG_7463.jpeg2 way adj QA1's would help. Car isn't really fast, just a street/strip car. Runs 7.30's in the 1/8 on a good day with 1.60 60" times. 1.594 is my best.

Don
 

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Discussion Starter #18
I will raise the pressure to 17 and put the rear shocks on 70/30 to let the tires hit harder. Who knows? Maybe I've been trying to bandaid a bandaid with a low tire pressure.
 

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Donny I have a 67 GTX with the same tire and I run 19 20 lbs ..and I have gone 1.43 60' but it took a while to get there ...first do you have Cal TRacs ? if not get them call them they have been so helpful get the whole system springs leafs shocks etc. front shocks are koni race ...but cal tracs make a front shock as well
 

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Discussion Starter #20
Donny I have a 67 GTX with the same tire and I run 19 20 lbs ..and I have gone 1.43 60' but it took a while to get there ...first do you have Cal TRacs ? if not get them call them they have been so helpful get the whole system springs leafs shocks etc. front shocks are koni race ...but cal tracs make a front shock as well
Ya, the Calvert 90/10's are a really loose shock. I don't have Caltrac monoleafs and bars though, I have B body Superstock springs with the required spring hangers. They must work somewhat because my old springs only got me 1.70 60' times. I have a young family and live in western Canada so racing funds are somewhat limited each year and parts are god damn expensive to have sent up here by the time our retarded gov't adds all the duty and 12% tax onto shit. Add 50% to the listed price and that's what we pay.
Anyway, enough talk about free trade!
I'm gonna change a few things around and try it out. My Dad has Caltracs on his Challenger and they have madè the car consistent on even shit track surfaces.

Thanks guys.
Don.
 
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