Radial tire issue ??

First time out this year with the big block dart. Makes 820 hp with a stock front suspension and four link rear. Ran it for years with bias tires on all fours and no issues.
This year I put on the good year rear radials. There a tad smaller than the 14x32 good year bias. There 31.5. With 17 lbs of air pressure. When I get to the 1/8 mile the steering wheel starts going left to right and the car starts rocking back and forth and I have to let out of it or I’ll wreck. It’s not tire shake, I’ve had that a couple of times but that was a the starting line. Anyone have any thoughts on the issue? Thanks for your input.

Air pressure too low? Wheels too narrow?

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Do you still have the bias ply tires on the front?

Air pressure on the front is 35 and 18 on the rear. Same wheels I’ve had since I built the car.

Bias tires are on the front. There 4.5 x 15.

Put bias back on the rear and see has it handles. I ran a radial slick and bias on the fronts with no handling issues on my old demon but, it had rms front suspension. Only time it go a little squirrelly on the big end when I lowered tire pressure.

Dunno, seems like you have to run all bias or all radial on really fast cars.

I run M/T radials on my Valiant 14x32 with 15 lbs of air with no issues. Fronts are M/T bias. They are recommended for Super Stock. The Goodyear 14x32 radial is recommended for a much lighter car like comp eliminator . Maybe this is the problem or maybe it is something else entirely. Car runs mid 8 seconds

Not much help I'm afraid but we've ran radial / bias fronts for many years with no issues, car is actually more stable than bias all round. Only doing 140 -145 at the moment. However, I have it in the back of my mind that radials are less forgiving than bias ply's when it comes to alignment issues but can't remember where I saw or heard that, Guessing that you've already checked tyre circumference, roundness etc when inflated.

how much caster do you have now ?
maybe adding adding a couple more degrees along with a little more toe-in might help.
i have mixed and matched radial and bias-ply on each end countless times without any problems, provided air pressure was correct and front alignment was spot on.

I had this exact problem running 14x32 radial slicks twenty years ago. I would check with a couple of sources for help Fist, the tire manufacturer. Then go to a SuperStock forum and ask.

Bias ply tires up front w/ radials out back is not your problem. I've been 156+ mph w/ a stock suspension 3800 lb car w/ 295-65 radials (15x8 wheels) on the rear and bias ply M/T Sportsmans up front. The car drove perfectly fine.

Is the problem originating in the front or the rear? From your description it sounds like the front is causing it due to alignment problems. Wheel starts moving....Bump steer issues? I would check that out first.

I have a hard time believing a radial slick would be more unstable than a bias all things being equal.

not the same, trust me. He has a 14 inch wide tire, which i believe is part of the issue . i went 8.78 at 153 mph and almost lost it due to "radial rock" like the author discribes. 3000 lb Dart. The car ocilates side to side violently. And when guys watching your 8.78 run ask why you didn't lift, it is very serious!

I googled “radial tire rock” and that’s what I have and lots of others. Just need to do some more research and figure this out. Thanks for your replies.

I had a radial rock problem with several sets Hoosiers 14.5x33. They were aware of the problem and their fix was to stop making large size radials. I then used M/T and never had the problem again. I think your problem is that the Goodyears are made for a lighter car. That is why I don't use them and that is why Goodyear doesn't recommend them for Super Stock. I run NHRA super stock and have never seen a super stock using a Goodyear Radial in recent years. Look at the AH cars that run automatic transmissions. They all run Mickeys