3074S M/T, a confusing and frustrating happening

[Woodfin]

Racers, I bring this topic back for an update.

To review, I installed, simply for maintenance, a new set of M/T #3074S [32 x 14 x 15S] The old set, although performing well, was two plus years old with many runs.

These are on my S-10, Super 10 super stocker that I also bracket race. It runs 6.30 - 6.40 in the cooler months, 6.40 - 6.50 in our Texas heat.

The stiff side wall has worked as expected for me with several other packages. Also, with my Truck, it has a 5.57 rear gear, 1.98 low and 6600 converter so it hits hard at the trans brake release, even with the small 327 engine.

So, again to review, the first outing with new tires produced chatter and slip. [same tire, same part number, same air pressure] I even talked with M/T to verify the tire was the same design, no changes.

After two frustrating outings of chasing the cause, and chasing the dial, and chasing the reaction times, at the recommendation of another race who runs the same tire and similar weight and performance, I made a drastic [for me] change. I am not prone to make large changes, I am usually slow and methodical with changing.

AnyWho, even though the truck had worked well at 11 pounds with old tires, and even though the general feedback was "hitting the tire too hard, needs more air" [we had it as high as 13 pounds]

Well, just go figger, dropped air pressure to 8 pounds and voila, dead hook with the expect ET.

It would be reasonable for a person to expect, at my age and with my experience, such lessons would have already been learned, yet, that expectation is wrong. It is my observation that the lessons are an on-going and never ending process.

[Mike Rietow]

Originally Posted by Woodfin

Racers, I bring this topic back for an update.

To review, I installed, simply for maintenance, a new set of M/T #3074S [32 x 14 x 15S] The old set, although performing well, was two plus years old with many runs.

These are on my S-10, Super 10 super stocker that I also bracket race. It runs 6.30 - 6.40 in the cooler months, 6.40 - 6.50 in our Texas heat.

The stiff side wall has worked as expected for me with several other packages. Also, with my Truck, it has a 5.57 rear gear, 1.98 low and 6600 converter so it hits hard at the trans brake release, even with the small 327 engine.

So, again to review, the first outing with new tires produced chatter and slip. [same tire, same part number, same air pressure] I even talked with M/T to verify the tire was the same design, no changes.

After two frustrating outings of chasing the cause, and chasing the dial, and chasing the reaction times, at the recommendation of another race who runs the same tire and similar weight and performance, I made a drastic [for me] change. I am not prone to make large changes, I am usually slow and methodical with changing.

AnyWho, even though the truck had worked well at 11 pounds with old tires, and even though the general feedback was "hitting the tire too hard, needs more air" [we had it as high as 13 pounds]

Well, just go figger, dropped air pressure to 8 pounds and voila, dead hook with the expect ET.

It would be reasonable for a person to expect, at my age and with my experience, such lessons would have already been learned, yet, that expectation is wrong. It is my observation that the lessons are an on-going and never ending process.

It might not be the new tires.

[Adger Smith]

It needed lower air pressure to "Work the Sidewalls" I ran into the exact same thing years ago with some 12" Firestones that we ran on a Super Stocker. We only ran the car at two racetracks and the car did the same thing at both tracks. Same deal as you Larry, small changes for me, but it took a real big change to get to the sweet spot that made the sidewalls work. I never got a picture of ours, but the wear on the tire looked like it had the sides hitting way harder than the rest of the tire. With the sidewall softer the footprint looked more even. I would just write it off to the way the MFG processes are. A Cooper tire plant is about 6 blocks from my home. I know a lot of tire builders and to hear them talk it is not rocket science.

[Woodfin]

Adger,

I have come to the same conclusion. The new tire sidewall is more robust than the old tire. Thus, requires less air pressure so the sidewall can work as designed.

We did employ a diagnostic tool, a cell phone video. It is amazing the video a modern cell phone can produce, vivid color, slow motion, stop motion, expand, what a tool!

[Woodfin]

to review, the confusing part of this issue is that I never had it happen before. [that is to say, never installed a new tire replacement of the same tire and had to change air pressure]

Of course, in hind sight, I now understand the happening.

"Drag Racing, a life long learning process"

[Adger Smith]

Didn't have all this modern Tech back in the late 60's and early 70's did we Larry. We night have been real dangerous if we had... even a weather station!
BTY: I started tracking some weather after I got my pilot's license in 1969. Before that I never knew what Air Density was.

[Jim Parsons]

I have been fighting this same MT tire issue/ inconsistency for over a year with a bracket car I mess with. Worked on the front end thinking it was about no pitch rotation hitting the tire, then shocks front and back, leave RPM, ladder bars, and even loaded the trunk with 80lbs. of weight!
Took your suggestion and went to the track last night and dropped the pressure from 11.5-12 psi to 8.5 psi and 60’ are back with in .005 for five runs.
Thanks
Jim Parsons