Anyone change brand of tire and notice an ET difference with ALL factors being the same(or very close) other than brand/weight?
What are your experiences and how fast of a car?

Its been some years since I made a back-2-back change, and since tires are on the winter to-do list....

Thanks for any input.

On changing from the same size M/T ET Radials to M/T ET Street bias plys, probally close to 20 lbs per tires differences, the radials will be faster on a good track and slower on a bad track than the bias plys will do to the traction differences, probally not the weight. I don't know if this helps or not I know some racers that have gone faster by removing the race tubes from the rear tires, they had excellent traction, and others tha had marginal to bad traction go faster with tubes Let us know what you do and the results

Just to get a good disscusion/argument going,,,,
1# rotating weight=5# static weight,,,some say higher than that..

This is really 2 seperate question. Trying to answer both at once is like trying several things at once to make the car faster. Too many variables to know what is actually helping or hurting.

The laws of Physics say that a lighter tire and/or wheel will be faster, all else being equal - particularly traction.

To get optimum traction, one should ask & look around at what brands and styles work best on combos similar to yours. Then tune your suspension to make it work as well (consistently) as it can under a wide variety of track conditions.

I noticed a fair difference between radials and non radials that were much heavier, 7 lbs per side to be exact. Total difference was .12 faster with the radials, but the 60 ft was poor with them . I picked up .02 60 ft with the bias heavy tires, but lost it down track to slow by .12 total ET.
DA difference was small run to run (1600ft), so the overall difference may have been .08 to .09. My take- the Radials on a fast car, can have what is called "radial rock". This is a rocking motion side to side that builds as you go! Not all those running radials talk of this, but it is common enough to have gotten its own name among tire makers and racers.
This problem is so bad at times I had to lift on about half the passes, and should have on the 8.77 run. So until the cause and cure is well established I won't be going back to them. They also are hard to hook, and track prep is very critical. If you look at the various SS/AH ETs in eliminations you will see what I am talking about.
These may be a big benefit to a footbrake racer running a glide, where traction off the line isn't as big an issue.

I can tell you that I went from 15x6 cragar's w/ 215/75/15's to 14x5.5 (don't recall the tire size 205/75 maybe) but the 14's were about 20lbs lighter (each) than the cragars and I didn't see a change in the et at all. (12.0) car.

Like the comercials say..."your results may vary".. . I know that you will see a drop in ET if you get rid of rotating weight. You speak of rear discs replacing drums..?..I KNOW for a fact this will help. Getting rid of the tubes in the slicks is a big help too. Some people claim as high as high as 8:1 on the weight ratio, but, I say in the 4/5 ratio is my experiences.

To elaborate a bit on what GREGSDART said - On Stock class cars using 9" tires, radials tend to be about a tenth faster than their bias ply counterparts and in my case, the Hoosier slicks that I use also made for slightly quicker reaction times. Radials also don't grow like bias ply slicks, so the tach will see more rpm's at the finish line. That may account for some of the ET benefits, at least if you're not over-geared to begin with.

Radials are more sensitive to track conditions so the will spin easier under marginal conditions. But the IHRA events have their tracks prepped fairly well. I run the radials all the time so I don't have to worry about adjusting for the RT's if I do have a heads-up run.

Hoosier has a variety of radial slicks, including lighter weight versions.

Hoosier tire specs