Reaction time difference, bias ply vs. radial slick

[Portatree Timing Systems]

Here is a bit of information on what effects rollout/reaction time. Weight is a huge factor. Front tire size is also important.

http://www.portatree.com/page--Tech-Tips--TechTip1.html

Happy Holidays!

[Bobby Fazio]

I am excited about Mickey Thompson's new line of smaller radials so I am really anxious to see how much it changes my RT and ET. I always ran 20lb in my bias ply slicks so I'm wondering if it will really change much.

[Eric Merryfield]

Originally Posted by Bobby Fazio

I am excited about Mickey Thompson's new line of smaller radials so I am really anxious to see how much it changes my RT and ET. I always ran 20lb in my bias ply slicks so I'm wondering if it will really change much.

The Gremlin is lobbying me to invest in a set along with a set of rims since I didn't know about the 26 inch radial till today! Gremlin also runs 20-2 lbs, but I could see running 30lbs in the radial with ease. Tire weight increase is around 5lbs a piece for the radial versus bias.

Don't know how it would affect RT in a beast like the Gremlin, might slow it down dead hooking into a crowd pleasing wheelie of say a couple of inches, vesus the pro-stock style launch it sports with the bias.

Whats the best equipment out there for measuring vehicle reaction time currently?

Eric

[7423]

Originally Posted by Eric Merryfield

Whats the best equipment out there for measuring vehicle reaction time currently?

Eric

The best equipment is your time slip and the best fix is seat time, lots of it.
A practice tree will tell what your RT is. The rest is in your car. The average foot brake racer is .20-.25. Button boys are a bit quicker.

[Joe DeMarzo]

Ed & Charlie, I run 18 to 20 lbs in my bias depending on the track conditions.

[b.guggenmos]

Is it still generally considered to not use a radial on a stick car and that they should be left on automatics? What makes me wonder is that with some of the small converters along with the high launch rpm and leaving from a trans brake they leave like a stick car. Hard. This should also apply to the reaction time question asked.

[Ed Wright]

Originally Posted by Joe DeMarzo

Ed & Charlie, I run 18 to 20 lbs in my bias depending on the track conditions.

Joe, mine is an SS car leaving with a Trans brake.

[Portatree Timing Systems]

Eric, Lebanon Valley Dragway has a vehicle reaction time setup that will tell you roll out. You have to mount a module to your car, and then an extra sensor that they have on the track will calculate the roll out of your car. It prints on the time slip. That is the most accurate way to determine the roll out.

[Dave Casey]

Originally Posted by b.guggenmos

Is it still generally considered to not use a radial on a stick car and that they should be left on automatics? What makes me wonder is that with some of the small converters along with the high launch rpm and leaving from a trans brake they leave like a stick car. Hard. This should also apply to the reaction time question asked.

It would seem that way, but the autos still are a fluid coupling, and don't hit the tire as hard initially. I have always had stick cars and the only time that I have used a radial was years ago when my Camaro ran L or M/S and I had a lot of wt and less power. It still loss in the 60 and 330 times, but made it up on the big end.

If there is any rt dif between the bias and radial, it certainly changes with the tire pressure.