Bracket Talk
Tire psi relation to wheel speed

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http://drr.infopop.cc/eve/forums/a/tpc/f/80760912/m/6187029296

March 25, 2020, 10:17 AM
TOP38
Tire psi relation to wheel speed
quote:
Originally posted by 27Keith:
This could turn into a very good topic. How about posting what you have found to be your sweet spot with your own set up? Tire ? Psi ? 60 ft.? E.t. ? Leave rpm ? And your .25 and .5 numbers. Even throw up a picture of a graph for those of you who know how to do that.


One issue with those numbers that can skew things a bit, how do you zero the run after down loading it? For those that use the start of the DS graph, this cam be very different depending on the number of magnets on the DS collar, their is a good difference between 4 and 8 magnets where the graph will start about .125 second earlier with 8 magnets vs 4! That's a large difference that could cause an apples to oranges comparison.

With 8 magnets you can see the wrap up of the sidewall of the tires that you can't with 4.
March 25, 2020, 10:41 AM
Ron C.
Yes,...8 mag is imparitive. Also just studying wheel speed is like studying fuel pressure without knowing volume. The G meter is critical to match up with wheel speed to understand exactly what is going on. It is the clue to what action you need to take at the exact moment in time. And like most things of this nature it takes experience to make the proper tweeks.


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MFI system, ProCharger Non-intercooled [6.02 @ 229 or 3.91/660' soft tune and killing power above 6K rpm]
Ron Clevenger
March 25, 2020, 10:52 AM
TOP38
quote:
Originally posted by Ron C.:
Yes,...8 mag is imparitive. Also just studying wheel speed is like studying fuel pressure without knowing volume. The G meter is critical to match up with wheel speed to understand exactly what is going on. It is the clue to what action you need to take at the exact moment in time. And like most things of this nature it takes experience to make the proper tweeks.


Yes the G meter is also very important. But it also never ends either, now monitoring tire temps on the run helps a bunch too!
March 25, 2020, 07:11 PM
Bucky
I will sometimes look at G meter, wheel speed, and shock position together.
I should add magnets sometime.


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March 25, 2020, 07:48 PM
27Keith
Top 38, I have found the G meter always shows movement before the DS even with 8 magnets. I zero on 1st movement of the G meter.


4 X Track Champion ( 2 & 2 )
2 X Run off Winner
March 25, 2020, 07:49 PM
27Keith
quote:
Originally posted by 27Keith:
Top 38, I have found the G meter always shows movement before the DS even with 8 magnets. I zero on 1st movement of the G meter.



4 X Track Champion ( 2 & 2 )
2 X Run off Winner
March 25, 2020, 11:03 PM
TOP38
quote:
Originally posted by 27Keith:
Top 38, I have found the G meter always shows movement before the DS even with 8 magnets. I zero on 1st movement of the G meter.


It has to as the DS needs two pulses to start which would be at least a 1/4 turn of the driveshaft.

It really doesn't matter how you zero the run for your own deal but when comparing to others it does. I use release of the transbrake which is about .025 seconds before the G meter starts for my combo.
March 26, 2020, 07:27 PM
inferno camaro
quote:
Originally posted by Bucky:
I would gladly post if I had unhooked data. I need to transition with my car. Forever it has been set up with a lot of initial bite. Probably too much even for a car with no shake issues. My problem was often making sure it didn't spin after initial hook because of the excessive plant.
As I try to lean on the new combo, I have found myself with tire shake. Hoosiers are less forgiving with this. I borrowed some M/T's and had no shake issues. But I did see more wheel speed. IMO, it's no secret why they shake less. They bite less so it is easier to get the wheel speed. I am hoping that by taking initial bite away with the four link, that I can slip the Hoosier enough to get through the shake area. I'm going to try a fairly flat top bar with a bottom bar with a little more rake down in the front than I usually run. Keep the shock tight on extension, and start off fairly low on air. Leave with all the timing in. I'm actually hoping to completely unhook the tire, and start sneaking up on this from that side. I really don't want to weld more things back onto this car.
I have heard some say that anything less than 1900 rpm on the driveshaft at .25 second is too little. I don't have anything near that now. I have a picture on my desktop of the car leaving at about 4 feet out. Wheels are up, and the track behind the tires is steamrolled out smooth. It is stuck hard with the tire even across the treadwidth.
We will see how this goes. If I can't get this 14.5" Co7 Hoosier to respond to these changes, I probably won't have any choice but to change tires.

That is interesting. My car would shake every time with Hoosier tires and Mickeys stopped it completely. Funny thing is the Hoosier had more wheel speed than the Mickey. Mine is a door car runs low 5's 1/8 high 8 flat 1/4.