Track Tac

How do you know when tire pressure is correct?

Wait. I've got it. We'll reduce the pressure in an attempt to get more rubber on the ground. To heck with rolling resistance and parasitic drag. Maybe we can make it up with ceramic bearings, low tension rings, and trick oil. Wait. Now our tires aren't touching in the middle. We'll pay some tire voodoo guy to cut away the outsides of our tires so the middle will touch again. Then we'll order some more tires, because these aren't going to last long, as thin as they are. Ain't racing fun. Lmao.....and the beat goes on. No really On. Still fun. I'm crazy and trying to enjoy every minute of it. Take Care Everybody.....:)
 
I'm not going to read my original post to see what I was thinking about when starting this thread, so I'll just hyjack it now. ... :)

I often get this mixed up, but I'll give it a go.

Years and years ago on here Joey explained it to us all.

1. You should match how hard or soft the tire is to how abrasive the track is. More abrasive track, harder tire.
2. Match sidewall stiffness to track grip. Hard sidewall high grip, soft sidewall low grip.
3. And lastly match air pressure to how hard or soft the track is, hard track high air pressure.

... now the bad part. I usually get 2 and 3 mixed up and as usual when I try to put this down on paper, wish Joey would say if it's right or wrong. I use to use it all the time when thinking about what to do with tires, when my memory was better. ... :)

What's neat with it is so many soften tires looking for grip, when you should be setting how soft the tire is, per either how hard the track is or how much grip it has. It means there is a functional limit, to how soft you want to make a tire. ... hummmm
 
I always ran as much pressure as I could to match the track. Or the type of racing. On sit up enduro racing, I ran a lot of pressure. Into the thirties. Even with harder smaller tires. The big radius turns and high speed you find on most enduro tracks call for a high-pressure tire. I could watch the competition fight their way through turns trying to overcome the wobbling of the sidewalls under low-pressure tires. There may be times, on dirt, where you need to run lower pressures, but I think some people go to extremes, especially on large radius turn tracks. I think you should run as much pressure as you can, up to the point where they're not biting enough. "Not biting enough" is a very vague term. If you could get through the corners with higher pressures, it's better than running too low a pressure. There are times when you need lower pressures, but there are times when you can run much higher pressures. On a large radius well packed dirt track, one it's got good bite, there's no need for low pressures. I think if you try it you'll find that you can run much higher pressures than you would imagine possible.

It's called tuning, and tuning is tough. (Al Nunley)
 
I went and started wading or wadding through my original post and stopped after reading the first few lines.

I'm going to add in here this and most all of what I write is not about how to do things, it's about trying to understand how stuff works. And the understanding will come from observing, relating one thing to another and experience both hands on and from talking to others about their hands on experience. The math is great to prove but I can't do the math nor prove most any of this. What the math is going to do is to say either "darn your right and you've been right all along" or to say it can't be because it just doesn't figure even though that seems to be the way it works.

... so, just some more thunkin, wandering and wondering. ... :)

Quoting me because nobody else would ever think to or want to do it: "Yes it's obvious this would be about slip ratio's. ...

Slip ratio is based on revolutions of a tire per distance traveled. Acceleration based on slip ratio states, maximum acceleration is at maximum wind up of a tire prior to slipping.

That's slip ratio in a nutshell."

... posting unfinished work so I can read it before adding on thoughts.

Ok moving on after reading. When I read the first part of the first post it occurred to me that since the two rear tires are different and hooked together with a solid axle, maybe their difference could relate to a number being put on the rotational effort possible out of the axle.

Yeah I can't do the math, but if there was a final number for rotational effort from the axle made up of different variables, we could see via a spread sheet maybe, how each variable effects rotational effort. It would still come down to how do you know if your getting enough rotation out of the axle, but if it's obvious you need more you would be able to go to the easiest way or combination of ways to get more.

Air pressure would boil down to just one variable. It and the rest of the variables, would effect how the slip ratio differs at each rear tire. Always another question and I think I have to ask it now.

How can you find the slip ratio or a number for potential slip ratio, for a tire?

If we could do that, then we could setup known inputs and know how the numbers would change, for each variable input effecting total rotation of the axle.

I think those who keep good records can use their records of answers, to know the direction of change when you adjust the chassis or tires. Nogoats cheat sheet is that sort of thing. If we could read slip ratio's for each rear tire, the cheat sheet could be refined to how adjustments will effect axle rotation. And yes how adjustments effect axle rotation still will be different during deceleration, rolling, the start of acceleration and final acceleration.

I have to stop now because thoughts I'm thinking and trying to put down in a logical progression, are again being confused by obvious multiple variables. I'll again have to post and read through this to see where it was going or might need to go. And without input from others, it can only go where I make it wander. With input from others it can and usually does take a different path.

One last thing for now. I think I do know how to easily put a number on a tire which accurately can represent slip ratio. I posted the idea many years ago on here, but now that I better see the value of it and since the past on here is gone, I'm going to keep it to myself. ... :)
 
ps... Al, I enjoyed reading your post. Thank you for your efforts.

paul

And ps again... Yes I do and did appreciate the efforts of others reading and replying too. I just wanted to give Al an easy time. I'm not really into always giving Al and others a hard time. ... :)
 
Got to head out to Eldora soon and I took the time to read through my post #25. Seemed sort of ok. I'm first interested in knowing if it was confusing or maybe fell in line with common thoughts about stuff. And as always interested in comments on it, so I can learn others thoughts. I tried to pass on others thoughts in this thread and don't know if I passed them on ok. It's tough enough trying to understand my own ideas and stuff. ... :)
 
You must log in or register to reply here.
Back
Top