How much HP = tire spin @ 60MPH?

[The T-man]

I am buiding my 406, and see a bunch of you guys saying you can haze the tires at 60mph, what kind of HP #'s are we talking about to pull that off?
450, 500, 600?

[Vegas69]

More like contact patch and tire compound.

[61ragtop]

Me too what is the equation for this? I would be happy with 40 mph.

[B_Alley]

I think what you want is a tractive force diagram. Basically, if you know the engine's torque curve, and you know all the gear reductions of the transmission and the differential, and you know your tire diameter, you can figure out how much force (thrust) is produced at the rear wheels. You then plot this force vs. velocity, per gear, this gives you the vehicle's force capacity.

Now for the tire spin: You need to make a separate plot of the tire's tractive force vs velocity. This data is usually collected from a tire testing facility like Calspan, but since you probably don't have the $30,000 it takes to run a tire test and analyze all the data, you can just assume a constant coefficient of friction for the tire. What do people normally see with street tires? .8-1? Our slicks will usually be around the 1.25ish range. Anyways, you know the normal load of the tire (and it does change for how much you accelerate due to weight transfer) and this normal load times the CoF is your tractive force, and plot that versus velocity.

And there you go, whenever your engine lines go above your tire line, you'll be traction limited, and power limited when under it. You can also do the same thing for aerodynamic drag. This is how race engineers choose final drives, transmission gears, and how good powertrain engineers, design engines.

Hope this helps, I can post some pics if you would like.

[67ragtp]

In simple terms guys like Jody and Tom Nelson do it with ease, but thats what twins will do for you.

Rich