Does tire pressure make a difference?
Does tire pressure make a difference? Just wondering if the tires being over inflated or under inflated will make a huge difference on how much the rwhp and torque is. Anyone know from first hand experience? What is a good tire pressure to keep your MT drag radials at when you dyno. thanks
I believe you want your tires aired up pretty good - basically about 35psi if you are not laying down some ungodly amount of power anyway. Most of us usually run our pressures down just a bit for better traction on the street ( I run 27 psi rear and 29 psi front) - but that causes a little extra drag on the drivetrain which eats up a little power and economy. I mention the part about cars with ungodly amounts of power because I have seen where cars in the neighborhood of 800+ rwhp can actually start to fight for traction on the dyno. I actually watched a Supra dyno over 1000 rwhp where they had 2 guys pile in the back hatch to try to help traction.
This is why I stopped using a roller dyno. If you have to ask yourself if your tire pressure will affect your numbers, then you are not ready to have the car tuned the right way. Eliminate all your variables, then you can see what she does.
Rick
Rick
QUOTE: This is why I stopped using a roller dyno. If you have to ask yourself if your tire pressure will affect your numbers, then you are not ready to have the car tuned the right way. Eliminate all your variables, then you can see what she does.
So whats your answer Rick? Does under inflation lower #'s.
So whats your answer Rick? Does under inflation lower #'s.
On The Tree
Joined: Sep 2004
Posts: 159
Likes: 1
From: Cape Coral, Fl
Yes...tire pressure does change results due to HP being used to overcome rolling resistance of the tire, absorbing HP before it gets to the rollers.
An easy way to minimize the variable is to use a consistent tire pressure and the least amount of downforce from the tie down straps as possible. Remember, a chassis dyno is just a tool...as good as its operator! Think of it this way, the motor generates HP(energy)...the HP(energy) has to travel through the drivetrain (tranni, u-joints, shaft, diff, axles, wheels and tires) to the roll, absorption unit and load cell. Try to eliminate as many variables as possible. The heat you feel in the tires after a chassis dyno pull is HP/energy that did not make it to the ground.
An easy way to minimize the variable is to use a consistent tire pressure and the least amount of downforce from the tie down straps as possible. Remember, a chassis dyno is just a tool...as good as its operator! Think of it this way, the motor generates HP(energy)...the HP(energy) has to travel through the drivetrain (tranni, u-joints, shaft, diff, axles, wheels and tires) to the roll, absorption unit and load cell. Try to eliminate as many variables as possible. The heat you feel in the tires after a chassis dyno pull is HP/energy that did not make it to the ground.
This is why I stopped using a roller dyno. If you have to ask yourself if your tire pressure will affect your numbers, then you are not ready to have the car tuned the right way. Eliminate all your variables, then you can see what she does.
Rick
Rick
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Originally Posted by Jimmy P
Thanks for your reply guys. Well Rick, I dont need to have my car tuned on a dyno. I did it the right way and had it tuned on the street by a local tuner. I just want to get it dynoed to see an estimate of what type of power it makes, and to shut up my buddy. He has 88 Mustang with a eagle stroker kit and forged pistons, a bunch of small mods, through a 5 speed and a 8.8 rear with 4.11 gears. I basicly want to prove him wrong saying that his will dyno more than mine.
Sounds good.
Rick
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