Getting truck put on Dyno, what size tires with 4.56 gears?

[dawson444]

I am getting a new computer chip burnt for my truck, which requires it to go up on a dyno. The guy who is doing it said that my 39.5" TSLs would throw the dyno off a lot being that tall. He said I should try to go for something smaller. What size should I look for? I have 4.56 gears, I can get my hands on some 31s, 275/60/R16/, 33s, 36 or anything else. Thanks!

 

[Derf00]

Gear Calculator

Here, plug in all the #'s and see what size tires you need to achieve the rpm's you want.

 

[84_Chevy_K10]

If you change tires it's not going to be accurate as to what you're putting to the ground with the big tires.

I would think that bolting smaller tires on it and reducing rolling resistance/mass is going to give you a false increase in horsepower compared to your day to day driving.

 

[jarheadk5]

If you're doing a dyno run for the sole purpose of collecting data to burn a new chip, I'd keep your "normal" setup intact. Let whoever is gonna burn the chip compensate for the loads the engine will normally see with your 39's.

 

[GMCLegacy]

i hear smaller tires magically creates more horsepower!
-according to a chevy made j**p guy

 

[mtn. burb]

[ QUOTE ]
i hear smaller tires magically creates more horsepower!
-according to a chevy made j**p guy

[/ QUOTE ]

/forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif

My friend said something like that. But with 42lb. Eaton wheels what kind of difference will it make? Nothing.

I told him going to smaller tires makes about as much sense as your woman having breast reduction surgery.

 

[Highjaxx]

Leave your truck alone, the 39's will rob some power but you want the truck tuned to work best in the form you will run it. Even regearing will not increase your dyno numbers, unless it makes the engine run more efficiently.

The dyno measures(or trys) HP and torque output from the engine, the dyno doesn't care what size tires or gears.

The only reason you would have to put on smaller tires is if it doesn't fit in the dyno room. /forums/images/graemlins/peace.gif

It's fun, and yet kinda sad to see how much power you lose to your drivetrain.

My TBI 454 put down 200HP and 300ft/lbs. /forums/images/graemlins/whistling.gif

 

[CyberSniper]

They might require you to run some mall terrains so you can get a good bite on the rollers. Depending on how much horsepower you make they might require you to run smoother tires because the tread is so open that it'll give little shocks of power to the dyno. If you've got a spare pair of tires I'd just throw them in the back and take them with you.

When I ran my truck on the dyno I ran it with both my snow tires (235x75r15) and my 33s. I think there was less than a 3hp difference. The 20 minutes it took me to change tires the truck got a chance to heat soak so I bet that's where it went.

 

[dawson444]

I will mention all these points to the guy and see what he says. I will let ya'll know how it turns out. Thanks!