do larger/heavier wheels/tires equate to less hp to the ground? If you were to dyno a set of 16lb 16"s vs 30lb 20"s would there be any difference, or is it just in the braking ability?

 

Yes, less power would be reported on the dyno.

 

The issue with rims is the weight/mass of the rim away from the hub. The more mass further away the harder to get into motion. You can have 2 rims that are both the same diameter and weight but can have different performance based on how much weight is centered and how much is pushed outward to the lip of the rim.

Each tire weigh differently as well.

 

^ +1, on a chassis dyno that leaves the wheels on (as opposed to the kind that measures power at the hub).

 

unless the dyno is connecting to the hubs (dynopack) you can always tweak the numbers a little by under inflating tires or over-inflating.

 

^ thanks for all the info I'm a noob haha

 

^ a noob with 5.000 posts? haha

 

I doubt it. The extra mass and moment of inertia would affect acceleration, but not steady-state horsepower.

 

Sounds familiar

 

Shhh.. it's a disguise

 

A Dynojet measures how quickly the engine can accelerate the drum over a timed period and rpm. The quicker and faster the drum gets the spun, the more power to the ground. Since the engine has to work harder to accelerate the heavier wheels, it will certainly show up in the numbers. Simple physics.

 

Final drives can also affect HP as well.

 

If you dyno at 1:1, how would the final drive change the dyno readings?

 

If you do a dyno run on one date with a 3.3 FD and then go back on a different date and dyno with 3.7 FD.

 

OK. I am only familiar with the type of dyno that applies a break to the drum, and reports the HP at each speed within the range - "brake dynamometer" rather than "inertia dynamometer."