Wheels and weight
 

How much of a difference does it make performance wise, to go from the stock Turbo II wheels to say the average weight 18's(23lbs without tire). I am really looking for people with a personal experience.

Another curious question: Does anyone know what the stock wheels weigh?

The Specifications sticky thread and the FAQ for FC sticky threads (both found at the top of this section as well as at the top of the New Member technical section) have some of the weights for the stock wheels.

And a good rule of thumb with wheels is that for every 5 lbs of weight per wheel (or twenty lbs per 4 wheels) subtracts 5 horsepower from the engine.

Therefore going with an 18 in wheel that weighs 23 lbs vs a S5 Turbo wheel that weighs 17 lbs will result in a 6 HP loss at the drive wheels.

Or more dramatic, going from say the 15 in BBS wheel found on the Convertibles, to that same 18 in wheel that weighs 23 lbs, you would have almost a 12 horsepower loss (and not even considering slower response of the suspension because of the extra weight).

This is based on SAE papers submitted/written by Honda on OEM and aftermarket wheel weights and their effect on driveline power losses.

Thanks

That was the exact kind of answer I was looking for.

That's a gross oversimplification. Weight is only part of the equation, equally important is where the weight is radially in relation to the center. As a wheel gets bigger, the weight gets farther away from the center, making it harder to accelerate because the moment of inertia is increased. Compare an equal weight 15" and 18" wheel and the 18" wheel will sap more power because it's bigger, and even with the same weight, has a higher moment of inertia.

Honda's study went up to Plus two standards, but found no increase in driveline loss at same weight.

That's a bit surprising, but the fact is that if you go up in size, you'll go up in weight to what you could have had with smaller wheels.

Wheel weight (and tire weight and sidewall height and stiffness) also have a big impact on ride quality and grip over anything but a smooth surface.

Lighter is better, as long as it's strong enough.

IMO it stands to reason that what Black91n/a has said is correct, but obviously it wasn't enough of a difference to show up on a dyno which has a certain margin or error.

I would suspect, mostly due to in decrease in rubber and steel of the tire on the smaller aspect ratio's, but I will have to find the report again and see if they mention anything on it.

I'd still be willing to bet that, even at the same total weight and same outer diameter and width, that a 15" wheel and tire setup will have a lower moment of inertia than a 17" one for example.

I wonder if it was just something that they rounded off as it wasn't within the repeatability of the dyno?

I'll see if my SAE account is still active and download and scan it for you