Ok, I have been told my 18's probably weigh more than the stock steel wheels. Guess, what 10 pounds each. So basically I have added to the rotating mass something like 40-50 pounds?

I was reading about the Perrin lightweight crank pulley. It stated, "That reduction is effectively the same as removing 100 pounds of weight from your vehicle".

So if I added 40-50 pounds of rotating mass by adding the wheel, then add a pulley which may or may not have an effectiveness of removing 100 pounds, does that mean I would have technically reduced overall weigh by say 50-60 pounds anad still benefit from larger wheels and tires and a lighter pulley?

Does that make sense? I am not a mathematical person, so how it all makes sense is beyond me. Hence the question at hand.

Thanks
Egg

 

your 18's are 10lbs? i hope that's with the tires off, even so damn thats light

 

No I mean 10 pounds over the stock steel wheels.

 

just dont tell your baby your trying to make her fat and say that it's all muscle. she may get upset. maybe throw you out(of the drivers seat). :D

 

No. . . uprgrading the pulley is like removing 100lbs from the vehicle. . . but that is really a lame statement they use to sell the product. You are really removing a few pounds of unsprung weight, and removing a ton of rotational inertia. By adding 10 lbs to each wheel, you only have to calculate for two wheels really, as they are the only ones connected to the drivetrain. Your 10lbs added to the wheels has a far more negative effect than the pulley. In fact, your 10lbs added is like 400lbs added to the overall weight, if you use the same analogy that perrin uses. Lightening the drivetrain is one of the best ways to make your car faster, as it puts less strain on your car, and more efficiently puts the power the engine DOES produce to the ground.

 

Your math is wrong. How can you reduce a pulley by such a small amount and gain so much weight loss and yet increase each wheel by quite a bit and gain so little weight? It doesn't just smell fishy, it tastes fishy. Blech!

Try adding 20 lbs per wheel and mulitplying that by a significant factor because of cintrifugal force. I think if you suspect 200 lbs you would be closer if not conservative. If smaller is reducing potential weight on the pulley, then larger is increasing potential weight on the wheels.

Think of it this way - larger tires increase coeficient of drag. Coeficient of drag equates to mass plus resistance. That's weight dude, plain and simple.

 

Are you saying it would help if I added a pulley to offset the added weight of the wheel

or

are you saying it would make things worse...

 

The discussion about the pulley was discussed in another thread about 3 months ago. The conslusion of that thread was you may in see an increase of 2 to 3 mpg but that is offset by the fact that you have to keep throttling your engine because your pulley being smaller causes the engine to idle down to quickly, almost to a stall. Hence, you use up the savings in goosing the engine more to keep it alive. The true benefit of a smaller pulley comes in quicker revs, quicker starts at low speed. More of a benefit to manual transmissions than automatics.

 

The Perrin pulley is not smaller only lighter, atleast that is what they state.

What I am trying to accomplish is somehow regaining some of the lost MPG due to the larger and heavier tires and wheels.

I'll look up the thread as well.

 

To make up for the extra weight and tire size you will have to plan on putting every gadget that promises fuel savings. No kidding. A bigger footprint guarantees higher rolling resistance. It's gonna take more fuel to get your car rolling and keep it rolling. That is an undeniable fact of physics.

 

There is no sure-fire formula that I have seen, but it is always the case that removing rotating mass has the effect of removing much more static mass. Removing weight off the engine where it affects how the engine performs by itself is another issue that I don't know much about, but if you were trying to lighten a vehicle, rotating parts are the place to spend your money.

Don't forget the tires: You may find the new tires weigh less than the stock ones (As was the case in a Geo Tracker this guy on another message board was building, which was surprising because he went like 6" taller), so that could offset the increased weight of the wheels.