Generally what is the HP/Weight Reduction ratio?

**xinthenight** · 08-27-2007, 06:41 PM

Well, I know that weight reudction doesn't exactly give HP, more like acceleration. But by the rule of thumb, what is the HP/Weight reduction ration?

I've found that 100 pounds is .10 faster and 100 is 2% better MPG.

**JonB** · 08-27-2007, 08:19 PM

Every 10lbs off your drivetrain or wheels is supossidly worth the same as 100lbs off the body.

**ATCharming** · 08-27-2007, 09:10 PM

i think he means like 100lb = 10hp.
which i think is correct. unless im missing a zero somewhere. who knows lol

**Hot Black Trans-Am** · 08-27-2007, 09:31 PM

Originally Posted by ATCharming

i think he means like 100lb = 10hp.
which i think is correct. unless im missing a zero somewhere. who knows lol

Your right.

**B34M3R** · 08-28-2007, 05:37 AM

There are also points of diminishing returns.

And not all rotational mass is the same. For example, removing 10lbs from your driveshaft would give less gains then removing 10lbs from your flywheel. Why? Because the flywheel has a much larger diameter, so the acceleration forces are actually different on an exponential level.

Erm, if I have explained that poorly, I'm sorry, I have a good analogy, but I dont feel like typing it up at this moment.

**thecorrectformula** · 08-28-2007, 06:27 AM

You'r correct B34M3R. It's the same way if you put lighter Rims on your car. Less rotational mass so you get the ability to spin faster but you also sacrifice torque when you do this. It's a give and take relationship. Not so much with the wheels and tires but definately with the flywheel.

**B34M3R** · 08-28-2007, 06:53 AM

Ok, well I'm bored now, so I'll type up that analogy now

Ok, you remember those merry go round things on the playground? You could get yourself spinning as fast as you could run, but if you pulled yourself into the middle of it, suddenly it would be spinning like twice as fast. Same principle applies here. Or even easier, if you have a computer chair that spins, spin yourself around with your arms out.... then pull them in to your chest... what happens? You speed up.

The reason for that is, weight placed further away from the point of rotation take more energy to spin. Thats why you start spinning faster as you pull that wieght in towards the center, because you already exerted the energy to get it going at the slower speed... the energy has nowhere to go, SO you go faster instead. Cool huh?

Whats that mean for you?

First off, a set of 17's that weighs 20lbs, is pretty decent right? Now, a set of 16's that also weighs 20lbs, is for sale that costs exactly the same as those 17's. Now, everyone and their mother would automaticly go for the 17's because theres obviously no drawback.... right? Wrong. Those 16s would still perform better because the weight is pulled into the center a little further. Also, the gains are twofold, because that is also unsprung wieght. Whats that mean to you? Its directly related to how quickly your suspension can react to inputs from you, and inputs to the road.

And while we are on the subject, one last thing. You know why drag cars run skinnies? Its not because they have less rolling resistance. Rolling resistance is a fucking MINOR energy draw... like serious, talking .001 1/4 time difference for that. No, its because of the wieght reduction. For some unknown reason, most people seem to think the wieght of you wheels only applies to the wheels that are connected to the drivetrain. WRONG. You think those wheels are accelerating themselves up to speed? Not likely. They are pushed by the car itself, which is pushed by the motor. Those front wheels have just as much to do with it as your rear. And vice-versa for FWD cars.

I laugh so hard when I see the people at the track throwing the steelies with crap tires on the drive wheels, while leaving the freakin DUBS on their other wheels. I mean, shit, at least leave the DUBS on your drive wheels, then you'd have traction at least.

Ok, hope I didn't come off to self-importent there... but thats a subject that peoples ignorence to bothers me.... I dunno, I just think its one of the more importent fundamentals of making a car go fast... and stuff.

**Hot Black Trans-Am** · 08-28-2007, 10:10 PM

Originally Posted by B34M3R

Ok, well I'm bored now, so I'll type up that analogy now

.... Or even easier, if you have a computer chair that spins, spin yourself around with your arms out.... then pull them in to your chest... what happens? You speed up.

The reason for that is, weight placed further away from the point of rotation take more energy to spin. Thats why you start spinning faster as you pull that wieght in towards the center, because you already exerted the energy to get it going at the slower speed... the energy has nowhere to go, SO you go faster instead. Cool huh?

Whats that mean for you?
.....

Thanks for that idea! It was very fun, but now I'm really frickin dizzy!!!

**B34M3R** · 08-29-2007, 05:09 AM

Lol

**JonB** · 08-30-2007, 09:21 AM

Originally Posted by JonB

Every 10lbs off your drivetrain or wheels is supossidly worth the same as 100lbs off the body.

I was just making a generic statment but B34M3R puts it to better terms. Every time I get into this subject with people they don't seem to comprehend it so I just threw out a simple easy to understand statement.