I've read about how the reduction of rotational mass can improve performance.

For example, the guys with one-piece aluminum driveshafts are reporting 2-3 tenths off of the 1/4 mile.

Sooo...does this same principal apply to lighter wheels? For example, if I replace all my wheels, which weigh, let's say 25lbs each, with lighter 20lb wheels, I have essentially reduced rotational mass by 20lbs. Could this potentially knock off another 2 tenths?

If this is the case, it would seem that the lighter DS and wheel combo could result in a 4-5 tenth e.t. reduction!

Please enlighten me!

 

Lighter wheels should help you. The engine would have to work less to overcome their inertia.

Any weight reduction should help for that matter.

 

in certain locations, weight reduction helps more than others. a little weight off of the driveline like a CF driveshaft will help more than removing the rear seat, lets say, even though the seat removes more actual weight. anyone relocated their battery box to the trunk? theoretically this should help, but I'm wondering about real world performance.

 

Any recommendations on a light-weight (yet not insanely expensive) wheel?

 

bogart or weld inc. draglites. don't know their pricing, but it is really hard to find a lightweight wheel that fits our car. for the money, i'd invest in something else. control arms and drag radials for better launches at the track. or if you want better "street launches" then swap the rear gears and get control arms.

 

Do some research on "Unsprung Weight" and you'll find the answers to this question.

Losing rotational weight is much better than losing dead weight.

 

Rule of thumb:
100lbs of weight lost = 1 tenth quicker
10lbs rotational weight = 1 tenth quicker
1lb unsprung weight = 2lbs total weight
10 hp = 1 tenth quicker
150' change in density altitude = .01

Most drive shafts save approx 25lbs over stock. After my ds install my car picked up about 2 tenths, when I installed the lightweight flywheel and clutch, 12 lbs lighter, I picked up about a tenth. Both these mods checked out close to the math.
The light weight wheels will count for rotational for the rears and unsprung for the front.
If you drop 20 lbs from the rears you should gain about 2 tenths, drop 60 lbs from the front and you gain about a tenth plus better traction out of the hole. Based on my experience with the basic rules of thumb I would say light weight wheels should get you about 2.5 tenths and a better 60' time.
For every tenth quicker at the 60 you should get about 2 tenths at the end.

 

Now that's an answer!! Thanks!

Other than all-out drag wheels, are there any street wheels that would provide significant weight savings and not cost and arm and a leg ?

 

Pretty much the only lightweight street wheel I have been able to find that will fit our cars is the 5Zigen wheels. You can probably pick up a set for under 1000.00 bucks. I keep looking at the FNo1R-c series. Looks like decent weight savings and decent price. I have e-mailed a few companies that sell them but haven't had a response. I'm going to take that as a "sign" for now. Both my tracks are closed for the season so I am going to wait and see what the next few months bring as far as light wheels for us.............

 

Sure, check out my post in exterior mods about my Wedsport 18x10 wheels..

http://forums.bradbarnett.net/showthread.php?t=56214

Only 19lbs and cost $350 each! I can tell a difference in not only exceleration but braking as well. The car just feels lighter on its feet, and it KILLS IT in the corners!

 

Do you have a link to their site, bro?

 

Hey, I like those...which size are you planning on going with? I'd like to stick with 18s, but not sure which width would be best...

 

OK, you guys would probably get an A in my physics class. I teach introductory physics at the local community college. I assume you know the formula for the moment of inertia for a cylinder rotating about its axis is 1/2 mr^2.

So, the torque applied to the driveshaft is equal to the product of the moment of inertia and the angular acceleration. Smaller mass = smaller moment of inertia and larger angular acceleration (for the same torque applied). In other words (like Rench says) ...you go faster.

 

Joe, I think Newton would have had alot more fun using muscle cars instead of apples.............

 

Man.... I am finally glad you said you go faster!!!!!!!!!
Scott

 

Rob, if I was going to go with the 5Zigens I would get the 17x9 for the rears and the 17x7 for the front. Those would be my track wheels and I'd be looking at a pretty decent weight savings over the stock 25 lb rims. I'm running a 17" 50 series drag radial that gives me decent sidewall height which gives much better grip than a 18 with a lower profile tire. I picked up 3 mph going from a 40 series to a 50 series tire. 25" at 40 -vs-28" at 50. This combo has been working really well for me with my 4.10's.
1600 for Bogarts, 2500+ for Weld Dragstars and you "can't" run them on the street. Under 1000.00 for the 5Zigens seems like a decent compromise and they don't look too shabby. Now all I have to do is get someone from one of the companies that sell them to give me some info and I may be in buisness. I'm pretty sure the offset available will work just not sure about brake clearance.

 

When I worked in a Phillips 66 gas station as a kid, we had a rodder come in with true Mag wheels. Yes, they were made out of Magnesium! Without a doubt the lightest set of wheels you could ever get. If you don't mind that they are brittle and burn terribly hot in an accident, it might be an option. Does anyone still sell them? They probably aren't allowed under DOT rules now, but they really are light.
Magnesium has a density of 1.74, compared with Aluminum's 2.7, so the Wedsport 19 Lb wheel would only weigh 12.25 Lb in Magnesium, all other things being equal.

 

The reduced mass driveshafts also happen to be larger in most cases (the radius increases).

 

SSR comps; 18X8.5 front & 18X9.5 rear. The wheels are light (approx 14 lbs front & 15 lbs rear)

http://grassrootsmotorsports.com/new...rd-mustang-gt/

But unfortunately not inexpensive, but nothing light is.

 

It's not just weight reduction when you are lightening rotational mass on the engine and drivetrain, that is power that is already there, but being used to turn the heavier mass.