QT unsprung weight Options

[rascobo]

I've been upgrading various suspension parts on my car and I know my non-stock wheels/tire combination is considerably heavier than stock, and adding unsprung weight. Is the added weight likely to cause any problems for a primarily street driven machine? If so, what can be done to do to relieve or compensate for the stresses created?
I've never seen this discussed in this forum, it may not be an issue (other than my OCD (IMG:style_emoticons/default/Jumpy.gif) ), but having done so much, don't want to ignore anything potentially important, and figured with all the racing members, someone would have an educated response.

[rick 918-S]

I think if you search for brake up grades you will find information about the effects of inersia, roll resistance, contact patch and the added force needed to slow a heavy spinning object.

Heavy wheels in motion are harder to stop. Add tire width and your grip increases. Increased grip multiplies the effect on the brakes. Other than that, I can't think of anything that jumps out at me.

If your brakes work fine I think your good.

[SirAndy]

Is the added weight likely to cause any problems for a primarily street driven machine?

No

[jetboy]

How much power is that 4.7L six putting out? If you were running with a stock 4 and only 80hp then you would notice the increase of maybe even 5lbs per wheel. If your pushing 200hp or more, it might take 10-15lbs per wheel to really notice. At that point the extra contact patch would probably make up for the unsprung weight. Although, the weight of the six and the additional wheel weight then upgrading to bigger and vented brakes might be the next step. Thats just my opinion, though.

[charliew]

It seems that if the new wheels are the sizes and weights on the 911 and can go those speeds then you might need the shocks and brakes that are closer to that cars specs.

[rascobo]

Everyone,

Thanks for Your replies.

scott

[jmill]

The more unsprung weight the harder it is for the tire to stay in contact with the road over surface bumps. The spring has to overcome the inertia of the unsprung mass. In a nutshell you won't see it in a DD.

[Brett W]

I beg to differ. You will see a huge difference in a daily car by changing the unsprung mass. If you drop 10+lbs per corner the car will ride better. I have experienced this personally. I went from a heavy 16in wheel and tire package to a light weight 15 set and the quality of ride on the elevated portions of the interstate around here was substantially better. The ride was smoother.

Lighter wheels also affect acceleration. They will make it easier to get the car rolling and can affect fuel mileage on a stop and go basis. Is it measurable by mere humans? Probably not, but you can definitely tell a difference in how the car pulls away from the red lights.