Very cool

 

Thanks all. I put smaller wheels and tires on my convertible . . . all a saga of trying to get a deal on rims to eventually put winter tires upon . . . but can't bring myself to toss out the rubber until its worn down. So I saved 8 pounds on each wheel/tire and have a diameter of 24 inches instead of 24 1/2, more or less.

Despite the obvious math the smaller, lighter tires give a distinct impression of quickness. Some is due to the fact they aren't runflats and so are not passing back heavy breathing and horror movie music from the road. Some is due to an effective lower gearing. Some might be due to rotational weight . . . hardly matters since it feels quick. Because it feels quick I find myself driving quickly'

To use a bicycle example . . . as I get older I can afford lighter rims. However, I am heavier. So if I save 50 g. on the rims and gain 25 lbs, does the bike feel faster. You betcha! And no younger lighter rider will hang back to contradict me.

For those of you turly concerned with speed, I'm sure lighter wheels and tires help mostly with handling. The energy calculations are most interesting (energy, work . . . keeping track of the units is most tedious). So from that standpoint, if I get back to my high school weight, about 165 lbs, it will be the equivalent of spending $3000 for wheels! How much can I save by having my wife loose weight?

 

The smaller diameter wheels may be the cause of the quicker acceleration.

 

The rolling diameter only decreased from 25.2" to 24.9", which would register as less than a 1MPH difference on the speedometer.

 

i'm sure there's one of those mastercard "priceless" ads somewhere in there, with things about keeping your wife happy, expensive wheels, go fast grin....

 

I second that. I purchased 16" rota slipstreams to replace my stock 15's on my acura integra.

Even though it was an inch larger, the braking and accelleration response was immediately felt... More so after the 500 miles break in for the new es100's.

Im glad I can use my wheelsets from my integra with my new MCS :D

 

To maximize the contact patch, if one were to significantly reduce the tire/wheel combination weight compared to stock setup, wouldn't you need adjustments to the suspension, too?

GoodFinder

 

Sadly enough I put mine on a scale and got 2810 :( ( Me the Kid and a full tank was 3000 :(((

 

All this is fine and good, nice talk going but...

1400$ on lightweight wheels and tires

OR

1400$ spent on track time with your local HPDE

what will gain you more?

Food for thought.

 

I got some lighter wheels for about $130 each. Sure, they're not SSR Comp light, but they shed 4-6 lbs per corner. And the tires get bought anyway if you drive hard, so you get "step up" to lighter wheels for less than the cost of most cat back systems!

And the above discussion only concerns the benefits to acceleration, but there are also benefits in unsprung weight that effect handling in many, some pretty suble, ways.

At the prices I pay, it was about 2 track days cost equivalent to shed the weight....

Matt

 

For street applications, durability is as important as weight. Running SSR Comp's through downtown Baltimore would not be a good idea. A quality, lightweight cast wheel might be a better choice – more durable than a true forged wheel, but significantly lighter than stock.

If one is looking for a performance boost, for street applications again, there are plenty of cheaper alternatives than ultralight wheels and tires. Its simply not a very big “bang for the buck” modification.

For competitive autocross, the lighter the better. Ultralight wheels matter more in stock classes, where there are very few allowed modifications. Basically, if a part is lighter than stock, and is an allowed modification, the competitive guys will buy it.

Automotive engineers have to build cars within a budget, making compromises with price, performance and NVH. What comes stock on the car may not be the “ideal” choice, but for the price, performance and levels of NVH that the designers were looking for, it may work just fine. An individual car owner’s priorities may be different, and that is where the aftermarket comes in.

 

I would probably be best to get track / Sport tires just to save the *regular* street tires and then spend more money on tunning the nut behind the wheel... ( nothing personal ) track time.

 

Competitive autocrossers almost always use a special set of wheels/tires for competition. Even in "street tire" classes. Tire Trailers are very popular.

I have three sets of wheels/tires - autocross (my OEM's with Toyo RA-1's), summer (Team Dynamics with Falken Azenis) and winters (15" OEM's with Nokian RSi's).

 

when I finally did do a corner balance, mine weighed in at 2610..... But for the puroposes of the model, that difference isn't significant. The whole point of this thread, long long ago, was to shoot down those "pearls of wisdom" that there's a huge multiplier in effective weight savings going to lighter rotating wheels....

Matt

 

So.... has there been any conclusion? Many of the technical arguments and thought experiments seemed reasonable, but their validity needs to be verified against measurements.

 

this is just simple math. And the numbers do seem self consistant, but it's not anything I'll ever test. Here's why. Our cars are pretty variable depending on idle time, IATs and the like. So each measurment will have some variability. The differences are going to be pretty small, so you have to take a lot of measurements to get the resolution to "see" the answer.

But the "effective mass" is a calculatable number.

Matt