I put on a set of Track v.1 wheels and tires that I bought used a week ago. I have the Track v.2 wheels as well as a set of Touring v.1 wheels. I took off the Touring and put on the Track v.1 yesterday.

It may be just power of suggestion, but I swear the Z felt a lot quicker in acceleration just in normal DD. Compared to the Touring, the Track wheels are about 8lbs lighter. Would 32lbs of unsprung weight be that easy to feel?

 

^^ Yes.

It isn’t just the weight of your wheels, but more importantly overcoming inertia when rolling a round-object (which is very different from dragging a weight).

--Spike

 

+1 ^

Reducing rotational mass on the wheels by 8 lbs a wheel is a GREAT improvement and would DEF be felt by the driver in both acceleration and in handling.

You must think of the wheel weight not in the sense of compounded to overall static weight, but rather in a seperate set of weight that the engine must produce power to rotate.

They are a totally seperate entity when compaired to other weight factors on the car, an entity where 8 lbs a wheel and 32 overall lbs makes a WORLD of difference when your dealing in a small range of 80min - 120max lbs in total weight being rotated.

 

Look at it this way. The 8lb saving off of the 50+ lb touring wheels will decrease unsprung weight which will help handling - can you feel it ? No. Maybe the car will go through a slalom 1/10 second faster.

It will also decrease rotational inertia allow for faster acceleration making you 1/10 of second faster in the ¼mile - can you feel it? No.

Sure it can be measured, sure there's a definite benefit but can you really feel it "seat of the pants"? I doubt it. You're only taking 32lbs off a 3200lb car, the overall effect is minimal in the big picture.

 

Dave, I certainly respect your opinion here, but would like to mention something I notice from personal experience.

This may not be a fair comparison, but I’ve have much better results when reducing unsprung wheel weight on my 4WD off-road vehicle. I notice this (and it goes way past “seat of the pants feeling”) when running a light weight 15” wheel with 33” tires on my off-road runs. I replaced the stock 18” wheels that came with the truck with much lighter 15” wheels (but still maintaining overall diameter I had with the 18” wheel).

The difference in weight was about 50 lbs. collectively on the wheels (and seemingly insignificant on a 4800 lb. vehicle) but the performance was noticeable (significant), especially when going steeply uphill. In fact this is something that 4 wheelers often do to get better off-road performance.

When I put 19”s on my Z (I “cheaped-out” to save $$ and didn’t go with ultra- light 19” wheels so I did add weight), I was disappointed for the same reason, and went back to smaller/lighter wheels. Certainly I maybe was “seeing ghosts,” but I really like lighter wheels.

My point is that it’s not 32 lbs. to the overall vehicle weight that makes the difference, but rather overcoming inertia when rotating these wheels.

But, with that said, I’m probably wrong. Without providing any facts, my argument isn't worth much. It’s been almost 40 years since I took my last college course in Physics, so I am unable to provide the formula’s that might substantiate my supposition.

--Spike

 

I've read numerous times that removing 1lb from a driven wheel has the same effect as removing 6-8lbs out of a vehicle.

I don't know about you, but when my winter Dunlops go on, I feel a huge difference in performance. The car feels notably slower to accelerate because they're 5 and 6lbs heavier than my Pilot Sports (which are extremely light weight compared to other tires). The weight saved from a set of rims or tires is definitely something you should be able to feel, assuming it's a considerably enough amount.

 

I'm familiar with the effect of unsprung weight, and agree completely. It is the effect of the amount of additional torque required to overcome the inertia of the wheel, but where that weight is distributed. Most of the weight delta is occurring away from the center of mass of the wheel. The farther away from the center, the greater the "arm" of the level and the greater the torque required to the move the wheel. Because of that there is an even bigger difference between my 19" Track v.2 rears and the 18" Track v.1 rears. Not only is the Track v.1 10 pounds light, the weight is a lot closer to the center of rotation.

I'm just wondering if it is something that could really feel in DD or if it just my imagination (much like a louder exhaust making us think the car feels faster)

I think you may be right. I think the effect is probably pretty large, but not so large as to be felt as seat of the pants.

 

While the benefit of reducing rotational inertia is faster acceleration, you are still having to accelerate the 3200lb car. F=MA the force (HP) is the same, the mass (weight) is reduced ever so slightly so the acceleration will be increased ever so slightly.

I can definitely feel the difference between my 18" track wheels and my 19" setup even though the 19" setup is lighter. The wider 19" wheels are farther out on each axle, meaning they have a greater effect on bumps, steering, etc. My 18" feels more nimble on the street. There a lot more going on than just weight reduction. You have a new geometry to deal with. Different tires have a effect (stiffness).

 

Went from Track v2 to TE37's, and I didn't really notice a day-to-day driving difference.

Then one day, just for fun, I lit 'em up. Now, keep in mind, I am close to 40, and tend to think of things like "damn, these tires are expensive to replace" instead of "hold my beer and watch this", but every once in a while the 18 year old buried deep inside makes a guest appearance.

Without question, I can tell a difference between the light TE37's and the heavier (almost piggish) Track v2 rims when doing a burnout. Easier to hold if you like taking miles off your tires.

 

What size tires? I find it a lot harder to spin the rears than the OEM setup. Of course, I went from 245 to 285 tires. A lot more rubber is harder to break loose. The illustrates one of the main problems with this whole discussion, in most cases we're not talking about comparing apples to apples. We buy new lighter wheels and don't have the same rubber on them so the comparisons are not valid.

 

265/40/19 on the Track v2 to 275/35/19 on the TE37... they are taller, and wider, theoretically making them tougher to get spinning.

But, to your point, I did go from OEM Potenza's to Nitto NT555's, so that could be part of it as well.

 

You're right Dave. The tires that were on the Track v.1 when I bought them are Federal SS595s in the stock size. That is a tire I never would have chosen, but they have a lot of rubber left so I'm going to use them for a while. The one thing I can tell right away is that they are a very noisy tire.

 

Exactly.

We are dealing in shaving 32lbs off rotational mass. This is much different than shaving 32lbs off of overall vehicle weight.