Decreasing unsprung weight

[WannaGTS]

I don't autocross but I like a responsive car. Most people change to 16 or 17" rims for looks or to upgrade the brakes but you racers probably agree that the brakes in this car are fine. Therefore, wouldn't it be a good idea to run on the street with lightweight 15" rims with super sticky tires? It would ride smooth with plenty of grip (15x7 with SO3 pole position) and, if the stock 15's are really 18 lbs (ouch!--the 16x7 on my Integra are 16 lbs), you could probably cut about 5 lbs off of each corner and forego the added weight of the bigger brakes. Isn't this more of an autocross or race mode of thought?

[autxr]

You are correct (others will argule about the brakes, but I agree with you).

The stock 15" rims are actually 17 pounds, but that is of little concequence.

I can get 15x7 SSR competition wheels that are 8.5 to 9 pounds.

In the end, I would probably stick with 16" just because you can get a little better tire performance out of a 225/45-16 than a 225/50-15 (IMHO), but the 15" would be close in performance.

Scott

[Raymund]

Reducing unsprung weight gives faster acceleration, better tracking. It makes it quicker for the spring and dampers to react to road conditions hence better handling.

Shaving off 5lbs on each tire is neglible. But, yes the improvement is there if you can extract it. If you are looking at 15" wheels you can do a lot more than 5lbs. RacingHart CP-035 15by7" tip the scale at roughly 9lbs. Thats half the weight of the stock wheels. Weight improvement is significant enough for you to notice.

[pitcrew]

you got it! The only extra issue for the street is durability. Super lightweight wheels often give it up in the strength area, not an issue on a track or AX course, but one when dealing with potholes, RR tracks etc. The 15x6 rage wheels that discount tire sells for 75.00 each are 16# (I weighed them, not from a list). The SSR comps are some of the lightest streetable wheels for the Celica but significantly more expensive. The smaller diameter also puts the center of gravity lower, gives crisper turn in and gives you slightly lower gearing for acceleration unless you opt for rubberband profile tires on the larger diameter wheels that shake your fillings out and definitely jepordize the wheels to road damage.

[WannaGTS]

I'm glad I posted this question to a lot of like-minded individuals. I bet I could cut 5 lbs/corner on the rims, 25 lbs out of the battery (Dynabat), and maybe 10 lbs per seat for a total of 65 lbs. If the car weighs in at 2520, this would drop the weight down to 2460, which is very light. I'm sure some of you could add some sane and street-legal weight reduction ideas.

[WannaGTS]

And I agree the brakes are probably fine, especially if tweeked with pads and steel lines. Also, I would run 205/55/15 on 15x7 which, if the car is under 2500 lbs, would be plenty of tire.

[erok]

After putting stainless brake lines and Porterfield R4-s pads on my car, it stops amazingly well. When the pads are heated up they will stop harder without triggering the ABS than the stock set-up. Better than any car I've driven, including a 300zx turbo and Porsche 944 turbo. Well worth the money.

As far as wheels go, the really lightweight wheels are really expensive! I'm still saving up the dough.

Anyone going to the autox at Hollywood Park tomorrow (12/09)?

[WannaGTS]

Thanks, erok. That Porsche reference carries a lot of weight; the stock 300zx turbo brakes were stinky--my brother had one and would fry them on the track. It all goes to show that stock brakes are usually pretty good, especially if massaged a little.

[Raymund]

Originally posted by WannaGTS
I'm glad I posted this question to a lot of like-minded individuals. I bet I could cut 5 lbs/corner on the rims, 25 lbs out of the battery (Dynabat), and maybe 10 lbs per seat for a total of 65 lbs. If the car weighs in at 2520, this would drop the weight down to 2460, which is very light. I'm sure some of you could add some sane and street-legal weight reduction ideas.

You want to know how much weight I managed to shave off? click on my sig..

[WannaGTS]

hey ray, did you scrape out the sound insulation; that stuff is pretty heavy. They did it in the Sport Compact Civic and dropped about 40 lbs.