Weight Reduction Questions.

[Geek SHO]

I can attest to lighter wheels, though not personally.
My friend Kuya put Centerline RPMs on his 2000 Accord Coupe (V6), and it dropped I think from a 16.3 to 15.9. Just from wheels. Though, he scored a really lucky deal on them. I know of another SHO that has/had RPMS on it too, and he said it was a huge difference.

You can see a video of Kuya and I racing out at Sacramento Raceway below. The video is fuzzy, and I got a terrible launch. I narrowly beat him at the end of the track. His only acceleration mod is wheels, and mine was only Y-Pipe and loud exhaust on a '91+ with 190k miles. So, it's 200 hp vs 235 hp.
Kuya vs Sean

 

[warmonger]

i knew i was close at 5lbs..thats the number i've read in over 30 posts on probetalk

 

[SeanMc]

I read somewhere that the seats are around 80lbs each, which is about the same as the power seats on the mustang. I plan on changing them to Corbeau Sport seats. I'm picking up a set of 17" TDs (15.7lbs compared to the 22-24lbs of the slicer) here in a week or so. So I'll be dropping some weight. Then I'll be getting a c/f hood, trunk...... 3300lbs ATX, here we come

 

[warmonger]

22-24lbs slicers? so what is the actual wieght of the wheels,i've been hearing 18lbs?

 

[SeanMc]

22-24lbs slicers? so what is the actual wieght of the wheels,i've been hearing 18lbs?

You heard wrong . Suckas are heaveeeee.

 

[92inPA]

SASHO91, you commented about looking at the moon roof and rear opera windows. I replaced all that with lexan. The net result was a 35 lbs reduction. And since that is all high weight, my CG lowered just a bit to boot!

I weighed my car before ever starting it on a diet. It started at 3,397# with no fuel. About a year ago I weighed it again and it was at 2,888. Since then I've done a few more diet mods. I will weigh it again within a few weeks. I'm looking for 2,850. I'll post the numbers when available.

99% of my mods are listed via the link in my sig.....

 

[SASHO91]

Bob, thanks for the numbers on the windows! I'll start looking into that.

From what i have heard, the slicers are 21-ish lbs. So if they are infact heavier, then my weight calculations are off. The wheels weigh 16lbs. and lets say the slicer is 23lbs... thats 7lbs of static weight, which equals to 28lbs then X4= what would "feel" like 112lbs... Hmmm... maybe i need to get the wheels first.....

 

[glass]

When I used to drag race I was told an easy way to drop 100lbs off your car was to look for 1,000 places to lose an oz. It sounds crazy but it's another way to look at. I weighed my slicers this weekend when I changed wheels and with 215/60 Cooper lifeliner's they weighed 38.5 lbs each.

 

[drivinhard]

slicers are 18.05 lb

Light weight wheels are always nice, but more importantly are light tires, as they are farther away from the axle centerline. Yes tires in the same size vary by weight, some greatly.

I'd rather have a 45 lb tire/rim combo with 20 lb tires and 25 lbs wheels, than 20 lb wheels and 25 lb tires.

Weight is one factor, but WHERE that weight is on a car can be as, or more important. All 3400 lb cars are not equal...

 

[warmonger]

i thought they were lighter than 23lbs..

 

[cmichaelo]

slicers are 18.05 lb

Light weight wheels are always nice, but more importantly are light tires, as they are farther away from the axle centerline. Yes tires in the same size vary by weight, some greatly.

I'd rather have a 45 lb tire/rim combo with 20 lb tires and 25 lbs wheels, than 20 lb wheels and 25 lb tires.

Weight is one factor, but WHERE that weight is on a car can be as, or more important. All 3400 lb cars are not equal...

Listen to what this guy is saying. This is golden advice!

Don't bother with rims if weight savings is what you're really after...cause it's unlikely that you'll gain anything. On the contrary. Well, yes maybe you'll save some if you stayed with a 16x6. But are you? Probabaly not.

Once you enter the 17"x7.5" and greater rims, it's nearly impossible to beat the slicer weight. And even if you do, don't forget that 17" have the weight concentrated further out than 16" rims. Therefore, two rims that weigh the same, say 18lbs, but one is 16" and the other is 17"...well, the 17" will effectively weight more and slow your car down.

If anything, IMO, the best spent money in the rotational department is to get a set of two-piece rotors from TCE...forget about Baer, and get some light-weight calibers. The TCE two-piece are a master piece and exceptionally light due to reduced mass in the rotor section (vanes are larger.)

Upgrading brakes, of course, is very expensive.

Upgrading the tire can also be effective, but again probably expensive.

Michelin PS2 is one of the lightest tires you can get, if not THE lightest. And you get some top notch traction and awesame wet performance at the same time.

Michael

 

[jedhead]

Listen to what this guy is saying. This is golden advice!

Don't bother with rims if weight savings is what you're really after...cause it's unlikely that you'll gain anything. On the contrary. Well, yes maybe you'll save some if you stayed with a 16x6. But are you? Probabaly not.

Once you enter the 17"x7.5" and greater rims, it's nearly impossible to beat the slicer weight. And even if you do, don't forget that 17" have the weight concentrated further out than 16" rims. Therefore, two rims that weigh the same, say 18lbs, but one is 16" and the other is 17"...well, the 17" will effectively weight more and slow your car down.

If anything, IMO, the best spent money in the rotational department is to get a set of two-piece rotors from TCE...forget about Baer, and get some light-weight calibers. The TCE two-piece are a master piece and exceptionally light due to reduced mass in the rotor section (vanes are larger.)

Upgrading brakes, of course, is very expensive.

Upgrading the tire can also be effective, but again probably expensive.

Michelin PS2 is one of the lightest tires you can get, if not THE lightest. And you get some top notch traction and awesame wet performance at the same time.

Michael

So when I went to my 17X8 235/45 tires and wheels that is 4 lbs lighter than 16X6 225/50 I lost handling, acceleration and stopping performance because the possiblity that the weight is concentrated on the outer edge of the wheel over the slicers? Going to the 17" wheels, the change in handling was dramatic. Turn in is now immediate, I can carry 7 to 10 mph more in the corners than before. I have not noticed any decrease in acceleration. My stopping distance is much shorter and fade resistance is much greater although I gained 1lbs in rotating mass going from the stock 10.2" rotor to 12.5" TCE rotors with my PBR calipers. Although I can still run slicers, I will stick with the 17" OZ that I have installed.

Bob

 

[drivinhard]

Michelin PS2 is one of the lightest tires you can get, if not THE lightest. And you get some top notch traction and awesame wet performance at the same time.

Very much so. The GY F1's that are on the C5 Z06's are pretty light, and the PS2's are ~3 lb lighter per tire over the F1 in the Z06 sizes. They probably give up a bit of dry grip to the F1, but noise/rain performance is light years ahead.

PS2 is great tire, very light, (in the ballpark of some full out race tires).

 

[drivinhard]

So when I went to my 17X8 235/45 tires and wheels that is 4 lbs lighter than 16X6 225/50 I lost handling, acceleration and stopping performance because the possiblity that the weight is concentrated on the outer edge of the wheel over the slicers? Going to the 17" wheels, the change in handling was dramatic. Turn in is now immediate, I can carry 7 to 10 mph more in the corners than before. I have not noticed any decrease in acceleration. My stopping distance is much shorter and fade resistance is much greater although I gained 1lbs in rotating mass going from the stock 10.2" rotor to 12.5" TCE rotors with my PBR calipers. Although I can still run slicers, I will stick with the 17" OZ that I have installed.

The OZ's are very light, but the gain you have is from the wheel width (and properly sized tire, 235 on 8"). Assuming the same tire compound, you'd pick up the same performance with a 16x8.

Nothing wrong with a 17" (16x8" are near impossible to find in the SHO sizes) as I run 17x8" to, but the point is where the weight is can be more important than how much.

there are so many variables, it's hard to say "X" and get "Y".

You could have a 20 lb flywheel with 16 lbs of it's mass concentrated at the center, and a thin/drilled outside that's 4 lbs and it's going to take less power/time to spin it to X speed, than a 20 lb flywheel with most of it's weight at the edges, applying the same power as before. In the same vein, lighter tires are more important than lighter wheels, since they are farther away from the axle centerline.

With that being said, the "spool up" effect is going to show itself less and less as you increase gearing, ie, since 1st gear is short and the gearing allows the engine to rev quickly, the inertia effects of the lighter flywheel (or tires) are going to show up more. Less pronounced in 2nd, probably some (very little) in 3rd, I'd venture by 4th gear, with the taller gearing and 100+ mph aero pushing against the car, the rpm climb rate is slowed so much mechanically, that it's not going to really be noticed. It probably shows up on the dyno (in 4th) as the drum spins up faster than a car does pulling from 2000 rpm in 4th to 140+ mph.

Also for drag racing, the alum unit (flywheel) isn't going to have the thermal capacity that a billet steel or cast iron unit would have. I see an alum unit if you are into road racing/auto-x where you want to cut as much (static) weight off the car period, and driveline rotational weight as well.

Since the SHO FW is only a 10" unit or so (material max of 5" from the crank center line) it won't have as much of an effect in a 1st gear pull as a tires (26" tall, max of 13" from the axle centerline) that are lighter. Tires will have most affect, followed by wheels, followed by 2 pc brake rotors since the light part (alum hat) sits right at the axle Also because a dyno drum spins up faster than a car will pull through the same gear on a road w/ aero drag, those things probably show up more on dyno numbers, than real world.

I have a TON of drag passes on my old 89, testing different parts. Going to a 8 lb flywheel over the stock showed no improvement in ET or mph. It was nice for road racing though, where it was easier to blip the throttle and if nothing else it's 13 less lbs (static) on the nose. Probably a bit easier on the synchro's to.

 

[SASHO91]

As Jonny5 would say "MMMMM!!!! INPUT!!!"

Thanks Mark.

Like i said though, im really not looking for an all out weight loss from the car.. just alittle lyposuction... So for the time being, I'll ditch the stock seats in favor for some lighter manual seats, and throw some 16lb-16x7 wheels on(the tires that im currently using are light-ish). After that, if im not satisfied, i'll look into pulling some other stuff out. but i think the seats and wheels will give me the "bump" that i need.

 

[SeanMc]

I could have sworn they were more than 18lbs. 18lbs isn't all that bad.

 

[drivinhard]

Like i said though, im really not looking for an all out weight loss from the car.. just alittle lyposuction... So for the time being, I'll ditch the stock seats in favor for some lighter manual seats, and throw some 16lb-16x7 wheels on(the tires that im currently using are light-ish). After that, if im not satisfied, i'll look into pulling some other stuff out. but i think the seats and wheels will give me the "bump" that i need.

To go back to what jedhead was posting, IMHO (and think he was eluding to this) *SOME* weight is a necessary evil. Case in point, the SHO (IMHO) needs 8" wheels. 16 or 17 or 18 dia, pick your flavor. But the SHO needs 8" wheels for it's size/weight. (editors note, I think in road racing terms). If all you want to do is drive to work and run at the drags, then some 6" or 7" skinnies may fit your bill. For me, I want lateral grip/contact patch/braking power.

So find the lightest 8" wheels you can, the lightest tire in the range/use that fits your bill, etc.

Same deal with brakes. On a dyno all things equal, sure your car is probably going to make a bit more wheel hp with 10.1" stock 89 brakes, vs some 13x1.1" TCE rotors. But come 'on, the 10" brakes were/are the biggest automotive joke ever. 2 laps on a road course and they'll be toast.

Some things come at a (small) price.

If you had 2 identically prep'd SHO's, and had to race a guy around a 2 mile road course, and you could knock 50 lbs off YOUR car anywhere you wanted, I'd do it in the wheels/tires (obviously you couldn't from that much weight, but for the sake of argument).

You basically got (in order of least offending):

1. sprung weight (attached to the car, supported by the springs/suspension). Things like seats, hoods, doors, your fat butt in the seat, etc.

2. Sprung Driveline rotational weight (clutch, crankshaft, flywheel, driveshaft/RWD, etc). Same as sprung in dynamics, but with an added category of affecting potential power output.

3. Un-sprung weight. Stuff not supported by the springs/suspension, (struts, hubs, knuckles, calipers), etc.

4. Un-sprung driveline rotational weight. Stuff not supported by the springs/suspension *AND* connected to the driveline (Wheels/tires/rotors), etc. The most offensive of all weight. :vomit:

 

[SASHO91]

I've found some nice 16x7 wheels that i really like at a great price... and while i do push the car hard sometimes... IMO, 8'' wouldnt nessecarily be overkill per se, but not needed for my uses. (if that makes any sense.)

I wish we could find some lightweight 11.6'' rotors... I remember Todd talking about making some awhile back... but @$500 a set... alittle out of my league.

When you say least offending... are you refering to them as piece's that are least effective? I think im following you....

 

[cmichaelo]

So when I went to my 17X8 235/45 tires and wheels that is 4 lbs lighter than 16X6 225/50 I lost handling, acceleration and stopping performance because the possiblity that the weight is concentrated on the outer edge of the wheel over the slicers? Going to the 17" wheels, the change in handling was dramatic. Turn in is now immediate, I can carry 7 to 10 mph more in the corners than before. I have not noticed any decrease in acceleration. My stopping distance is much shorter and fade resistance is much greater although I gained 1lbs in rotating mass going from the stock 10.2" rotor to 12.5" TCE rotors with my PBR calipers. Although I can still run slicers, I will stick with the 17" OZ that I have installed.

It makes sense you have better handling and braking with a 17x8 wheel than with a 16x6 wheel.

I believe your OZ Superlegera are 16lbs each and that it is a cast type rim.

However, 16lbs is by no means the norm for a 17x8 cast rim. 17x8 cast rims WILL weigh more than 18lbs in 99% of the cases.

To get 17x8 rims that weigh less than 18lbs, you'd typically have to pocket out a lot of money for a forged type rim.

Btw, what is the load rating of your rims?

Michael

 

[cmichaelo]

So when I went to my 17X8 235/45 tires and wheels that is 4 lbs lighter than 16X6 225/50 I lost handling, acceleration and stopping performance because the possiblity that the weight is concentrated on the outer edge of the wheel over the slicers? Going to the 17" wheels, the change in handling was dramatic. Turn in is now immediate, I can carry 7 to 10 mph more in the corners than before. I have not noticed any decrease in acceleration. My stopping distance is much shorter and fade resistance is much greater although I gained 1lbs in rotating mass going from the stock 10.2" rotor to 12.5" TCE rotors with my PBR calipers. Although I can still run slicers, I will stick with the 17" OZ that I have installed.

It makes sense you have better handling and braking with a 17x8 wheel than with a 16x6 wheel.

I believe your OZ Superlegera are 16lbs each and that it is a cast type rim, no?

However, 16lbs is by no means the norm for a 17x8 cast rim. 17x8 cast rims WILL weigh more than 18lbs in 99% of the cases.

To get 17x8 rims that weigh less than 18lbs, you'd typically have to pocket out a lot of money for a forged type rim.

Btw, what is the load rating of your rims?

Michael