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Are FD's left-side weight biased ?

Old 09-06-11, 09:25 AM
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Are FD's left-side weight biased ?

Aside from adding ballast to the right-side, what else are people doing to get an almost perfect Left-to-Right side ratio ?

Stronger springs on the Right side ?

BTW: my cross-weights and Front-to-Rear ratios are both at 50/50.

More details including worksheet here:
https://www.rx7club.com/suspension-wheels-tires-brakes-20/fds-left-side-heavy-968542/


Thanks,
:-) neil
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Old 09-06-11, 10:52 AM
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Looked at your other thread, a few comments,

You cant change the F/R or L/R weight without pulling weight, moving weight, or adding weight. I suppose you could change the balance by a small amount if you drastically jacked the ride height of one side or end, but thats not going to get you a good handling car.
Being L or R heavy shouldnt make any tangable difference on track as when the cross weights are even the car should respond similar in L and R turns. All LHD FD's will be left biased and Im betting all RHD fd's will be right biased.
When doing corner weights I load driver weight and set my ride height first, then wheel alignment, unhook sway bars, then balance. If you do the balance right you wont change ride height at all. Hook up sway bars and done.

Depending on your track and experiance as a driver and experiance setting up cars I wouldnt mess with spring rates between the left and right side (can be effective to have L / R specific alignment, springs, weights, etc. when you only run one track). Given the difference in manufacturing tolerances you could have an uneven car in both the dampers and spring rates already causing it to feel better with a passanger, of course depending on quality of components and if they have been tested...

I dont have my weights handy but they are roughly 52% left biased and 51% rear biased, but 50.0% cross and the car is very predictable both left and right.
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Old 09-06-11, 12:05 PM
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Neil, it's always going to be heavier on the left side than the right unless you add a good bit of ballast. What is important is the front rear and cross... which yours are 50/50 according to the sheet. Your car will be fine.

With my car, I added 200lbs of ballast(the max I can add for my class) to have a more desirable power to weight ratio as well as I added wider tires and had to add some weight(In NASA, we take a penalty the lighter we are). That basically compensated for me in the driver's seat. In doing so, I was able to put the weight where I wanted to and essentially have a 25/25/25/25 balance on all 4 corners as well as lower my center of gravity. I think it helped alot, but I have also ran your current weight configuration and it works really well.
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Old 09-06-11, 11:30 PM
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Originally Posted by Brent Dalton View Post
Neil, it's always going to be heavier on the left side than the right unless you add a good bit of ballast. What is important is the front rear and cross... which yours are 50/50 according to the sheet.
I've seen some set-up guys I really respect state that keeping a 50/50 L/R *front* weight is helpful for braking performance, and close to 50:50 F:R but you can sacrifice some cross to get the L/R front weights similar. Not really sure about it myself...
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Old 09-07-11, 12:42 AM
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Are you sure those scales are right? 3,090 lbs is oddly heavy for a modded FD. My R1 was ~2800 lbs with my fat 180lb *** in the car and a full tank of gas.
https://www.rx7club.com/showpost.php...&postcount=678

Did you set ride height with the car loaded w/ driver weight?

where is the battery located?
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Old 09-14-11, 09:48 AM
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Originally Posted by gracer7-rx7 View Post
Are you sure those scales are right? 3,090 lbs is oddly heavy for a modded FD. My R1 was ~2800 lbs with my fat 180lb *** in the car and a full tank of gas.
https://www.rx7club.com/showpost.php...&postcount=678

Did you set ride height with the car loaded w/ driver weight?

where is the battery located?
3k is correct for an fd with all accessories wet with a 50lb roll bar, big brakes, big smic, big aluminum rad, big dual oil coolers, harnesses, fire ext etc.... What you take out you end up putting back in with cooling and safety upgrades.

my car is 2650 mostly gutted and 2800 with me in the seat:
all panels stripped but the door panels and bins
no carpet
no stereo
no ac
no ps
light weight SSR comps with light weight hoos
light weight battery in the passenger bin
single turbo
sparco seats (fairly light weight)
no passenger seat belt
and lots of little stuff taken out

Heavy stuff added:
m2 bar
big brakes
v mount
dual 25 row coolers
fire ext
harnesses

I suspect you've removed more than you realize or the scales are wrong.

Dry weight of a bone stock 93 r1 is approx 2780
Dry weight 93 touring is approx 2830
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Old 09-14-11, 10:13 AM
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Originally Posted by gracer7-rx7 View Post
Are you sure those scales are right? 3,090 lbs is oddly heavy for a modded FD. My R1 was ~2800 lbs with my fat 180lb *** in the car and a full tank of gas.
https://www.rx7club.com/showpost.php...&postcount=678

Did you set ride height with the car loaded w/ driver weight?

where is the battery located?
Yes, the scales are correct.

She's that heavy because I'm in it, along with roll-bar, fire extinguisher, big aluminum radiator, heavy CCW wheels, etc., and 1/2 tank of gas. Battery (51R Optima) in the stock location.

Remember, this is a FD touring, and still very much a street-legal car, with air-conditioning, air-pump, full rat's nest, cruise-control, etc.

:-) neil
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Old 09-15-11, 03:28 PM
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Interesting.

fwiw, I was able to get my front weights within 1lb of each other screwing around in my garage. Dumb luck for the most part. I set ride height to 25.25" up front measured to the fender lip with me sitting in it. The guys at the shop who do nothing but suspension and setup were shocked. I wasn't as lucky on rear ride height as it took a lot of time and I gave up after a while but it was still pretty close.

My battery (Optima red top) is relocated to the pax bin and I'm running a V-mount but am still on sequential twins and all accessories. I still run the air pump and a high flow cat, Racing Brake BBK, 17x9 SSRs. I have a 93 R1. I'll have to double check the print out but I'm pretty sure my values are correct as stated.
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Old 10-22-11, 10:56 PM
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Here's my first corner balance...also left side heavier about 2%.

Balanced with:
220lb driver
5/8 tank gas
No spare
No A/C compressor
No Air pump
Single turbo, resonated mid pipe, RB duals
Huge V-Mount
Large dual oil coolers
Front AP BBK
285/30/18 R888's all around on Enkei RC T4's
Optima 51R driver side bin (should have installed in passenger side)
Huge dedicated front splitter with steel frame/bracket
No GT wing, even though I run one at the track
RZ Recaro's
25.75" all around ride height


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Old 10-23-11, 07:18 PM
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A couple of things stand out-

first, there is absolutely no use in corner balancing a car with missing pieces, without the driver in it, or in a configuration it does not run in. If you run a wing, cool suit, etc you need to have it in postion and mounted, and cool suits need to have the equivalent weight of ice in the cooler. Drivers weight must be calculated fully suited including suit,helmet, Hans, etc. so the lead or sand driver willbe accurate, also the weight needs to be spread out as if the real driver, meaning that the weight of the legs needs to be in the footwell etc.

Second- cross weight is what is important here. Mechanically moving wieght does help, but the key to a good race car setup is to start at one end of the string and work to the other. First the basic alignment- ride height/castor/camber/toe/rake/ etc. , then the cross weights. While you are crossweighting the car it is VERY important to consitently recheck the ride height so as to not skew it badly.

While conventional wisdom is 50/50 weight bias front to rear is "best", in a FR car you will generically be faster with more rear weight bias. In fact, until recently SCCA Pro racing limited the amount of rear bias to 50% so that teams that knew how to set the cars up this way would not have unfair advantage. In fact, in the RX8's I would love to have more rear weight, however there is just nothing else we can physically move to the rear of the car to gain more rear bias.
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Old 10-25-11, 04:25 PM
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Originally Posted by D Walker View Post
While conventional wisdom is 50/50 weight bias front to rear is "best", in a FR car you will generically be faster with more rear weight bias. In fact, until recently SCCA Pro racing limited the amount of rear bias to 50% so that teams that knew how to set the cars up this way would not have unfair advantage. In fact, in the RX8's I would love to have more rear weight, however there is just nothing else we can physically move to the rear of the car to gain more rear bias.
this is true. We ran spec E30 for a season, and the rental car we were using was something like 2450lbs, and minimum weight for the class is 2750lbs. the E30's are front heavy, due to the iron block 6 ahead of the front wheels. one race we added the 200lbs of ballast to the rear of the car, and it actually lowered our lap times at infineon.

the conclusion is that WHERE you put the weight matters.

anecdote #2 was watching the Porsches go thru turn 1&2 @Rennsport. the boxsters look MUCH better on turn in than the 911's do.
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Old 11-21-11, 02:13 PM
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Originally Posted by gkmccready
I've seen some set-up guys I really respect state that keeping a 50/50 L/R *front* weight is helpful for braking performance, and close to 50:50 F:R but you can sacrifice some cross to get the L/R front weights similar. Not really sure about it myself...
Oldie....but, this is ^^^ the method employed here....rhd FDs aren't left biased at least.

From memory, about 30-35kg more on the right rear going equal fronts.....fat bastard driver in archaic measure of ~ 220lb, wedged up front.
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