I have been playing around with the ballast but not sure if it does any good, at least not so much that ive seen so far. It came in handy racing stock cars in the 80's but not sure how it translates to the game and mostly high end supercars. Any thoughts and suggestions would be appreciated.
Ballast-Does anyone adjust that?
- Thread starter Cyborg65
- 31 comments
- 2,377 views
It's great if your running a race with friends that's either weight/power or PP restricted.
I reduce the weight below the allowed limit then use ballast to get back to conformed spec however I use the placement of the balance to get the car closer to a 50/50 weight balance. For instance if the car is 60/40 f/r weight split I remove 20% past the limit, then add it back in ballast then play with how far in the rear to put it, changing the balance closer to that optimum 50/50.
I reduce the weight below the allowed limit then use ballast to get back to conformed spec however I use the placement of the balance to get the car closer to a 50/50 weight balance. For instance if the car is 60/40 f/r weight split I remove 20% past the limit, then add it back in ballast then play with how far in the rear to put it, changing the balance closer to that optimum 50/50.
- 1,139
- budious
Using your 60/40 to 50/50 using ballast example above, this is how to do it. I used 1000KG car as easy example:
FR Spring Rate 9.0
RR Spring Rate 6.0
FR Weight Distribution = FR SR/(FR SR + RR SR) x KG
= 9.0/(9.0+6.0) x 1000KG = .6 x 1000KG = 600KG
RR Weight Distrubiton = RR SR/(FR SR + RR SR) X KG
= 6.0/(9.0+6.0) x 1000KG = .4 x 1000KG = 400KG
Ballast Distribution:
1000KG x .60 = 600KG FR
1000KG x .40 = 400KG RR + 200KG Ballast
200KG x 0.00 = 0KG FR
200KG x 1.00 = 200KG RR
Position -50 is 0.00 at Front, +50 is 1.00 at Rear..
For this example, you would put the full 200KG ballast on the rear axle at position +50.
Then you just set the spring rate from the front shock to the rear shock if you want to keep the feel.
FR Spring Rate 9.0
RR Spring Rate 9.0
FR Spring Rate 9.0
RR Spring Rate 6.0
FR Weight Distribution = FR SR/(FR SR + RR SR) x KG
= 9.0/(9.0+6.0) x 1000KG = .6 x 1000KG = 600KG
RR Weight Distrubiton = RR SR/(FR SR + RR SR) X KG
= 6.0/(9.0+6.0) x 1000KG = .4 x 1000KG = 400KG
Ballast Distribution:
1000KG x .60 = 600KG FR
1000KG x .40 = 400KG RR + 200KG Ballast
200KG x 0.00 = 0KG FR
200KG x 1.00 = 200KG RR
Position -50 is 0.00 at Front, +50 is 1.00 at Rear..
For this example, you would put the full 200KG ballast on the rear axle at position +50.
Then you just set the spring rate from the front shock to the rear shock if you want to keep the feel.
FR Spring Rate 9.0
RR Spring Rate 9.0
- 3,359
- California
- PumpinNumbies
You're basing the cars weight distribution on the cars 'default' spring rates? I I don't think that's a good idea. But honestly, I haven't checked RL weight ratio's to compare, so they may be right, but I thought I read something about them being wrong.
Out of curiosity... Can you show me an example of when you would ever not put the ballast at +50, using your equation?
Rotary Junkie
Premium
- 9,810
- Canton, MI
- RJs_RX-7
Yeah that's not gonna work.
Look at most AWDs, note rearward-biased spring strength. R32s most definitely aren't rear-heavy, for example.
- 3,359
- California
- PumpinNumbies
Yeah that's not gonna work.
Look at most AWDs, note rearward-biased spring strength. R32s most definitely aren't rear-heavy, for example.
That's what I thought, just didn't want to make a definitive claim, with only partial knowledge. Gotta leave myself room to go back on my statements. God forbid I should be wrong!
- 1,139
- budious
FR Spring Rate 6.0
RR Spring Rate 7.0
FR Weight Distribution = FR SR/(FR SR + RR SR) x KG
= 6.0/(7.0+6.0) x 1000KG = .461538 x 1000KG = 461.538KG
RR Weight Distrubiton = RR SR/(FR SR + RR SR) X KG
= 7.0/(7.0+6.0) x 1000KG = .538461 x 1000KG = 538.461KG
Ballast Distribution:
Front .461538 x 1000KG = 461.538KG + 77KG at -50 = 538.538KG
Rear .538461 x 1000KG = 538.461KG
77KG x 1.00 = 77KG FR
77KG x 0.00 = 0KG RR
Position -50 is 0.00 at Front, +50 is 1.00 at Rear. (or well swapped in this example, there is probably a better way to represent that... just think about whether you want the most weight at the front or the rear, start at 0 as 0.5 and count forward or backwards; so .69 for weight bias on front axle is .19 units away from 0 towards into the negative range)
For this example, you would put the full 200KG ballast on the front axle at position -50.
Then you just set the spring rate from the front shock to the rear shock if you want to keep the feel.
FR Spring Rate 7.0
RR Spring Rate 7.0
-----------
Ballast Distribution:
Front .461538 x 1000KG = 461.538KG + (77KG + 61.5KG) = 599.538 KG
Rear .538461 x 1000KG = 538.461K + 61.5KG = 599.961 KG
Ballast Position @ -19
FR 200KG x .69 = 138KG
RR 200KG x .31 = 62KG
The combined weight of the car jumped from 1000KG to 1200KG so 20% stiffer shock is required to retain the original feel.
((FR SR + RR SR) x 1.20) / 2 = FR+RR SR
FR Spring Rate 7.8
RR Spring Rate 7.8
---------
You're thinking too realistically about weight distribution. Internet figures don't apply to GT. You can try it my way and it works. See the old ballasted RUF tune on my thread if you want to see that method applied on a tune. GT doesn't model suspension linkage differences or motion ratios. I have the most of the rest of the formulas worked out or nearly worked out, the logarithm usage for the equation to damper application is holding me up from perfectly reverse engineering it at the moment, when I get it all fitting together perfectly I'll be more than happy to write it all up in an article.
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I've put together a Excel spreadsheet using your formula to easily test it out. Great work BTW, it seems to work very well, thanks for sharing.
First thing I notice is that as you change the suspension (stock/sport/semi-tunable/tunable) each progressive part progressively increases the stiffness of the spring rate, while doing this the weight distribution based on this calculation stays relatively constant. This is making a good case.
Seeing what PD uses as stock settings being so different from real world specs I'm leaning towards this as a good formula.
However when looking at a FF ITR fully tuned (not RM'ed) it's giving me 416.25kg up front and 582.75 in the rear. I find it shocking and hard to believe this car is rear heavy, when in reality it most certainly is not. PD is hurting me with this one (could it be they are so off) how could they represent a front heavy FF car as rear heavy? Could the physics be so off they need to do this to compensate? Would the cars drive more realistically if the real world settings are used? (this I'll be testing for sure) would real world settings applied to the cars be useless as they are balanced all differently in the game?
So frustrating that they don't have a physics engine good enough to use real world specs, this is kinda pissing me off.
On the other hand I now have a sweet excel spreadsheet that will calculate the in game weight distribution for me
First thing I notice is that as you change the suspension (stock/sport/semi-tunable/tunable) each progressive part progressively increases the stiffness of the spring rate, while doing this the weight distribution based on this calculation stays relatively constant. This is making a good case.
Seeing what PD uses as stock settings being so different from real world specs I'm leaning towards this as a good formula.
However when looking at a FF ITR fully tuned (not RM'ed) it's giving me 416.25kg up front and 582.75 in the rear. I find it shocking and hard to believe this car is rear heavy, when in reality it most certainly is not. PD is hurting me with this one (could it be they are so off) how could they represent a front heavy FF car as rear heavy? Could the physics be so off they need to do this to compensate? Would the cars drive more realistically if the real world settings are used? (this I'll be testing for sure) would real world settings applied to the cars be useless as they are balanced all differently in the game?
So frustrating that they don't have a physics engine good enough to use real world specs, this is kinda pissing me off.
On the other hand I now have a sweet excel spreadsheet that will calculate the in game weight distribution for me
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- 567
- aGrenadeShark
- aGrenadeShark
Well, I don't have any cool formulas to play with. But, I do use ballast to even out a rear heavy car (MR,RR). I generally put it at -25 on MRs and -35 on RR. I don't always use the max amount.
Hmmmm checking out the stock spring rates of the real world RSX, they use stiffer rear springs then the front just like in the game but market the car as f/r 61/39.
Then while looking at the results in my formula it dawned on me that Duh the weight is reversed.
Our result shows rear heavy, but I think the formula is reversed as the result for our rear weight is the front weight and the rear weight is the front. Things look much more logically correct.
Hmmm
Then while looking at the results in my formula it dawned on me that Duh the weight is reversed.
Our result shows rear heavy, but I think the formula is reversed as the result for our rear weight is the front weight and the rear weight is the front. Things look much more logically correct.
Hmmm
- 1,139
- budious
When you consider the weight on the track loaded with fuel and a driver, both sit between the axles though, as does the engine in a MR so the weight becomes more evenly distributed than would be reflected by dry weight.
http://en.wikipedia.org/wiki/Curb_weight
European curb weight figures even include a 75KG driver so we can only guess at what metric PD actually used to represent the weight of car, whether the weight displayed is the one actually reflected on the race course, or if those weights are constant between a fuel and driver weights with tire wear off and tear wear on. You can see in of my other recent posts in which I found adding a 1KG user defined ballast to the car with tire wear on help to normalize the lap times suggesting that this is indeed the case and setting a user defined ballast exposes a flaw in that system.
I also tend to look at PD's model for weight distribution to produce different driving characteristics on cars to be based on ballast code. Picture a skateboard and then set two bricks on it; if you put both bricks at front and rear axles it would have a 50/50 weight distribution but would have more nose and tail forces at work then placing both bricks closely together at the exact center between the two axles where it would also have a 50/50 weight distribution but be mid-center localized to reduce those unpredictable cornering forces. This model would explain why you can have a 50/50 weight distribute in a rear engine RUF but it still has a meaty feeling in the rear.
Curb Weight
http://en.wikipedia.org/wiki/Curb_weight
European curb weight figures even include a 75KG driver so we can only guess at what metric PD actually used to represent the weight of car, whether the weight displayed is the one actually reflected on the race course, or if those weights are constant between a fuel and driver weights with tire wear off and tear wear on. You can see in of my other recent posts in which I found adding a 1KG user defined ballast to the car with tire wear on help to normalize the lap times suggesting that this is indeed the case and setting a user defined ballast exposes a flaw in that system.
I also tend to look at PD's model for weight distribution to produce different driving characteristics on cars to be based on ballast code. Picture a skateboard and then set two bricks on it; if you put both bricks at front and rear axles it would have a 50/50 weight distribution but would have more nose and tail forces at work then placing both bricks closely together at the exact center between the two axles where it would also have a 50/50 weight distribution but be mid-center localized to reduce those unpredictable cornering forces. This model would explain why you can have a 50/50 weight distribute in a rear engine RUF but it still has a meaty feeling in the rear.
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I been on this all day. I'm close to positive your formula works but as I said earlier in reverse. Your result for the front weight is actually the rear weight and vise versa. If not spot on, pretty damn close.
I spent the day with the Integra Type R premium model. The real world spring rates mirror the GT stock settings & when using the formula (in reverse) it gives an identical F/R weight distribution to reality.
I'm at the point of grabbing the real world wheelbase, using a formula to get a rough CG height then calculating the rough amount of weight transfer at 1g.
I spent the day with the Integra Type R premium model. The real world spring rates mirror the GT stock settings & when using the formula (in reverse) it gives an identical F/R weight distribution to reality.
I'm at the point of grabbing the real world wheelbase, using a formula to get a rough CG height then calculating the rough amount of weight transfer at 1g.
- 1,139
- budious
Except if you reversed it then you would have a heavy front end on a light rear end on a rear engine car like the RUF. So I don't think it is reversed, there are just other factors and hidden variables to account for.
Both of these cars were tuned using the above methodology if you want other test ready subject cases.
budious
I think the Ruf cars are a poor choice for testing. For starters it's a real pita getting the suspension specs from the real car for comparison. Not to forget the Ruf is a modified Porsche & sports a tuned suspension. Without the real world data your guessing.
It's better for us to use cars with readily available specs for comparison. So far every one I've check follows the rule (your formula reversed) I find it hard to believe most FF cars to be rear heavy as your method would suggest when using the formula reversed not only returns it to a logical front heavy car, but also mirrors the cars real world weight distribution numbers.
Frustrated getting mixed results the more cars I test.
What seems to be consistent is the weight split, just wether it's the front or rear is varying.
Frustrated, need to work my head around it. Are the cars that the formula works in reverse for correct or vise versa. I guess I'll do an average to see if it's generally one way or the other.
My excel sheet is getting nuts formulating formulas going both ways lol.
Hmmm could be the spring rate is based on the split but wether the spring rate is F stiff / R soft or R stiff / F soft is man/car specific. However (usually going one way over the other) I'm going to test some more cars.
What seems to be consistent is the weight split, just wether it's the front or rear is varying.
Frustrated, need to work my head around it. Are the cars that the formula works in reverse for correct or vise versa. I guess I'll do an average to see if it's generally one way or the other.
My excel sheet is getting nuts formulating formulas going both ways lol.
Hmmm could be the spring rate is based on the split but wether the spring rate is F stiff / R soft or R stiff / F soft is man/car specific. However (usually going one way over the other) I'm going to test some more cars.
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- 864
- NorCal
- oppositelock27
There's nothing to get your head around. There's no direct correlation between weight distribution and spring rate. You might as well try to calculate your tax return by charting lunar cycles. If you have to force convoluted and illogical theories (i.e. "some cars are reversed!!!!1") on it to make it work, it doesn't work.
- 863
- oops_sorryy
I'm no expert but if you take a look at the Supra RZ, it's spring rates make no real seance when you figure it has a 53/47 weight distribution. Spring rates are dependent on weight but not soley so. When tuning with a ballast it helps to know were the engine is mounted, and this can be more difficult than it sounds. You have Audi who mounts their engines right on the front bumper, some cars mount over the front axle, and some like the Supra mount the engine as far back as possible making them a Front Mid Engine. Then you have your MR and RR cars which are easy to figure out. I put ballast (if I think I need them) in what I think is the exact opposite position that the engine is, which will give me a much more neutral feel, than +50 or -50 usually will.
- 864
- NorCal
- oppositelock27
Don't want to get demolished again? Can't blame you. At least your ballast theory had some sort of scientific rigor behind it. Your weight distribution vs. spring rate theory on the other hand is 100% pure voodoo. I'm not sure I even want to bother going 2:0 with you. Seems redundant.
budious
I ain't sweating them, I'm finding you were most likely right I just chose a bad car to start with (ITR) it's got softer front springs when it's front heavy, funny enough I'm still getting close to real weight splits even when the stiffness is reversed from usual, could be the weight split dictated the spring rates just they reverse tuned it.
- 1,139
- budious
You're reasonable from pointing out how real world tuning works but we are making apples and oranges comparisons here, I have only being trying to explain how a programmer would approach simulating a system from a computer science perspective. There is little point to implicate a more sophisticated system that mirrors actual suspension physics and operation when they can create a system that is close to mimicking that behavior with much less overhead in coding. If you couldn't tell the difference from GT4 to GT5 tuning physics, I can promise you the PS2 hardware had nowhere close to the capability to run the kind of precision physics you are suggesting, and the additional capabilities of the PS3 were better put to use elsewhere.
- 864
- NorCal
- oppositelock27
No complex physics are required to model motion ratios, a simple formula would suffice. Spring rate (X) times motion ratio (Y) equals wheel rate (actual suspension stiffness) (Z). If PD didn't factor that Y in somehow then all these cars with wacky spring rates (which seem to correspond to their real life spring rates) would drive horribly and not at all like their real counterparts. Personally, I don't find that to be the case. Admittedly, how they model it is a mystery. Maybe they take the stock spring rates and weight distribution and then make an assumption about what Y should be. In any case I think it's safe to say that X does not always equal Z, thereby throwing a wrench into any attempts to concoct a spring rate system or formula.
- 1,139
- budious
Well I have found a pattern and reliable formula for (X) (Z) as you have defined as they relate to ride height (RH) and I have a similar suspension stiffness factor sf(x) but I haven't found a place where (Y) would fit into that formula which would suggest it is a universal figure. Still something I am playing with and trying to perfect but my results with keep improving with every revision.
Edit: Actually, I do know where it should go. I just don't drive too many of the cars you guys were talking about with the offset motion ratios front to rear. Most of the ones I drive are 1:1 probably, which throws the formula off a little bit for which I was attempting to patch up with a faulty method; the results would vary even more wildly if the motion ratio was incorrect and non 1:1, but looking at it now I think there is a way to compute it. What you could do to help is find me cars in game that use these non 1:1 motion ratios between front and rear, and then find me reliable weight distribution figures for the real life cars. I will attempt to work through the data set and see what I can extract from it.
Edit: Actually, I do know where it should go. I just don't drive too many of the cars you guys were talking about with the offset motion ratios front to rear. Most of the ones I drive are 1:1 probably, which throws the formula off a little bit for which I was attempting to patch up with a faulty method; the results would vary even more wildly if the motion ratio was incorrect and non 1:1, but looking at it now I think there is a way to compute it. What you could do to help is find me cars in game that use these non 1:1 motion ratios between front and rear, and then find me reliable weight distribution figures for the real life cars. I will attempt to work through the data set and see what I can extract from it.
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- 863
- oops_sorryy
So car the only car I know of for sure, is the Supra, it's stock weight distrobution is 53/47 and yet it's rear springs are near twice as strong as it's front springs.
- 863
- oops_sorryy
Length-------------4,520mm
Width--------------1,810mm
Height-------------1,275mm
Wheelbase---------2,550mm
Track (front)-------1,520 mm
Track (rear)--------1,525mm
Ground Clearance---130mm
I also have found the stock tire size, but because the Supra came with two options for wheel size I'm not sure which one was used so I'll post them both.
Tires (Front/Size 16)----225/50ZR16----Rim Size (Front/Size 16)----16x8JJ
Tires (Rear/Size 16)-----245/50ZR16----Rim Size (Rear/Size 16)-----16x9JJ
Tires (Front/Size 17)----235/45ZR17----Rim Size (Front/Size 17)----17x8JJ
Tires (Rear/Size 17)-----255/45ZR17----Rim Size (Rear/Size 17)-----17x9.5JJ
If you need more info on the Supra go here.
Edit: I actually found that in real life the Supra RZ (stock factory springs) carries spring rates of 430lbs/in (Front) and 219lbs/in (rear). Not sure why it's different it game but it is....
Width--------------1,810mm
Height-------------1,275mm
Wheelbase---------2,550mm
Track (front)-------1,520 mm
Track (rear)--------1,525mm
Ground Clearance---130mm
I also have found the stock tire size, but because the Supra came with two options for wheel size I'm not sure which one was used so I'll post them both.
Tires (Front/Size 16)----225/50ZR16----Rim Size (Front/Size 16)----16x8JJ
Tires (Rear/Size 16)-----245/50ZR16----Rim Size (Rear/Size 16)-----16x9JJ
Tires (Front/Size 17)----235/45ZR17----Rim Size (Front/Size 17)----17x8JJ
Tires (Rear/Size 17)-----255/45ZR17----Rim Size (Rear/Size 17)-----17x9.5JJ
If you need more info on the Supra go here.
Edit: I actually found that in real life the Supra RZ (stock factory springs) carries spring rates of 430lbs/in (Front) and 219lbs/in (rear). Not sure why it's different it game but it is....
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