Compound Tuning

[dadoors]

There are a few very technical aspects of tuning that iam beginning to learn and understand. I would like to take as much guess work out of tuning as possible and the biggest issue is when trying to tweak a car and one value is changed, one or many other values are directly affected and will also need adjustment to get maximum performance.
[ex: increase spring rates when better tires are used]

could someone please elaborate or point to a tread that better explains the complex and unforeseen positive/negative/neutral effects of tuning?

 

[chuyler1]

I can explain the tire issue for you. It's a matter of physics (as is the case with most tuning changes).

When turning, a tire holds a certain amount of grip. The g-forces cause the body to roll and weight to transfer from the inside tires to the outside. In order to keep body roll in check, you need to run certain spring rates and antirollbars that are tailored to the car's weight and other characteristics.

When you increase the amount of grip a tire can hold, the added g-forces cause the body to roll more than before and in turn, more weight will transfer from the inside to the outside as the outside springs are compressed further than before.

If you do not increase spring rates, the outside suspension has the potential to bottom out meaning there is no more travel left to absorb bumps. When the suspension is fully compressed any bump in the road can cause the car to skip and break traction.

So you increase the spring rates to prevent bottoming out. Now the car's inside tires tend to lift off the ground when you corner. This is when you should start reducing the ride height to lower the center of gravity of the car. Of course lowering the car may again cause bottoming out, so you may need to increase the spring rates further until you find a good balance between grip, ride height, and spring rate.

 

[Ronald6]

Is tyre wall height also simulated? Irl comfort tyres have a taller wall for, well, comfort. The wall height gives more cushion that the suspension doesn't have to deal with. When you switch to sports or racing tyres their walls aren't as tall so don't flex as much, less comfort but better grip.

 

[budious]

Is tyre wall height also simulated? Irl comfort tyres have a taller wall for, well, comfort. The wall height gives more cushion that the suspension doesn't have to deal with. When you switch to sports or racing tyres their walls aren't as tall so don't flex as much, less comfort but better grip.

I have noticed on a RUF Yellow Bird that I setup to use Sport Medium front and Sport Soft rear, that the equivalent next step up to maintain the driving ratio without adjusting camber is Sport Soft front, Race Medium rear. So the difference in cornering grip ratio from Sport Medium to Sport Soft is about the same as the difference between Sport Soft to Race Medium, at least from this particular observation.

 

[PINION 6]

There are a few very technical aspects of tuning that iam beginning to learn and understand. I would like to take as much guess work out of tuning as possible and the biggest issue is when trying to tweak a car and one value is changed, one or many other values are directly affected and will also need adjustment to get maximum performance.
[ex: increase spring rates when better tires are used]

could someone please elaborate or point to a tread that better explains the complex and unforeseen positive/negative/neutral effects of tuning?

Very complex......A big world and it comes down to your ability to feel.
Example,
Your car understeer's, now you have to know what type of understeer it is,
Is it downforce understeer, suspension understeer, weel alignment understeer, drivetrain understeer [FF will allway's understeer more as you know]
The way to learn the feel is to take a stock car and Time Trial it till you know it, then tune it slowly, one part at a time, and feel what the part's doing, then when the next part goes on you'll know how it's affecting the part before, and in time your car will be fully tuned and you will know what every part feels like and how it's affecting the others.

For me to explain every vairiable in the GT tuning page you would have to be here, to wright it would be a book, but try a slow tune like i've mentioned and I think you'll clock it......

 

[nomis3613]

^ agree 100%

It is an excellent question, dadoors, but I don't think anyone's ever specifically asked it before! Here's a couple of examples:
downforce: gear ratios, possibly brake balance
gear ratios: pretty much independent of other settings
engine parts: transmission, LSD accel
spring rate, dampers, ride height and stabilisers are all very interrelated

There are lots of conflicting theories about brake and LSD settings, so I'll leave it to someone else to open that can of worms!

 

[dadoors]

That is exactly the kind of break down i was looking to hear nomis but even more detailed and in depth. i realize lsd tuning is insanely controversial atm, but i dont care so much about the theory's on what should happen when tuning but rather "in game" results.

another question not getting too far off topic is how successful have tuners been changing the default ratio values? i have only found a few cars if any (with the exception of rear toe and df) where i have gained performance by changing, say, camber with a default ratio of 1:1 (0.5/0.5) to 2:1 (2.0-1.0). and if successful what type of car/drivetrain?

 

[HKS racer]

That is exactly the kind of break down i was looking to hear nomis but even more detailed and in depth. i realize lsd tuning is insanely controversial atm, but i dont care so much about the theory's on what should happen when tuning but rather "in game" results.

another question not getting too far off topic is how successful have tuners been changing the default ratio values? i have only found a few cars if any (with the exception of rear toe and df) where i have gained performance by changing, say, camber with a default ratio of 1:1 (0.5/0.5) to 2:1 (2.0-1.0). and if successful what type of car/drivetrain?

Trying to answer to your question, one thing you can do is take a car from a tuning garage, buy and run the stock version, then buy a fully customizable suspension kit and set the tuner's values, you will recon a difference, then buy all the other parts needed, install and set them slowly, basically you need to know how a new part it's affecting the car..

 

[nomis3613]

That is exactly the kind of break down i was looking to hear nomis but even more detailed and in depth.

Glad it was useful, here is a bit more detail:
downforce vs gear ratios: unless you're making massive changes to downforce, the effect on top speed is minimal (I included this more as a theoretical example than something you would actually do in GT5). But in theory, more dowforce means lower top speed so you can set shorter ratios (higher numbers) so that you accelerate quicker

downforce vs braking: increase the brake balance at the end of the car you are adding downforce, and vice versa. The extra downforce gives the front/rear more grip so you can give it more braking force

power upgrade vs gearing: lets say you have increased the bhp and are now getting wheelspin in 2nd. You should make the 2nd gear taller (lower number), this will both help avoid wheelspin and let you have the rest of the gears closer together (which gives better acceleration)

power upgrade vs LSD accel: if your power upgrades now mean the inside wheel is spinning out of tight corners, increase the LSD Accel (or you could increase LSD Initial which has different side effects...this is one of those GT5 religious debates! I'll just say that you could do either and there are threads out there which (vehemently) debate the difference...

springs vs ride height vs dampers: textbook theory states that stiffer springs means stiffer dampers and lower ride height. People have different opinions on whether this is true in GT5 (I personally believe it often isn't). Sorry for not being definite! But I will warn you to not be surprised if the textbook theory of "stiff front = more understeer, stiff rear = more oversteer" often doesn't work. At times you will find that a stiffer front actually reduces understeer.

rear toe vs wheelspin: using negative rear toe on a rwd car often results in more wheelspin. So be careful when using negative rear toe to reduce understeer.

camber vs ???: Opinions vary, but I believe camber can usually be tuned independantly of other settings.

Looking back on this list, I had hoped to be able to include more "compound effects" than this. I can't think of much else because most of the relationships between settings are complicated and vary according to other factors, which is why tuning can be a black art...

<slightly off-topic rant>
This list is the obvious relationships which come to mind. Tuning is a balance, so for example increasing LSD accel can increase high speed understeer. You could compensate for this with either more front downforce, negative rear toe, or many other options. The possibilities are endless for this kind of stuff!
</rant>

i realize lsd tuning is insanely controversial atm, but i dont care so much about the theory's on what should happen when tuning but rather "in game" results.

Ok, I'll try to distill the LSD debate into some agreed "in game results":
- increasing Accel reduces wheelspin on the inside wheel. After a certain value it then causes wheelspin on the outside wheel. How this affects handling has caused forum debates spanning many pages.
- increasing Initial reduces the tendancy to yaw (aka pivot, so that you can turn the corner). This sounds like a bad thing, but sometimes you want less yaw because the car is hard to control. Also, increasing Initial means less change in handling when you apply and release the accelerator (if your Accel or Decel are high)
- increasing Decel makes the car less able to yaw while you are braking. Often useful for RR cars.

Sorry I can't be more "practical" with these LSD points. I consider these to be the more commonly accepted results of LSD workings, even then some people will think otherwise. You were probably hoping for some tips like "increasing X cures understeer", unfortunately that is getting into highly opinionated territory and often the situation is more complex than "understeer" or "oversteer". But, for a new tuner, I recommend erring on the side of lower LSD values. In GT5, high LSD settings can mask the effect of other settings.

another question not getting too far off topic is how successful have tuners been changing the default ratio values? i have only found a few cars if any (with the exception of rear toe and df) where i have gained performance by changing, say, camber with a default ratio of 1:1 (0.5/0.5) to 2:1 (2.0-1.0). and if successful what type of car/drivetrain?

downforce: don't worry about keeping the stock ratio, use whatever feels best
ride height: there are many competing factors, so you need to experiment
spring rate: this is the setting where it's most important to keep the stock ratio. Altering the ratio often produces nasty handling effects. That's not to say you should never adjust the ratio, though.
camber: feel free to mess with the ratio, however keep in mind that the axle with the most weight usually needs more camber
everything else (dampers, toe, brakes): don't worry about keeping the stock ratio

Hope this helps,
Simon