*** UPDATE *** Improved guides for - FF cars - FR cars have been made. Guides for other drivetrains are planned (one day!). My original post is here, but a lot of my theories have changed since his was written. *** /UPDATE *** I've been working on a tuning method to extract maximum speed. Have a read, try it out and let me know what you think. Yes, this is similar to a previous thread of mine, I've tried to put the tuning tips into a “start-from-scratch” method this time. The guide is incomplete (and always will be...unless I get to speak to Polyphony physics programmers...), these are the areas I'd like to improve in the future (suggestions welcomed): - LSD tuning for AWD cars, I really don't know what I'm doing here (in a rear-biased setup, so the front axle be higher so that the rear wheelspins first, or should it be softer to allow the car to pivot better? ) - should dampers be set to suit spring stiffness? - brake balance controller- see here - downforce vs tyre wear - the difference between damper bound and rebound for response to bumps - using spring rates to change overall balance (instead of just stabilisers). -------------------------- STEP 0: RAMBLE Tuning is a balancing act, where speed gained in one area is often balanced by speed lost in another. And each handling problem can be “solved” by various fixes, each of which has a different side-effect. For example, power understeer can be reduced with negative rear toe, stiffer rear stabilisers, softer front stabilisers, negative front toe, more front downforce, etc etc. But which method is the best? This method aims to find the best handling setup for a car, not only in front to rear balance, but also in maximising grip by trying to avoid “2 wrongs make a right”. To keep the guide brief, I'll use a fair bit of car tuning jargon. If you don't understand something- please don't be afraid to ask, I'm happy to explain even the most basic question. Also, the guide is purely written for GT4 so when I say “this works like this...”, I mean for (my understanding of) GT4, which may or may not be the same as real-world physics. Tuning is an iterative process, so there is no correct order. Try to focus on the questions in each section, and ignore the rest of the handling characteristics. But there are times you will need to a) fix something drastically wrong before you can continue tuning (eg add rear downforce if the car is totally unstable at high speed) or b) go back and tweak a previous setting because you have changed something else which has a related effect (eg reduce front toe after stiffening the rear stabiliser). So feel free to jump around the steps, but I believe this order is a good starting point. ------------------------------- STEP 1: NEUTRAL SETTINGS These settings are a good 'neutral' starting point to help you tune: brake balance: 3, 3 spring rate, ride height: 1/2 way dampers: 4, 4, 4, 4 toe: 0, 0 camber: 0, 0 stabilisers: 1, 1 driving aids: 0, 0, 0 LSD: minimum VCD: minimum downforce: 0, 0 ------------------------------- STEP 2: CAMBER Most tuning involves trading grip between front and rear tyres etc, however the camber angle is unique because it determines the maximum potential grip for the tyre. Setting the wrong camber angle is just throwing away speed! The camber angle is the first thing to be tuned, so that we're starting off with the maximum possible grip from the tyres. Tyres have an optimum camber angle to produce the most grip. In GT4, this angle is the same for all 3 types of grip (cornering, acceleration, braking), which makes tuning much easier. The optimum angle for the rear tyres is 0.5 deg less than the front tyres. Sport tyres have an optimum angle (for the front tyre) between 2-3 degrees, compared with 1.5-2 degrees for the front tyres. The simple method is just use 1.7 front and 1.2 rear for racing tyres; and 2.5 front and 2.0 rear for sport tyres. This will be somewhat near the optimum angle. For those who want the absolute best speed possible, time-consuming testing is needed within the above ranges. The best way is using braking distances (cornering takes too long and acceleration tests are too much affected by launch revs and shift points). On the twin ring circle track, measure the braking distance (using the data logger) as you brake from 200 to 100km/h. Actually, brake from 210km/h to 80km/h but only measure the 200-100 section; this will give more reliable results. Try to brake in roughly the same place on the track each time (on a flat section of the straight), but don't it's not critical. After each test, increase the camber by 0.2 and try again (I told you this was time-consuming!). Work your way through the rear camber angles first, then repeat for the front. ------------------------------- STEP 3: GEARING This is hard to explain, so I'll just describe a method which works for most cars, instead of delving deep into theory. Decide what maximum speed you want (remembering that higher max speed = less acceleration). Move the top gear slider all the way to the right, then adjust the final drive until this speed is achieved at maximum revs in top gear. Set 1st and 2nd gears all the way left, then space out 3rd, 4th and 5th gears evenly in between. If a gear is causing wheelspin at low revs, then the ratio can be moved left without reducing acceleration, this will allow the other gears to be spaced closer together for better acceleration. For each track, the gears which are used most should be spaced as tightly as possible. For example if a track mostly uses 3rd and 4th gears: set 3rd as far left as possible and 4th as far to the right. Often 1st gear is only used for standing starts, because it just results in wheelspin for slow corners. ------------------------------- STEP 4: BODY ROLL, DIVE UNDER BRAKES This is where the real handling tuning starts. Choose a track to be your testing venue- I like Apricot Hill for its mix of corners, but it is up to you. Now you will start pounding out laps, making small changes and testing the difference. First step is body roll... I believe that body roll does not affect grip in GT4, so spring settings are mainly used to suit how the driver likes the car to feel. Drive around your testing venue (yes, the grip of the untuned car may be doing strange things, but try to ignore them- we are not worried about understeer/oversteer/etc for the moment) and focus on these questions during turning and braking (how the car feels over bumps and kerbs will come later): “does the nose dive too much under brakes” > needs stiffer springs “does the car feel too sharp and twitchy” > softer springs “does the car feel too soft and floaty” > stiffer springs At this stage, use the same spring rates front and rear. Rant about ride height: Overall ride height is pretty useless in GT4. Lower heights do not result in more grip (despite what the scrolling text says) and body roll/dive under brakes is only affected by spring rates. Unless your car is bottoming out and producing sparks (I've only ever seen the Le Mans and F1 cars do this) then there is no reason to change the ride height. Personally, I set the ride height to be the opposite of spring rate (eg if springs are at 25% of max stiffness then the ride height is 75%) but this is out of superstition alone! The only real use for ride height is if a rear- or mid-engined car is too unstable, using lower front ride height than rear will push the weight forward and make the car more stable. ------------------------------- STEP 4: DRIVING OVER BUMPS Now concentrate on how the car behaves over bumps and kerbs “does the car feel harsh and lose lots of grip over bumps” > decrease all 4 dampers equally “does the car feel too floaty over bumps” (very rare) > increase all 4 dampers equally To avoid extreme damper settings when tuning the dampers, the springs can also be adjusted in the same method. ------------------------------- STEP 5: FRONT TOE The first time you will think about whether the car is under/oversteering. Like the scrolling text says, front toe is the trade off between initial turn-in and maintaining front grip later in the corner. “does the front end lose grip after the apex” > decrease front toe (to higher negative values) “is there not enough turn-in, but too much front grip exiting a corner” (very rare) > increase front toe The feeling for this is hard to explain: it's basically a lumpy feeling as the front end gains and loses grip through the corner: one moment you're following the desired line with plenty of front grip, then suddenly the car starts to understeer, then if the corner is really long the grip will come back again. ------------------------------- STEP 7: BRAKE BIAS The brake controller adjusts the “reserve” grip (left over for cornering) during braking “is the car too easy to spin while braking” > increase front brake and reduce rear brake “is the car too hard to turn while braking” > reduce front brake and increase rear brake Don't set any of the brakes above 12. If you need settings more extreme than this, there is probably something else wrong with the tuning anyway. ------------------------------- STEP 8: BRAKING WEIGHT TRANSFER Concentrate on how the car feels as you first hit the brakes, especially if you are already turning at the time. As the weight moves forward under braking, this can be controlled by the front bound and rear rebound dampers. “is the car too unstable when you start to brake” > increase the front bound or rear rebound “does the car refuse to turn when you start to brake” > decrease the front bound or rear rebound This all sounds similar to the brake controller from the last step, so what's the difference, right?! Hard to say! The dampers are more about the initial weight transfer at the start of braking, while the brake balance has greater effect towards the end of the braking. In the end, the effect of brake bias and weight transfer are so similar that the best setup will be determined by making sure the tyre wear is the same for front and rear tyres. However, If the car is RR, the braking weight transfer is usually the cause of the problem so try this first. As for whether you should stiffen the front or rear, this is a change to use the side-effect to your advantage. If you have been thinking that the car is understeering (so needs a stiffer rear) then stiffen the rear bound or rebound instead of the front (vice versa for oversteering). ------------------------------- STEP 9: ACCELERATION WEIGHT TRANSFER Think about what happens as you accelerate out of a corner. “does the car understeer when you start to accelerate” > increase front rebound or rear bound (note: the difference between this and front toe is that front toe deals with understeer that occurs even when not accelerating (ie mid corner). Acceleration weight transfer deals with how acceleration causes the front tyres to get “lighter” (and lose grip) as the weight moves rearwards) For FF only “does the car oversteer when you start to accelerate” (very rare) > decrease front rebound or rear bound For all other cars (than FF), it is likely that any exit oversteer is caused by the engine torque, not the lack of weight transfer; it is better to fix this using LSD settings than dampers. ------------------------------- STEP 10: 4WD TORQUE SPLIT The VCD controls the amount of torque going to the front wheels. Changes to the LSD settings will mean you should look at the VCD again. “do you get wheelspin coming out of tight corners” > increase VCD (note: if the car is very overpowered and all 4 wheels are spinning, VCD cannot help) “does the car understeer when accelerating out of 3rd gear corners” > reduce VCD Tuning 4wd cars is another level of complexity and possibilities. I prefer to set the car up as mainly RWD (less turn-in but power oversteer on exit is possible), but it is also possible to set the car like a FWD (more turn-in, power understeer on exit) if you like that feeling. If you prefer the feeling of typical FWD then set the VCD to max before Step 3. ------------------------------- STEP 11: OVERALL UNDERSTEER / OVERSTEER I know it's been hard to ignore the basic balance of the car through the previous steps, but finally you get to fix it! Actually, I find that most cars are well balanced once the above problems are removed so only minor tweaks are needed here. “does the car oversteer in general” > stiffen front stabiliser “does the car understeer in general” > stiffen the rear stabiliser or decrease the rear toe (higher negative numbers) note: stiffer stabilisers causes more grip loss when 1 wheel hits a bump, so use as little stabiliser as possible It is also possible to tune the overall balance with the spring and damper rates but I prefer to use just the stabilisers (so that springs can control bumps / initial weight transfer and the dampers look after the weight transfer). However any extreme settings can have strange side effects, so if a car needs max front stabiliser and min rear (or vice-versa) to be balanced, then I would change the spring rates so that less extreme stabiliser settings can be used. Spring rates are the wrong way around in GT4: stiffen the front or soften the rear to cure understeer (opposite for oversteer). This means that softening the rear could be a good way to cure understeer in a rwd car, because the softer rear will also reduce wheelspin when accelerating. What about using downforce to adjust the balance?? We'll get to that later... ------------------------------- STEP 12: LSD Higher settings reduce wheelspin (as long as only the inside wheel is spinning, it can't help if engine power is enough to spin both wheels), but they also reduce the cars ability to pivot (ie turn). So you only use as much LSD as you need to control the wheelspin. ALL CARS “does the car feel unstable and spins easily, especially at the start of braking” > increase initial or decel “is the car hard to turn, despite good grip balance” > decrease initial or decel RWD CARS “does the car wheelspin of oversteer when accelerating” > increase initial or accel FF CARS “does the car wheelspin when accelerating” > increase accel (note: it is difficult to tell when you have too much LSD accel on FF cars, but it will cause increased understeer. So slowly increase the accel until you have enough) 4WD CARS This is complex! (and I don't understand it properly...) If you are using a low VCD setting, only increase the accel or initial on the rear, or the front only if the VCD setting is high. You can (and will probably need to...) play with the LSD and VCD settings for hours until you find the perfect combination. (all cars) As for whether you should change the initial or the accel/decel, consider whether you would like the car to be more stable (increase initial) or easier to turn (decrease initial) in general, as well as the effect you are looking for. If so, change the initial, but if you are happy with the stability / ease-of-turning and just want to fix your secific problem, then just change the accel / decel. Keep in mind that using accel / decel will cause the car to change behaviour as you brake / accelerate, so it is better to use higher initial settings and less accel and decel. That way, the car is more consistent in all phases of cornering. ------------------------------- STEP 13: DOWNFORCE Now that the handling is balanced, the downforce is the last thing to tune (to avoid “2 wrongs make a right” tuning). Set the front downforce to maximum. The car will be very easy to spin, especially at high speed. Increase the rear downforce until the handling feels balanced again. If the downforce has reduced the top speed too much, reduce the front downforce and repeat the tuning of the rear downforce.