General Tips/Help for tuning out understeer in AWD cars

Hi… The title says it all hopefully. I’m looking for general tips/techniques/practices for helping to eliminate understeer in AWD cars, mainly tarmac…

I’m an average tuner and can generally get a tune together than can beat pro and sometimes unbeatable levels but I do often seem to introduce understeer in my AWD tunes… I’d love to be able to reduce some of the understeer and was wondering which components to focus on to help that.

Appreciate in the absence of a specific tune/setup, this question is more general in where would tuners go to if they had a car that was generally good in performance/straight line grip etc, but just can’t get into corners… I’ve played with toe-in a bit but it doesn’t seem to make much difference. i’m wondering if its my diff settings that are not right or if caster will help here.

thanks in advance…

Although there’s some general guidelines you could go by, the method to fix the understeering issue is usually different between vehicles.

In order to help you, we’ll need a bit more information.

  • What vehicle are you currently working on?
  • What PI class is the vehicle built for?
  • What tire compound & tire widths are you using?
  • Is the understeer occurring during low-speed corners or high-speed corners?
  • Is the understeer occurring during corner entry, mid-corner, or corner exit?

thanks for the reply… It isn’t really just one car that i’m trying to tune as i seem to have a common issue across most of my AWD cars (at least the ones that I tune rather than stock)… the graphic in this thread and advice on ARB’s makes a lot of sense so will give some of that a go… Appreciate the response though

I usually quick fix my AWD cars by just softening the front ARB (if I’m not trying to tune it perfectly, just make it drive-able, I’ll drop the front ARB by like 5-10 depending on the car and the default setting)

For more betterer tuning though; I balance my ARBs to the weight distribution of the car, then adjust the front down and/or rear up until understeer goes away.

There’s a flowchart I use for this type of tuning occasionally for Motorsport, let’s see if I can figure out how to post pictures to a forum…

Tuning chart

I like this chart because it reminds me which thing to mess with depending on where in the corner the car has problems (but fwiw I find this much more helpful in FM7 than FH4)

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Thanks for the reply… That makes a lot of sense and the graphic is a huge help… I must admit i don’t generally play too much with my ARB settings, generally leaving them default, so seeing as i have understeer in most of my AWD tunes regardless of the car/PI etc, I suspect I need to do some manual tuning with the ARB’s in the way you mention… I’ll give this a go…

Nice one, thank you

I’m having the same issue, and I made a similar post. I’m trying to tune a 2015 Corvette Z06, but it seems that the car loses front wheel traction under hard turning. It is very difficult to race in the cities, and some other road, but the car will turn absolutely fine when at a speed of 30 miles per hour.

It’s not the only car I’ve had this issue on either. Had this issue on a Camaro, and the Lancia Stradale. I tried using the chart, but I think with some specific cars that there is a specific issue.

Dampers.

I tune everything proportionate to the cars F/R weight EXCEPT dampers. I’ve found that this where you can easily fine tune the cars behavior with little or no ill effects.

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That’s interesting. I used to set my springs, then aim for 60-70% critical damping.

I’ve also tried setting bump to control compression and rebound to control the spring. I really don’t like packing so 80-90% bump:rebound is the lowest I’ll go. If the springs are at a decently supportive yet compliant (Horizon 4 roads suck, I have yet to go as high as 3hz successfully), 1:1 bump:rebound seems to work ok.

Recently I read (can’t find the link in my history) that dampers should be set irrespective to the springs, simply to control the car’s inertia, and a wide range of spring rates will work with nearly the same damper settings. I’ve been using this method more or less in CarX with good results (I mod the game in singleplayer for full control over the dampers instead of the default 10-step preset system…).

The game just doesn’t differentiate as much between Damper, ARB and Spring changes on the road as it should, so there is definitely more than one way to make a competitive car. I’ve found that this system works for me though. Just because I tune Springs and ARBs proportionate to the f/r weight ratio doesn’t mean that I am always running the same overall stiffness. I start with the same equation Hoki Hoshi and a lot of others use and then alter Springs and ARBs + or - X% based on other factors. Only the f/r ratio is maintained in those settings. I always leave dampers at stock settings for intial tests, but usually end up running the equation for a baseline and going into more intensive damper tuning from there.

Some notes on Damper tuning:

Corner Entry Understeer: apply -F Bump / +R Rebound
Corner Exit Understeer: apply -F Rebound / +R Bump
…vice versa for oversteer

Rebound will be raised or lowered proportionately with the bump if the car feels like it is leaning/rolling too much or too little while cornering. Remember that some weight transfer/shift is beneficial to cornering. Rebound can behave sort of like the ARBs in this manner but will not effect steering response or create snap oversteer as much as ARBs can.

I usually start with bump at 65% of Rebound. A cool exercise is to tune a RWD Vehicle as you usually would and play with bump settings. On an oversteery vehicle, you will actually feel an odd vibration through your controller as the rear tires start slip under hard cornering. This vibration is tuned out and the traction can be regained as you lower the rear bump. It acts sort of like Tire Pressure does in the game without compromising as much grip or stability.

-On the rare occasion that it is beneficial to not go full custom suspension, such as tuning to a very low PI class. You can tune ARBs and Tire pressure to control behavior as sort of a cheap substitute for damper settings. This is not preferred for the reasons listed above, but is still preferable to a grossly underpowered car.

A common early mistake is to try to tune things like bottoming out and extreme spring compression or stiffness with dampers rather than springs. They simply will not increase or decrease your spring tension and your cars f/r weight is fixed, so I try to maintain f/r proportionate rates and this has worked in my experience. Dampers aren’t there to make your springs softer or stiffer, they’re used to alter the way your springs react and your cars behavior a long with it.

Another note is that I tend to keep my tires around 29psi for race, 28 for Offroad only and 28.5 for everything else. I used to run some pretty extreme tire settings based on another formula I’d found and the problem with this was that pressure doesn’t seem to react as much to car weight as it should in the game. Regardless of weight, you go too far above this and your contact patch shrinks killing grip, too low and lateral stability is compromised imitating sidewall flex. Again, bump in particular helps to a degree here. Running 80-90%bump/rebound seems really high to me, I’ve more often seen extremely low bump settings like 10-30% bump/Rebound. Those extremely low settings can help a lot with RWD oversteer but neither is preferred with my method. That doesn’t mean it can’t work, just that it needs to be compensated for elsewhere. The game gives us more than one way to skin a cat, the method I’m using is simply what I’ve found to be the most expedient and effective.

Finally, diffs and alignment are tuned separately from all this.

That was a lot to throw out there. Not sure if it will make a lot of sense or be helpful. The important thing is to go drive and experiment. It’s fun to research the heck out of this stuff, but Forza is not a perfect simulator and that means we’ll find different ways of beating the competition, or at least having a car that feels good enough to. ; )

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I’ll try to use Hoki Hoshi’s front equation and see if that gets me anywhere.

Looking at my tunes before I tuned by ride frequency, I like 1.9hz on dirt, A class in general, lighter cars, and around 2.5hz for dedicated road cars, S2 cars, up to 2.7 or 2.8 if suspension travel is limited in high-downforce cars.

Here are the sheets I’ve since arranged, if you’re interested.
https://docs.google.com/spreadsheets/d/1iWcYonZNbOZA6N1w6y7qjK6B6EUo98MufapvST8Xj0Y/edit?usp=sharing

I’m a little confused when you mention Hz for springs. Can anyone elaborate on what this means?

It’s a representation of stiffness, with respect to the car’s weight and weight distribution. 2hz ride frequency on the front axle of a 2000lb 45% front car will be the same feel as 2hz on the front of a 3000lb 55% car, but one will have a spring rate of 300lbs while the other will be 550lbs.

Sort of like horsepower vs torque… torque means nothing without revs… spring rate means nothing without weight… ride frequency is the weight-factored stiffness of your springs.

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