Tuning question

I’ve have given a go with a few tuning calculators and have noticed a general trend compared to my tunes.

My tunes tend to have a turn in that I like better but don’t feel like they continue the turn as hard and aren’t as stable in the corners. The biggest difference in my tune vs tuning calculators on a regular basis is tuning calculators use much more aggressive camber and toe settings combined with much softer ARBs and slightly softer springs. I am sure the camber and toe is where most of the difference is coming from in relation to holding the turn and stability in the corners. I like the sharper turn in response I get with my tunes however I liked the stability and ability to hold the corners better in the calculator tunes. The alignment settings I have never messed with because it is the only part I don’t really know that well in terms of effects. Thus I have lived with default basically. I know to find the solution of the middle ground I want is to play around with it. However this is my question which of the three most directly impacts what I am looking to adjust (if any one does more than the other 2) and what should I expect in terms of changes (if any) to handling in terms of tight or loose, reactions to bumps et cetera as I use a fairly stiff ARB set up with rather soft springs?

Also note that I do not use Forza aero as much as possible to preserve the original look and used the tuning calculators with that “calculated in” if you will when it applies thus add more downforce isn’t a potential solution to the problem.

Regarding ARBs, bear in mind that the stiffer these are, the less independent your suspension is because they tie each side together. The stiffer you go, the more bumps in the road will impact the side of the car that did not hit the bump. If you feel a lack of mid corner stability, there’s a chance that you may need to dial this back and increase your spring stiffness.

Also have a look to see if you’re bottoming out. This will also cause some pretty dramatic mid corner stability.

Regarding camber, this really depends quite a lot on the car you’re tuning. But the trick is to have a look while you’re on a drive and ensure that as your outside compresses, that it’s not going too far into the positive (generally an issue with MacPherson strut cars). If this happens you have two choices, increased roll resistance via stiffer spings or ARBs to keep the suspension from compressing far enough that it is an issue, or adjust add more static negative camber. Remember that this will both impact braking in a straight line and mid corner balance between front and rear.

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Regarding the stability the bumpiness of the road is not the issue. On smooth tracks the instability is there as much as on bumpy tracks. When I am talking instability here I am talking about the car not handling as if it is on rails like with the calc tunes and squabbling about during cornering closer to the limits. The reason I think it is the camber, toe or caster is that I think the instability is due to the fact that the default settings don’t have the tires set with enough for solid cornering grip and are set more ideally for straight line grip. This is just my current;y prevailing theory as to what is going on.

That being said I do have issues regarding getting thrown aside by moderate or bigger bumps that I have always just accepted. I will lower the ARBs a bit to see if it will help but small bumps do little to bother my car.

Also I will try the two tunes and give them a go. It might be a bit later this week before I can though.

Edit: Double post.

Serious suggestion for you. Drop your rebound to about 5.4/5.1, bring your bump stiffness up to between about 8.2/8.5 then halve your ARB settings and try that.

The effect that has is that you’re using your damping or (Spring assist) to prop the car up and keep a flat ride.

The options in the tuning menu are the same as the tuning options in performance motorcycle suspension and have the same effect on the cars in game for what ever reason.

Bump stiffness on a car tends to be a a crush mushroom used to stop the suspension travelling too far in the first place on the compression stroke. The higher the value the more progressive and slower the stroke, the less rebound you need to run.
It also serves another purpose in that it aids pitch and roll, so the stiffer the bump the less you nose dive, the more poised the car. It also means you can get away with a much softer ARB keeping the suspension working more independently so you’re much less effected by bumps, camber changes, curbs, love taps and standing water.

Running a softer rebound insures that the wheel isn’t forced back to the ground too quickly which prevents bouncing and loss of traction. It also stops you getting pitched and rolled when hitting a high curb.

Hope that helps.

Quick question. Matter of factly… In Forza 4 1.0 bump and something like 8 rebound was a common way to increase your grip. Bump was almost always 1.0, and rebound scaled with car weight. Springs were set to soft or medium soft depending on suspension travel distance. Usually something like 400lb/in in the 2000lb range. 600lb/in in the 3000lb range. This was by far the best way to setup your suspension.

As far as I can tell bump and rebound are completely different and I have different dampening setups. Bump is softer, meaning 2.0 to 3.0 drives like the old 1.0. I assume rebound is the same. Meaning I guess some people are probably running like 9-11 rebound on some tunes.

Bump can be swapped out for spring rate to a degree. I just call it “riding on dampening”

I have a Honda NSX TF tune that is rock stable on rio running like 300 springs at 2400lbs, 7’s bump and high 11’s rebound. It eats curbs for breakfast.

All my low bump ratio tunes are too bouncy on rio, but its unnoticeable on something like Catalunya. It wasn’t like that in Forza 4 since the settings were borked. The only way to get body roll like manufacturer suspension was to use 1.0 bump. It seems like actually calculating proper dampening and spring rates is most effect. I have a formula based on the Donkervoort (which has a custom setup by default for low springs, high dampening) that seems to work well for grip, stability, and kurbs even on rio for cars up to about 3200lbs. The caveat is that this is so long as you have enough susension travel or else things get goofy.

How are people tuning cars that bottom out easily?

For me that depends on the track. I was goofing around with a Golf R on Lime Rock, a track which is brutal on bump because of the really big hill that causes really rapid compression going up it, and then down again leading onto the front straight.

I gradually increased increased the bump stiffness to keep it from immediately flopping to bottomed out, then I started to gradually increase the spring rate to help. After adding a bit of each over several adjustments I managed to get a pretty decent lap time out of it.

…and then I ran that setup on Rio, where it was completely undriveable due to the high spring rates not getting along well with the super-rough track surface. lol

Great post, but I want to comment on this specifically. The rebound setting affects how quickly the spring extends. A stiffer setting means that the spring will decompress more slowly, and a lower setting means that it will decompress more quickly.

The damper does not force the suspension down on rebound, it restricts the rate in which the spring decompression occurs to a greater or lesser degree depending on how high or low you’ve set it.

In effect, a softer rebound means that the wheel is going to go back to the ground more quickly, assuming it was off the pavement as a result of compression in the first place.

A catastrophic symptom of too much rebound is bottoming out the suspension when you hit a series of bumps that quickly hammer up at the suspension and it can’t decompress fast enough to deal with the next bump. But I don’t think you’re likely to experience that in Forza. The only place I can see this happening is in a RWD hard acceleration on a track that has nasty rumble strips like Hockenheim, maybe also in a braking zone if you go wide onto the strip.

I currently set my bump/rebound to something like that. Say a car has 50/50 weight distribution. I will set bump to 9.0 with rebound to 5.4 on front and rear. 9.0 to counter low springs to deal with the bumps and 5.4 because 5.4 is 60% of 9.0 and I read a long time ago that a good rule of thumb to go by is having rebound at about 60% of bump. If a car is say 52/48 I will set bump/rebound on the front to 9.0/5.4 and rear to something like 8.5/5.1.

I run properly configured springs, high bump, low rebound, between -0.2 and -1.4 camber depending on the car, 0 toe. Try out my 15 Camaro or the Ferrari 360cs (think there’s a non aero version shared) if they have the feel you’re looking for I’ll let you know what I’ve done.

What’s the reason for high bump and low rebound?

If you don’t use Forza Aero try -0.1 front and -0.1 rear toe as poor mans aero. I guess you could do -0.2 front & rear toe. I’ve done it before, its fine. Anything more and its too much drag.

When your tires are -just- about to leave the ground due to any reason (bump, hill, etc.) it gives you that last bit of control that you need.

I don’t know why this is… it just is.

I first noticed it on Sedona in Forza 4 where you would crest alot of hills and try to accelerate over bumps, and it also helps the front tires as well.

I think of toe now as more of a lifting/sucking of the tire. Positive toe lifts you off the road a bit and lets you kind of pivot, negative toe plants you down. Any car with aerodynamic lift is going to have road contact issues cresting hills and over bumps. I’d highly advise against positive toe without aero. I’d suggest negative toe just for funsies. Equal negative toe front and back is fine.

Anyway your problem is probably that the ARBs are too stiff. Riding on ARBs leads to terrible handling.

A good default tune is to knock 100-150lbs/in off the springs, put arbs to 0/0 and knock the bump dampening down to a 0.5 to 0.66 ratio of the rebound (higher one). Or you can just take off 1.0 bump. Either way. Softer is generally better. Check and make sure you aren’t bottoming out from just regular braking and turning or you will have unpredictable handling. From there you can add light ARBs to fine tune the turning balance. I usually try not to exceed 10. Sometimes 15, rarely 20 and beyond. The default ARBs are stupid stiff.

I don’t follow how stiff ARBs would be the cause of the instability in my set ups vs the calculator set ups I found over the camber, toe and caster changes. The last turn on Sebring doesn’t even give my high ARB set ups much issue, if any, at all. Thus it is obvious that any potential bumps, unless serious ones, is not the issue I am experiencing.

I’d start with ARBs too. Remember softer = better grip but softer also equals more body roll. Forza seems to have really stiff ARB settings by default. I’ve got a few cars with ARBs set to 8.0 front and 4.0 rear. The default setting was probably 27.0 and 22.0.

as far as tuning for bottoming out i bring the bump up small amounts till it stops…i was tuning an opel kadet yesterday and was happy with springs arb ride height etc, but under braking the front was bouncing my damper settings for front where 7.2 rebound and 3.2 bump i ended up with 6.2 bump to stop it and the car handled like a dream!