Massive Understeer At The Track, What To Do?

[nelsonian101]

I am certainly going to do some more reading on this as I really only have a limited understanding.

So moving to the stiffer front sway bar has also brought more understeer at the same alignment settings, so why not go back to the stock bar with the stiffer springs and shocks that are on the car now? Is this also an option? I know the car feels a lot flatter now though through corners with the fatter front bar. Less body roll is supposed to be better yes?

I am far more inclined to remove the rear bar now and see how that affects the front. Though I will do that after an alignment at Pedders to gauge how each change feels. Do it all at once and I won't understand what has done what.

A stiffer rear bar is going to move more weight to the front when shifting weight in a corner? Hence taking weight off the rear? So in theory going to the stock front bar would have similar effect?

Every "expert" has a slightly different opinion. Set up is an art form and not easy!

Just keep it simple.

I prefer/recommend what has been proven to work in practice or works for your individual driving style.

For your next track day:

- Keep your stiffer springs/shocks and bigger front bar.

- Fit an adjustable rear Whiteline bar and play with the settings. As mentined previously, I found the hardest setting best to reduce understeer but it may be different for you as you have different springs/shocks and driving style.

- If your current settings provide a huge amount of grip at the rear, perhaps just change the front tyres to some Falken RT615's, next step up from the 452's if you are happy with this brand.

In the meantime, remove your rearbar and drive some twisty roads with your current set up. It's a no cost experiment. It may well be perfect for you personally and you won't need to purchase an adjustable rear bar.

[Smoke them tyres]

Set up is science isn't it????????

Less body roll is not necessarily better. What we are looking for is a "window" that the car will be happy with.

When I went the 680 front springs in mine, it had less cornering grip than the 620's for the same grip tyre. The tyre tended to slide at it's limit because there was not enough weight transfer ie high side load with limited downward weight applied. On the link I posted, there should be a graph that shows grip vs applied weight. It is not linear....that is why it is a "window" I suppose.

What we want is the softest suspension settings that will do the job. Fitting stiffer and stiffer components to the car can effectively "lock" the suspension in one position. Hardly dynamic or balanced at the limit.

A sway bar is too stiff when you get the car feeling like it has a side to side shimmy/rocking in it over different bumps on each side of the car. The bar should stiffen it up, but not to the point that each wheel cannot move independently of each other without rocking the chassis. It should complement the springs, not override them.

The 27mm bar with the Lovells springs and shocks at the front is in the zone. The rear springs that are std are also in the zone. I would keep those ON the car.

The std rear bar and the zero camber settings on the front have been put into the car to give it some understeer/push so that the average person does not get themselves into too much trouble. This is at the detriment of front tyre life. These are the 2 combined ways of managing the understeer in these cars. I don't believe it will be PROPERLY ELIMINATED due to the weight and limited tyre width of our cars, but they can be MUCH better.

I don't know why people are so obsessed about keeping the rear bar on. The utes don't have them from what I have seen. Just because it is fitted std, doesn't mean it has to stay there. This certainly works in the engine bay dept. What weight is there in the rear end anyway?.....basically sheet metal paneling as even the fuel tank is within the wheelbase now.I haven't had the rear bar on for a long time now and I am not convinced that I need to re-fit it anytime soon.

I think you are on the right path by getting the work done and doing a back-to-back comparison. Baseline testing is always the way to do chassis adjustments.

Edited 03/09/10 05:57 AM by Smoke them tyres

[Erko]

Interesting read. Spring rates need to have a relation to the tyres used...street tyres are meant to have a lot of slip angle, semis not so. You can get away, and exploit the potential of R tyres with heavier rates. I am not a fan of unsticking the rear with a bigger bar in order to fix "balance". I would also give the rear bar removal a run. I have seen it work on other RWDs before, and it would certainly help power down on exit on tight corners as it will help keep inside wheel planted.

My preference above all else would be to look for a 9' front at +30 or even a 9.5 +25 or so and run them "square" with matching rears (not staggered).

[XR6TWolf]

I'm with Erko on not adding bigger bars to the rear simply to "unstick it"....the thing was "stuck" in the first place for good reason.

Camber has always worked for me...in the case of the BA I have gone beyong -3.0 to get it where I want it. Oddly I still get even tyre wear

Other often forgotten things which have dropped my circuit times dramatically are decent wheels (read: lightweight) and trying to shift a little of the weight the BA/BF has sitting in all the wrong places.

[xr_velocity]

This is what Whiteline have to say about alignment on a BA I6:

Wheel alignment settings are of critical importance on any car and it seems Ford has all the settings pretty well

sorted. Front castor is left factory-standard (at a fairly generous 7.5 degrees) as is camber (at about -1.0 degrees),

but Whiteline elect to change from 0.5mm toe-in per side to neutral. This improves turn-in response. At the rear,

camber remains at -1.0 degrees while toe-in is reduced from 1.5mm per side to 0.5mm per side. Again, this enables

quicker direction change response.

Jim says the Ford has quite good front-end geometry that exhibits minimal bump-steer. "For 20mm of compression,

the front-end toes-in by an extra 0.5mm." At the rear, however, 30mm of compression gives another 1.5mm toe-in,

which is partly responsible for a counter-steer effect that Jim says is common to late-model Ford Falcons.

I was looking to try to get -2 to -2.5 camber in the front, standard caster and 0mm Toe in. The rear to have 1.0mm camber, 0.5mm toe in the quote above. All I have done is increase the camber on the front using whitelines settings, but I have no idea how more camber on the front affects toe in etc. So this is really an uneducated guess.

Would this be an acceptable set up with also removing the rear sway bar?

[Smoke them tyres]

-The reduction to zero toe should improve initial turn/tip in (only). Race cars do this and sometimes even have toe out. That will make it "feel" sharper, but will not change ultimate sustainable grip in a corner....that's dependent on other factors. The question is whether this is sufficient toe at -1degree neg camber to maintain even tyre wear. The toe balances out the camber from a tyre wear point of view. I'm usually pretty attuned to chassis changes and I don't know if I could pick 0.5mm per side toe change????? Don't know how much effect it will have with std rubber bushes. Poly ones would definitely help the settings though.

-As far as the front camber is concerned, the std wheel alignment settings call for that but mine could only achieve that with the shims removed (BF Dec05 build). It didn't look anything like that std with a critical eyeball passed over it, and the wheel alignment confirmed that (in my case anyway). Mine has definitely responded to more camber and a moderate amount of more caster. Don't know if I would class the std setting for castor "generous", but it depends on how hard it is to be driven. Have a look at one of our cars on full lock parked....I wouldn't say it is generous. Some of the old Merc's....now they have generous caster. We don't want quite as much as that though.

-I thought the only adjustment for XR's in the rear was for camber via the lower control arm eccentric. Changing it will change toe with camber, but not independently. BA's might be slightly different here. From what I have seen, the Territory's get an adjustable toe link, but fixed lower control arm pivot. The XR's are the other way around.....why?....who knows? Don't know how they can keep the std camber but take some toe out of it with the std fixed length arms in the XR case?????

-The added toe via suspension compression in the rear ("countersteer") is caused by the arc of the rather short toe link as far as I can see. To my understanding, it will add understeer (?) as the front and rear "axles" now have different thrust lines. I believe that the effectiveness of this will change between low and high speed corners, but I may have to read up on that myself.

-If you could get that much camber into it with a touch more caster, that would be a vast improvement. Grip and tyre life will be much improved. With that camber, you will need about 3mm toe in per side (1/8") for even tyre wear. That is what I run and it is very streetable. Zero toe, with that camber will wear the insides. With the rear, I reckon you could get away with removing the bar and fitting the blade links with poly as you want to do. Have a good look at the std ones when they are removed, and you will see they have no hope of wheel control. Mine feels like the suspension has much better control of the wheel just by fitting that bush to each side. As a side benefit, axle tramp will be vastly lessened, aiding diff bush and cv life.

-These settings will mean that the full contact patch will be used and the outer edge of the tyre will still do it's bit, but it WILL stop the outer edge from taking most of the load, and literally destroying itself. Bit of a shame to have good tyres and have to replace them just because the outer edge is buggered. Sort of gives you that ripped off feeling.

-Even though our cars have double wishbone suspension at each end, the front needs more camber for 2 reasons:

-the shorter upper arm on the rear is much more effective at countering the outward roll of the upper pivot because it is on a sharper arc....ie shortens it's effective lateral distance as it moves up. This is due to it's pivot point being much closer to the wheel axle line than the front. The std camber here should be fine. Mine on this setting remain happier with cornering loads than the front from a wear pattern point of view. The rear bar removal will also aid suspension compression, helping this effect. Traction should not be affected as the sway bar doesn't act in a straight line anyway....it should actually help traction over uneven surfaces as the wheels can now move independently more freely. The front however, does not fully counteract this camber gain under cornering, so needs a little extra initial camber in this respect

-it is the end yawing the car. The rear simply has to "follow".

When are the bushes to be replaced?

Edited 06/09/10 12:29 PM by Smoke them tyres

[Smoke them tyres]

The other reason that geometry and all of the rest of this becomes important is because of the reduced "give" in the shorter sidewalls of large diameter rim/tyre combos. The larger diameters will be more sensitive to this with a narrower window.

[xr_velocity]

Thanks for your help.

I am getting the bushes fitted today then the alignment.

I have asked them to get as much camber into it as they can up to -2, with a little toe in, they also suggested a little more caster to pull the wheels into the way the car is turning. Rear I asked for -1 camber and 0.5mm toe per side.

Might need different upper control arm mounts on the front to achieve the camber I want. Shall soon find out though.

[Guest XR09]

I guess this is why it pays to do it in bits and pieces. Good tires first, alighnment while your there. Then springs and dampers and Bushes. Then bars if you need them. The way a car handles is a very personal thing based on your driving style and ability.

And then you put on a different type of tire and back to square one. lol

[xr_velocity]

Bushes all fitted. Max camber on the front was 1.2, couldn't get anymore than that with stock control arm mounts. A small amount of toe in.