yellow01

I went to a bit more toe in front and experienced some more understeer than I seem to remember (this was my first drive this season).

It may have been the older tires or driver characteristics but I'm wondering if I should back off the toe a bit?

Curious on inputs.

Thanks,
Jon

RAFTRACER

I dont like front toe-in period. Car doesn't turn in too well like that and there is not enough ackerman in the front..........................Use "some" toe out for road course and "more" for autocross

acrace

yellow01 - what are you using the car for? Also, when you reflect on it, is the understeer at initial turn-in, is it in steady state, is it during corner exit, or some combination thereof?

Excessive toe-in (or even moderate toe-in) for autocrossing will cause your car to not want to transition.

yellow01

Sorry sorry guys. I worded it poorly.

I meant front toe-out [space] in front Toe-out was assumed. Sorry for the poor wording. now, same question again, sorry.

I noticed it mainly in a fairly tight sweeper. It may have been too much speed (if I sawed a little bit at the wheel I massaged it in a bit). I just don't remember it handling like that before. I'm asking to try and learn.

Last time out I ran -1.5 in front, now I'm at -2.3 and a bit more toe-out. I don't have the sheet in front of me (sorry again).

Turn-in was fantastic (I like the toe-out for that) but I'm wondering if I went too far.

emf

Depending . . . yes, technically anything can cause understeer in some component part. I'm with Al -- where in the turn are you seeing understeer? Is it consistent?

I'm guessing that you're not running 2.3deg out, but rather 2 degrees camber . . . . if you ARE running 2 degrees toe, you're WAY too far out IMO. For road courses, I'll normally run 1/16th out [f] and 1/16th in [r], but have run up to 1/8th out. Much more, and the car started getting unpredictable (again, IMO). For an 18" wheel that 1/16th translates to ~ 0.2 degrees IIRC, for comparison sake.
Not saying that toe is your culprit, but it could be a factor depending on where you're seeing understeer (as Al mentions)

dmwhite

at road atlanta this year i was "helped off the track" at T7 in a race, i spun and when i went off it tweaked my right front alignment (significantly more negative camber and subsequently more tow out)...the car did not want to turn left after that (it understeered at corner entry)...

so yes, in my experience, too much tow out in the front can cause understeer

yellow01

emf,

I'm not being very clear today am I

-2.3* Camber and .12* out (this is between 1/16 and 1/8th, 17" front so probably closer to 1/8th).

I changed camber and toe all at once so am trying to learn what response that got me.

Straight line is fine, and turn-in is fantastic (actually feels a bit like a small car and less like a 3400lb gt).

RAFTRACER

Sounds like a UIP to me ( user induced push) . Too much toe-out in the front will generally cause a mid corner push or steady state. The important thing to remember here is that there is only 100% of front tire traction available. If you are using 80% for braking , you can not use 50% for turning. Real speed and handling will be attained by he/she that uses 100% of the friction circle the longest. You are also better by only using 85% of the friction circle than 115%.
You still haven't said if this ws an autocross or road course ??? Front toe settings will be different between the two. FWIW I use alot of toe-out in the front for autocross ( helps car change directions rapidly ). Remember too much of anything is bad, including front toe out. Another thing to remember is alot of alignment settings are driver preference oriented.

yellow01

Could be very likely. That's what I'm trying to get a feel for.

It was a road course, but not a standard de weekend, it was part of a big corvette show at TMS and it was 8 laps and get back in line. It was also open to anyone, and people classified their own experience level - read not too many hot laps so I didn't have a lot of time to try different entry speeds etc.

I was using it mainly as a tune-up of the brain and a quick run on the new alignment settings before my first full out of town weekend of this season coming up.

Thanks!!

emf

... actually, it's closer to 1/32" out, but who's counting

AU N EGL

Sounds like your finding that one setting can not be use for street, auto-x and track / road racing which is normal.

I use
front

-3.5 camber
1/16" toe out
max caster and equal on both sides ( 7* if i rember corectly - one side could get 7.75* and the other only 7* so made them both 7*)

rear
-2.5 camber
1/16" toe in

equal tire ware across both front and rear tires. Dont have a pyromiter yet to be sure.
Works well for me, so far, but car is not perfectly corner balanced either.


for most multi use vettes

front
-2*
1/16" toe out
max and but equal caster

rear
-1.5*
1/16" toe in

wtknght1

Please tell me you weren't the one driving that T2 BMW.

MitchAlsup

Front Toe-in increases stability in a straight line. Front Toe-in increases stability in a straight line by inducing/generating/creating understeer. It is hardly surprising that you noticed it.

If you took a car, cornering at constant speed, and aligned the car exactly for that cornering speed, and then returned the steering to dead straight, you would find that the Front tires would be toed-out. A small amount of Front toe-out reduces the scrubbing forces at the front, leaving thses forces for increasing the ability to corner.

Most race cars use Front toe-out because it reduces the scrubbing losses while cornering, and because the race car driver already has great concentration and can tollerate the wander and other negative effects of Front toe-out.

Front Toe-out also increases the sensitivity to steering input, and many cars respond by turing in easier/faster with a bit of toe-out.

Front Toe-out can compensate for agressive camber angles and tone down the wander of the front end when agressive camber angles are used. and enable better wear characteristics by leaving the contact patch more evenly loaded.

yellow01

hmm... I must have misheard the guy... I'll have to check the sheet.

Yeah. I never auto-x, only track, and street miles are slowly falling off. I currently do drive the car to events, and occaisionally on the street so I can't get too too agressive at the moment.

UIP - not surprised Always was a distinct possibility in my mind


Mitch, thanks but I worded my post poorly - was always referring to toe-out in front.

RAFTRACER

.

The car will gain some toe-out or reduce toe-in (depending on static settings) due to Ackerman when the wheels are turned anyways.

MitchAlsup

Steering with Ackerman will toe in less than steering without Ackerman.

The reason the steering toes-in (with or without Ackerman) is because the inside tire wants to take a smaller radius around the turn then the outer tire. To get toe-zero in a turn, you have to start with a little toe-out straight ahead. Ackerman lets you get away with less toe-out straight ahead.

RAFTRACER

Thats what I said in a nutshell wasn't it ???? Ackerman creates toe-out when turning

Olitho

So where do I find Ackerman and how do I get him to align my car?

MitchAlsup

Not quite, Ackerman creates an amall amount of toe-out that is subtracted from the significant amount of toe-in caured by the different radii (inside to outside). But the end result (when there are slip angles on the rear tires) is that the total toe-in still increases, just not as much as it increases without ackerman.

100% Ackerman causes no toe change when the slip anges on the rear are zero (such as at padock speeds). So if the car is set with toe == zero going straight, it will have toe == zero with the steering turned and the car can be pushed eaily around in the padock.

Dirty Howie

I was following this very well until AKERMAN showed up

Seriously......what is Akerman


DH