wheel alignment

[DOHC]

The adjustable top suspension arm is in place, everything is clean and ready to race. But I need to set the right angles. I do 6 races every year with my -73 2000 and use TOYO 881 tyres. I was planning to set the camber at -2, caster at +4 but am not sure about the toe in. Any suggestions, please. And now all I want is for the snow to melt so I can drive to the tire guy....
Christian

[60sRacer]

Well, the right answer really is to get one of those IR temperature guages (I got mine at Costco for $32) and measure temperature across the tire after a test run, make a few adjustments, etc to get good times and uniform temp.

R

[Andrew]

Would toe be different from stock? I think it's 3mm total toe-in? I guess less toe-in allows for better turn-in, but less straight-line stability.

Andrew Watry

[papajam]

Given the physical dynamics of a tire with negative camber rolling down the road, theoretically it should be toed out. However, doing so does not always produce the intended, or desirable, results. Tire width and road conditions can be factors as well.
For the camber, I agree with 60sRacer. An IR pyrometer to check tread temps so camber and tire pressures can be adjusted to conditions.
Caster at +4 will aid in straight line stability but, combined with wider tires, will make the thing a bear to steer in slow corners. It will also increase steering component wear.
I'd start the toe a couple of millimeters out and adjust from there depending on your particular equipment and conditions.

[Alleggerita]

One of the things to remember about toe-in or out is that if you have little of either if you have bump steer you can have change from toe-in to toe-out or vice versa which makes the chassis exceedingly unstable. For auto cross and lower speed work generally toe out is preferable (better turn-in), wheras for high speed and road toe in is commonly preferred (more stability). If the car has been bumpsteered you can run less amount of overall toe which reduces scrub and increases speed.

[genericwood]

I agree. Knowing what your car does in bump is very important. If it hasn't been lowered at all, you can expect that toe won't change much when you stand on the brakes. But if has been lowered without being bump-steered, you will get significant toe out under braking. If you start out with static toe out and then get more toe as the front dives, it can get pretty interesting! If not bump steered, I'd run a little toe-in. My car is bump steered and I run it without any toe. It wanders a little, but not bad at all.

Erik

[DOHC]

Thanks for all your input! I will probably set the toe to 0 and see what happens. The car is lowered and the racing I do is all on proper race tracks. I have, by the way, also moved the steering wheel and the shifter back and are really looking forward to the first race in may. AND I just bought Minilites (6x14) for $125 and they were in almost mint condition!
Christian

[bryan]

Quote:

Originally Posted by genericwood My car is bump steered and I run it without any toe. It wanders a little, but not bad at all. Erik

[genericwood]

Bryan, from the factory, every car is designed so that the steering arms and a-arms move in carefully prescribed arcs. This ensures that the effective length of the steering arms stays the same as the suspension goes from compression to droop. So for example, when you stand on the brakes hard, weight transfers to the front of the car and the front springs compress considerably. The front wheels continue to point straight ahead.

On a significantly lowered car, the relationship between the arcs of the a-arms and steering arms is altered. As the suspension moves into compression, the steering arm becomes effectively shorter and the wheels toe out (on 105/115) cars. When you bump steer a car, you are moving the steering arc to correspond with the lowered a-arm arcs. This is typically done by replacing the outer tie rod with a rod end (heim). The rod end can be spaced down until bump steer can again be brought under control.

For the vast majority of street cars, this process is unnecessary. But if you car has been lowered 2 inches or more, it's a good idea!

Erik

[bryan]

The car will be lowered considerably, but is there a way to help the problem with out using heim joints? Should I just start with a little more toe in (like an 1/8th)?

thanks

[davbert]

bryan,

you can modify your short stub steering arm on that nice late stepnose upright of yours.

porsche guys run a little spacer gimzo bracket to offset the outer steering arm ball joint lower and in a more neutral horizontial position. it looks rather universal in its application and may work on 105's

typically when you brake hard and the front end feels like its trammeling simultaneously indicates bumpsteer. this usually happens on a car lowered more than 2inches

keep that nice project of your rollin

davbert

[bryan]

can we get a link or pic of this porsche spacer?

What if I just mount the arms on opposite sides? so instead of the arm turning up, it turns down. That would move it in the right direction, no?

[genericwood]

If you switch the arms left to right, you will also change the direction in which tie rod end inserts. That will defeat the purpose. I think Alfaholics sells a kit that converts the tapered hole on the steering arm to a long stud. This makes it easier to use with a rod end and spacers to get it just right. If you decide to replace the tie rod with a rod end, you will need a 14mm.

Erik

[gtv27]

I used to run zero toe, 3 deg neg camber and 3 deg caster on my 105 2.0.

It had no bad stability problems either at high speed (apart from lift induced) or under brakes and turned in like a demon.

I used the Toyo R881's for a while too and it probably needed another half a degree negative for them, but 3 is all I could get cause of the way my top arms were done (was fine with A032 though).

[davbert]

Quote:

Originally Posted by bryan can we get a link or pic of this porsche spacer? What if I just mount the arms on opposite sides? so instead of the arm turning up, it turns down. That would move it in the right direction, no?