Rear Camber

[nrider42]

Well my first vee race with my Mysterian at Mid Ohio is in the books and it was a mixed bag. One of the most interesting parts of the weekend was making major changes to the rear camber on the car. Full disclosure, I had NEVER driven a vee before this weekend.

My first two practice sessions were pretty exciting as the car was very loose in the rear. Every corner was a catch the car situation with a nice gentle spin into the mud in the carousel.

In the afternoon I was asking for some advice and one very knowledgeable guy looked at the rear of the car and said I had too much rear camber. We measured it at -9 degrees total with me in the car. We measured it at droop but I don't remember the number. There was a lot of travel in the rear and it felt soft.

Before I knew it I had three very nice guys helping me adjust it to -5 degrees total loaded and -2 degrees on the droop. We also adjusted the rear shock compression and rebound. The resulting changes also raised the rear ride height. The travel was more limited and the rear felt stiffer.

I went out for quali the next day and it was a different car! I was able to lean on it in the corners and I started dropping lap times.

Now I am trying to understand what happened? What is my lesson other than these settings are better? It certainly is possible that there was improvement in the squishy bit behind the wheel but it seems that the setup changes had a major effect.

I would love to have enough time to dial these settings in independently to understand their individual effects but that is unlikely.

Is there any common wisdom on the range for rear camber settings and how it effects the handling?

Thanks,

Nate

[FVRacer21]

....

Is there any common wisdom on the range for rear camber settings and how it effects the handling?

Thanks,

Nate

Welcome to Formula Vee.

What you have there (-5 total, -2 droop) is the middle ground, a good starting point. You are trying to balance what the car wants vs what the tire wants.

The more you stand up the tire (less negative) the less friction you get in the fulcrum plates in the tranny. Less friction = more speed.

But they you sacrifice cornering speed. So the compromise. Challenge Cup tires are different so I will defer to those guys for the settings.

The new SCCA spec slicks seem to be more tolerant of less camber so if you run them as is, watch you do not overheat the inside of the tires.

But you are in the ball park - remember to check the camber with you in the car, as raced with fuel.

If you run a pressured shock, be aware that pressure changes will affect camber.

Don't forget to check your toe if you made a major camber change, although leading arm cars (like the Mysterian) I think are a little more tolerant of this than trailing arm cars.

Others will fill in more detail.

Have fun!

ChrisZ

[S Lathrop]

It has been a very long time since I have worked on a FV. But maybe I still can give you some insight into how a FV rear works.

When you corner with a FV, the rear rises up because of the jacking effect of the rear suspension design. The car can be thought of cornering against the droop limiting system and the movement of the rear is more about rolling as the tires pass over an uneven track surface. Because the rear jacks so much, is why the guys helping you looked at what the camber numbers were in droop, the rear wheels off the ground.

As the car travels in a straight line, the rear acts like you would expect but as you turn into a corner and the lateral loads increase, the rear rises. and stops going up when the droop limit system stops the rise of the rear. The trick is to have the tire at the optimum camber angle as the car goes around the corner.

[veeten]

Nate
I was behind your for a bit and I think you will need to a full camber check both front and rear
The front should be 1.5 negative . If you can get there without binding.
after camber is set then move to next step
Have someone sit in car as you raise and lower front suspension. looking at bump steer.
Front and rear toe should be last thing thing to check.
See you at Pitt

[problemchild]

An incredibly simplistic rule to a very complex dynamic situation is:
to change the basic balance of a FV on corner entry and the critical mid-corner ----- adjust rear droop and rear shock rebound
to change the basic balance of the car on corner exit (after power application) ------ adjust rear camber and rear shock compression

All the other adjustments (front shocks, front droop, front ARB, steering geometry, rear roll steer, rear bump steer, rear droop limiter style, relationship between rear droop and rear camber, etc) have much more to do with driver feel through transition, than generating grip or balance. The single most important adjustment for FV handling is the rear droop setting and rear rebound setting! Find that sweet spot and maintain it as you tune everything else!

[lbacon]

An incredibly simplistic rule to a very complex dynamic situation is:
to change the basic balance of a FV on corner entry and the critical mid-corner ----- adjust rear droop and rear shock rebound
to change the basic balance of the car on corner exit (after power application) ------ adjust rear camber and rear shock compression

All the other adjustments (front shocks, front droop, front ARB, steering geometry, rear roll steer, rear bump steer, rear droop limiter style, relationship between rear droop and rear camber, etc) have much more to do with driver feel through transition, than generating grip or balance. The single most important adjustment for FV handling is the rear droop setting and rear rebound setting! Find that sweet spot and maintain it as you tune everything else!

Greg, thank you for the simple explanation! I have been experimenting for years and the receiver of much advice. This makes sense!!

Thank You !

Larry Bacon