Author Topic: why it is important to prevent rear wheel tuck-under  (Read 6594 times)

0 Members and 1 Guest are viewing this topic.

Offline Carlos

  • 1000 cc
  • ****
  • Posts: 8
Re: why it is important to prevent rear wheel tuck-under
« Reply #15 on: October 28, 2007, 11:19:44 AM »
Hello!
What kind off pice is this ?

Offline Pantdino

  • 2000 cc
  • *******
  • Posts: 315
  • 500
Re: why it is important to prevent rear wheel tuck-under
« Reply #16 on: October 29, 2007, 05:08:13 AM »
The second picture is too small for me to see well, but the thing looks like a "camber compensator".

It is like an upside down leaf spring that prevents the swing arms from dropping into too much positive camber.

Jim

Offline zippyfiat

  • 2000 cc
  • *******
  • Posts: 185
  • 500
Re: why it is important to prevent rear wheel tuck-under
« Reply #17 on: October 29, 2007, 02:45:48 PM »
Yes,  these are called a "camber compensator" and are meant to limit camber change, as Jim noted.  They were a popular add-on 30 or so years ago.  I do not believe that Abarth offered them, but I know that Faza (Al Cosentino) used to sell them.  My 1300/124 came with one on it, but I will be removing it because it is non-original.

I have no idea how well these work, and have never heard of one for a 600 based car.   I imagine they would have to affect the handling of the car a bit?

Gil

Offline Carlos

  • 1000 cc
  • ****
  • Posts: 8
Re: why it is important to prevent rear wheel tuck-under
« Reply #18 on: October 29, 2007, 05:33:58 PM »
Thank you for information!

Offline Paul vander Heyden

  • 2000 cc
  • *******
  • Posts: 179
    • Scuderia Topolino
Re: why it is important to prevent rear wheel tuck-under
« Reply #19 on: November 04, 2007, 04:15:45 AM »
The camber compensator was first developed for use on VWs with swing axles.  It works in such a way that in a left hand turn, with the right rear suspension being in "bound" condition (pushed up into the fender), the compensator would tend to push the left hand side down to keep the tire in contact with the road.  This is the same concept behind the "Z bar" which is a derivation of the stalibizer bar, where the arms at each end go in opposite directions.

The real issue to consider is that in order to make the car handle better you want to limit chassis roll.  If you are successful at this, you will automatically solve much of the rear wheel lift problem.  This process is always started at the front of the car with a heavier stabilizer bar.  If the front chassis roll is reduced to 3-4 degrees, then and only then should attention be paid to the rear suspension.  The first I would do is limit the amount of positive camber that can be generated in a way that adds the least amount of weight to the car. (This eliminates the camber compensator straight away)  Then, once this is done, either by cables, straps, rods  etc., the a rear stabilizer bar should only be added to "fine tune" the overall suspension package. 

One note of caution:  When lowering the Fiat 600 be very careful how much shock travel you have left after you lower the car.  If you lower it such that you take up most of the shock absorber travel of the original length shocks, you will have a go kart (been there - done that, although it was many years ago).  This condition of course means that the suspension can no longer absorb ANY chassis roll and you will lift the front wheel (and sometimes the rear wheel) from the ground.  This is very spectacular for spectators. 

Hope this helps.

Paul Vanderheijden
Scuderiatopolino.com

Good luck

Offline zippyfiat

  • 2000 cc
  • *******
  • Posts: 185
  • 500
Re: why it is important to prevent rear wheel tuck-under
« Reply #20 on: November 04, 2007, 10:36:32 PM »
Paul, what is the recommended procedure for providing enough travel space for the shocks?  Raise the height of the top of the shock supports?  Or, somehow lower the bottom end?  I had a 600 about 15+ years ago that I lowered several inches, and I raised the top mounting points for the shocks by welding in some steel tubing.  I worked well.  On my current project, I want to be able to retain the stock rear seat though. 

What's typically done? 

Thanks,
Gil

Offline Paul vander Heyden

  • 2000 cc
  • *******
  • Posts: 179
    • Scuderia Topolino
Re: why it is important to prevent rear wheel tuck-under
« Reply #21 on: November 05, 2007, 03:32:06 AM »
Gil,

Any time that the car is lowered significantly you must be able to recover the lost shock travel.  So if the car is lowered 2 inches (50mm) you have reduced the shock travel by the same amount.

The later TC and TCR cars that had independent front suspension homologated (not the interim ones where an "helper" coilover, mounted in the same location, in conjunction with the standard leaf spring) had the upper shock mount moved as high as possible in the front fender, while still retaining the proper caster.  See the following photos.




For the rear I had custom 20 position adjustable coilovers made that are compact enough to fit in the standard shock location, without altering the chassis.  Secondarily, these also act as the swing arm "limit devices", as I had special provision made for the shock to act in place of a limit strap or cable.



 


The only thing that you have to be careful of is the adjuster for the rear shock, as it is inside the car (under the rear seat).

Hope this helps with the illustrations.

Regards,

Paul Vanderheijden