Monday, August 20, 2012

An ARB question

from OldF:

"...Not knowing what you are going to write about, one issue I can’t recall you have been writing about is the anti-roll bars. I know they’re stiffer on tarmac rallies (as the whole suspension set-up) compared to gravel rallies but what is the relationship to other suspension set-ups (spring stiffness, dampers settings etc.)?

Is the suspension set-up chosen for a tarmac or gravel rally and the anti-roll bars stiffness by the suspension set-up or are they chosen independently (slow and twisty tarmac / gravel rallies compared to fast tarmac / gravel rallies or any combination of these)?

I’ve read some book that by the choose of a stiffness of an anti-roll bar, you can make a choose if the car is more under steered or over steered."

Hi OldF,

I hope I understand your question correctly. By the time I got to drive the '04 car there was obviously all the set-ups already determined by Markko and Francois which were in my opinion the best you could have for that car given what they had to work with. To my knowledge we did not modify the ARB's (anti roll bars) during the rallies for slow/fast conditions unless it rained, then we changed the whole setup. The thing the team played around the most with was damper specs and settings. I believe there was a different damper spec for every event or almost.

ARB's, on the other hand were generally always the same for given surfaces.  Sometimes a driver would go one step up or down on front or rear to tweak the car balance. Springs were the same philosophy, generally always the same for a given surface...maybe 2 or 3N up or down for tweaking. Cyprus had the same springs as Finland or sweden...!

Diff maps were the other thing everybody played around with ALL the time.

"I’ve read some book that by the choose of a stiffness of an anti-roll bar, you can make a choose if the car is more under steered or over steered."

Sure, for example I often ran very soft ARB's on the car to improve the grip on the rear. The reason for this is I always liked to drive a car "from the rear" if you know what I mean...? The rear ARB's was so thin on my car that it broke on occasions.  The difference is very subtle, and in my experience it's especially the case on tarmac. I had a case in Catalunya, on a long stage that we ran for the second time, where I could not find a good flow and rythm...something was off and the time was slow. I was confused and thinking really hard what was wrong on the road section...the car felt ok! Then when I rotated the tires I noticed the rear ARB link was hanging down, broken. In my experience the ARB is extremely important for the car balance but the changes it makes are very subtle to feel. It's not like if you change springs...

In my opinion this car was what the french call "une auto pointue" which in my definition book meant that the car was hard to set-up efficiently, because it was difficult to feel the subtle but important differences. Sometimes the only way to know was to look at the clock but please don't get me wrong, the team knew how to setup the car in the best ways. I was extremely happy with my suspension setups.

I hope this answers your question.

1 comment:

  1. >Diff maps

    The Focus WRC 03/04 was fully active and I guess no one (not even Loriaux) fully understood it :-)