Wednesday, September 7, 2011

Chapter 18: Swedish wheel of fortune

If I remember correctly the first WRC cars appeared in 1997.  I remember the first ever pic I saw of one was that of the SUBARU WRC in tarmac spec.  The cars had suddenly become much wider!
Then for a number of years I noticed that cars were running wheels with this sort of offset on the Swedish Rally: 

These wheels reduced the car's track width! Why would you want to do that?

I ran with these wheels on the 2003 and 2004 Swedish Rally as well. 

I noticed that the works cars had flat wheels (no offset) from 2003 onwards.  I wondered why.


As I understood it back then, there was an issue as far as driving was concerned, which had to do with how wide your track was and its relation to the width of the ruts dug by the other cars that ran in front of you.  The issue only took place on the second run over stages where dozens of narrower tracked cars had gone through (hours ago on the first pass). 

In the Swedish Rally, it's slippery, yes.  That is clear I think we can all agree.  The thing is that, depending on the thickness of snow and ice (which for some climatic bizarreness is seldom thick in the Swedish Rally area), all the braking points in the stages get dug up, exposing the gravel, in the ruts mainly.  Therefore the level of grip under braking gets dramatically improved. 

So the word out was: it could be a problem to run a wider track car.  The car could jump out of the ruts because it doesn't fit!  Since it was absolutely crucial to hang in the ruts under braking, it made sense to me.
Funnily enough I did not experience anything of such.  Not even in 2005 when I ran the no-offset wheels for the first time.

   2004 spec Focus

That year, I learned something else, what might have been the major advantage of those wheels:

Their strength.

The feeling with the 2004 Focus was better than with any car I had ever driven.  For the first time, I felt comfortable pushing hard, so I punched it up step by step.  I remember specifically one stage:

The rhythm was fast.  While in a high speed left hander, I was just following the line, looking far ahead for the next corner when suddenly "BANG".  Big impact in the front left wheel.  I thought for sure this will have consequences.  Only a puncture if I'm lucky.  But no, nothing.  I kept going, stressed out.  Then another impact!  I thought "OMG what is this?" 

The impacts were due to small but very sharp bumps and pot holes.  Invisible due to the fact that it was cloudy and as you may know it's very hard to see shapes and details on a white background.  Our shocks were extremely soft, the car was running very low and the speed was high.  All these factors mean that the slightest sharp impact on a wheel will bump it through to the shocker's bump stop and "BANG".

I thought I had been extremely lucky because my front left wheel was fine. 

Mikko Hirvonen was not so lucky.  We rode in the same bus to the hotel that day and he told me that his wheel exploded on one of those bumps.  He was running the offset wheels. 


On that day I understood from first hand experience that there was a huge difference between the two types of wheels as far as impacts were concerned.  Not mentioning the handling improvement, this in my sense is obvious.

As I started writing this post I got interested to find out who ran the flat wheels first.  The earliest shot I could find was this one from 2002: 

Good idea.

Just a thought that came through my mind about sharp impacts.  If ever you are driving and for whatever reason you are about to have a wheel go over a nasty bump, stone, pot-hole or whatever, make sure you have the steering wheel straight at the moment of impact.  Straight wheels will greatly enhance your chances of not suffering damage.  This goes for tires as well as suspension parts.  It may seem like a trivial thing but this reflex may well be the difference between walking home or driving home. 


  1. Wow, very interesting! Top info there! I guess it's hard for teams to predict, there aren't 50 privateers digging up ruts when top teams are testing. Seems kinda funny though, in this high tech era with aerodynamics and telemetry, that teams would change their basic geometry parameters by 10cm from year to year.

    Also, I'd add that people should especially avoid locking their brakes over uneven, hostile surfaces.

  2. Subaru on "flats" 1997 -

  3. Good find. Prodrive ahead of its time.