Wednesday, April 6, 2011


Did you know that tire pressures sometimes reached in excess of 3.5 bar in stages?

Pretty high huh?  And rather scary, I have to say. 

One simple reason for this: Mousse.  The mousse gets so hot it kicks up the air pressure.

In some rallies, and especially Deutschland Baumholder zone, the conditions being: extremely high speeds on slicks and rough roads, we were stunned to see this sort of pressures after stages.

Situations were a bit difficult.  I was often presented with the dilemma of what to do... It happened that I came out of a stage with 3.5bar in my tires.  To give you an idea the ideal running pressure is 2.2bar hot on tarmac.  The problem is I had another stage to run in, for example 20 minutes, so what do you do? Let a bunch of air out ? Right, but moderately because there could always be delays and you could find yourself at the stage start with cold tires down to very low pressures...

So the team had a nice solution to this problem, they gave us little air guns with gas cartridges to fill up the tires if need be.  One cartridge replaced about 0.2bar.

Of course nowadays there is no mousse anymore...

Worn out gravel tire with mousse showing.  I actually drove back to service on this thing.


  1. Thanks Antony for your experience.

  2. Interesting that you could drive on that puncture!
    What kind of mousse like hair mousse? Does that make the tyre stiff like hair and or is there like a hair mousse type thing in their instead of air to keep it up ?

  3. The mousse was like a foam rubber ring that they put inside at same time as tire is mounted on the wheel. Rather difficult task, Michelin had a special machine to do that. It is compressed and stays quiet inside the tire, but as the tire starts to heat up the mousse activates. As soon as there is a sharp drop in air pressure it expands fast and fills the hole.
    Only downside to it was if you punctured very early in the stage with cold mousse... In this case there was a danger it would not work. It was a good thing to avoid cutting too much at start.