Those guys are nuts! :-)

I didn't know it was a bike trail. The maps I found were of road courses.

How did I find it? I think I did variations on "Venosc bike altitude" "Venosc bicycle altitude" and so forth and followed a few links.

It looks like that run may be the one they describe here:

http://www.venosc.com/anglais/vtt.php

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IN VENOSC

25 km of marked trails from Venosc to Bourg d’Oisans , and a downhill run from les Deux Alpes to Venosc In les Deux Alpes: Change in level from 3200 m to 720m

With the bureau des guides des 2 alpes, you'll cycle with a guide with your or our bike : initiation, perfectionnement, difficult rides!

From 20 € for an half day . +33(0)4 76 11 36 29 guides2alpes@yahoo.fr

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If that's not the run, it must be in the vicinity.

Cheers,
Scott.