Choice of ways for the climb

A recommendation relevant to any of theses ways: be at the top before noon (10 or 11 am) to reduce risks of clouds on summits, Mont-Blanc itself included.

To look at the profile of each of the ways, click on this blue image:

To locate these ways on the map, click on this green image:

Steepest area: between Mévoutier and Combe-Emeru (slope rate 13.5%)

Do remember this area to avoid putting you "in the red": if the gear ratio was already too long during the previous slopes (at 10%), you will have to do zig-zags or go on walking ... until the end of the area to ride again the bicycle.

Respectively in 1997 and in 2000, Pantani and Virenque escaped for the win in this area (at the very same place: PK 6.5, photos). Armstrong got there in 2000 the unique failure (document) he has ever caught during a Tour de France.

Km-averaged slopes: dependence on editors

One of the reasons is that the starting point of distances is not posted on the same place by each of them:
- reference to a monument: church, main place, castle,
- geographical reference: slope break of the access road in the valley (case of this site),
- position such as the top of the pass finishes exactly with a full kilometre (i. e. the length of the climb is, as a result, an integer number of km, case of Tour de France).

The table below shows, about the Normal way of Col de Joux-Plane, how averaged slope varies according to the position of the starting point of distances. Moving this position has as a result the shift of hectometers (100m) easy (or steep) from the km n to the km n+1.The slope-irregularity of Col de Joux-Plane makes this phenomena stronger.

Needed effort - Quotation

With power measured (under medical control, ECG under effort) of 175 W at 130 pulses / minute, it is :
- possible to hold 27 km/h on flat road alone for 2 hours (at the beginning of the cycling season, living at sea level),
- impossible to climb thoroughtly the Col de Joux-Plane after some days of living there, even with a racing bicycle equipped of triple chaining on the front (weight cyclist + bicycle = 82kg).

To be able of more over 175 W does not let a leasure cyclist coming from sea level to climb thoroughtly the pass at the first trial.

After accustomed to efforts in mountains:
- it is possible to climb thoroughtly the pass in 100 mn including 6 minutes to stop (to drink without loss of breathe, because drinking enough prevent of breathing !), with the shortest gear: 30x24 almost from bottom to top, at steady 130 pulses / minute,
- the steepest area (13.5% topic above) may be ridden with 30x24 (too long / physical capacities) without zig-zags,
- performances in parisian district (sea level) are enhanced: the same effort lets perform 31 km/h.

Besides, effort tests in shelter at atmosphere pressure  =  5000 m high have proved, for various persons, that this elevation divides by 2 the power an used-to-hight person can run.

My conclusion is that for a given body effort, power available at sea level is very more than the one at 1000 m high (and, a fortiori, than the one at 2000 m), and this effect, I think, is proportionnal to the decrease of the atmosphere pressure. So at 700 m high (Joux-Plane bottom), pressure decrease -10%, power available -10% of the capability at sea level for the same effort.

Therefore, usual quotations of pass difficulty (called as well "estimated powers") seems to me too optimistic if they do not involve altitude: it is their cost to pay for the easyness of their calculus formula.

Parameter Irregularity

Applied to a pass with irregular slopes, quotations, usually based on slope averaged over a kilometre, are valid only for a cyclist equipped of gear which let him climb steepest hectometres (100, 200, 300m) than the km-average (and still clear-minded to use this right gear). Cyclist equipped of the gear just compliant with his/her physical resources versus the slope average will find more difficult a slope-irregular pass (maybe, will walk) than a constant rate one.

Oddly, economical importance of a pass is correlated to this difficulty criterion irregularity:
- small economical importance = few investment to improve roads = laying out fits closely the relief shapes = irregular slope,
- importance (to feed a significant resort, to link cities) = investments = banking up and cutting = steady rate.
This correlation is not so amazing since cyclist effort has the same cause than vehicles (caravans, trailers, lorries) to go at a reasonable speed at climb and to brake at descent.

Therefore, quotation should be given with the slope maximum, to assure cyclist of a climb without unpleasant and unexplained surprize. In default, interdiction to vehicles of more 3,5 t shows local slope(s) maximum very stronger than the slope average.