STATS
Total miles: ~18.6
Total elevation gain: 4,528 to 4,626 feet
Average grade: Miles ~0-9: ~2.5-3%. Miles ~9-18: ~8-10%
Altitude at summit: 7,743 feet
ROUTE BREAKDOWN
Miles 0-~10
Beginning in Guillestre, the route follows a gentle, false-flat, twisty route alongside the beautiful Guil river. You will pass through a few short tunnels. Traffic can be heavy but we never felt unsafe. The road continues to climb up gradually. You will reach a roundabout and turn left.
Miles ~10-16
After the round about you head towards Les Moulins and then to the village of Arvieux. This is where the gradient starts to kick up. For the next several miles, there are long stretches (which can be windy) ahead of you. The average grade is between 7-10% but there are sections between 10-12%. The exposed road through the villages turns into a forest which offers some covering from the sun (if warm out). I suggest bringing a jacket if the weather is ~75 degrees or less when you start as it will feel really cold at the top.
There are a few switchbacks that help break up the climbing but it's mostly long stretches of road. Make sure you have plenty to drink for this climb as it can take 2 hours or more from the bottom.
Miles 16-18
Here you reach the Casse Déserte. The trees clear out into the stark, lunar landscape that give Izoard it's true identity. There's a short descend to let your legs recover before the final 1 mile push to the top. There's a small store at the top (and bathrooms) but it can be closed depending on weather and time of the day. Make sure to take a picture with the monument. Then bundle up for the long descend into Briancon.
My stats (8/17):
19 miles
4555 elevation gain
1:57.28 climbing time
For this ride, we parked outside of Guillestre (gravel lot off the main road) and rode to Izoard and then descended to Briancon. We then followed my race course (with a few adjustments) back to the car. Our ride was 59.8 miles, 4:22, ~6800 feet.