IF for a 8-9 hours gran fondo

The only way to really know is to target something and do it and see how you come out. Earlier this year I did a century event at .75 IF optimized with Best Bike Split, but I had some rest stops. .75 was not easy (particularly late in the ride on climbs) and I was not doing a specialty endurance plan with TR at the time, just general Build.

I’d target somewhere between .7 and .75 for your first attempt.

I can’t help but think that paying too much attention to power and IF I’m these type of events would take something away from the experience?

Why not just keep a lid on the power when needed and focus more on enjoying it than aiming to hit numbers. You’ve got a pretty solid power to weight ratio, just go out and smash it!

Good luck today, hope you get your gold time!


I did the Trois Ballons last Saturday, for the first time in my life trying to finish a Gran Fondo as quickly as possible instead of waiting on friends or taking my time in rest stations.

Ideal weather, sunny and 15-20 degrees celcius and little wind. Pacing a bit aggressive in the first hour to keep the wheel of some bigger guys on the flat roads, but that’s the risk I was willing to take to get full advantage. Did all climbs at my own pace, letting groups go or passing groups reasonably based on the wattages prescribed by the Best Bike Split app on my Garmin. Quick peeing stop at 2 hours and made only stop at a rest station to fill my three bottles at 110km, only ate my own food (gels, Maurten, cliff bar cookie, etc.) that I had in my pockets. I think I ate and drank enough.

NP at 175W at 5 hours in the race which is an IF of .76, which did make me a bit nervous although I still felt strong at that time considering the time already spent on the bike. Halfway on the fourth (out of five) climbs I suddenly started to fatigue much more, also cramps in hamstrings and the inner side of my thigh but able to keep on pushing with reasonable wattages.

NP at 172W at 7 hours in the race, with one last climb to go: La Planche des Belles Filles, a steep climb with 12% average grade in the first kilometers and a nice 20% 200m stretch just before the finish. Stopped 5km before the climb for one last peeing stop, in total 10 minutes off the bike in the whole race.

The final climb was a total struggle, already cramping again on the 3%ish slope to the start of the Planche where you can already the way steeper pitch of the next kilometer or so. Alternating sitting and standing on the pedals I managed to avoid most of the cramps while crawling up the mountain at 2.7W/kg or 8.5 km/h a literally counting down every 100m to the finish line keeping repeating “don’t you stop” in my head. A 40min sufferfest but I got to the finish line without stopping after 210km at 8h58 with a NP of 169W (0.73IF, 2.9W/kg, 500 TSS) and then I needed to lie down for 20 min to come out of the mental and physical hole I dug during the climb.

So my gut feeling that I went a bit too fast became true, but that was the gamble. With more proper pacing, maybe I would have finished 10min quicker, definitely not more than 15min. Absolutely it was an experience I would not have wanted to miss. Well inside the range to earn the “gold medal” for my age group. I finished 214th of the 444 participants in my age group, I thought I was reasonable fit but still literally middle of the pack. Good reason to train a bit harder when I’m recovered from all this.


Paying attention to your power so that you don’t completely blow up with 2 hours to go could probably add a lot to the your gran fondo experience.


I may be missing something, but doesn’t BBS work out the optimum IF for you? For sure you can enter it yourself or edit it once set, but I thought you gave it the route, your FTP and other data, and the race plan (and hence IF) was what it produced.

BBS asks for either target time or IF or TSS for the race. So you make a bet, and BBS gives you tactics to execute it.

Hi Enrico, mooie prestatie heb je daar neergezet! Ik ben erg benieuwd naar je trainingsplan voor deze granfondo. Welk plan heb je gevolgd? Ik heb vorig jaar de Marmotte gereden en wil in 2021 de Marmotte Pyreneeën rijden. Het standaard programma (“Century”) geeft op Mid volume ritten van maximaal 2 uur, weliswaar 2 x 2 uur op za en zo achter elkaar, maar toch… Hoeveel lange ritten (4-7) uur heb jij gedaan?
Gr. Bert

It will depend on how good your endurance is. If it is good 0.8 and Ok 0.75.
The most important thing for me would not be to go too far over 0.8 IF early on.

I have gone 0.82 for 7 hours no stops 0.83 with stops.
I have gone 0.84 for 5 hours no stops.
I have gone 0.91 for 3 hours no stops.

Agree with the .75-.80 as good targets based on endurance. Those other numbers are really top end from my perspective. I am a pretty decent endurance guy and those targets are probably are ~.02 higher across the board from my best performances when I’m in good endurance shape. Great numbers to aspire to for sure, but I wouldn’t recommend going into an event at anywhere near that level without testing the waters first.

My approach for determining target power is to go out and test a target for a lesser duration and adjust based on that performance for race day. If your event is 8 hours and you think you can hold 200 NP for the duration, go out and do a 5-6 hour ride @ 200. You’ll have a pretty good feel for whether another few hours is possible and can adjust your target accordingly. The power curve is getting almost flat once you get out to 5+ hours assuming you can do the fueling and hydration required to maintain.

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I did the 3 Ballons 7 times so have enough experience in this one. I think you started out to fast in the first hour, that always have an impact on the last part, certainly with La Planche in mind :).

I did Marmotte in 2018 in 8u02 NP225 - IF0,80 - TSS530. But you also have to bear in mind the elevation correction. Aboven 1000-1500-2000m, you can not push the same power as on sea level. In WKO I can you use the elevation correction chart. And if I look at that number, my avg power would be 15watts higher. So if you ride a gran fondo on higher altitude, keep that in mind…