A 39 small ring. Don’t know if I could survive that so not surprised you struggled. and I’ve done plenty of centuries and some of those with maybe 10-12k feet of climbing and I’ve done 1000m climbs in one hit. Would not want to do any of that with a 39. I weigh 82kg.

I’ve got a 36 on my road bike and a 30 on my gravel bike. There are still hills around here that I have to get out of the saddle for.