I was wondering if the boot forward lean for a touring ski boot needs to be readjusted for missions that involve carrying a backpack in the range of 15-35 lb? I was recently skiing a touring setup on the resort and didn't have any issues at all. A month later I toured with 15 lb backpack and on the way down something didn't feel right with the balance on the very same setup (I had an excessive burning feeling in the quads just above knee area on the way down); based on how far I went and what I skied I shouldn't have been tired like this.
Any suggestions for checking the forward lean at home? I have two sets of very different boots so if there is a more or less universal method it would be very helpful.
Hi @Dmitry ! Glad you're getting some turns in this season!
This is a subject that many folks who tour with packs encounter: you ski your setup unloaded and get the 'feel' of the ski/boot system- where it skis best with your weight distributed fore/aft, etc.- then put on a pack and all of a sudden you've got burning quads and the ski just doesn't feel as quick or responsive.
While forward lean is something to consider, it's not the only factor. On the surface, it looks like if a skier has added 20-30 lbs on their back behind the center of gravity, we can just change forward lean to rebalance weight about the center of gravity. While this can help some, it won't resolve the issue entirely.
The real crux here is the concept of 'sprung weight'. Your legs are the 'suspension' and everything above your hips is the 'suspended' or 'sprung' weight. For most folks, the weight distribution above the hip to below the hip is about 60:40. if we take a hypothetical 175lb person, that equals 105lb above the hips- not counting gear/clothing.
If we add a 25lb pack to that person, that's a ~23% increase in weight that the legs need to carry uphill and then work as a 'suspension' to support while skiing. More off-axis weight up top that the legs have to maneuver around in order to move in the direction you want to go adds even more effort. It gets easy to see why legs get tired so much quicker when carrying a pack.
That said, forward lean is an issue that can help correct for this to a very slight degree. I would resist the urge to change the fit of your boot to accommodate a pack, however. Changing things here can have unexpected and significant consequences to the way you’re able to ski.
I’ve found an appreciable difference in how my skis mounted with different touring bindings feel while skiing with a pack. Part of this is a result of the difference in binding ramp angle between bindings- that is, the delta of difference in heights between two binding’s heel and toe pieces. There are surprising differences between brands and models. Here’s a chart from Wildsnow that shows those measured differences. I feel a significant difference between skiing Radicals (∆15.16mm) vs. skiing Kingpins (∆9.7mm). This may seem insignificant, but using a little geometry, we can figure out that even this small ~5.5mm difference at the foot ends up shifting the center of mass of your torso/pack rearward about 100mm, causing your body to have to work differently in each binding to correct the imbalance.
These are all just interesting factoids, and no cause to go obsessing over whether you’ve got the correct binding. The simplest solution is just to pack the heavier items in your pack closer to your back, keep it cinched as snug to your body as is comfortable, and keep doing leg blasters on your off days to make those quads strong.
Hope this is helpful, or at least interesting- -Enjoy your turns!
Thanks a lot, this is really helpful.
I have two ski pairs, both have Dynafit Rotation 10 mounted on them, and two pairs of boots, Scarpa Maestrale RS2 and Dynafit TLT8, both boots a set for 18 degree forward lean. This is bordering on having too much but I tested both boots recently on the resort and I feel pretty comfortable on these. I also found out that 15 degrees (the only alternative on Dynafit) won't let me contract without getting into the back seat. So, I don't plan to re-tune the boots unless I absolutely must.
I have not realized that due to the "sprung weight" argument the effect of the added weight is nearly twice as large as if merely derived from the person's total-to-backpack weight ratio. On the last tour I was carrying BD Cirque 45 backpack which has the avy gear compartment essentially in the outer pocket, furthest from my back. I guess this is done for the safety reasons as no one wants the shovel to be driven to the lower back in the impact, and avy gear is not the lightest stuff in the set.