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Boot Flex Index

post #1 of 14
Thread Starter 
Does anyone know what the numbers actually stand for when measuring the "Flex Index" on boots? I realize a number of say, 120 is fairly stiff, 70 soft, etc. It must be some type of force/torque measurement. Any clues?

post #2 of 14
Not sure, but I noticed that different manufacturers use different scales. For example retail Atomic boots have scale from 4? to 10.


Speed does not kill, the difference in it does...
post #3 of 14
not sure either. Just that Salomon DR110 on the boot is pretty damn stiff. Check out the knee bend thread about how skiable these real stiff boots can be and maybe you won't be so concerned about the DR rating and instead you can worry about other stuff.
post #4 of 14
I differ, dchan. Too stiff boots are anathema to an average skier like myself. My experience has been to ski better and enjoy it more when the boot is not concrete stiff.
post #5 of 14
Ok Oboe,
I concur,
I guess I meant not to fixate on the DR rating but more the feel for you. I ski with a very stiff boot for my heigth/weight but manage it quite well but others may be different. My point was more that you should find a boot you like and fits well and if the DR is way up there then thats fine but if the DR is lower it doesn't mean you are a wuss. No need to be obsessive about the DR.
post #6 of 14
One other thing often not taken serious enough is what happens to a boot once the thing is outside , each plastic has it's own characteristics. What they feel like in the shop is not what they are going to feel like outside , people tend not to listen to boot fitters on this issue and then find they are in a boot that is to stiff fo them. Personally I like a very stiff boot.
post #7 of 14
There is no consistency between brands. Lange rates their stiffest stock boot (the L10 Race) as 100, then compares the rest of the boots to that. But there is no way to compare a Lange to a Rossi to a Sally to a Technica, etc.

FYI, I'm a Lange rep, and that info came directly from the Lange Boot department folks at Skis Dynastar in Colchester, VT. So I'm fairly certain it's good info.
post #8 of 14
Thread Starter 
John H,
So they are just numbers for reference purposes and have no actual value as far as force goes?

post #9 of 14
RTS, my understanding is JohnH is correct. The numbers are relative to other boots by that manufacturer, but have no comparison value to other boots made by other manufacturers, even if they appear to use the same scale. Like skis, each boot manufacturer has a flavor or reputation for building a certain type of boot. For example, IMO Lange is noted for building for a rather narrow foot, Technica is known for making very stiff boots.
post #10 of 14
Actually, Technicas are relatively soft compared to other "racing" boots.
post #11 of 14

That is correct. Only a reference within the line.

I had gotten curious about this a few months ago, when somone posted that some other boot line was rating their flexes at 100, 110 and 120. I ski in a Lange L10 Race, which is just damn stiff, and is rated 100. I couldn't imagine a boot 20% stiffer for the general consumer. So I called Lange/Dynastar, and talked to the boot guys about it. There is NO standard flex rating or test that all the companies use.
post #12 of 14
This is an interesting topic. I know an engineer and level III instructor who was involved in a project to set stiffness standards.
They developed a machine to flex the boot and measure the force required to do so. Okay sounds simple right? The problem was the machine tests did not correlate to how stiff people thought the boots were. The same boot had a wide range of interpretation for different people. So the standards idea was abandoned.
Oh well, nothing with ski boots is straightforward!
post #13 of 14
Variation in the plastics and their reaction to temprature probably vary widely. My Lange F 7's were soft as butter at sixty degrees last week and I had a lot of fun during the afternoon pushing through the tongues. As soon as the temp hit 45, they went back to being a medium/stiff flex.
post #14 of 14
Thread Starter 
JohnH and All,

Thanks for the info, much appreciated.

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