Someone on PinkBike recommended this to me. This is fascinating. It's like I've finally found an intelligent and comprehensive explanation for understanding travel and spring rate. I think some of the less comprehensive explanations are still valid and important. It helps at times to view these things with a bit of horse-sense, so it becomes easier for most to visualize in simple terms. But when he lays it out like this, with more scientific detail, the simpler explanations mean more. I'm about to watch the second vid (part 2), and I'm attempting to conceptualize my own illustration to better understand what MY BIKE is doing and/or trying to do when I'm putting it through its travel. I ALMOST decided on a FS bike that had a bit more travel than what I got, which is now 150f/140r. Riding it more, it feels like I shouldn't have gone with ANY MORE than what I did--still wondering if I SHOULD have. After watching this I feel great because it seems I lucked-out and have about the maximum I should be riding. As far as progressivity is concerned, there ARE things that intrigue me about coil shocks that get me thinking, but SOME OF THIS STILL comes down to personal feedback with the bike. The rougher I ride my FS, the more I desire that progressivity of the air shock (and air forks) coupled with the progressive Cascade link I installed. Maybe it's the handling, my riding style, how I interpret the feedback from the terrain--or how I react to it while riding--but as I increased the progressivity I've displayed much more capability over varying terrain. I have to watch part-2 now, and get sKoooL'd by this guy once again! Wow, great stuff! ~JSV

The insight that the suspension has a specific energy capacity drives so much, and we have intuitive knowledge of that but most don't think about the ramifications of that. A shock that can take in that much energy is going to have to release it too (preferably in a damped fashion that doesn't buck the rider), and repeating this means that energy is all turning to heat (spoiler alert - this is why companies are dumb for speccing tiny shocks on long travel bikes). As a big boi on the bike, all of those weight numbers just move up, and this is why the old adage for use clydes used to be 'bring more travel than you need', not because that extra travel worked better, but because that was the only way to get a bike specced to handle that much energy throughput without losing damping performance. Only recently has it been possible to get good trail bikes in sizes for tall people AND pair that with suspension up to the task that actually fits in the frame. I think there is a decent body of existing data on what the peak G limit humans can withstand through the pressure points - it's probably between 6-8 G's at the limit, although that assumes a lot of things in order to get there and remain in control on a bike. Given some non-linearity there and progression in either the spring (air, progressive coil) as well as most suspension kinematic designs, I think that still keeps us in the right sort of sag regime we usually care about (25-35%). I know this is why anytime a journalist or casual rider tries out a pro bike, they're amazed at both how high the spring rates are, and how much damping is present - it's just that being in really good shape means they crumple at a higher limit, and therefore can set the bike up to absorb even more energy before they'd be unable to ride it - and that's part of why the stupid fast guys are stupid fast.

love this channel. Keep them coming ! Cheers from Costa Rica

Love it, can't wait for part 2!

Another great discussion topic. Thanks for sharing your expertise and thoughtful explanations.

Love the content. I watch most of your videos twice.

optimized travel! great stuff as always Steve, keep it up.

Awesome episode, very well explained concepts that myself (and I am sure many others) had never considered re: travel and relative force.

Subscribed after the third video. Loving these!

Glad to see you are back making videos! They are very interesting to watch. I love hearing more of an engineering discussion on bike setup and design. One note: The V10 reduced the travel to 8.5 inches when moving to 27.5 wheels. Keeping the full 10 inches of travel didn't really fit with the larger wheel size. You see the same problem now with the 29er DH bikes. Most are not offered in a small frame size or have reduced travel from the older 27.5 model.

And here I am, getting jealous of the suppleness of my buddies' forks every now and then when doing parking lot comparisons. The obvious reason is probably just that I ride much less travel (120 mm compared to 140-160 mm. And of course it doesn't help that I keep procrastinating the long overdue service on my fork). Looking forward to part 2!

great video as always

Amazing content , Greetings from Chile!

Awesome! Looking forward to the next one. I can't put into words how much I have learned in the past year (from ya'll) and applied to my riding. People are scared to change things, especially suspension. But Listening to all these TT's motivates me as a rider to dig deeper and truly achieve the performance that my bike was designed for! The reason I know it's right is when someone else can see my interactions/handling from a distance on the trail. And then approach me asking what the secret is 😎 Thank you for the knowledge, the luftkappe, the rider wisdom, and teaching me how to view my riding differently! I think about all of this when Im on the podium ✌️

As usual, great stuff (usually get this on Pinkbike?). I've been riding bikes in the 130-140 travel range and never really bottomed out, at least not harsh enough to notice, and usually have a good 5-10% that I don't use depending on the trail. Well, I moved to an area that has trails with bigger features and thought a 160 travel bike would be good. Even hitting some of the moderate features (I'm too old to hit the big ones, risk/reward ratio has changed over time), I was basically using the same amount of travel as my previous bikes and now had a lot more travel left over that I didn't use. Plus, the longer-travel bike really didn't "wake up" unless bombing downhill at speed. I did mess with spring rates a bit, but it screwed up the handling significantly if I went too soft. I went back to a 140F/130R bike and couldn't be happier. I can't really tell a difference on the fast downhills, but a big difference everywhere else. Basically, I learned that if you have your sag/spring rate set up right and aren't always blowing through all of your travel, you probably don't need any more.

As an engineer I find this all very interesting:).

Not sure if I agree the statement "none of us NEED mountain bike"

Step one of Tuesday Tune. Smash the like button!

I hope you release part 2 today as well :)

Hey Steve, Love your video series! Could you consider doing a video on what the benefits/down sides of using a longer/shorter shock size would be when designing a bike around a fixed amount of travel? ie. longer stroke shock but lower leverage ratio vs shorter shock with a higher leverage ratio... most bikes seem to have settled around the 3:1 ratio. Is it not better for the shock to have more control over the wheel travel per shock stroke with a lower ratio or is there a point of diminishing returns?

Why all XC bikes has 100 mm of travel? Is 100 mm the lower limit for bike suspension?

This guy could be a physics professor!

This is one of the better YT video’s.

Theory and reality are two different things.

You made the statement that “adjustable travel is bad”, I have a Guerilla Gravity Megatrail that allows travel and leverage curve adjust that makes for an extremely versatile bike. I bought it for this reason and have been nothing but happy with the results given the wide variety of trails I ride. Can you elaborate and clarify what you meant? Thanks for all the great videos!

I've set up my 140mm Trailbike to not bottom out harshely on big hits, but things get out of hand quickly when bombing down the rough stuff, where multiple hard hits follow one another. Yesterday I crashed hardly where a friend with comparible riding skills and an enduro bike had no problems at all. I would claim that the terrain and my skill level have grown out of the trailbike category.

Can't wait til that Pole guy chips in again :)

haha reppin the aussie accent

simple answer: MOAR!

Man, use metric.