Saw this cool video dissecting a trophy truck. when shocks are is discussed (14:37 in the video), they show dampers with bypass tubes in the shock body which provide increased shock tuning.
has anything like this ever been used in MTB? i'd imagine the stroke of a mountain bike shock is way too short for this to be applicable, not to mention the springs and shock body being completely separate on a trophy truck compared to our one-piece units.
could the idea apply to a fork since its travel is longer?
i also figure if the system isn't used on motorcycles (or is it?) then there's no way we'd need them on bikes.
would love to hear all your thoughts on this though. i'm mesmerized by trophy trucks and how they perform, so this is an excuse to post about them HA!
My understanding is that the "touchdown" feature on the Rockshox Vivid rear shocks is a simplified version of this.
Long time listener, first time caller here. These by-pass tubes are a version of position sensitive dampers. In the race car world in series where these can exist, they are a great sounding concept that can be made difficult if you try to use them for super precise applications. Knowing exactly what ride height you encounter the condition you want to control is difficult. If you are simply trying to increase damping as you get closer to bottoming out, the decision gets simpler. But in that case, mountain bikes already have some easier ways of getting that behavior with air spring ramping or just the fact that usually velocity will be fairly high on the damper as you get to bottom out anyways and relatively you don't have a bunch of weight to control. I think in a very specific application you can definitely take advantage of it, but you would really have to keep up with it as you changed air pressure and ramp qualities. Currently you would be better off putting work into mass dampers or I would work on making a hydraulic inerter for a mtb and see how that could help things...This is all just my opinion as a motorsports engineer with a mountain bike hobby though, so I reserve the right to change my mind at a moments notice!
Touchdown is a very simplified form of a bypass. Instead of flowing through a tunable port, the ID of the shock body flares outward for the top 10% of travel so that oil can flow around the piston. With bypasses as seen on trucks, each bypass acts more like a position specific HSC. External bypasses are as seen above. On Fox internal bypass shocks they have an inner and outer shock body so that oil can be routed through the area between them. The oil flow on those shocks is controlled by a sort of finger shaped shim stack. Trucks get the vast majority of their bottom out resistance from damping so the base tune on the shocks is super stiff. The bypasses are necessary to keep it from feeling like harsh garbage at ride height. But even then it's a different world because the tire is used to deal with a lot of what would be considered small bump for bikes.
At the most simplistic level, we're looking at damping ratio that changes as a function of shock position. In that sense, HBO would fall into the same category. That would imply that position sensitive damping is applicable to bikes. Although that doesn't mean its applicable in the exact same capacity. Manitou has a damping unit on the Dorado that supposedly has two different circuits. I've never ridden one so can't comment on how it behaves, but definitely intrigues me. On the rear, leverage ratio actually does a lot of what a bypass would achieve on any bike that is considered as progressive. These bikes generate more damping force for a given wheel displacement speed than at the top of travel.
All that said, trophy trucks often weigh north of 6000 lbs and have 1000ish hp. A Mason Motorsports 2wd truck is listed at 6000-6200 lbs. I'd imaging the 4wd version is a little heavier and that's what a number of the top guys are driving right now. Its a very different world in terms of what is being asked of the suspension.
I find it strange the trucks are so heavy?
Is it because they're steel and they want them to survive a crash? And to be strong enough to take the impacts they have to be so heavy?
They are pretty overbuilt things. Definitely one of those "to finish first, first you must finish" types of racing. Without seeing what these trucks do in person, it's a little harder to fathom how wild it is. I do think it's a bit of a feedback loop, though. They get more power and need to be beefier to handle the resultant impacts. Then they need more power to keep the speed they had before they got beefed up and so on.
Yes. Have you seen what they drive through?
Marzocchi had a super basic (like really basic) bypass compression circuit in the 888 from 2004, with progressively smaller holes drilled in the side of the tube and the Vorsprung Smashpot is a much more advanced version of that, both acting as HBO circuits.
DT swiss and some specialized brain forks had a touchdown-esque design that deactivated damping in the very top part of the stroke too
The Manitou TPC+ design is/was kind of speed + position sensitive - a second piston could float up and down until a large enough impact caused it to hit an end stop so oil was forced through it, and you could adjust how much float it had before it hit the stop.
Bring back the boost valve.
is there anything suspension related more epic? and thanks for all the replies, everyone! very informative.
More whoop related content that I think gives a good perspective on how big the whoops actually are. From down low they can get visually ironed out a little. The vast majority of these trucks are on 40" tires. Some of the whoops are about that tall. The other crazy thing is the amount of stress it puts on the drive trail going from fully loaded to no load over and over again. Plus there's the additional stress from your front or rear wheels touching down and not being at the same speed as the wheels on the other end.
I can't believe what differentials and rear axles will put up with.
Yeah i have, that's why i thought they would be lighter, the heavier they are the stronger they need to be as the forces are larger.
I'm guessing a lot of it relates back to how heavy the engine and 4wd system is, and how heavy the wheels and rims are. These must be enormously strong and don't use composites so must be enormously heavy, and the chassis weight just goes up from there to accommodate such a heavy system overall.
Another interesting aspect is that they use separate bump stops and its not built into the spring or damper assembly, but instead operates directly from the axle (or A-arm for the front)
They are also substantially bigger than you'd think. The track width of a 6100 truck is usually about 92 inches, a stock '23 Raptor is 74" inches. (The widest year) and a new Tacoma is only 63". Trophy trucks are a strange breed, they could be substantially lighter if they wanted but it's actually slower. Look at Ultra 4 4400 class cars, they are usually almost 1000 pounds lighter (or more) and in some ways are more capable than a trophy truck, but they aren't faster. Desert races aren't won accelerating, they are won maintaining speed, the heavier truck has an easier time maintaining speed over whoops etc. When you have 1000+ horsepower adding a thousand pounds isn't that big of a deal. They use the weight to tune the ride of the truck, and many of them run weights in the rear to achieve the right balance.
They also have a wheelbase that’s about 20” shorter than a gen 3 raptor. Very different proportions haha. Seems like the finish rate for ultra 4 trucks in the 1000 is a lot lower. Someone was telling me they just aren’t designed to be ran flat out for that long. Stuff like KOH is a whole different beast in comparison to the 1000 though.
So trophy trucks are the ebikes of motorsports, got it
Obviously, I know what a hydraulic inerter is... But maybe you could explain it to sspomer here and I'll review?
On the more serious note, is the RS touchdown tech purely for feel? I can't imagine unweighted bike damping bypass plays much of a role in suspension performance.
First let me say this is an awesome and informative thread so keep it up because I want to learn more.
Now, my inner 10 year old that I can't seem to control, who knows very little about trophy trucks other than they are the coolest thing on the planet, and desperately wants a Raptor because its the closest thing he'll ever get to one, wants you to know he spent his entire birthday money on this in 1989.
All i know is baja trucks go baaaaaa bhaaaaaaa baa baa baa baa bhhhaaaaaaaaaaa while the wheels go b b b b bbb bb bb b b b bbbbbb b b and I'm here for it.
Ive been using bypass on my offroad cars for decades and shocked that this has not trickled down to MTB... it would be awesome!
Yes, watching a TT blast the whoops in plaster city or zoo road is absolutely memorizing, but I think a TT suspension setup is pretty far from an idea mtb setup. The TTs are amazing in the the whoops and rough bits, but kind of shit on the smoother twisty gravel sections and especially tarmac.
That said, if you look at the mtb system (bike + rider) it is one of the most advanced suspension systems and far superior to TTs. (Bare with me) your bike's suspension is really all "small" bump and a means to generate mechanical grip much like the big soft tires on the TT. It's your arms and legs that are essentially equal to the suspension on the TT allowing for the absorption of the big hits and maintaining balance in the system. Since this "suspension" is controlled by your brain, it can react, learn, and predict better then any computer based active suspension system. I would bet a few TT drivers have wished their truck could bunny hop the telephone pole booby trap the baja locals put on the course. (Yes, I have seen the Chinese supercar video at ces this year and the Bose Lexus hopping speed bumps, super cool, but not yet at the level of our brains.)
As to the original question, yes, position sensitive damping does have merit, but implementation is all about balancing the pros and cons within the whole system.
Also, the progression in this video is so cool, especially when you consider that 2006 truck won the baja 1k that year.
Energy is proportional to half the mass time velocity squared so adding weight has less effect on the impact forces than physically travelling faster. So if the extra weight enables you to go faster then its more than worth it. Obviously there is a trade off in terms of acceleration and cornering, especially in a powered vehicle but thats separate to impact strength. The bump stop thing is pretty cool - you can definitely tune it much better when you aren't constrained by packaging it with the damper. Could be cool for frame designers to build this in which would allow you to run a more simple shock! Scott in the 90's and more recently cannondale tested individual spring and dampers but its never been a main production thing. Packaging would be tough, finding the space and somewhere strong enough to install it
@Eoin lighter low speed damping is good for grip at the top of the stroke where spring force is low and dealing with very high frequency bumps. Not sure how much improvement it provides for that specifically, but I do know the second glide ring helps in other ways (sealing high speed rebound from deep impacts)
If you'd like to see something heavier that races similar terrain, I'd direct your attention towards Dakar trucks. Those things make a TT look light.
This is off topic but I went to high school with Nick and his wife! It's been so cool watching what they are doing now. They have come so far from mobbing nearly stock Rangers in Ocotillo! 😅
As @CascadeComponents put it, the feedback loop makes a lot of sense on how they got to the weight they are now. Not sure where I heard it, but the typical TT rear axle is over the 700lb mark these days.
I swear my first gen 888 20+ years ago was the best fork I've ever had. Could be the passing of time but I don't think so.
I almost died in maybe the biggest crash of my life the first day I rode one of those 888's! I came through a fast piece of track that dropped out in to a rutted 4wd track so much faster than I used to with my old Manitou that I was in no way ready for it 😅 Another nugget about that fork which I found funny is that Dirt ran a comparison between those, the (brand new) Fox 40, manitou Dorado and Rockshox Boxxer and declared it the winner even though the other forks were light years ahead technology wise. It just showed how good an open bath coil sprung fork with decent stanchions was, due to its low friction and the rest of the features arent that important (this holds true today by the way!)
The Dakar Rally (and a few others) has an electric class. So no, Trophy trucks are not the E-bikes of motorsport, they have their own electric versions already.
If anything Trophy trucks are like the Enduro MTB's of real pros Vs. the Bros who think they're pros set up. Remember the gasps of horror and disbelief when they did that bike check video and everyone was riding 40lb (or nearly) bikes?
My last one was stolen along with the Stab Deelux it was on in Whistler 😪.... I liked that you could tune a 888 with oil weight. I think that's missing today.
Doesn’t seem very heavy when that’s the curb weight of a Ford Raptor, and I usually see those used for grocery shopping instead of the Baja 1000
WP have produced their Trax shock for motocross/enduro for quite a long time (pre ktm linkage days) that has a mechanism allowing the rebound circuit to rapidly open when the wheel leaves the ground. It's only available as an aftermarket product and I don't believe any of the other suspension manufacturers have a similar product.
I spoke to a friend who had one on his enduro bike about it and he reckoned it helped keep the wheel on the ground and driving forwards and prevents the shock feeling like its packing up over repeated bumps as you're always hitting the next bump higher into the stroke. One of the downsides he found was descending steep hills, you probably want the rear to be squatting into its travel but the shock would be extending every time the wheel left the ground, feeling like you're too far over the front and thus also increasingly loading the fork.
This video covers it starting at 06:21.
Post a reply to: Bypass tubes on mountain bike shocks or forks? (Trophy truck tech)