Sag and Negative Travel - Discuss

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sspomer
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sspomer
Edited Date/Time 5/7/2018 6:19pm


This discussion is really just an excuse to post this Instagram video from FOX haha.




But seriously, understanding bikes don't have motors and throttle for propulsion, do modern DH and long-travel enduro bikes under-utilize deeper sag and negative travel for traction? Maybe it's not even applicable to consider bicycle suspension in a way like off-road racing, but holy crap that video is unreal.
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sspomer
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sspomer 2/1/2018 8:00am
2/1/2018 8:00am
the very beginning of this vid shows how deep the sag is when the truck isn't mobbing (like most desert racers)

Big Bird
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Big Bird 2/1/2018 8:08am
2/1/2018 8:08am
Well, the original version of the Santa Cruz V10 was all about extra sag and negative travel. And they've gone away from it with the newer versions. Perhaps it was overkill for the higher frequency impacts of DH racing?
sspomer
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sspomer 2/1/2018 8:12am
2/1/2018 8:12am
Big Bird wrote:
Well, the original version of the Santa Cruz V10 was all about extra sag and negative travel. And they've gone away from it with the newer...
Well, the original version of the Santa Cruz V10 was all about extra sag and negative travel. And they've gone away from it with the newer versions. Perhaps it was overkill for the higher frequency impacts of DH racing?
i wondered about that bike too. unless the track was completely high speed and full of the grossest big hits you could skim over with speed (like the truck in the vid), major negative travel just must not be worth it, eh? bring back mount snow : )
TRex
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TRex 2/1/2018 8:19am
2/1/2018 8:19am
I think more negative travel would be good, except for the fact that in cycling, rider inputs are paramount. If I driver in the desert could 'pump' or absorb anything with their bodies, I think the negative travel would decrease, as they could get away with slightly less travel, and in turn have more stable cornering (lack of body roll). For bikes, if the amount of negative travel is increased, it means a lot more work for the rider to move the bike around after the compression is done. I think that would be due to the fact that to unweight the tires, it better be a really big (eventually tiring) movement.
Fredleth
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Fredleth 2/1/2018 9:41am
2/1/2018 9:41am
Wasn't that kind of the idea with the old Millyard bike? I think I remember seeing a video of it where it looked ultra soft. Even though that new'ish Nitro Shock is not supposed to be that soft.
just6979
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just6979 2/1/2018 9:44am
2/1/2018 9:44am
@TRex, the tires will get unweighted, even if the bike is still sitting into the negative travel. They might not leave the ground with the same rider movement, that will take a bigger move, but they should approach the same weighting for the same movement.
bizutch
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bizutch 2/1/2018 10:21am
2/1/2018 10:21am
So very little applies to a vehicle of that nature versus a DH bike. I'd like to see them develop a suspension system for that same truck, only for it to ONLY descend a rocky hill at a high rate of speed. Every concept applied to setting that trophy truck up would have to be thrown out the window. It would destroy itself with minor changes. It would take drastic and rather unconventional techniques (for motor sports) to get that truck to haul ass down hill. That one element (descending) throws all negative travel applications out the window and puts you on a different drawing board.
ThomDawson 2/1/2018 10:45am
2/1/2018 10:45am
If anything I think too much emphasis is put on using the fabled 30% sag and not enough on how different riders, different riding styles etc may work better with varying amounts of sag. In fact I think that even talking about sag misses the point. I don’t think the amount of sag necessarily matters, it matters whether the suspension is behaving the way you want in order for you to achieve whatever you want to do on your bike. Our interaction with our suspension is dynamic and unique for every rider. We should unshackle ourselves from parameters and remember that guidelines are just that. Find the setup that works for you personally, not for the bike and not even what the suspension tuners tell you is best. Experiment. If in doubt set it hard as fuck and ride faster until it feels good.
TRex
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TRex 2/1/2018 12:02pm
2/1/2018 12:02pm
Of all the words here, I kinda like ThomDawson's the best: " If in doubt set it hard as fuck and ride faster until it feels good."
TEAMROBOT
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TEAMROBOT 2/1/2018 12:10pm
2/1/2018 12:10pm
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad idea out of left field. "What if we wrapped a taco IN a Quesadilla, and then wrapped that IN a burrito?"

We can run 50% sag on our current bikes, we just don't because it would suck. Try running one spring-rate too soft some time. AMAZING traction over small bumps and at speed in a straight line, but un-fucking-rideable where terrain undulations and rider inputs come into play.

Future Spomer forum questions: "What if we put little shocks in our spokes?" or "What if our tires were filled with nacho cheese?" or "What if we rode bikes in outer space?"
jeff.brines
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jeff.brines 2/1/2018 12:17pm
2/1/2018 12:17pm
Wentz beat me to it. The ability to actively manipulate the location of the largest mass on the vehicle (the rider) basically makes a lot of automotive suspension theory go out the window. To add, the way weight transfers on a vehicle, how the motor turns, where it sits, bla bla bla, is just so different.

That said, for a newer (older) rider riding rough terrain, I do think letting them run more travel and run it soft with the right (progressive) frame is an excellent idea to help them build confidence. (this is what most bike parks should be renting...lots of travel, soft, slow rebound) Its just a crazy muted ride where your input doesn't do a whole lot. Your good rider would hate it. Maybe it'd work better in terms of giving the rider control, but I'm not sure it'd be faster.

I've been playing with negative travel a lot on my sled through whoops. Its pretty crazy how good I can get my snowmobile to track in these situations with negative travel. Its paramount to pounding through stuff like this. But my sled weighs 2.5x what I do. I only bring up the analogy as its somewhere in between a trophy truck and a bike. I can pump and jump doubles, but not nearly as quickly or as easily as I can on a bike (and I try!)
jeff.brines
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jeff.brines 2/1/2018 12:19pm
2/1/2018 12:19pm
TEAMROBOT wrote:
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad...
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad idea out of left field. "What if we wrapped a taco IN a Quesadilla, and then wrapped that IN a burrito?"

We can run 50% sag on our current bikes, we just don't because it would suck. Try running one spring-rate too soft some time. AMAZING traction over small bumps and at speed in a straight line, but un-fucking-rideable where terrain undulations and rider inputs come into play.

Future Spomer forum questions: "What if we put little shocks in our spokes?" or "What if our tires were filled with nacho cheese?" or "What if we rode bikes in outer space?"
I can't lie. I laughed.

I like these questions. I also think its winter...and if you are into bikes, this is the time to chew on random shit.


sspomer
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sspomer 2/1/2018 1:05pm
2/1/2018 1:05pm
TEAMROBOT wrote:
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad...
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad idea out of left field. "What if we wrapped a taco IN a Quesadilla, and then wrapped that IN a burrito?"

We can run 50% sag on our current bikes, we just don't because it would suck. Try running one spring-rate too soft some time. AMAZING traction over small bumps and at speed in a straight line, but un-fucking-rideable where terrain undulations and rider inputs come into play.

Future Spomer forum questions: "What if we put little shocks in our spokes?" or "What if our tires were filled with nacho cheese?" or "What if we rode bikes in outer space?"
had you used a funyun flavors analogy, it would have been way funnier. i don't smoke either. plenty of people tell me i should though. i'd get worried all i'd end up doing is watching youtube vlogs.

i only bring up this topic b/c i've heard it discussed recently by some "names" on "the circuit." sure 50% sag may suck on bikes we have now, but what if everything was designed around that much sag? is that R3ACT design on the marin/polygon mentioned above designed around a bunch of sag? i'm not a tech dork, but i get turned on by desert trucks going through 22 inches of travel at 90mph. you can't tell me that desert truck has too low a spring rate just b/c it's super sagged. it's designed around all that sag right? what if bikes were too? AND i did mention at the very beginning, maybe this can't apply to bikes at all. didn't you ride a V10?

nacho cheese in tires has been done (le system) and also too late for shock spokes (super bummed, total shark tank gold...we could have partnered up)


i wish you'd post here more and lurk less! you're entertaining and i like that.
iceman2058 2/1/2018 1:17pm
2/1/2018 1:17pm
TEAMROBOT wrote:
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad...
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad idea out of left field. "What if we wrapped a taco IN a Quesadilla, and then wrapped that IN a burrito?"

We can run 50% sag on our current bikes, we just don't because it would suck. Try running one spring-rate too soft some time. AMAZING traction over small bumps and at speed in a straight line, but un-fucking-rideable where terrain undulations and rider inputs come into play.

Future Spomer forum questions: "What if we put little shocks in our spokes?" or "What if our tires were filled with nacho cheese?" or "What if we rode bikes in outer space?"
I'm so eating that new Taco Bell dealie if they make it. I might even have to buy those three things and stuff them into each other just to see if it's as good as it sounds. Like, if they don't decide to actually make it for some reason.
HodRaske
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HodRaske 2/1/2018 1:49pm
2/1/2018 1:49pm
I'm just imaging trying to hop over something with 50% sag. Not fun.
Falcon
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Falcon 2/1/2018 2:31pm
2/1/2018 2:31pm
TEAMROBOT wrote:
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad...
Spomer, you're like the Taco Bell Menu Department. I assume you get baked and look at available product until you come up with some kooky bad idea out of left field. "What if we wrapped a taco IN a Quesadilla, and then wrapped that IN a burrito?"

We can run 50% sag on our current bikes, we just don't because it would suck. Try running one spring-rate too soft some time. AMAZING traction over small bumps and at speed in a straight line, but un-fucking-rideable where terrain undulations and rider inputs come into play.

Future Spomer forum questions: "What if we put little shocks in our spokes?" or "What if our tires were filled with nacho cheese?" or "What if we rode bikes in outer space?"
iceman2058 wrote:
I'm so eating that new Taco Bell dealie if they make it. I might even have to buy those three things and stuff them into each...
I'm so eating that new Taco Bell dealie if they make it. I might even have to buy those three things and stuff them into each other just to see if it's as good as it sounds. Like, if they don't decide to actually make it for some reason.
It's like Turducken. Only, in this case it's "Tacodillarito."
jeff.brines
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jeff.brines 2/1/2018 2:35pm
2/1/2018 2:35pm
Fun side point. Back in my "full time" (lol) racing days when I was on the JV Cannondale team, I ran about 45% sag as a result of CG's suggestions (he ran about the same). We were running a crazy progressive shock, so we could get away with it and not feel like we were hitting bottom all the time.

Was this fast? Probably not. I think we really liked it because it made our headtube angles slack and lowered our uber tall bbs. Plus, those bikes only had about 7" of travel.

Either way, its been done, I just don't think its fast in the world of bike riding...
luisgutrod
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luisgutrod 2/1/2018 2:59pm
2/1/2018 2:59pm
the 30ish% sag is only because the LR&Wheelpath are designed around it, coupled with BB height&drop. Koolaid tastes gooood... cheers..
matmattmatthew
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matmattmatthew 2/1/2018 5:28pm
2/1/2018 5:28pm
Pretty sure Foes had a bike a few years ago that had a secondary shock that had 2-3inches of negative travel. You would think that if it was actually useful on a DH bike that Brent Foes of all people would have figured it out.
sspomer
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sspomer 2/1/2018 5:56pm
2/1/2018 5:56pm Edited Date/Time 2/1/2018 5:56pm
matmattmatthew wrote:
Pretty sure Foes had a bike a few years ago that had a secondary shock that had 2-3inches of negative travel. You would think that if...
Pretty sure Foes had a bike a few years ago that had a secondary shock that had 2-3inches of negative travel. You would think that if it was actually useful on a DH bike that Brent Foes of all people would have figured it out.
yeah, good point about brent. the 2:1 stuff that foes did was always "pretty saggy" and planted too, wasn't it? for a mount snow course or vds, it could be gold, but for leogang, hmmm.

here's the FFR bike you're talking about
https://www.vitalmtb.com/photos/features/2014-Sea-Otter-Classic-Pit-Bit…

--------
The new Foes FFR downhill bike prototype was the highlight of our Day 1 stroll through the pits. Like all Foes bikes, the FFR was handmade in California. What makes it truly unique isn't the 27.5-inch wheels, but rather the suspension design, which is unlike anything we've seen before.

Speaking with Brent Foes, he told us that the goal of the system is to increase negative travel, helping to keep the rear wheel on the ground more often. This will, in theory, provide more traction and better braking. Much like the trophy trucks with ample negative travel that Brent has spent plenty of time working on, the rear wheel should be able to follow the contours of the ground much better with this design.

Brent achieved this by incorporating two shocks into the linkage - a traditional Cane Creek DBair and a custom made 1-inch stroke shock that is only active when the Cane Creek is fully extended. The bike has 8 or 9-inches of travel via the DBair and the single pivot linkage PLUS and additional 3-inches of bonus travel that comes via the second shock. The second shock is actuated by a few small links connected to the swing arm. Accessing the full 12-inches of travel is only possible when the bike is unweighted and the rear wheel can drop down.
JamesR_2026
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JamesR_2026 2/1/2018 8:05pm
2/1/2018 8:05pm
Intense M16 runs 240mm travel in the big setting and my Propain Rage runs 220mm.
Lets you run more sag and does feel trophy truck-esque when you are bombing in a straight line. I can still pump it through features pretty well though and it corners amazingly. Maybe not the most efficient rig around to pedal though...

Would love to try out that Foes on a proper DH track!
thom9719
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thom9719 2/1/2018 10:18pm
2/1/2018 10:18pm
The goal of the negative sag on a bike vs trophy truck are different. The issue is power transmission. The trophy truck needs that negative travel to ensure proper traction when supplying 600+ hp to the rear wheels. Downhill bikes don't move forward due to rear wheel power transmission (for the most part). They move forward due to gravity. This changes the suspension requirements to value the ability to skim over and pop off obstacles instead of plowing through them. Charlie is correct, 50% negative travel would suck. The reason is due to the goals you are trying to accomplish with negative sag.
JamesR_2026
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JamesR_2026 2/1/2018 10:46pm
2/1/2018 10:46pm
A trophy truck also runs all that sag to maintain forward momentum through big hits without getting sent. Keep in contact with the ground and you stay in control. Which is also what we are talking about on dh bike. Traction for drive is only half the story on the trophy truck analogy.
It would require a different riding style and suspension setup. Think Danny Hart vs Loic Bruni at Andorra last season. Danny looked like he was riding an angry bull down the hill. Loic looked like he was riding down to the shops for milk! I reckon Ohlins is running more sag as well as better controlled damping.....
Tristan_Mayor 2/1/2018 11:59pm
2/1/2018 11:59pm
The early versions of the carbon V10 had 2 shock positions so you could run 8 or the big 10" of travel.

You could run the same spring weight with both; the 10" position had about 5" sag and the 8" position had about 3" sag. So both felt similar after you'd gotten past the sag.
There may have been some extra traction in the 10" mode, but overall the 8" just felt better pretty much everywhere. Hence why Santa Cruz eventually did away with the option of 10"
ThomDawson 2/2/2018 1:04am
2/2/2018 1:04am
luisgutrod wrote:
the 30ish% sag is only because the LR&Wheelpath are designed around it, coupled with BB height&drop. Koolaid tastes gooood... cheers..
I am aware of that but there seem to be fewer considerations made in the design process for sag than a few years ago (I could be wrong, these are very much just a lay persons observations). More and more people are seeing the advantages of a simple rising (shock) rate and I think that says a lot about the riders relationship with the suspension. It should be seen more as an extension of ourselves and tuned to the way in which each individual rides their bike with an equal emphasis on suspension theory and vibration isolation etc. I imagine mountain bike suspension tuning is a very tricky business because there are so many variables; the usual complications with the addition of a dynamic mass who is able to manipulate the suspension almost infinitely. I’m sure I’m not telling anyone anything new, I just wanted to point out the importance of the riders role in our suspension. Which with so many cool and ever technical, cutting edge suspension features available to us (the end user) is easy to overlook. I fully appreciate the incredibly knowledgable tuners out there but for me many tuning issues are solved by simply using a higher spring rate.
sideshow
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sideshow 2/2/2018 3:40am
2/2/2018 3:40am

I'm going to join Spomer on the side of, "This footage is sublime and I can't stop watching it…"
Since first seeing the introduction of Chain Smoke 2, I've had a mild obsession with Trophy Trucks - they just boggle the mind in terms of what they can do, from a mechanical standpoint.

The reason why it's difficult to compare a TT to an MTB is a laundry list of points:

Weight and the distribution of it
Approach angles of obstacles
Speeds/Forces
Chassis size and balance
Torsional forces
Mixed Materials
General terrain of uses
How momentum is generated
Inertia of vehicle
Static vehicle with no input outside of throttle, steering, and objects/undulations v. rider input
Etc.

In MTB, the rider is heavier than the "machine"; the overall ratio of size and weight of the bike v. rider is significant, as is the ratio then of the bike to the objects it's impacting. There are only two wheels, and fewer forces to account for (on a relative scale, mechanically speaking). The bike is heavily controlled by the rider's input, and thus the suspension has less to work to do when compared to the truck, as there are no extra limbs to act as shock absorbers or downward forces from a body to create non-weight oriented negative sag.

Then, it needs to be noted that the suspension systems on the TT v. a MTB are laughably more complex and insanely adjustable. With that much more control due to volume, it's no wonder TT can perform as they do. It is also by in MTB Ohlins are so heavy - they have more going on inside as to better control the forces. They eschewed the industry "light is fast" mantra and followed the path of "correct engineering is fast".

Better to learn and appreciate in this case than compare because at the end of the day, to get a bicycle to ride like a TT would be a fool's errand due to the fact that the applications are vastly different and the way they each need to interact and function with their respective pilots is not even remotely similar.

For reference, TT suspension.
More reading on TT suspension.
Blake_Motley
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Blake_Motley 2/2/2018 7:34am
2/2/2018 7:34am
Best downhill suspension I ever had was an Intense M9 in the 9.5inch mode with 50% sag. Never once bottomed out and it tracked so good and generally felt good over everything
NWDommen
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NWDommen 2/2/2018 9:37am
2/2/2018 9:37am
Tristan_Mayor wrote:
The early versions of the carbon V10 had 2 shock positions so you could run 8 or the big 10" of travel. You could run the...
The early versions of the carbon V10 had 2 shock positions so you could run 8 or the big 10" of travel.

You could run the same spring weight with both; the 10" position had about 5" sag and the 8" position had about 3" sag. So both felt similar after you'd gotten past the sag.
There may have been some extra traction in the 10" mode, but overall the 8" just felt better pretty much everywhere. Hence why Santa Cruz eventually did away with the option of 10"
I had a first gen carbon v10 and the 10" mode was sick for super rough tracks. Just sit on the bike do nothing and smash through everything with ease, the traction it had was amazing.
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Pedal4life 2/3/2018 9:47pm
2/3/2018 9:47pm
So let’s say we had a fork with 220 of travel but bike manufacture say bike best set-up with a 200mm travel fork set @ 30% sag so you could get to this point of small bump & better contact with the ground when it gets sloppy

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