Agree. As I was looking at the results in the Linkage Design website, I was thinking he must have assumed some standard shock tune to develop the curves. And that the curves could meaningfully change with different shock tune or settings.
For example - here’s the anti squat for my bike, the Trek Fuel.
I’ve got to believe when the shock is “locked” the curve is flatter, but still starts at 100%.
But given the reasonably flat AS curve, the shock tune/settings on the Trek wouldn’t impact the AS curve as much as, say, the Niner in the above chart.
Shock tune does not affect anti-squat, same way that shock tune does not affect leverage ratio.
When a shock is locked, it is effectively 0% sag/0mm wheel travel unless there is a float section at a certain travel portion like the brain.
Easiest way to think about anti-squat is to attach a string at the end of a piece of wood, where one end is fixed to a rotating point and the other is driven by the string. Depending on the placement of the pivot point and the direction that you are pulling the string, the wood is going to move in an arc in one direction or another.
If the pivot point is above the level of the string, the wood is going to move in a downwards arc, which in the context of mountain bikes is consisdered antisquat because when you pedal, the suspension swingarm is actually moving down towards the ground rather than up. The value of anti-squat is how much effective force goes in one direction versus another relative to the movement of the suspension.
The shock acts like a damper if there is upward movement, but doesn’t affect the angle of these forces generated by the chain.
If a shock is fully locked, then the bike becomes a hard tail and the AS is 100%.
If the shock is not fully locked, but is more stiff (the shock on my Fuel does not have a full lockout), my understanding (and experience riding the bike) is this affects the AS curve in practice - as there is a dynamic component to pedaling / acceleration forces.
So on paper, given “infinite” time for the shock to react to pedaling / acceleration forces, the AS curve is not affected by shock tune/setting. But in practice, with finite time to react, the AS curve does change with tune/settings.
Yup. But the damping level in the shock affects how fast it reacts, hence how in practice under dynamic pedaling conditions, the AS changes.
Edit: I’m in the process of learning the nitty gritty detail on this stuff. This is my current understanding, and reserve the right to change my view as I learn more .
Using our wood analogy, anti-squat is how much force goes up or down based on the force on the string. The shock compression tune would be like a second person putting their finger on the upward movement of the wood.
Those two forces are independent of one another and while they both play into how the bike rides, they don’t affect each other.
Also agree. Hence why in practice, the AS behavior of the bike is affected.
Think of it this way: let’s say the shock is heavily damped, and takes 10 seconds to compress to sag point with, say, a 100kg load. The suspension will react very slowly, and the bike will probably pedal more like a hard tail.
Agree. The shock tune would not affect the AS curves that you might see on the likes of the Linkage Design website. So it that respect, shock tune does not affect AS.
Thanks - That’s the better way to describe the effect I’m getting at.
I was not being clear on talking about AS as a calculated value, vs. AS as a characteristic of how the bike behaves.
Looking for some wisdom. I currently have a 2017 Spark 935 (alloy frame, fox performance 34, 11spd GX RD, NX cranks and shifters, Deore brakes, syncros wheels and syncros dropper). I love the bike and has served me well getting back into MTB (XC and light trail).
Next year 2022, I’m looking at doing the Crocodile Trophy here in AUS and as such, exploring the idea of a new bike. I love the fact that alloy handles rock strikes and crashes without too much issue, I’ve not owned a carbon MTB and the thought of killing it on a seemingly small impact plays heavily.
The bikes I’m considering are: Epic, Epic Evo, Norco Revolver FS 120 or just spend to upgrade the Spark (wheels, cranks, cassette etc)?
My biggest issue with the Epic and any bike running proprietary components (brain, AI, switch link or cables and housing through the headset. I love the clean look, my spark is a birds nest of cables). Given that Specialized don’t hold spares after a certain time frame for their bikes and their availability in AUS is even worse, long term I worry that, issues arise and cannot be repaired. I’m not into replacing bikes year on year and want something to last. Therefore I’m leaning more to the EVO and Norco.
I’m interested to hear if anyone else has ridden these two bikes against the Epic and why they chose them over something else. Also am I’m gaining much by going carbon over just upgrading my current Spark?
The Epic Evo will ride more similar to your Spark than the Norco, but honestly either would be a great choice. The regular Epic with the brain off pedaled well enough to where I can safely make assumptions about the Evo, since it has a bit more pedaling efficiency built in since it doesnt have the Brain.
The Norco should feel more plush than the Evo during active braking through choppy sections, but not everyone necessarily is sensitive to this. It should also be a little bit more durable since I’ve heard through many sources that it’s quite overbuilt to avoid warranty issues.
That being said, for a marathon XC bike, I think the Evo wins out for being able to carry two bottles for me personally. It’s a simple design from a large brand with nothing weird component-wise and you shouldn’t have to worry about warranty that much with Specialized.
I’d get the bike frame wrapped if you are worried about crashes and you should be just fine.
Just curious for those who have tried both, as a FUEL EX owner I always wonder how much faster a Top Fuel would actually be. Maybe not for these bikes but similar ones, anyone tried both an XC FS and a Trail FS bike back to back? I went FUEL EX for versatility even though I don’t ride rowdy trails I figured it would be more forgiving
My preference is still the efficient leaning short travel trail bikes. If you’re focused on XCO style racing and results and your local terrain is slightly less rowdy, I’d bet the Top Fuel would be a good choice. For my riding, I’m enjoying my Ripley V4 exponentially more than my Blur, to me that’s more important. I’ve learned that my training and preparation makes a lot more of an impact to my results than a bike choice that might be more racing oriented, on paper.
A friend of mine won a pretty big endurance race on his Trek Remedy (back when it was still 26"), sure he could have gone even faster on a lighter bike, but, well, he won and definitely made time on the rough descents.
That said, if I can get my hands on a new school XC rig this year… I’ll probably make a bad $ decision.
Fuel EX on the left, Top Fuel on the right. They don’t look THAT different, and I’m also still using a lighter Fox 34 51mm offset fork that lengthens the wheelbase and sharpens up steering a bit. The one thing I wish my FEX had was a steeper seat angle, and the TF isn’t much steeper. I also don’t run the 2.6” tires (opted for 2.4), my bike probably falls somewhere between the FEX and TF on paper. That said trek isn’t exactly daring with their geometry so I dunno how these compare to other trail and XC bikes
With the fork and tire and geometry combo I have my trail figure is actually 10.8 so it def steers a bit sharper than the fuel ex with a 44mm offset fork
I’ve owned a couple of a EXs although they were back in 26 days. Still one of my favorite bikes, super active especially under braking (as advertised) only neg was the proprietary shocks trek loves. If that character exists in the new models (heard that it does) it’s a great bike. Funny that 75 is considered not steep for a seat tube now, but I get what you’re saying, trends. Still a 2 degree difference in HTA while won’t influence fit much does drive a bunch of the bikes character.
You set up the bike like I would, 34, 51 offset, send it.
I had no choice, TREK gave me a 2021 frame to replace my 2018 under warranty so I transferred my fork and wheels over, but it turned out good. I did have them install the 140mm shaft into my fork for proper slackness, definitely doesn’t feel lazy at all nor is it a porker, 28lbs with AXS X01 and the heavy 175mm AXS dropper.
Thankfully the shock on the FEX now is a standard size and not proprietary anymore
That’s interesting in itself really isn’t it, the 2021 Top Fuel is essentially a renamed 2018 Fuel EX, not that they’d have replaced your bike with something different, but you essentially went from a down country to all mountain bike?
They may have if I asked, but I’ve always had the FEX so stuck with it. The 21 frame is super stiff laterally, more so than the 18 for sure, when my buddy was doing clear wrap on it for me he said it made his old Scalpel feel like wet spaghetti. I can’t recall now but there were other reasons I didn’t go with the TF, I think it was surrounding the fork and tire clearance because I was reusing old parts
The TF is probably better at climbing, maybe more efficient, but I feel confident hitting stuff with the FUEL, my strength is pedaling and my weakness is handling so I think my logic was if I get a bike that’s more forgiving I’ll be more confident, even if I could do it on the TF sometimes knowing I have a more capable bike on paper let’s me hit that obstacle or drop and not feel like I’ll be on the edge of what my bike can handle
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