Answered Fox ebike forks, need loads of pressure?

[deanFBM]

I'm running a fox 36 e-bike chassis on my normal bike, 29" @140mm.
This uses a smaller diameter air piston than a normal for 36, the air shaft assemblies from a fox 34 in fact, so I'd expect required pressure to be a bit greater than that in a normal fox 36, more in line with a fox 34.
Crux of it is both the 34 and 36 charts recommended about 100psi for my weight, I'm at 140psi to get 15%, this is above max recommended.

Similar story for others?

 

[Rich-EMTB-UK]

Fork legs internals are same width on the E36 as the none E 34 version due to thicker material. Maybe this accounts for it.

 

[raine]

That's why it's just a "recommendation" - in the end you still set your fork's air pressure to a sag point between 25-30% based on your fully loaded "ready to ride" weight.

 

[RickBullotta]

I'm running a fox 36 e-bike chassis on my normal bike, 29" @140mm.
This uses a smaller diameter air piston than a normal for 36, the air shaft assemblies from a fox 34 in fact, so I'd expect required pressure to be a bit greater than that in a normal fox 36, more in line with a fox 34.
Crux of it is both the 34 and 36 charts recommended about 100psi for my weight, I'm at 140psi to get 15%, this is above max recommended.

Similar story for others?

Why so little sag? I'd always run at least 20% on a 140mm Fox fork.

Also, make sure you cycle the fork as you're filling it to equalize the negative air chamber. If you haven't done that, I'd recommend lowering it back down to almost no air, and add 20 psi, cycle the fork up and down, and repeat (add 20 more, cycle the fork) until you have your sag set up.

Also, sag should be set in a normal riding position, *not* with all of your weight on the front end.

 

[Bryan Wells]

my standard fox 36 factory on my ebike is at 90 psi and i weigh 180lbs, it feels great, if you need more support maybe look at compression

 

[RickBullotta]

15% is way too low. You're cheating yourself out of the optimal performance of the fork, both in terms of plushness and in terms of its ability to "track" and maintain ground contact in choppy/uneven terrain. Go to 20% and you'll notice all kinds of yummy goodness. It will also probably corner better.

 

[Varaxis]

I presumed that Fox sag recommendations were based on sag measured when seated. When seated, a lot more of your weight is supported by the rear wheel, so it would sag to something more like 20% when standing.

Self-defined optimal performance aside, every rider should do "bracketing", which are tests to feel what you like better in back to back tests. This is highly subjective and personal. I personally hate a fork that dives/wallows. I also don't aim for using full travel on a typical ride, preferring it to only use full travel on rare hard hits, and have a particular feature with a lot of freefall and a front wheel first impact to test on. I basically want a fork that I have confidence in, where I use the brakes less, and usually that means a high level of predictability and support. I credit geo preservation as the reason why I run relatively firm suspension, rather than aiming for some arbitrary sag %. I get defensive and firm up my own body if I feel the bike is pitching me over due to the dive. I also feel compelled to hold back on putting out pedal power out-of-the-saddle if it's bobbing too easily. These things hold me back more than small bumps; small bumps actually remind me to loosen up, and get me in a mindset to ride better, focusing on higher priorities. Rather not get into the habit of firming up my own body, and getting back, not trusting in my bike and compromising my readiness to use technique.

I used to pump my fork to have my riding weight in kg to reach a starting point, but that's changed with EVOL (and Debonair). If you're not sure, you can use shockwiz to assist with your susp tuning. Wouldn't worry about the actual # except to tune that specific fork again, but more about the performance you feel on the trail. It could very well be different from expectations. I haven't used the emtb Fox 36, so am just generalizing. Part of my generalization is based on knowledge that adding a Vorsprung air piston in the same fork requires more air pressure due to even greater negative air volume.

P.S. Stiffer forks corner better. Dual crown forks, including lefty, and rigid and shorter travel versions of big forks like the Lyrik, all corner noticeably easier. Also tracking the ground isn't necessarily the best. Skipping over holes, rather than tracking into them, is way to remove spiky feedback. You can skip over them with technique and speed, but you'll need a firmer spring for those anyways. Being on the brakes too much leads to arm pump--better to trust the bike, rather than to contribute to braking bumps by clamping down in them. In the MX world, it's common for people to try and open/soften suspension in braking/washboard bumps, being confused about not being able to tune them out, but veterans recommend doing the opposite, increasing spring rate and compression damping. It goes from jackhammering (tracking entire bumps) to feeling like a series of shaved off humps (tracking the tops of bumps, where the damping rounds off the edges). Part of the theory is that the sound of the bumps makes the rider "feel" the impact, even if it's absorbed, and the way they react to the impact sounds is messing up their ride experience. A lot more than you think is mental...

TL;DR, long way of saying who cares about the specific amount of pressure. The same ride concept applies: go faster, and tune the fork to be firmer for such speed, and things will be easier and small bumps become more ignorable. It's a noob trap to soften up suspension, which would compel you to use the brakes more.

 

[RickBullotta]

P.S. Stiffer forks corner better. Dual crown forks, including lefty, and rigid and shorter travel versions of big forks like the Lyrik, all corner noticeably easier. Also tracking the ground isn't necessarily the best. Skipping over holes, rather than tracking into them, is way to remove spiky feedback. You can skip over them with technique and speed, but you'll need a firmer spring for those anyways.

Laterally stiff, yes, but oversprung forks can have a tendency to corner worse. And in tech terrain (rock gardens, roots) "skipping over holes" isn't an option. I'd rather have a fork that can provide good tracking when carving a turn on that kind of gnar than an overly stiff rattler.

 

[raine]

Why is everyone making this topic more complicated than it is?

It's simple. OP should set their sag to a pressure to a sag point between 25-30% based on their fully loaded "ready to ride" weight. Get that starting point within the correct range first.

Then if they want they can dive into over-thinking lateral stiffness and bracketing

 

[RickBullotta]

Why is everyone making this topic more complicated than it is?

It's simple. OP should set their sag to a pressure to a sag point between 25-30% based on their fully loaded "ready to ride" weight. Get that starting point within the correct range first.

Then if they want they can dive into over-thinking lateral stiffness and bracketing

This! ☝?

 

[Changleen]

I agree that I needed a bit more pressure than ‘recommend’ in Fox e36s to get it how I liked. Been tooling about with it a fair bit now and currently have 85psi for a 72kg rider, plus maybe 1/5 of the high speed compression. One or two clicks only of low speed. Recommend low/high rebound though seems nice for me though.

 

[Gardcol]

Why is everybody so down on the 15% sag? Fox recommends 15% for firm and 20% for plush on the 36. I know Rockshox recommend more but I think Fox know their own forks. Personally I am only 72kg and run 95psi with no tokens to give 15% sag and find it perfect. Very linear rather than progressive. I tried 1 and 2 tokens with less pressure but found the ride much harder on my hands and more skittery so went back to zero tokens and higher pressure.

 

[RustyIron]

Personally I am only 72kg and run 95psi with no tokens to give 15% sag and find it perfect. Very linear rather than progressive. I tried 1 and 2 tokens with less pressure but found the ride much harder on my hands and more skittery so went back to zero tokens and higher pressure.

That all sounds reasonable to me.

 

[steve_sordy]

What is the Fox-recommended sag measurement method for forks?

Sit on saddle, attack position, something else?

 

[Gardcol]

What is the Fox-recommended sag measurement method for forks?

Sit on saddle, attack position, something else?

 

[Gardcol]

Normal standing neutral position.