Knocking from SR Suntour Aion Fork

[Stibbs]

Same here 24 clickes on the rebound adjuster

 

[deksawyer]

I have a socket for the fork tops at work (ie not here), but can't remember what size it is? What else fits? Can you get an alloy Spanner or something?

 

[Stretch40]

Hi its 27mm I made a ring spanner flat one and use that ?

 

[benshamb]

The pcs rc2 damper made a difference on mine too. As did increasing the travel by 20mm. I had a nasty top out sound before the increase, now its just a kinda creaking springy sound. Still using the 3 std air spacers as I run around 100 psi.

Thinking about trying some heat shrink on the neg springs to see if that helps. Or maybe just a shed more grease...

Hey man, did you ever put heatshrink over the negair spring? Thinking about doing this.

 

[deksawyer]

Hey man, did you ever put heatshrink over the negair spring? Thinking about doing this.

Not yet, but I'm going to remove a volume spacer first when the new fork top socket arrives as there's 3 in there from the factory...... Probably a different solution to a different problem, I know.

Might try more grease or oil as a few ml escaped when taking them apart.

It's definitely making a squeaky, springy, creaky sound on rebound. Before increasing the travel to 140mm it made more of a definite clicking/topping out sound on rebound or when lifting the front end (it felt like a loose headset).

Even before fucking about with it, when the bike was new, it still made a noise on rebound. Maybe that's just how they are....?

 

[GrandPaBrogan]

Just in case someone needs/wants to DIY the fork maintenance...

 

[deksawyer]

Interesting, there was no oil in the damper side of the fork, but there was in the air side, as most of it escaped when taking them apart. ?

 

[GrandPaBrogan]

Interesting, there was no oil in the damper side of the fork, but there was in the air side, as most of it escaped when taking them apart. ?

I didn't see any oil come out of the sliders either, so maybe they just shot the video without showing the old oil escape, so its not messy. They did inject 25cc of oil into both sliders during the reassembly - which I think is just there to lube and replenish the seals (when tipped upside down occasionally, as recommended for most forks). Being only basic 80wt gear oil, that's all it can be.

Oils for dampening are special purpose and are usually thinner - 20wt with additives that stop it from frothing. The damping oil for the Suntour Aeon, I'm guessing is inside the sealed damper cartridge enclosed within the right stanchion tube, that doesn't need dismantling during fork slider servicing.

 

[GrandPaBrogan]

Found a great reference video regarding what that “soft” negative spring is all about, as @Stretch40 mentioned earlier.

 

[GrandPaBrogan]

Update on the Suntour Aion "Soft" Negative spring... for anyone wanting to get one, here's the part number: FEP736
Mine arrived last week and I've been doing tests on it.



I'm only beginning to understand how this fork works. I cringe when I re-read my earlier posts... ?

These observations are subjective and specific to my bike set-up so may not apply to everyone, but I'll post it anyway in case it helps.

• The Aion does NOT have a negative AIR spring chamber so the earlier post I made about incrementally pumping the fork is irrelevant. It uses a steel spring (as we now all know) so you can pump the forks all the way up to the correct pressure you require in one go.

• The "Medium" negative spring that came stock with the fork will ONLY allow the fork to fully extend from around 90psi or more - regardless of how many tokens there are. Three tokens came installed on the left leg top cap with mine. I get progressive mid to end stroke, ramping-up behaviour with 3 tokens - but then a more linear characteristic with lesser tokens.

• If in order to get the right amount of sag you need to have 80psi or less (for lighter riders), the stock Medium negative is too strong and overwhelms the air pressure in the main chamber. The result is that the fork won't extend out fully - the video above explains that. What it doesn't say of course is that - as an unexpected consequence, the initial movement of the fork in this condition is actually super plush, BUT at the expense of losing about 10mm of travel at the beginning of the stroke. It's great for riding over roots or rock gardens at speed, and I get predictable feedback.

• Installing the Soft negative spring won't overwhelm lesser air pressure (supposedly 80psi or less) and so the fork will extend back out fully. On a manual bike, you can even go as low as 40psi and it will extend fully as the video above shows. BUT... on our much heavier eBikes (standing up, but no rider sitting) I noticed that 60psi and lower isn't enough either to keep the fork fully extended. Fork sag already kicks-in.

For my weight (79kg) and riding style (not aggressive) my preferred pressure is 75psi with one token with the medium negative spring... but my actual fork travel is actually reduced down to 140mm. I still like how it performs though.

With the soft negative spring, I can get the full 150mm extension on my fork at about 70psi... BUT the initial start of the fork movement is not as plush as before. It doesn't soak up the small stutter bumps as well and I just couldn't bond with it - so I reverted and put the medium negative spring back in.

???‍

I've read somewhere that the Suntour Aion can be lengthened from 150mm travel to 160mm by simply removing a black spacer. I'm toying around with the idea of doing that in combination with the medium negative spring to keep the initial movement super supple. I'm expecting to lose about 10mm stroke so that will take it back to 150mm fork travel... but... right now, I've got this saying echoing in my head... "if it ain't broken, don't fix it?"

.

And oh, my fork also slowly developed a ticking noise (the type that happens every time the legs lifts and moves back down). Checked everything, cables, head set, seat post... nothing. Then I switched on the lock-out lever on the fork and pumped the handlebars a couple of times. When I turned the lock-out back off, the noise was gone. It's not a permanent fix though, but when it returns I just do the same. Could be just an idiosyncrasy specific to my bike, but might be worth trying in case it works for others. I have to say though, that when I had my rebound setting on just very slight, I have never experienced the ticking sound. It only turned up since I increased my rebound setting some months ago. Not intending to change my rebound cartridge... I can live with it easy.

.

 

[Stretch40]

Hi I made my fork 160mm u just remove the little black spacer I've also fitted the upgraded damper r2pcs I think what a difference I'm 85kgs in kit I run 80psi 3 tokens 1 low speed comp 2high speed compression if I run 2 tokens I bottom out sometimes on jumps or drop offs oh and I've got the softer spring in I really do believe this is easily as good as my yari if not better ? hope that helps ?

 

[GrandPaBrogan]

Hi I made my fork 160mm u just remove the little black spacer I've also fitted the upgraded damper r2pcs I think what a difference I'm 85kgs in kit I run 80psi 3 tokens 1 low speed comp 2high speed compression if I run 2 tokens I bottom out sometimes on jumps or drop offs oh and I've got the softer spring in I really do believe this is easily as good as my yari if not better ? hope that helps ?

This black spacer... is this the one at the very top of the negative spring pole? Like... it's not a whole cylinder so there's a gap on one side, so you can just flick it off?

 

[Stretch40]

Hi yes like a c clip sort of thing with it removed I measure about 157mm travel I don't think u ever get full travel ?

 

[deksawyer]

@GrandPaBrogan The travel adjusters are the black clips in the bottom of the pic like you say.

 

[Stretch40]

That's them ? biggest the fork will go is 160mm but that's fine u can also change rear travel there's a 2.5mm spacer in the shock so instead of 140 u get about 148mm ISH wheel doesn't touch anything at full travel I checked ?

 

[daddyo]

Is this the annoying noise ? My wife bought an used Flyer Goroc 3 with AIOn35 and this noise is making us crazy. Sooo annoying while riding