Knocking from SR Suntour Aion Fork

[super_claret]

I'm getting what can be best described as a knocking sound from the front forks when going off road. It doesn't happen on road sections when the suspension is locked. Any ideas what this might be?

 

[GrandPaBrogan]

Fork noises can be caused by so many things… but maybe my set-up could be helpful for you.

On a brand new bike, my Suntour Aion fork had 120psi out of the box, and I wasn't getting the enough sag (I'm 85kg). Had to bring it down to 80psi to get the right sag... 38-45mm (25%-30% ball park).

The fork freed-up nicely after about 3 weeks break-in period, but then I began to notice a clunking sound at the very beginning of the stroke… I can make it happen when I slightly lift and drop the front wheel rapidly - on and off the garage floor.

The very start of the stroke seems too whimpy - like there’s not enough air pressure to push the sliders back out fully. The auto negative spring circuit (air too I’m assuming) may play a role in this, but let’s not go there.

My main concern was the stroke was too progressive for my weight and riding style (soft at the beginning but gets increasingly harder). Although it soaks up stutter bumps quite nicely through the first half of the stroke, my type of riding isn't aggressive enough for the fork to travel past 2/3 stroke… so I’m basically riding around with a 100mm-ish travel fork.

Thankfully the Suntour Aion has air volume spacers inside - so I can make it more linear. Mine had three spacers stacked when I opened it up, so I took one out to begin with. Turns out to be perfect. With more air volume in there now, the middle section of the stroke is more lively and resistance only ramps up near the end. I’m reaching 140mm travel now on rides with technical drops, and I have 10mm headroom as a back-up if I ever hit something real hard.

Interestingly, the clunking noise at the beginning of the stroke is now gone.

 

[GrandPaBrogan]

If you haven’t done this before and would like to try it, it’s pretty straight forward. But you’ll need a 27mm socket. Don’t be tempted to use an adjustable spanner or an open crescent wrench, otherwise you’ll wreck the hex corners of your chamber cap. Don't forget to let the air out first via the valve.

You should find x3 spacers stacked together inside. I was surprised the spacers are made of soft rubber, but that just makes it easier to pry one spacer off the stack. Screw the chamber cap (with x2 spacers) back on and that’s it. Don’t over-tighten this, in fact just tighten it lightly if you don't have a torque wrench - there’s no operational force or vibration capable of loosening it. Its the O-ring that creates the seal, and it’s not reliant on brute twist force.

(Although the mod is standard tuning procedure, implementation is at your own risk.)

Momentarily run your fork with 100psi, then back off the pressure until you get the right sag... between 40mm and 45mm for me.

 

[super_claret]

Thank you for that info. I’ll try it as soon as I get chance.

 

[GrandPaBrogan]

Let us know how you get on. It would be interesting to know if the knocking noise on your Aion is a common characteristic.

 

[Russell]

My suntour aion forks made a constant knocking sound, it used to really annoy me. I was glad when they died at about a year and 9 months old. I thought they were total crap in every other way, super harsh, blow through all travel on little jumps. I replaced them with ohlins rxf coil forks and couldn't be happier. Twice the price and 10 times better.

 

[GrandPaBrogan]

My suntour aion forks made a constant knocking sound, it used to really annoy me. I was glad when they died at about a year and 9 months old. I thought they were total crap in every other way, super harsh, blow through all travel on little jumps. I replaced them with ohlins rxf coil forks and couldn't be happier. Twice the price and 10 times better.

Oh really? Good for you.

 

[Rusty]

My only experience with Suntour forks was on my Surly Karate Monkey SingleSpeed. Put them on as a cheap replacement for the fully rigid forks and found them to work reasonably well if with a little weird sound - that sound was the tire hitting the frame as they flexed under braking when down in the travel. If I put more air in them they just did not work and still flexed badly.

My 68kg buddy bought them off me and has used them for 4 or 5 years with only a couple services.
Not the best around but also not the worst. Like any suspension component - setting it up correctly can make them work as they are designed and resolve issues many don't even realise they are experiencing.

 

[GrandPaBrogan]

I'm getting what can be best described as a knocking sound from the front forks when going off road. It doesn't happen on road sections when the suspension is locked. Any ideas what this might be?

@super_claret How's your fork doing?

If it's still making a knocking sound, try this:
SLOWLY release all the air from your forks then do "periodic equalisation" as you re-inflate your forks at 50psi increments.

If you're not familiar, go here:
Have you Equalized your FOX Float EVOL Air Sleeve? (rear shock) - EMTB Forums

The thread is initially about a Fox DPS rear shock, but as I later found out - it works wonders for the SR Suntour Aion Fork as well.

 

[Evolution Stu]

Mine has an annoying “crack” when the front end is dropped down into something. During a step down for example.
Doesn’t happen if it’s fist compressed, like riding UP an obstacle, only when dropping down one...

BLOODY ANNOYING.

 

[Stretch40]

Hi mine did the same I found the problem on the bottom of the lower leg air side the bolt was just a tiny bit loose I git half a turn and no noise ?

 

[Stretch40]

Oh nearly forgot if u r under 90kgs u can change the negative spring for a lighter one there £15 made mine much better ?

 

[steve_sordy]

Ref tightening the chamber cap on the fork. Keep an eye on the fork pressure. If you don't tighten it enough the fork will slowly lose pressure. just a slight bit more tightening and all was fine, but still nowhere near the 40Nm recommended!!!!

BEWARE! Keep your hand firmly on top of the socket to ensure that it remains fully engaged on the chamber cap. The hexagons are low height and are easy to round out.

 

[Evolution Stu]

Will check the lower bolts, thanks

Ref the spring, Typically, I am 90.5 kilos. ?

Better in what respect mate? Happy to take a punt at that price!

 

[Stretch40]

Hi its more supple less jarring works better on multiple hits ?

 

[Evolution Stu]

That sounds ideal. my two best mates have the same bike But versions 2 and 1, both with Fox 36 and theirs is MUCH better over fast, cobbly type terrain.

Comfortable even, mine is harsh and tiring. We were all surprised when we Swopped bikes due to my whinging. ?

 

[GrandPaBrogan]

Hi its more supple less jarring works better on multiple hits ?

Where can I buy this? Is it just the spring itself or a kit?

Is there a way to identify if I already have the lighter spring since my Trance E+ is a size small.

 

[Stretch40]

Hi I got it ftom grey ville there the UK importers tbh I don't know if yours will have it in?

 

[Stibbs]

Hi
Any other tips for the aion35 forks? Mine too were knocking so I took 1 spacer out and did the add 30 psi and pump the forks 20 times and so on but I think I might need the softer spring as I've only got 80 psi in the forks, and there's still a slight knock, would removing another spacer help? These are brand new suntour aion 35 rc forks
Thanks

 

[benshamb]

Hi
Any other tips for the aion35 forks? Mine too were knocking so I took 1 spacer out and did the add 30 psi and pump the forks 20 times and so on but I think I might need the softer spring as I've only got 80 psi in the forks, and there's still a slight knock, would removing another spacer help? These are brand new suntour aion 35 rc forks
Thanks

Hey man, I've got the same issue on my set. Just got them too. I've heard that covering the negative air spring with grease can help keep the knocking at bay. I have my own theory though. The negative air spring has this little spacer to keep the spring from bending, and it seems to be able to slide back and forth under the spring. This might be the source of the noise but I doubt it. I'm in your exact situation, having taken out a volume spacer and my fork being set at 80psi. I've got the softer spring coming tomorrow so I will let you know if that fixes the issue. Cheers

 

[Stretch40]

Hi sifter spring works much better makes off the top alot more gentle and controlled also take the black spacer off and u have 160mm slackens bike a bit and just gives u that bit more?

 

[Stretch40]

Oh forgot to mention check the nut on the bottom of the fork air side mine was loose tightened it knocking stopped failing that if u r in UK call Pete at greyville ?

 

[Stibbs]

My knocking has stopped now for whatever reason??? An I've ordered the softer spring from suntour
Did you fit yours?

 

[Stretch40]

Sort of my old bike shop that closed the mechanic did it but I was there lol tbh I could do it but I've got 4 young kids so time is short to get a ride I'm lucky lol

 

[Stibbs]

I was after a verdict lol has it made the forks better?

 

[Stretch40]

Ha yes it made it maybe 30% better but tbh fitting the r2c pcs damper made an even bigger diffrence it's a very good fork now I wouldn't say lyrik but it's better than my yari ?

 

[Stibbs]

Yes I've been thinking of adding the Rc2 pcs cartridge to mine now too, had it made a huge difference?

 

[Stretch40]

Hi yes it's hard to explain but I run low comp open high comp 3 clicks rebound 8 clicks and 80psi with 3 spacers it just feels do much more planted more cornering grip I can actually feel ? I'm an average to decent at time rider and I can actually feel the diffrence mind on my yari if I go 2 clicks either way I couldn't tell the diffrence same with tyres tbh most the big brands have tyres with more grip than I can use?

 

[deksawyer]

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...

 

[Stretch40]

20mm I've gone up to 160mm but that's only 10mm I thought the fork would only go to 160mm and tbh I measure it at about 155-156 til top out make an awful bang when u top out mind ? I'm 6ft6 but only about 82kgs I've stopped it topping out on most my trails now it's only the odd big drop to flat or something?