So thanks to a lot of good advice on this forum I managed to have built a Surly Karate Monkey OPS steel 29er hardtail, as seen in the last post of this thread, and fly it back home safely.

I decided to go for the Suntour Epicon forks, but the issue is the LBS got ones preset to 120mm instead of the 100mm I specified. I didn’t realise this until I got it home to a different country from the LBS, and now I’m on my own. The fork does have travel-adjust and long-term moving that down to 100mm is probably the best solution. While doing so doesn’t seem too difficult in their instruction video, I don’t have the tools right now and was wondering, for the time being, whether:

1. – If I increase the sag will that have a roughly similar effect in lowering the front end a bit while riding and help with the uphills? I supect the sag is a bit low anyway as it’s 20mm now and the max extension seems to be around 75mm, see pic below taken after my usual ride.

2. – If do want to increase the sag but don’t have a shock pump available, can I just press on the Schrader valve button briefly to let out a bit of air? Or will that let out a lot very quickly and it would be too much too quickly?

Sorry for the newb question but these are the first air forks I’ve had… Thanks!

Reducing the sag should have a similar effect, but you’d ant to do so by upping the -ve spring pressure while keeping the +ve pressure at what is right for you (riding, weight etc).

If you just press the valve you will likely let out all the air – the volume is tiny.

Personally I’d just ride it as is, you will likely adapt to the extra 20mm travel. However, if you are only getting 75mm of the 120mm then a bit less air would help.

Get a pump before you start messing with the air pressure. As Al says it will come out pretty quickly and you have no means to add air if needed.

Thanks, not sure about this -ve and +ve aspect, the fork only has one schrader valve I think.
Thanks also re: the pressure – in that case too risky to try without a pump. At least it’s still quite rideable now, but if I let all the air out by accident then I’m in trouble.
Guess I will have to wait until I can find a shock pump…

@dangerousbeans – with a 120mm fork what kind of maximum travel (in terms of where the blue ring is after a ride) should I be trying to aim for? I guess not the full 120mm?

You do want the whole 120mm travel but it should be sagged even when you are not on it so it won’t measure the full 120mm – only way to find out is to release the air and compress it fully.

So basically increase the sag in increments – say 25mm, then 30mm, etc – until after my ride the blue ring starts getting close to the top of the stanchion?

No, first you want the correct +ve pressure, play around with that until you are getting full travel (see my post above). then play with -ve pressure (if you can) to change the sag.

Keep the stantions cleaned. They look filthy.

if you are just mincing along smooth trails you should not be using all the travel, if you are riding reasonably hard on it with a few drops then I would expect you to use most of the travel.

Confused about this +ve and -ve pressure thing. The fork has only one air input valve, plus a rebound adjust knob. I’ve read it has a “sealed cartridge” if that’s relevant.

Re: the dirty stanchions that was at the end of the fork’s first ride and there was a fair amount of oil on the stanchions that picked up dust. Subsequent rides have picked up less but the conditions here are dusty red earth so I guess some is inevitable. I’ve been wiping them after each ride with a cloth though, I’m not leaving them like in that picture.

The trails I ride are a bit rocky and rooty but no big drops. I tried to ride that trail as hard as I could to maximise the travel.

I suspect the Epicon fork you have is a single chamber affair so you can ignore the advice regarding the negative chamber.

Basically you need to put enough air in for an appropriate amount of sag, typically between 20% and 30% to suit you and how you ride. You should, occasionally, use all 120mm of travel.

I would wait until you have a shock pump then you can raise and lower air pressure til you get it how you like it.

Thanks for the advice guys… will try to get hold of a shock pump.

Managed to borrow a shock pump and reduced the pressure from 110psi to 90psi, was dead easy, which gave an increase in travel like this…

Think I’ll stick with this for the time being until I can buy a shock pump of my own and experiment some more. Thanks to all for your advice.