Hi.
After a period of not riding my trance properly (mainly using it for bad weather commuting) I have started using for proper rides again. I have only ever had coil forks before so forgot that the fork needed air. When riding the bike felt soft, wallowy and still recovering from the last bump when hitting the next one. I then remembered they needed air so I checked the fox book that came with them, put in the recommended 60% of my body weight in pounds in psi. This equalled 117 psi.
The forks feel great and I am enjoying riding it but I have noticed that I’m not getting the top 50mm of travel. When looking for a torque setting on the fox service site I had a look at the air pressure values which differ considerably from what my book recommends. For my weight it recommends around 80 psi.
I’m going to start experimenting with the pressure over the next few rides. Now I have a base line for the harder feel I can experiment from there.
I always thought I preferred a softer fork but after running them harder on the trance the shiver sc’s on my stiffee felt far too soft.
Andy

I put in enough to achieve 33% sag when I put my weight on the front of the bike. I was supprised how much pressure that was, I think it was about 80psi

Reduce the pressure slightly and increase the low speed compression a couple of clicks.

What Flaperon said – 12.5st in my Birthday suit, 70psi and 4 clicks of LSC leaves me a plush fork 7% on average travel unused and left for emercencies or all of it used if I do something stupid.

No low speed compression settings on an F-Series Fox..

That does sound like a lot of pressure, I’ve about 85psi in mine.

Check the air chamber isn’t full of lower leg fluid like mine was- this reduces the air chamber volume and makes the fork very progressive preventing you from using full travel.

theroadwarrior – Member
No low speed compression settings on an F-Series Fox

I can absolutely assure you, my F120 has.

My forks are the rc so i don’t have the compression.
Is it better to work off the sag measurement than a psi figure?
Does it matter what position you are in on the bike when you set the sag. e.g. standing up over the bars will probably put more weight on the forks than sitting down?

Ahh yes, I assumed the RL fork- i.e. open bath. Didn’t actually realise you could get an F-Series FIT… every day’s a school day.

I gave up setting the sag on my fork- loads o’ stiction meant I ended up with about 4psi to get the correct sag. I set mine to the recommended pressure in the end and fiddled 5-10psi either side until I was happy.

I’ve got two bikes with fox rl open bath forks. The newer set (140)have always seemed a bit disappointing with more stiction and seemingly ramping up quicker an not really giving much more travel than the 120’s. This despite doing an oil and wiper service when first getting them as nearly new.

Last night I looked at this again and let all the air out to check what station travel total would be and noticed that the last bit of station is only exposed when you pull down on the wheel (in a bike stand) – negative pressure?

Anyway it’s not scientific but after doing this then putting air pressure back up to just 65psi (way less than the 80-90 recommended for my heft) they felt brilliant last night. No stiction and really supple.

Worth a try maybe?

I’m running the Fox F125RL forks on my (2012) Trance at around 60psi which is well below the 60% weight guideline that was mentioned. Even then I never get the last inch of travel.

Last ride I was bimbling along the trail minding my own business when I went trough a puddle. It looked no different to the dozen other puddles I’d just gone through, but the front wheel sunk into the mud, hit a rock and I was thrown over the bars. Ironically I had a set of knee pads in my pack, which I was carrying for use on a section later in the ride when I thought I might crash! but I digress. Once I’d picked myself up and dusted myself down my first thought was “that should have used the travel at least”. But no, there the O ring sat, mocking me, a good inch from the top.

I did notice, when letting the air out to make sure that the fork could go all the way (it does with no air in) that some green oil came spurting out of the hole. I’ve also seen a few posts about oil getting past the seals and restricting travel. One mentioned just turning the bike upside down and letting the air (and some oil) out a few times, which sounds a bit crude, but is at least simple. So I might give that a try.

Cheers,

Andy

Andy – you almost certainly have what I had. The lower leg lube oil (30ml) works its way up into the air chamber which should just have 5ml of blue float fluid in it for lubrication.

If you’ve got green lube oil coming out the air cap then this is your problem.

You need a 26mm socket to take off the air top cap (Once you’ve let out the pressure) and then drain out the fluid. Replace with 5ml of float fluid and also put 30ml of lube oil in the lower leg and if it’s anything like mine it will feel like a totally different fork. Mine is now considerably more linear but still ramps at the end as it should. Last weekend at Antur Stiniog I was using full travel finally and the fork felt much plusher.. previously I reckon I was getting 80-90mm travel out of a 120mm travel fork.

Thanks. The oil that came out when I let the air out was certainly green and not blue, so I guess that’s pretty conclusive.

Since the bike is only a few months old I guess I should take it back to the shop and get them to take a look. But that means being without it for a while and I’ve got a shed full of tools (plus more years than I care to mention spent messing with road bikes), so it’s tempting to take a look myself.

Cheers,

Andy

I changed the oil and cleaned the wipers on mine the other day because they hadn’t been done for a while and wondered if that was contributing to the missing travel but it made no difference. When checking the pressure before some bright greeny yellow oil came out but when I removed the top cap to view into the air chamber there was definitely no oil from the lower leg. When I drained the lower legs all the oil that came out was the same colour (normal fork fluid colour). After putting the new oil in but before filling with air the forks sat with about 25mm of station hidden. When pumped up to what I thought was the correct 120psi all the travel is visible but the top 50mm not usable. They did compress through the full travel with no air in though so hopefully I just have too much air in. I’m going to let some out when I get home and ill report back later
Andy

Ahh yes, I assumed the RL fork- i.e. open bath. Didn’t actually realise you could get an F-Series FIT… every day’s a school day.

Mine are open bath and have compression damping.

Anyway, let all the air out the fork and see if you get full travel. If not, there’s probably too much oil in the damper. If it’s ok, it might be too much oil/ fluid above the air chamber – as theroadwarrior notes. I’ve seen suggestions that you can even reduce below 5cc of float fluid if you’re still haveing problems.

Right,
I let all the air out of the forks yesterday morning and confirmed that all the travel is available. I then put in the recommended 80 psi in for my weight taken from the fox website.
The forks felt like new (I serviced them last week). they were buttery smooth and I’m getting the full travel.
God knows why the giant handbook says to put 60% of your body weight in pounds in psi into the fork. With my weight this meant around 120psi.

Andy

Are you sure your Giant manual says “fork” and not “shock”? Its unusual for a bike manual to include the fork, as even the OEM fork varies from month to month.

If its shock, I could understand the instruction….

I booked my Trance (with its F125RL forks) in for a service next week, but being the curious soul I am I couldn’t resist a tinker over the weekend. I turned the bike upside down and let all the air out, along with a lot more than 5ml of greenish oil that came out too. Pumped it back to 65psi and took it for a ride. The forks felt fine (they always have) but if anything it was using less of the travel. Probably just because I was actually running at 50psi last week.

I’m 11st 11lb (165 lb) in my birthday suit and 60% would be around 100psi. So I’m running at not much more than half the recommended pressure and still not getting more than three quarters of the travel.

Of course it could just be that I’m a hopeless mincer, but the rear shock is running at 170psi (i.e. the recommended 100% of body weight) and the ring is pretty much always off the bottom of the shock after a ride.

I realise that all these body weight based settings are just a starting point and you should use sag, but getting an accurate sag measurement isn’t that easy. Mu best guess (from multiple readings) is that I have around 20% sag on the rear and 30% on the front, yet still bottom out the rear and never use more than 75% of travel on the front.

Cheers,

Andy

Definitely the fork. The book has Guidance on setting up the fork and the shock. It a little booklet produced by giant and was included in the handbook that came with the bike. The rear shock guidance recommends inflating to 100% of rider weight in pounds in psi. I might check and experiment with this when i’m happy with the front setup.

They’ve made a mistake there… 80 – 90psi is much more like it!

I have never heard of the oil in the air chamber problem but it seems to be the cause of my limited travel. How does the lubrication fluid work its way in to the air chamber???? Whenever I do a seal and wiper service I do notice that there appears to be less lubrication fluid in the air side- I guess now I know where it has been going!

There is a big thread on MTBR about it, although I don’t have a link sorry.

My (Limited) understanding is that there is a foam ring (Like the one below the lower leg dust wiper seal but much smaller dia) on the air piston designed to keep the air seal lubed. However what actually happens is over time as the fork moves through it’s travel the ring wipes lower leg oil into the air chamber. The 2012 forks do away with this and replace it with some sort of updated scraper seal I think.

Simply job to drain the excess out of the air chamber.. the trouble is knowing it needs doing in the first place!

theroadwarrior- if you drain all of the fluid out of the air chamber by depressing the air valve and compressing the forks does anything then need to be topped up again besides the normal lubrication fluid as you would with a dust wiper/ seal service?

You need 30ml of 10wt green fox oil in the sping side lower leg and 5ml of blue fox float fluid in the air spring chamber just for lube.. You’ll need a 26mm socket to take off the top cap so you can access the air chamber.