[Closed] Erm, So, Suspension Tuning then...🥵

Simple solution - feed him moar pies and extra pudding, he'll then weigh enough to need some pressure.

Or.. talk to the folks at TFT or wherever who will tell you what they can do - stock air forks and shocks generally start to struggle below about 55-60kg.

Mrs_oab is a flyweight.

In forks I've mixed a slightly lighter oil in with the recommended oil weight - it's guess work but usually about 25%, we also run minimum pressure according to manual. Even then it can not be as plush as needed.

Rear shocks we just run as low as needed and (see my thread in a moment) keep bearings smoothly running.

Take him bikepacking and get him to carry all your kit too.

Or PM weeksy for some advice.

So it’s either friction or damping.

A service can help - less seal friction etc - but costs.

Changing the oil weight may help (is the rebound damping as open as possible already?)

Fork juice is cheap and can help.

I read it as a combination of friction and some 'hidden' pressure here and there. Both RS and Fox have minimum pressures, below which the fork doesn't work.

We also found that even light compression tunes = didn't work, hence my bodge of a bit of lighter oil to get it flowing more easily.

got Samuels shock tuned by J-tech which makes a world of difference. lower viscosity oil will affect the LSR but not much else.

It's a problem us light riders have. Suspension works better when there is more load to begin with, so any resistance caused by friction isn't noticeable.

My 130mm Pikes always sat 10mm into their travel due to the friction casing more force than the pressure at near full extension. This wasn't a pos/neg chamber issue. The forks just didn't like very low pressures. I ended up putting a 140mm air shaft in which made them 130mm with very low pressure.

This may not be a great solution but try putting a backpack on him with some small weights in there. Be good fitness training too.

A few rocks in his backpack?

Get him some knee pads (heavy ones if you want)

looking at the pics above the forks seem pretty deep in their travel? even if they are 100mm forks.

i dont think i run 30% sag on any fork i own. try less sag - 15% or something. remember youll need to reduce rebound and compression damping when you drop the air pressure.

maybe look at a coil fork if it still doesnt work properly? my kids are on coils and have no issues like this (yes its heavier - though but what is better? - suspension that works or extra weight?)

Shouldn't be using sag to tune suspension.

kids don't have enough weight to move coil forks well. If they are the cheaper end they have next to no damping.

Did you compress the fork up to 50% a few times to balance the negative and positive chambers?

i dont think i run 30% sag on any fork i own. try less sag – 15% or something. remember youll need to reduce rebound and compression damping when you drop the air pressure

In my opinion you are in the minority running only 15% sag. Pretty much all manufacturers suggest 20%-30% sag. But end of the day it’s what feels better for you that counts.

sag should be set with all the dampening at the full open setting. So compression damping at the minimum and rebound set to fastest.

Shouldn’t be using sag to tune suspension.

Yes you should, it’s the first step to adjusting your forks. Every suspension fork manual or setup guide I’ve read read regardless of manufacturer says to start with setting the sag then move on to adjusting rebound and compression settings.

Yes you should, it’s the first step to adjusting your forks. Every suspension fork manual or setup guide I’ve read read regardless of manufacturer says to start with setting the sag then move on to adjusting rebound and compression setting

You start with air pressure not sag. Sag is just ride height. 30% sag on one fork will not act the same way as another make because the air springs are different. Couldn't tell you what my sag is.

You start with air pressure not sag. Sag is just ride height. 30% sag on one fork will not act the same way as another make because the air springs are different. Couldn’t tell you what my sag is.

So how do you know what air pressure to put in? After all, 100psi in one fork will not act the same way as another make because the air springs are different.

Most full suss frames don't have a linear relationship between axle movement and shock compression, and will be designed around having the sag point of the shock at the appropriate point of the suspension travel - set too little or too much sag and your suspension won't work as designed.

I put 2.5wt in some Reba's for my eldest when she was ~8 and very, very low pressure and backed the damping way off, they also had a negative chamber which I deliberately used to reduce ride height.

Are you sure there's not a negative air chamber in the fork that you've not let some air out of?

But definitely back off damping and consider a lighter weight oil...

So how do you know what air pressure to put in?

you can use the guide on weight and air pressure as a start.

consider a lighter weight oil…

lighter oil has next to no difference on compression

@poah, the air pressure is setting the sag. Every bit of suspension literature I've read says to start by setting sag. On an air spring the sag is controlled by the air pressure. So you add some air pressure and check the sag, if not correct then make adjustments and recheck sag until its at the desired level.

@thegeneralist try getting your boy to bounce around on the bike a bit, this will cycle the fork and rear shock and rebalance the negative and positive air chambers and try setting the air pressure again with all the damping controls set to their most open position. Again cycle the fork and shock a few times to rebalance the pressures and then try taking the sag measurement. If they still doesn't work, it maybe time to talk to a suspension tuner to see of they can modify the fork and shock to work within a different weight range.

kids don’t have enough weight to move coil forks well.

my kids do - 9 and 12 - depends on teh spring weight you use obviously. one is on a 2008 marzocchi bomber (cant recall which version) and the other is on a rock shox tora uturn with a soft spring set at 100mm.

they are defo not using a spring for a 90kg rider! they may not be at 'manufactures sag' but hte forks definitely work for them - you can tell from teh dust rings after a sesh.

the older kids had a air fork and it seemed a bit divey - she complained about it feeling wierd. she rode the coil one and prefered the consistency. i was suprised she noticed as as she is only 12 and doesnt ride that much!

i also couldnt tell you how much sag i run. i pump it up to roughly 20-25% sag and adjust to suit based on feel. same with a sprung fork - you get the spring for your weight and then see how it feels and go up or down a spring weight to suit.

So you add some air pressure and check the sag, if not correct then make adjustments and recheck sag until its at the desired level.

@jairaj why would you check sag and what is the desired level of sag?

What is sag telling you that helps with tuning suspension?

I think you guys are basically arguing the same point. Setting sag isn't a way to get a good setup, it's just a way to get a not-terrible starting point. Same as using the pressure chart on the fork. Usually more effective ime, since the charts are sometimes absolute horseshit.

But they're both just start points.

I would got for less fork sag in the sitting position. You can see i your pics lots of fork compression, so perhaps too little air all round?

Fork service is worth it as well, new wipers and fresh oil always frees things up a bit and cheap / easy to do and same perhaps play with volume tokens - perhaps take some out?

but 35kgs is very light, perhaps just accept going to get less travel, or as above speak to JTech etc to see what they can do.

or the pie barm diet is the other option! 🙂