What to the firms e.g. TFtuned actually do in a standard shock service (not the push tuning or similar)?

Is it much else apart from the air can service with new seals?

Cheers,
J

Yes, what I do is completely strip the shock, with the seals inside the damper unit being replaced as well as the oil and nitrogen gas charge (if applicable)
There are a number of other things that get done to rectify any manufacturing defects to get the shock to work better too.

Yeah they get right into the damper, clean that out, put in new seals & oil and rebuild. Takes around half an hour on the jobs I’ve seen.

Time of the job depends on the shock (and technician/engineer 😉 )

ah ok, so how do you know when the damping needs a service? Is it just on feel, or will it start making funny noises?

Stick to the service guide lines and you should be ok, squelching and inconsistant damping are a good indicator that the unit needs some attention.
The oil in the unit will ‘go off’ over time leading to a slow reduction in performance, which you won’t necessarily notice.

The main issue with leaving the shock unitl it ‘blows’ is that this may cause other damage within the shock and consequently cost more to fix.

I just changed the oil in my DHX air it wasn’t too hard. It was messy but that is to be expected as I didn’t have the correct tools that the likes of LoCo use. It took me about an hour overall but I was taking my time as I hadn’t done it before. Problem with a home service on a DHX is that you can’t buy the replacement seals from mojo so if you want to do the job properly then you will need to take out all the o-rings and go to a local supplier to replace them. It should be cheap but will be a bit of a hassle. Not sure if I would attempt to service the likes of an RP23 due to the nitrogen but I would definitely consider it.

My shock feels loads better than it did previous to the oil change I just hope it keeps feeling better, until I am ready to do a full seal change too.

well its an rp23 that i’ve got. Came on a second hand frame so im not sure of the service history, if any! Nothing feels wrong with the shock but I’ve bought a seal kit now so ill change those and see if it makes any difference

out of interest what role does the nitrogen gas charge play in shocks which have it?

It is used to fill the IFP.

It is used to fill the IFP

Well that’s cleared that up then 😕 wot’s an IFP?

Ifp is a piston in the damper. Oil on one, side gas on the other.

On some shocks e.g. boost valve rp23 it is used to adjust damping rates depending on the position of the shock through it’s travel.

I *think* on others e.g the old style rp23 it is mainly used to prevent the oil cavitating hence when the damper loses it’s charge it can’t function properly.

It’s used to keep the oil under pressure and stop the oil from frothing or cavitating to keep damping consistent. For the same reason that a bottle of coke can be shaken when it’s new and will barely fizz, but once it has been opened and closed again (under less pressure) it will fizz like crazy…

IFP = Internal floating piston.

I could be wrong but without the IFP and therefore the nitro or air the shock would effectively hydrolock because there needs to be some sort of expansion room. The pressure and volume of nitro or air that is in that part of the shock effects how the shock feels in terms of damping performance. If there is a higher pressure you get stronger compression damping etc.

The IFP is floating because there is nothing mecanical holding it in place apart from the O ring that forms the seal between the gas and the oil. The IFP moves forward and backward slightly when the shock is in action.

The reason most shocks/manufactures use nitrogen is because there is no moisture in it and it is relatively although not totally inert. Air is used in some shocks such as DHXs and I think some rock shox use it but Im not sure. The theory is that using nitro is more predictable because it is just one gas and with air there are a number of gasses and some moisture and that could adversely effect the shocks performance. IMO probably not enough for a normal person to notice tho.

You go in with your bike and they go boooooooo!

Nitrogen is more thermally stable than air too, I.E less affected by increses in temperature.
The IFP does affect damping in relation to the pressure behind it, it also stops the shock cavitating and giving inconsistant damping.