Hi

I have a set of MX Comps from a few years ago (Black with red decals) on my Inbred and I have put up with the sh*te performance for long enough. They seem okay whilst going downhill, but when you climb they are APPALLING !!! Like a bouncy pair of pogosticks. Utter crap. What do I do ?

They have 2 air valves (Schrader) on the top of each leg. On the right hand leg, they have a sticker saying internal rebound adjustment and and + – arrow but when you take off the red anodized aluminium cap there is only the valve. There are 2 bolts on the bottom of the legs but they look like they hold everything together.

Now I am 90kg and they feel like they are set up for my son. What do I do? I have a shock pump, but it was for my old RockShox Duke XC's which if I remember correctly had a huge high pressure requirement. Do I use a track pump and if so what pressure ? And how do I access this internal rebound thingy ?? And do I want + or – ?? Sorry complete Luddite Fork Numpty !

Thanks guys
Sean

I've got a set of these which I've run for years without any problems – the older ones are great forks if they're set up correctly. From memory I think you need to screw off the valve to get at the rebound adjustment. The forks came with a "wand" which you could then use to adjust it.

Have got a manual for them somewhere…. <shuffles off to attic>

Have you changed the oil? It deteriorates over time and damping is reduced

IIRC the rebound adjuster is under the top cap – you need to take that off using the correct socket – 24 mm and then a way down inside the fork leg is the adjuster – an allan bolt. You need more rebound.

Set up the air pressures to give the correct amount of sag.

Edit – thicker oil will give more compression damping as well which might help

Found the manual… if they're the MX Comp Airs, and your 90Kg, you need 2.9 to 3.8 bar (42-52 psi) positive air pressure. This is in both legs if they are the non ETA version. Right leg only with ETA. I used a standard shock pump. Recommended sag for XC is 15-20%.

For the rebound adjustment, pretty much as TJ says above ( the wand thing I referred to earlier is basically a really long, bar-shaped hex key) – if it's the non ETA version with no external adjustment, you need to take the dust cap off the right leg and first let the air out. You then want to use a socket set or 21mm cap key to remove the internal cap. Insert the long hex key into the adjuster inside the fork – turn it clockwise to reduce hydraulic damping, counter clockwise to increase. Once done, put it all back together, and re-inflate.

The point about oil is a good one – have to admit that I haven't changed mine in the 4 or 5 years I've had the fork, and haven't noticed any deteriorations (the MX Comps are always a bit squelchy when cold) but may be worth doing if you can't get it sorted.

The rebound won't have much of an impact on pedal induced bob i'm afraid. More shock pressure will reduce the bob, but will reduce the sensitivity of the fork. You should set up the air pressure or about 20% sag when stood on the pedals in 'attack'(!) mode.

When pedalling uphill aim for a smooth pedalling motion with a fairly brisk cadence, and avoid standing to pedal. This will help reduce the bob.

Thanks guys, I'll get to it. As for my pedalling style, as my name suggests I am a big time roadie and a real spinner these days which is why I struggle so badly with the boingy boingy nature of these bad boys !

Ta again.
S

like what the other say. IMO you want to run a little more than 15% sag. Although its personal preference, I found my MXC's to be very linear once the were moving.

The MXC's are pretty basic forks and you're never going to get them to resist pedal induced bob particularly well, but if you're running the correct pressure for your weight it can be minimised.

I'm about 93kgs and found that the standard 7.5 wt oil was too light to adequately control the rebound at the pressures I needed. Theres not much rebound adjustment provided by the internal ports anyway, so I put 10 wt oil in and they were much improved.

YMMV

MXComps are THE SHIZZLE!

bullet proof, and can be adjusted to the ends of the earth if youve got a certain amount of mechanical sympathy and dont mind getting the bathroom oily.

though admitadly they do lack anti pedal bob valving or lockout, but ime, on forks of that price range, its the lockout that explodes in a fireball first and makes the fork useless. better to do without.

compression can be adjusted by mixing oil to the consitency that works best for you (heavier oil slows it down, lighter speeds it up)

rebound is THEN adjusted via the internal adjuster, for which you need the long brass wand jobby, and you can make it either a bit slower, or a bit faster than the compression.

spring rate and curve can be djusted by fiddling the oil levels an air pressures in both legs. which is kind of tricky to explain:

higher oil levels, mean the curve ramps up quicker, higher pressure raises or lowers the spring (obviously)

by fiddling the two, for example, you can have twitchy linear top stroke, and then at 60% travel, have it ramp up quite quickly to stop it blowing through the last 30% of travel and bottoming out.

or example 2, on my lasses bike, who doesnt weigh much, and doesnt ride hard, we lowered the oil levels right down* so that its very sensitive and linear, so she gets all 105mm of travel, without having to batter down descents.

(*just make sure the oil is above the valving)

at the very least, if your 90kg, i would agree with changing the oil to a 10wt or 15wt oil to slow it down.
easy to do!, take the top caps off with a 21mm socket, and pour it out!!
cycle the fork up and down a few times with it upside down to clear out the valves, and then put in the same quantity as removed, of heavier oil!.
(if you dont want to measure it, the quantity is, with the fork compressed, crown down to the seals, to approximatly 3cm below the level of the threads of the top caps (iirc)

you can make up intermediate oil weights if you feel the need: 1 part 10wt and 1 part 30wt oil = 20wt oil etc etc

Thanks again guys, where do I buy this heavy oil ??

Also has anyone got a wand thingy that they could lend me ? I'd happily pay postage and buy the guys a beer, or we could meet in London and I'd buy you a beer, or I live in Harpenden so anywhere near is good for meeting !

S

both can be bought/borrowed from your LBS.
they may even give you a rebound wand, as they often get taken out of the boxes when the forks are sold.

size of the adjuster depends on the age of the fork.

Fork oil can be bought from any motorcycle shop or such places as halfords.

an allan key socket on a long extension will do