Pace RC35MXCD rebuild help

[c33]

Hi folks, I'm a little stuck trying to rebuild some folks I got recently, I've got to the point that the elastomers are stripped out, and the left hand stanchion is totally stripped down. That was nice and easy. However, the skewer on the right side moves up and down freely and adjusting the little dial at the top doesn't seem to have any effect on the movement of the skewer and I can't figure out how to strip it any further it investigate. There is a button head fastnener on the top of the dial but trying to unscrew that seems to turn the whole of the internal gubbings. Any clues?

Regards
Iain

 

[Adam_S]

Sounds like the damper needs an oil change.

If it's anything like the RC36 that same along a year later, you'll first need to undo the little allen bolt on the top of the damper cartridge. The damper adjustment dial should then come off exposing the cartridge itself. There should be a c clip holding the top of the damper on. Please remove this with a proper set of circlip pliers, not some tiny allen keys and a screwdriver. Please don't ask me how I know about that.

With the top of the damper off, hold the fork upside down and pump the push rod for the damper up and down until all the oil has drained out. According to this it needs 50ml of 5wt damper oil. You can get this from any half decent motorbike shop or possibly somewhere like Halford's. Go to a chemist and get a large plastic syringe and use it to fill the damper up with fresh oil. Reverse the steps you followed to disassemble the fork.

Also get a grease gun and some RC-7 grease off of Pace's website. The fork will run much nicer if you give it a couple of squirts of grease in through the grease port before every ride.

 

[c33]

Thanks Adam, I've got all that open now...
However...the skewer still wont come out. The chamfered piece at the bottom of the stanchion does that unscrew? It looks like there could be another top out rubber in there like on the non-damper side.
Regards
Iain

 

[Adam_S]

Why do you want to take that out? As long as you've got the top of the damper cartridge off you should be able to do an oil change. For the rest, just give it a good wipe down and pack it full of fresh grease and you should be fine.

 

[c33]

Hi Adam, the skewer on that leg tops out with a metallic clunk so it there was a top out rubber in there it is no longer!
Regards
Iain

 

[Adam_S]

Isn't there normally an elastomer stack on there?

 

[KDM]

http://www.retrobike.co.uk/gallery2/v/M ... rs+Manual/

 

[Adam_S]

Can I just clarify that it's these forks we're talking about?

http://www.shop.allthingsbikes.com/all- ... ike-forks/

What's inside the top part of the upper fork leg on the damper side basically looks like this:

The skewer goes up through a seal into the damper cartridge. On the end of the skewer is a little piston. When the fork compresses it pushes the piston through the oil in the damper cartridge. This opens up a little valve on the underside of the piston which lets the oil through in a controlled way giving compression damping. When the fork extends again the piston is dragged back the other way which closes the valve and forces the oil through another channel in the side of the cartridge. By fiddling around with the dial on the top of the fork you can change the amount of oil that can flow through this channel altering the amount of rebound damping.

I don't really know what's stopping the skewer from coming out of the cartridge altogether but I'd guess that there are some little metal circlips inside the damper somewhere which go around the skewer and keep it in. It may be possible to disassemble this with sufficient determination but it's really not a good idea. The skewer passes through a seal in the bottom of the cartridge and if you do manage to get it out, getting it back in again without damaging the seal may be problematic.

As you can see on my crappy sketch, there is nowhere for a top out bumper to go inside the damper cartridge so don't worry if there doesn't appear to be one. The elastomer stack that sits on the lower part of the skewer will stop the fork from bottoming out completely. Unlike a coil spring, the elastomer never really fully compresses.

The thing inside the non-damper side isn't really a top out bumper. It's more there just to stop the top part of the skewer from rattling around causing a nuisance.

Hope that helps.

 

[justbackdated]

Re:

The damper cartridge in the RC35 MXCD has no topout bumper under the piston. The piston is screwed to a short damper rod which goes though a seal in a hole in the base of the [VERY brittle] acetal cart body. the rod is then screwed and locknutted to the skewer rod which in turn passes through the base plug of the outer stanchion and sticks out where you fit the elastomers etc. The base plug of the stanchion is bonded in and not removable. All the cart, rods etc. come out of the top of the stanchion once it has been removed from the crown and the elasto taken off the skewer. On no account try to pry the top of the cart body out; it will break and they are very rare.

The safest way to pull the damper is to refit the control valve and circlip[sharp side up] and fit a bolt in the adjuster lever hole and use it as a puller. Removing the cart is the only way to replace the 3 seals in the body that have probably failed by now, hence the lack of damping oil. The oil controls the damping by being pushed by the piston though an adjustable[by the control valve] hole in the cart body side and returning through another hole at the base 'behind' the piston. The reed valve[weak and probably broken] under the piston is purely a safety valve to allow bypass of the oil if the piston is moving too fast to push the oil through the hole if the fork hits something big and fast.

Hope that all helps, let me know if you would like it rebuilding, I have all the seals, oils, Loctites and greases that are required to do the job fully

Cheers
Tim

 

[c33]

Thanks Tim...I may well be in touch - it needs elastomers anyway. Could you PM some contact details.
Regards
Iain