Instructions 4 – Front forks

The final stage of the build is the front forks.

Parts Used

1 * Front triples – SHP013
1 * Front fork damper mounts (pair) – SHP014
1 * Front hub – SHP012
2 * Alloy fork leg – CNC010
1 * Front axle – split – CNC008
1 * Front king pin – CNC011
2 * Carbon fork leg – FF001
2 * Igus bush for fork leg – FF002
2 * Front wheel bearings – BRG001
2 * Fork damper – FF003
6mm shims – SPR004

Build Tips

i) The forks are the trickiest part of building any bike and the key is PATIENCE. Take your time and allow for a little fettling and you will be rewarded with some nice smooth forks that are low maintenance and do not bind.
ii) There is a tolerance on the dampers and before you assemble the forks check that the dampers are a nice sliding fit in the carbon tubes. If they are over sized then they will need to be skimmed in a lathe. It is easy to do yourself but if you do not have access to a lathe then give Kamtec a call to sort it out.

iii) You can use an M3 taper tap to start the threads off in the printed parts but don’t over do things, as it’s best to have the threads tight than loose. Alternatively run a 2.5mm drill in to the holes to clear out any unfused nylon and then it should be easier to start the threads.
iv) If you need to remove any of the fasteners secured with thread lock and they seem stuck then you need to apply some heat to melt the thread lock, eg with a small gas torch.
v) The bearings are normally a nice press in nylon parts. If they are loose then you can secure them with a tiny drop of super glue gel and if they are overly tight then use a hobby knife to carefully chamfer the outside of the hole a little and ease them in.

Assembly

It is worthwhile reading the building tips before you do any assembly of the forks, especially (i) and (ii).

1) The Igus bearings need to to be fitted to the carbon fork tubes. It’s always worth checking the ends of the fork tubes to ensure there’s no burrs and clean them up if necessary.I normally then just tap the bushes gently home with a rubber mallet.
2) The fork tubes can then be fitted to the triples and clamped in place with two M3*10 low cap head screws. The 14mm hole in the triple may need a little fettling. I run a 14mm straight rearmer through mine and you can also use a round file. You want the tubes as a nice tight fit – rather than loose. You don’t need to remove the leg to service the fork so a tight fit does not cause any problems and is better than loose. Again I gently tap the legs in place with a rubber mallet if needs be.
3) Prepare the dampers. The dampers come with a range of springs and you need to fit the hardest one and ‘fill’ with 10 weight oil.  The dampers are an emulsion type so there is no diaphragm to cater for the shock shaft as it moves in and out. Hence when filling the damper fill it to a little way from the top and then gently screw the cap down but not enough for the o-ring to seal. Then gently compress the shock, allowing any excess oil to come out of the unsealed cap. Once you happy you can extend the shock again and then fully tighten the cap. If you have too much oil in the damper then, once assembled, you won’t be able to fully compress the shaft. If you haven’t used enough oil then the damper will feel a little lumpy and not nice and smooth. It sounds harder than it is and once you’ve got the hang of it then it’s easy. Some kitchen towel is handy for catching the excess oil as you compress the shock when filling it.
4) Next thread the ends of the shock shafts on to the alloy fork legs. It is important that you use some strong thread lock for this.
5) The 3D printed damper mounting caps can now be pressed on to the tops of the dampers.
6) The fork legs are then lowered in to the carbon tubes through the top of the triples and heal in place by an M3*22 button head screw that goes through the upper triple and the hole in the damper/fork cap. If you need to work on your forks then you remove the M3*22 bolts and lift the legs out upwards and hence the triples and carbon tubes stay as one assembley.
7) Press the wheel bearings in to the front hub.
8)  The front hub can then be mounted using the split front axle. The shorter section of the front axle aligns with the shorter side of the hub and the longer section of the axle aligns with the longer side of the hub (on which the wheel is mounted). See the photo below for details. The axle is then fixed to the fork legs using an M4*10 button head bolt each side. Tip – Once assembled the hub should float a little bit on the axle. Use some 6mm shims to adjust this – it normally takes 0.3-0.5mm of shims and you want to aim for as little float as possible whilst ensuring the hub rotates freely and the forks do not bind. Rather than put all the shims on one side, try to shim each side evenly to keep the front wheel centred.Again remember to be patient as once it is done, you won’t have to do it again! If you are going to be running Roadies, rather than GRPs, then remember to fit the optional Roadies front spacer at this point.
9) Fit the forks to the headstock and retain with the king pin and two M3*4 grub screws that thread through the holes on the front of the top and bottom triples. Tip – When aligning the triples with the headstock it will initially feel like the fit is too tight. You need to ease the triples on and once you get the hole in the triples aligned with the hole in the 5mm headstock bearings it will all feel nice and free. This is because the centre of the bearings are recessed a little bit. Make sure you aren’t too heavy handed and don’t be tempted to remove any material from the triples to make the initial fit easier. Once it is all lined up then it should be all nice and free with no slop.
10) Add the steering damper. The M3 balljoint is threaded in to the triples and then the damper just pops on. I always put it on the right hand side.

 

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