As I haven’t seen a “How To” for this subject and have had a slow leak from my front tyre for some time now, I thought I would have a go at resolving the problem and document it.
If you have an ongoing air leak check the basics before you start, i.e. confirm the tyre valve is not leaking, check the tyre for any punctures causing a slow leak and last but not least check the tension of your spokes.
If your spokes are loose ensure you tension them correctly (I am advised thecorrect tension is 6 to 7 Nm) and then retest the wheel/tyre for air leaks. This last point may have the affect of improving or deteriorating the seal at the leaking nipple, I have experienced both outcomes.
You can establish that you have a leaky spoke nipple by inflating the tyre to 50 psi and then submerging the bottom section of the tyre/wheel in a tray of water so that it is above the level of the lower spoke nipples. This is probably most easily done with the wheel removed from the bike.[You must be registered and logged in to see this image.]
NOTE: using a soapy water spray will not do the job like it might on a tyre leak, as often the spoke leak is very small and will require the wheel to be under the water for some time before the minor bubbles are evident. In my recent experience where I identified 10 of my front wheel spokes leaking, a couple were only evident after I observed the submerged spoke nipple for at least a minute.
Once you determine which spokes are leaking make sure you mark the individual ones that need to be repaired. I used zip ties or twisted wire to note the problem ones but anything will do.
Depending on the number and your skills, you are either going to dismantle the wheel and start again or just do the defective ones.
I choose to only do the spoke nipples I identified as defective as this allows me to do them one at a time and once re-tensioned correctly, avoids the chance of the rim being misaligned or distorted.
As they were spread around the wheel I started with one and then went to the other side of the wheel working in a clockwise direction. By alternatively working on spokes on the opposite side it reduces the risk of misalignment or rim distortion, if done one at a time the adjacent spokes when tensioned correctly will maintain the rim position.
Parts required: available from your Guzzi parts dealer
ß Spare rubber O rings (a few extra is sensible as you will see later).
ß Spare spoke nipple locking clips.
ß You might also want a few spare Spoke nipples (in case any are damaged).
ß Suitable lubricant grease to apply to rubber spoke seal O rings.
1. If doing more than a couple of spokes it is dramatically easier to remove the disc rotors especially on the front wheel but not as critical on the rear. Before removing the disc rotor, ensure you mark the wheel hub and rotor with aligning marks so they are re-installed in the original position, (I used paint dots for the marking). Also clean the wheel with warm soapy water or similar to make the process easier and reduce dirt from being caught in the sealing area.
2. Next remove the tyre valve insert to deflate the tyre and then break the bead on both sides of the rim (if you mark the tyre side wall next to the valve stem you can realign the tyre in its original position which will reduce the chance of the balance being altered). You can remove the tyre fully (if removed mark the rim for the direction of rotation) or as in the photos, remove one side which will give you enough room to remove the spoke nipple.[You must be registered and logged in to see this image.]
3. As you have already tensioned all of the spokes correctly select your first spoke nipple to be repaired. Remove the nipple safety clip
, I would do this with the rim lying on the ground so the clip doesn’t fly away in to the magical place where missing parts go to hide, these clips are easy to loose. It can be dislodged by tapping on the end with a small screwdriver.[You must be registered and logged in to see this image.]
4. Loosen the spoke nipple tension with a suitable spoke spanner, make sure the tool you use is the correct size so you don’t round off the nipple head.[You must be registered and logged in to see this image.]
5. Once loosened you can use an 8mm socket on the hex head to undo the nipple from the spoke and then remove the spoke nipple from the wheel rim.[You must be registered and logged in to see this image.]
6. If the spoke can be removed from the hub (this is not always possible depending on their position) this will allow you to clean the spoke and thread before reassembly. This should also and can be done, if the spoke has to stay in the hub.[You must be registered and logged in to see this image.]
7. When the nipple is removed from the rim lift off the O ring and be careful not to scratch the O ring recess, then clean the nipple with some alcohol based cleaner or similar, which will not leave a residue which could compromise the rubber O ring.
8. Also clean the hole in the rim with the same material and a clean coth so there is no residue left behind, this can compromise the sealing surface.
9. Once the parts are clean lubricate the nipple surface to allow the new O ring to be mounted (put the old one somewhere so that it isn’t mixed up with the new ones).[You must be registered and logged in to see this image.]
10. I used some electrical tape around the nipple to provide a smooth surface on which the O ring can slide to reduce the chance of any damage. (Obviously remove the tape after the tape O ring is installed).[You must be registered and logged in to see this image.]
11. Then ensure the inner surface of the rim around the hole is clean before applying the lubricant grease around the surface and inside the sealing hole where the O ring seats.[You must be registered and logged in to see this image.]
12. Clean the spoke thread and check that the nipple screws on to the spoke easily.[You must be registered and logged in to see this image.]
13. Once this is confirmed you can reassemble the pieces by centralising the nipple and gently pushing it through the hole so it is seated in the rim and start it on the spoke thread. Ensure the spoke is fully seated in the hub. Then slowly screw the nipple on to the spoke so it pulls gently through the rim until it is firmly seated.[You must be registered and logged in to see this image.]
14. Once this is done it is simply a matter of using a spoke wrench to fully tension the spoke, (between 6 to 7 Nm, do not over tension the spoke).
15. Finally install the securing clip to the nipple and then you can move on to the next one or refit and inflate the tyre.
16. Retest the tyre for any leaks before reinstalling the disc rotors and fitting the wheel to the bike.[You must be registered and logged in to see this image.]
Points to note:
• In my instance I replaced 10 seals, some of these involved fitting new nipples that I had as spares with O ring seals already fitted. (I will clean the old nipples and fit new O rings for future usage).
When I retested the wheel for leaks, 4 were defective and these were all new nipples I had installed. When I removed the tyre and checked them I found that 2 of the new seals had split and the other 2 had small sections missing, these were all new rubber O rings. I replaced the 4 with new replacement O rings, reassembled the wheel and when I rechecked for leaks, all was ok (Inspect each O ring before installation to ensure they are in a sound condition).
Moral of the story, when the spokes are repaired retest for leaks before any further reassembly and make sure you have sufficient spare O rings for this type of situation.
• I would suggest you borrow or obtain a spoke tension wrench for the job. These are not especially cheap but it is fairly likely you will use it more than once.
• Cleanliness is critical because the sealing surface is quite small so it would only require a small bit of grit to affect the seal.
• This is not an overly complex job if you take your time and have the right tools but it can be tedious, so be patient.
• Use a suitable industrial lubricant grease which is compatible with the rubber O rings. The one I used was Molykote 55 O ring Grease, recommended by Uzidzit.