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Mechanics Quick Question Thread [Ask Questions Here]
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Posted: Aug 18, 2022 at 2:41 Quote
gabriel-mission9 wrote:
davetvr wrote:
Looking for some advice on a Rockshox Monach Debonair RC3 fitted to a Canyon Strive.

Symptoms: During compression there is a sudden change in compression stiffness.
As the shock is compressed (even really slowly), the spring stiffness suddenly increases.

This is evident with the shock fully depressurised almost like the sudden change is more to do with the damping system rather than the air spring. I'm thinking that maybe a seal or port has a problem.

We've done a 100 hour service on the main shock and still exhibits the same problem, The only parts we haven't touched are the bound and rebound adjustment systems.

Any suggestions welcomed,
cheers,
Dave

Possibilities:

If the shock has recently leaked a load of oil (either out through the rebound adjuster assembly, or into the inside of the air can), then the IFP will have moved up the damper body to compensate. If this happens, the main piston will crash into the IFP somewhere in the stroke, and you will feel a very sudden increase in springrate. This will also likely (depending on the exact layout of the internals, which RS in their wisdom make various wild changes to every now and then) be doing pretty catastrophic damage to the rebound shim stack.

If the nitrogen has leaked from behind the IFP into the damper fluid, this will cause really inconstant damping. At first you will get the symptoms you are describing, with a sudden and significant change to the damping force as the piston hits the surface of the damping fluid. After a few bounces the damper fluid will become aerated and damping will get a bit more consistent, (although way too underdamped) until you leave the shock for long enough that all the air settles out of the fluid again after a few minutes and the symptoms return. If this is your issue, any movement of the suspension will make a horrendous sucking/squelching noise.

Finally, if your particular monarch has a "dish valve" type lockout assembly, it is possible the valving has worked free from the top of the piston, and is randomly activating/deactivating itself at various points in the stroke, whenever the valve plate happens to float close enough to a port to block it temporarily.

It could also be other things, Monarchs are pretty mental on the inside. I'm not sure what drugs Rockshox engineers were on when they designed the monarch platform, but they must have been strong ones... A full service/rebuild on the damper may fix the issue. However, Rockshox being rockshox, it's not unlikely that the £5 part required to fix the thing either isn't something they want to sell, or they will sell you it but you have to wait for 2024 for them to actually get round to manufacturing it.

If you have the cash, I'd strongly suggest upgrading the shock to something more robust. Fox CTD's are incredibly reliable little shocks if you are on a budget. If you aren't on a budget then the world is your oyster. If you aren't inclined to do that, send the monarch off to a good service center, who will be able to have a look inside the damper before advising you further.

The shock was just rebuilt by a 13 year old who's not that sh*t hot on the level of attention to detail that's required to rebuild this type of thing. With zero pressure in the main can you can definitely feel the change in damping force so my guess is that there is still air in the oil system.
Also need to service the bound and rebound systems.

Posted: Aug 18, 2022 at 3:36 Quote
davetvr wrote:
gabriel-mission9 wrote:
davetvr wrote:
Looking for some advice on a Rockshox Monach Debonair RC3 fitted to a Canyon Strive.

Symptoms: During compression there is a sudden change in compression stiffness.
As the shock is compressed (even really slowly), the spring stiffness suddenly increases.

This is evident with the shock fully depressurised almost like the sudden change is more to do with the damping system rather than the air spring. I'm thinking that maybe a seal or port has a problem.

We've done a 100 hour service on the main shock and still exhibits the same problem, The only parts we haven't touched are the bound and rebound adjustment systems.

Any suggestions welcomed,
cheers,
Dave

Possibilities:

If the shock has recently leaked a load of oil (either out through the rebound adjuster assembly, or into the inside of the air can), then the IFP will have moved up the damper body to compensate. If this happens, the main piston will crash into the IFP somewhere in the stroke, and you will feel a very sudden increase in springrate. This will also likely (depending on the exact layout of the internals, which RS in their wisdom make various wild changes to every now and then) be doing pretty catastrophic damage to the rebound shim stack.

If the nitrogen has leaked from behind the IFP into the damper fluid, this will cause really inconstant damping. At first you will get the symptoms you are describing, with a sudden and significant change to the damping force as the piston hits the surface of the damping fluid. After a few bounces the damper fluid will become aerated and damping will get a bit more consistent, (although way too underdamped) until you leave the shock for long enough that all the air settles out of the fluid again after a few minutes and the symptoms return. If this is your issue, any movement of the suspension will make a horrendous sucking/squelching noise.

Finally, if your particular monarch has a "dish valve" type lockout assembly, it is possible the valving has worked free from the top of the piston, and is randomly activating/deactivating itself at various points in the stroke, whenever the valve plate happens to float close enough to a port to block it temporarily.

It could also be other things, Monarchs are pretty mental on the inside. I'm not sure what drugs Rockshox engineers were on when they designed the monarch platform, but they must have been strong ones... A full service/rebuild on the damper may fix the issue. However, Rockshox being rockshox, it's not unlikely that the £5 part required to fix the thing either isn't something they want to sell, or they will sell you it but you have to wait for 2024 for them to actually get round to manufacturing it.

If you have the cash, I'd strongly suggest upgrading the shock to something more robust. Fox CTD's are incredibly reliable little shocks if you are on a budget. If you aren't on a budget then the world is your oyster. If you aren't inclined to do that, send the monarch off to a good service center, who will be able to have a look inside the damper before advising you further.

The shock was just rebuilt by a 13 year old who's not that sh*t hot on the level of attention to detail that's required to rebuild this type of thing. With zero pressure in the main can you can definitely feel the change in damping force so my guess is that there is still air in the oil system.
Also need to service the bound and rebound systems.

I'm mad impressed that a 13 yr old even got the thing vaguely functional. Defo don't be too hard on them for not nailing it first time. Most cytech qualified bike mechs with years of experience dont even know the difference between an air can and a damper service.

But also yeah, it definitely sounds like it needs to be opened up again.
As for servicing the adjusters, you will NEED shaft clamps to complete this. DO NOT let little 13yr old try and remove the shaft by gripping it in some old innertube and a clamp. Ppl always try this. It never works.

IFP height and pressure is critical also. Measure it with an accurate tool.

Posted: Aug 18, 2022 at 6:25 Quote
TimMog wrote:
gabriel-mission9 wrote:
TimMog wrote:
I don't disagree, I'm baffled. I'll try and take photos later, but it's a Hope Pro 4 hub

This is a long shot, but Hope hubs are extremely adaptable so it's worth asking...
Is the hub definitely set up for 15mm boost? The hubs are available in boost and non-boost versions, and with a whole host of possible end caps.
If your hub is non-boost, and/or set up for a 20mm axle, this could cause the issue you are describing.

Yep, definitely the right hubs and endcaps for my fork. I bought the wheels and forks together from a friend, and it was fine for the last year, this issue has only happened recently

Follow up, I just put a new tyre on there and now everything is dead bang centre. I can't explain that one, the old tyre leant to the same side regardless of which way round the wheel was put.

Either way, all sorted.

Posted: Aug 18, 2022 at 12:56 Quote
gabriel-mission9 wrote:
davetvr wrote:
gabriel-mission9 wrote:


Possibilities:

If the shock has recently leaked a load of oil (either out through the rebound adjuster assembly, or into the inside of the air can), then the IFP will have moved up the damper body to compensate. If this happens, the main piston will crash into the IFP somewhere in the stroke, and you will feel a very sudden increase in springrate. This will also likely (depending on the exact layout of the internals, which RS in their wisdom make various wild changes to every now and then) be doing pretty catastrophic damage to the rebound shim stack.

If the nitrogen has leaked from behind the IFP into the damper fluid, this will cause really inconstant damping. At first you will get the symptoms you are describing, with a sudden and significant change to the damping force as the piston hits the surface of the damping fluid. After a few bounces the damper fluid will become aerated and damping will get a bit more consistent, (although way too underdamped) until you leave the shock for long enough that all the air settles out of the fluid again after a few minutes and the symptoms return. If this is your issue, any movement of the suspension will make a horrendous sucking/squelching noise.

Finally, if your particular monarch has a "dish valve" type lockout assembly, it is possible the valving has worked free from the top of the piston, and is randomly activating/deactivating itself at various points in the stroke, whenever the valve plate happens to float close enough to a port to block it temporarily.

It could also be other things, Monarchs are pretty mental on the inside. I'm not sure what drugs Rockshox engineers were on when they designed the monarch platform, but they must have been strong ones... A full service/rebuild on the damper may fix the issue. However, Rockshox being rockshox, it's not unlikely that the £5 part required to fix the thing either isn't something they want to sell, or they will sell you it but you have to wait for 2024 for them to actually get round to manufacturing it.

If you have the cash, I'd strongly suggest upgrading the shock to something more robust. Fox CTD's are incredibly reliable little shocks if you are on a budget. If you aren't on a budget then the world is your oyster. If you aren't inclined to do that, send the monarch off to a good service center, who will be able to have a look inside the damper before advising you further.

The shock was just rebuilt by a 13 year old who's not that sh*t hot on the level of attention to detail that's required to rebuild this type of thing. With zero pressure in the main can you can definitely feel the change in damping force so my guess is that there is still air in the oil system.
Also need to service the bound and rebound systems.

I'm mad impressed that a 13 yr old even got the thing vaguely functional. Defo don't be too hard on them for not nailing it first time. Most cytech qualified bike mechs with years of experience dont even know the difference between an air can and a damper service.

But also yeah, it definitely sounds like it needs to be opened up again.
As for servicing the adjusters, you will NEED shaft clamps to complete this. DO NOT let little 13yr old try and remove the shaft by gripping it in some old innertube and a clamp. Ppl always try this. It never works.

IFP height and pressure is critical also. Measure it with an accurate tool.

Yeah, he's done very well to get this far Smile just needs a bit of support, quite proud of him I rebuilt a motorbike engine and gearbox at that age...
I machined a shaft clamp for the main damper shaft and using a mitutoyo calliper to set depth of the IFP.

O+
Posted: Aug 18, 2022 at 13:38 Quote
Anyone have tips for fixing the black surface treatment on seatposts that have worn off? Specifically I have a OneUp post that I scratched to hell when it was on a different frame with deeper insert.

Posted: Aug 18, 2022 at 13:39 Quote
davetvr wrote:
gabriel-mission9 wrote:
davetvr wrote:


The shock was just rebuilt by a 13 year old who's not that sh*t hot on the level of attention to detail that's required to rebuild this type of thing. With zero pressure in the main can you can definitely feel the change in damping force so my guess is that there is still air in the oil system.
Also need to service the bound and rebound systems.

I'm mad impressed that a 13 yr old even got the thing vaguely functional. Defo don't be too hard on them for not nailing it first time. Most cytech qualified bike mechs with years of experience dont even know the difference between an air can and a damper service.

But also yeah, it definitely sounds like it needs to be opened up again.
As for servicing the adjusters, you will NEED shaft clamps to complete this. DO NOT let little 13yr old try and remove the shaft by gripping it in some old innertube and a clamp. Ppl always try this. It never works.

IFP height and pressure is critical also. Measure it with an accurate tool.

Yeah, he's done very well to get this far Smile just needs a bit of support, quite proud of him I rebuilt a motorbike engine and gearbox at that age...
I machined a shaft clamp for the main damper shaft and using a mitutoyo calliper to set depth of the IFP.

More kids need adults like this in their lives. You're teaching the man (boy) to fish and that is so much more valuable than being given a fish. Not saying we all need to be master bike mechanics before we finish puberty but having someone who can support a young person to pursue something technically difficult that forces them to problem solve, think critically etc is rare AF. I aspire to give my sons and daughters that level of engagement and provide support for them to pursue their passions.

I salute you sir. Salute

Posted: Aug 18, 2022 at 14:02 Quote
mtb-thetown wrote:
Anyone have tips for fixing the black surface treatment on seatposts that have worn off? Specifically I have a OneUp post that I scratched to hell when it was on a different frame with deeper insert.

It's most likely anodised, so apart from dismantling it and getting it professionally re-anodised, your choices are a) live with it, or b) touch up paint

O+
Posted: Aug 18, 2022 at 19:35 Quote
TimMog wrote:
mtb-thetown wrote:
Anyone have tips for fixing the black surface treatment on seatposts that have worn off? Specifically I have a OneUp post that I scratched to hell when it was on a different frame with deeper insert.

It's most likely anodised, so apart from dismantling it and getting it professionally re-anodised, your choices are a) live with it, or b) touch up paint

Sorry, by fix I meant what touch up paint, or other techniques, do people recommend? Sharpie? Spray paint? Paint pen?

Although I didn't think of re anodizing. Maybe in red to match other bits? That would be awesome

Posted: Aug 18, 2022 at 19:46 Quote
mtb-thetown wrote:
TimMog wrote:
mtb-thetown wrote:
Anyone have tips for fixing the black surface treatment on seatposts that have worn off? Specifically I have a OneUp post that I scratched to hell when it was on a different frame with deeper insert.

It's most likely anodised, so apart from dismantling it and getting it professionally re-anodised, your choices are a) live with it, or b) touch up paint

Sorry, by fix I meant what touch up paint, or other techniques, do people recommend? Sharpie? Spray paint? Paint pen?

Although I didn't think of re anodizing. Maybe in red to match other bits? That would be awesome

There are some products that are used in industry specifically for touching up anodizing, but most of them are pretty weird, not easy to get in non-industrial quantities, and never look perfect anyway. I’d go with black sharpie and see if you can live with it before going down that route.

Posted: Aug 19, 2022 at 2:11 Quote
davetvr wrote:
gabriel-mission9 wrote:
davetvr wrote:


The shock was just rebuilt by a 13 year old who's not that sh*t hot on the level of attention to detail that's required to rebuild this type of thing. With zero pressure in the main can you can definitely feel the change in damping force so my guess is that there is still air in the oil system.
Also need to service the bound and rebound systems.

I'm mad impressed that a 13 yr old even got the thing vaguely functional. Defo don't be too hard on them for not nailing it first time. Most cytech qualified bike mechs with years of experience dont even know the difference between an air can and a damper service.

But also yeah, it definitely sounds like it needs to be opened up again.
As for servicing the adjusters, you will NEED shaft clamps to complete this. DO NOT let little 13yr old try and remove the shaft by gripping it in some old innertube and a clamp. Ppl always try this. It never works.

IFP height and pressure is critical also. Measure it with an accurate tool.

Yeah, he's done very well to get this far Smile just needs a bit of support, quite proud of him I rebuilt a motorbike engine and gearbox at that age...
I machined a shaft clamp for the main damper shaft and using a mitutoyo calliper to set depth of the IFP.

Excellent work!
I rebuild motorbikes as a hobby. (just finished a '64 Norton 650 and it's flippin lovely), and just cos im a dick... I'd say rebuilding gas charged suspension is easier to mess up than rebuilding engines and gearboxes. I reckon the kids got you beat lol lol

Posted: Aug 19, 2022 at 9:30 Quote
melanthius wrote:
mtb-thetown wrote:
TimMog wrote:


It's most likely anodised, so apart from dismantling it and getting it professionally re-anodised, your choices are a) live with it, or b) touch up paint

Sorry, by fix I meant what touch up paint, or other techniques, do people recommend? Sharpie? Spray paint? Paint pen?

Although I didn't think of re anodizing. Maybe in red to match other bits? That would be awesome

There are some products that are used in industry specifically for touching up anodizing, but most of them are pretty weird, not easy to get in non-industrial quantities, and never look perfect anyway. I’d go with black sharpie and see if you can live with it before going down that route.

Probably won't be able to do much as the sharpie will just rub off. I would order an Stanchion from one-up and a service kit to replace the pins and bushings.

Posted: Aug 19, 2022 at 10:36 Quote
What's the trick to remove the axle from my hub (Dartmoor K-Drive)? I'm trying to replace the hub bearings but can't seem to remove the axle. Thanks!

Posted: Aug 19, 2022 at 10:46 Quote
DavinG wrote:
What's the trick to remove the axle from my hub (Dartmoor K-Drive)? I'm trying to replace the hub bearings but can't seem to remove the axle. Thanks!

Usually a hammer and some sketchy hits to it does the trick. It does differ though on hubs and I’m not entirely sure which one you have. A picture would help

Posted: Aug 19, 2022 at 11:10 Quote
Ah yes, I got it out…just had to pound the h*** out of it.

Posted: Aug 20, 2022 at 4:10 Quote
DavinG wrote:
Ah yes, I got it out…just had to pound the h*** out of it.

If the bearing was super tight to come out, make sure everything is dead clean before refitting, and if possible heat the hub shell up before fitting the new bearings. Pouring boiling water on the outside of the shell will do, make sure you dont trap any water inside the hub though. A heat gun would be better, but dont go crazy. You dont need to go up to 300 degrees C or anything. Any warmth you can get into the shell will make the bearings press in much more easily.


 
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