Shock Absorbers

[ChrisOfBristol]

This is not a specifically e-bike question, but I am considering moving my motor to this bike, so I hope it is permitted.
I need to buy a new shock absorber for my mountain bike. The current one (marked DNM torch) has snapped in half. First I need to understand a bit more about how they work. I understand the spring bit. There is also damping, I'm guessing there is oil or air inside the cyclinder which is squeezed through a small hole. What I don't understand is the knob marked "R" at one end. I assume it stands for "Rebound damping" and adjusts the strength of the damping, but I can't see how it works. The shaft is hollow, is there an air valve in the end with the knob? Wouldn't that need a hole to the outside and wouldn't that get blocked with mud?

 

[saneagle]

This is not a specifically e-bike question, but I am considering moving my motor to this bike, so I hope it is permitted.
I need to buy a new shock absorber for my mountain bike. The current one (marked DNM torch) has snapped in half. First I need to understand a bit more about how they work. I understand the spring bit. There is also damping, I'm guessing there is oil or air inside the cyclinder which is squeezed through a small hole. What I don't understand is the knob marked "R" at one end. I assume it stands for "Rebound damping" and adjusts the strength of the damping, but I can't see how it works. The shaft is hollow, is there an air valve in the end with the knob? Wouldn't that need a hole to the outside and wouldn't that get blocked with mud?

Do you do serious off-roading? If not, the only thing that matters is the length. You can transfer the bearings and spacers from one to another, though you could check the widths of the ends to make sure. DNM make loads of shocks from cheap to expensive, which you can find on Aliexpress, Amazon and Ebay. On the road, you probably won't feel much difference, though air ones generally give a bit more comfort.

 

[matthewslack]

This is not a specifically e-bike question, but I am considering moving my motor to this bike, so I hope it is permitted.
I need to buy a new shock absorber for my mountain bike. The current one (marked DNM torch) has snapped in half. First I need to understand a bit more about how they work. I understand the spring bit. There is also damping, I'm guessing there is oil or air inside the cyclinder which is squeezed through a small hole. What I don't understand is the knob marked "R" at one end. I assume it stands for "Rebound damping" and adjusts the strength of the damping, but I can't see how it works. The shaft is hollow, is there an air valve in the end with the knob? Wouldn't that need a hole to the outside and wouldn't that get blocked with mud?

Damping uses oil not air. Adjustment must be controlling size of hole between two internal spaces.

 

[ChrisOfBristol]

DNM make

I should mention the the original was a Fox Vanilla R, so I don't need to get a DNM in particular. Since you haven't warned me off them, I assume they are OK, and if they do a good range I might find something suitable from them.

Do you do serious off-roading?

No, I've been riding motorbikes, pedal bikes and e-bikes for decades and I've recently been riding mountain bike tracks with an e-bike with V-brakes and front suspension. I'd like to try downhill tracks with bigger jumps. It's only for fun, I won't be competing.

 

[ChrisOfBristol]

controlling size of hole between two internal spaces.

The oil could go down the hollow shaft, but I can't see where the oil could be going in the small end with the adjuster. There doesn't look to be enough room for air and oil.

 

[chris_n]

If th

I've taken the bolt out of the swinging arm end (as can be seen in the first photo), but it doesn't want to come off. I am going to assume it is just a tight fit and I just need to use some force. Let me know if there is something I have missed!

If that won't move then that will be why it snapped in the first place. A rear shock will only snap if the ends aren't able to move (rotate) while the suspension moves.

 

[ChrisOfBristol]

...why it snapped in the first place.

I think the seat tube was lowered so far that it hit the middle of the shocker and snapped it.

 

[saneagle]

I should mention the the original was a Fox Vanilla R, so I don't need to get a DNM in particular. Since you haven't warned me off them, I assume they are OK, and if they do a good range I might find something suitable from them.

No, I've been riding motorbikes, pedal bikes and e-bikes for decades and I've recently been riding mountain bike tracks with an e-bike with V-brakes and front suspension. I'd like to try downhill tracks with bigger jumps. It's only for fun, I won't be competing.

I think itjust a question of how much you want to pay. Non-Chinese established brands will probably last longer, but are a lot more expensive. I think if one of my shocks went, I'd give one of these a try, but I only ride on the road. Off-road, performance of the shock becomes much more important.

DNM MTB Bike Absorber Shocker Bicycle Rear Air Shock Absorber AOY-36RC 125mm 165mm 190mm 200mm XC Mountain Bike Rear Shock Part - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

My Fox Float has been on my bike for 10 years and 10,000 miles. I've never even topped up the air. The spacer-bushes at the rear end are completely worn, but they're not part of the shock.

 

[soundwave]

a decent shock will cost more than the hole bike, cheap crap and big jumps dont work.

 

[ChrisOfBristol]

I think itjust a question of how much you want to pay.

All good common sense. Thanks. I'll have a more detailed look.

I've taken the end of the shocker apart (the spring end plate is missing). the knob assembly screws into the hole in the middle of the black bit. There is a taper on the chromed screw in rod. I thought initially that it might have been a valve which allowed air from down the main shaft of the shocker to escape - but I couldn't see where to.

Pushing a spoke down the shaft I can feel something moving, so I think it's a valve in the main body of the shock. There must have been a control rod along the inside of the shock absorber shaft to push that. The rod must have been lost when the shocker was broken. There's a couple of centimetres of movement compared with a couple of millimetres from the tapered chromed rod though, which is odd.

I can see now how it might work despite the small size of the bit at that end of the shocker. It should help with choosing a new one.

 

[soundwave]

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