- Thu Mar 11, 2021 7:05 pm
#95652
I fitted a pair of 345mm shocks to my trials bullet (off a YBR125 as it happens). This is a good 45mm over standard. Excellent for ground clearance. Disastrous for chain alignment. So with this setup, if the chain tension is set to fully tight at full compression, the chain is dangerously loose at full extension.
I've seen the trials sprung tensioners and frankly, they look like a recipe for getting something stuck in your spokes at 50mph.
What I did notice is that the rear brake pivot on the Indian Bullet frames is located handily near the chainline so I had this turned up out of EN8.
So it's like a standard brake pivot but with an extension towards the centre of the bike that the pictured industrial nylon roller/bearing (think skateboard wheel) will run on.
You land up with something like this:
You can see how much tension it's adding to the chain with the bike resting on its wheels. However when the suspension is fully compressed, the chain line straightens out and nearly lifts up off the roller:
Brake lever loosely attached:
Not road tested it yet but it seems to be able to keep sufficient tension in place when he supension is unloaded to keep the chain on while not going over-tight at full compression. Small mod for a significant gain in rear ride height.
It's a little more than the gain from fitting a 21" rim on the front giving me overall just over an inch of ride heigh while at the same time tightening the rake angle. I make it 26.5 degrees. Still slack for a trials bike but a lot less slack than using a 21" rim on a 300 or 310mm shock.
I've seen the trials sprung tensioners and frankly, they look like a recipe for getting something stuck in your spokes at 50mph.
What I did notice is that the rear brake pivot on the Indian Bullet frames is located handily near the chainline so I had this turned up out of EN8.
So it's like a standard brake pivot but with an extension towards the centre of the bike that the pictured industrial nylon roller/bearing (think skateboard wheel) will run on.
You land up with something like this:
You can see how much tension it's adding to the chain with the bike resting on its wheels. However when the suspension is fully compressed, the chain line straightens out and nearly lifts up off the roller:
Brake lever loosely attached:
Not road tested it yet but it seems to be able to keep sufficient tension in place when he supension is unloaded to keep the chain on while not going over-tight at full compression. Small mod for a significant gain in rear ride height.
It's a little more than the gain from fitting a 21" rim on the front giving me overall just over an inch of ride heigh while at the same time tightening the rake angle. I make it 26.5 degrees. Still slack for a trials bike but a lot less slack than using a 21" rim on a 300 or 310mm shock.