Chain adjust with aftermarket shock

[texasplumr]

I have been told and have seen it written that when you add an aftermarket shock or even a 6mm shim that it changes the adjustment on the chain from what is in the shop manual. I can't seem to grasp the reasoning of this. Why would it change when the tightest point in the chain is when the front sproket, swing arm pivot and the rear sproket are in perfect alignment? I just don't see why the amount of travel would make a difference. Maybe I'm missing something.

I'm sure there are those with much more experience than I who can explain this.

Thanks!

[Redbird]

The more downward angle the swingarm has when you set slack, the more it will tighten as it moves into line with the front sprocket and swingarm pivot. If the shock is lengthened or a shim is added, the swingarm will be at a different angle when you set slack. OEM chain slack recommendations assume you're dealing with the stock angle, so you have to compensate a bit for the new angle.

All that said, with a 6mm shim or equivalent added length to the shock, on the loose side of OEM spec is fine on the XX. When in doubt, find a heavy ass friend or two and compress the rear suspension through it's range and make sure the chain doesn't bind.

[texasplumr]

The more downward angle the swingarm has when you set slack, the more it will tighten as it moves into line with the front sprocket and swingarm pivot. If the shock is lengthened or a shim is added, the swingarm will be at a different angle when you set slack. OEM chain slack recommendations assume you're dealing with the stock angle, so you have to compensate a bit for the new angle.

All that said, with a 6mm shim or equivalent added length to the shock, on the loose side of OEM spec is fine on the XX. When in doubt, find a heavy ass friend or two and compress the rear suspension through it's range and make sure the chain doesn't bind.

That makes sense, thanks!