Durability and versatility were the two main criteria behind our choice of chain and sprockets for our DRs.

Chain

We decided to stick with a 525 chain. The reason is quite obvious, it last longer than a 520 chain. There is a lot of talk on the interweb of “520 conversion” and as usual a lot of confusion. Gizmology hosts and excellent article on “Sprockets and chains”
As shown, a 525 chain as the same pitch and roller diameter as 520 chain, but the rollers are wider resulting in more surface to spread the load, which is good for longevity. More surface of contact also means more friction and a heavier chain, which impacts performance.
Since our primary concern is longevity the choice was obvious.

Sprockets and transmission ratios

Our DRs come stock with a 15/42 transmission resulting in 2.8 transmission ratio. We felt this ratio worked well for the road but wanted to ability to easily increase the ratio for dirt section. Dropping a tooth on the front sprocket is the easiest way to achieve this. It would have been easy to just purchase a couple of 14T front sprockets but it came to our attention that Kientech sold 45T rear sprockets. More teeth once again mean more longevity, we therefore settled for the following setup:

• Rear: 45T
• Front: 16T for a 2.8125 street ratio
• Front: 15T fo a 3.00 dirt ratio

We also found the following info on the JT website. Most useful if you try to find a compatible sprocket while on the road.