My TW came stock with 14/49 gearing. I like the ultra low first gear and being able to putt along at 3 mph without slipping the clutch. But, I'm one of those people that thinks that wringing out a 4 stroke at high RPM's for long periods causes premature wear and I felt like 40-45 mph was as fast as I wanted to go with stock gearing so as to not be revving the motor like crazy. I need to be able to cruise at 50-55 mph in order to get to some of the trails I like, so I did the dual rear sprocket mod by adding a 45 tooth rear sprocket. The 45 tooth sprocket only raised my 1st gear putting speed to ~4 mph, but raised my comfortable top end to 50-55 mph. Even with 14/45 gearing, 1st gear is so low that I rarely use it, even on hard single track trails.
I then changed my stock tires out for the 26x8-14 Duro Power grip in the rear and a 120/100-18 Kenda Trackmaster up front. The circumference of the Duro tire is 85'' and the stock Bridgestone tire circumference is 77''. This equates to a 10% increase in speed at any given RPM. That bumped my 4 mph putting speed to ~4.4 and bumped my comfortable top end cruise to ~55-60 mph, with 14/45 gearing. Running a Duro rear tire with 14/45 gearing is essentially the same as running the stock tire with 14/42. Likewise, running the Duro with stock 14/49 gearing is like running the stock tire with 14/45. I had not considered the difference in tire circumference between the Duro and stock when selecting my gearing, so I'm posting this as an FYI.
With the stock tire, you can have a 5 tooth spread in rear sprocket teeth for your dual sprocket setup, without changing the chain length. The Duro tire is so big that you can't slide the axle all the way forward in the adjusters because the tire will hit the swing arm. Because of this, you can only have a 4 tooth spread in rear sprocket teeth without the need to add or subtract extra chain. To me, not needing to change the chain length is key to the dual setup because it makes the swap so much easier to do when on the side of the road.
On my un-calibrated, cheap, bathroom scale the Duro Power Grip weighs 24 lbs. The stock Bridgestone only weighs 15. That's a huge increase in rolling weight. Because of the extra weight and the larger tire circumference, the Duro makes the bike noticeably slower and less responsive.
Since I love the 14/49/45 dual sprocket combo with the stock tire, I'm going to go with a 14/49/52 combo with the Duro, to maintain the same speed/RPM's as I had before. You could go with an even bigger rear sprocket to 'feel' more power, but I really don't need to go be able to go any slower in 1st gear and like to keep cruising RPM's down. With the Duro tire and 14/49 gearing, I can ride the gnarliest, rockiest, steepest, single track trail and have plenty of traction and power at the speeds I need it. (Power is relative - this is a slow bike designed to be ridden slowly, so keep that in mind here.)
You can keep the stock chain guard when running dual sprockets with the Duro too! Just bend both of the guard mounting points to align the guard over the two sprockets while keeping it away from the tire.
Here's what everyone wants to know: Seating the bead of the Duro is hard to do. I've probably mounted 50 motorcycle tires, and this was by far the hardest. It sat in a cage at 90 PSI for 3 days and didn't seat. I removed the tire, trimmed the bead on both sides (trim the inside edge of the bead, to increase the diameter of the 'hole'), remounted it, and the bead seated at 40 PSI. SAFETY NOTE: The Duro tire is only rated for a MAX of 20 PSI. Over inflating it could cause a huge explosion, ruin your wheel, and hurt you.
I then changed my stock tires out for the 26x8-14 Duro Power grip in the rear and a 120/100-18 Kenda Trackmaster up front. The circumference of the Duro tire is 85'' and the stock Bridgestone tire circumference is 77''. This equates to a 10% increase in speed at any given RPM. That bumped my 4 mph putting speed to ~4.4 and bumped my comfortable top end cruise to ~55-60 mph, with 14/45 gearing. Running a Duro rear tire with 14/45 gearing is essentially the same as running the stock tire with 14/42. Likewise, running the Duro with stock 14/49 gearing is like running the stock tire with 14/45. I had not considered the difference in tire circumference between the Duro and stock when selecting my gearing, so I'm posting this as an FYI.
With the stock tire, you can have a 5 tooth spread in rear sprocket teeth for your dual sprocket setup, without changing the chain length. The Duro tire is so big that you can't slide the axle all the way forward in the adjusters because the tire will hit the swing arm. Because of this, you can only have a 4 tooth spread in rear sprocket teeth without the need to add or subtract extra chain. To me, not needing to change the chain length is key to the dual setup because it makes the swap so much easier to do when on the side of the road.
On my un-calibrated, cheap, bathroom scale the Duro Power Grip weighs 24 lbs. The stock Bridgestone only weighs 15. That's a huge increase in rolling weight. Because of the extra weight and the larger tire circumference, the Duro makes the bike noticeably slower and less responsive.
Since I love the 14/49/45 dual sprocket combo with the stock tire, I'm going to go with a 14/49/52 combo with the Duro, to maintain the same speed/RPM's as I had before. You could go with an even bigger rear sprocket to 'feel' more power, but I really don't need to go be able to go any slower in 1st gear and like to keep cruising RPM's down. With the Duro tire and 14/49 gearing, I can ride the gnarliest, rockiest, steepest, single track trail and have plenty of traction and power at the speeds I need it. (Power is relative - this is a slow bike designed to be ridden slowly, so keep that in mind here.)
You can keep the stock chain guard when running dual sprockets with the Duro too! Just bend both of the guard mounting points to align the guard over the two sprockets while keeping it away from the tire.
Here's what everyone wants to know: Seating the bead of the Duro is hard to do. I've probably mounted 50 motorcycle tires, and this was by far the hardest. It sat in a cage at 90 PSI for 3 days and didn't seat. I removed the tire, trimmed the bead on both sides (trim the inside edge of the bead, to increase the diameter of the 'hole'), remounted it, and the bead seated at 40 PSI. SAFETY NOTE: The Duro tire is only rated for a MAX of 20 PSI. Over inflating it could cause a huge explosion, ruin your wheel, and hurt you.