Singlespeed & Dinglespeed Gearing
|Crankset and chainrings ready for dinglespeed install.|
For those who know about dinglespeed and don't care about chain length math, skip down a bit...
What's a Dinglespeed:A dinglespeed setup is like having two singlespeeds. It has two front chainrings and two rear cogs. Large chainring/ small cog for a commuting high speed and small chainring/ large cog for a hill climbing low. It only takes a minute to stop, flip over my bike, pull the rear wheel off, switch the chain and jump back on the bike. What makes the change go quick is having the same chain length for the two speeds so you don't have to adjust your chain tension when you switch.
The Math:The conventional way to maintain equal chain length is by having the same amount of total teeth. For me this was a 32T chainring with a 17T cog as my high gear (32+17=49) and a 30T chainring with a 19T cog as my low gear. (30+19=49) Simply put a change of 2 teeth between cog and chainring. I figured this out through some trial and error with my existing 32T chainring and assortment of cogs. But I also did the math with an excel tool I made. Download the excel Gearing Calculator.
The high speed of 32/17 should allow me to cruse a respectable 22-27km/h (around 17mph) and provide me with 57.4 gear inches. Still low enough to climb a hill on my commute but high enough to keep up with and pass other cyclists. The low speed of 30/19 should max out around 18-23km/h (around 14mph) and provide me with 48.1 gear inches. This should be plenty low enough to climb up steep single track and yet just high enough to maintain good momentum though rolling hills and valleys.
|32/17 vs 30/19 (2 teeth change) calculations.|
My dinglespeed gearing of choice.
|34/16 and 28/22 (6 teeth change) gearing calculation.|
If you were skipping over the boring stuff then start reading here...
The Build:As written above I chose to build my dinglespeed with a 32/17 high and a 30/19 low. Fortunately, I only had to buy one 30T chainring to make that happen. I bought a TA 30T 64bcd aluminum chainring. I bought this one because it had no negative reviews, it was inexpensive and I could get free shipping.
|Unboxed TA chainring.|
|Removed crankset and chainrings.|
|Stock Shimano XT Deore tripple crankset.|
|Replaced the original 24T 64BCD with the new 30T TA.|
On my Jones Plus I adjust chain tension with an eccentric bottom bracket. EBBs are notorious for being a pain to adjust. This pain is the main reason I don't want to have to adjust chain tension on a daily basis. Some trial and error adjusting chain tension finally resulted in some disappointing news. Even with the theoretical difference in chain length of only 0.9mm it is either too tight or too loose. Trying to split the difference by making the 32/17 high gear just loose enough to still let the crankset spin freely (about .25" of chain slop) still makes the 30/19 low gear have about 1.5" of chain slop which is considered too loose by most standards. (Ideally there should be about 1" of chain slop.)
|Finished side view.|
I've done a few rides with this dinglespeed setup and will continue to commute across town and climb hills to see how well it works. I haven't noticed any extra wear, friction or drag in the tight high speed. The loose low speed has also been doing well and hasn't been skipping teeth or dropping the chain. I have noticed the extra slop in low gear does allow the chain to occasionally rub against the side of my tire. For now I can live with this setup and see how it goes. However, I may add a chain tensioner in the near future to stop the chain from rubbing the tire and so I can run a slightly wider range of speeds. Something like a 34/15 and 30/19.
|Chain to tire clearance is minimal in low gear. The extra |
chain slop allows slight contact on rough trails.
|Inline view from first ride. Chainline is a bit off.|
|Side view from first ride at the top of a local sledding hill.|
|Finished inline chainring view.|
|Finished inline cog view.|
Reference:Actual Bike Wheel Sizes:
Other Gearing Calculators: