Technical > Transmission

What rear sprocket do I need to help me get up hills and mountains easier?

(1/7) > >>

Hi I'm new here  :)
I'm the proud owner of a Koga Worldtraveller Signature 2.0 with Rohloff and Gates belt. I have a 50t front chainring and a 19t rear cog with a 120t beltdrive plus Schwalbe Almotion 28" 50mm tires with 2293mm wheel circumference.

On my last trip I noticed that I lacked low gears when climbing and now after a lot of research I am still wondering which rear sprocket I should fit to improve this? Many say the lower the better, but I also have to take into account that I don't have to replace my belt too because that would make it twice as expensive. So basically I'd like to put the lowest rear sprocket possible while keeping my current belt, and using the tools Ritzelrechner and the Gates Carbon Drive Bicycle Calculator I get the following possibilities (FYI my chainstay length is 460mm, my crank is 170mm) :

A 22t sprocket is best compatible with a 459mm chainstay so can I keep my current belt with that? (at 60 cadence = 18,2>95,8 Gear Inches - 1,45>7,65m development - 3,25>17,1 mph / 5,23>27,5 km/h Speed)
A 23t sprocket is most compatible with a chainstay of 456mm so a little too short. (at 60 cadence = 17,4>91,6 Gear Inches - 1,39>7,31m development - 3,11>16,4 mph / 5,01>26,3 km/h Speed)
A 24t sprocket is most compatible with a chainstay of 465mm so a little too long. (at 60 cadence = 16,7 Gear Inches / 1,33-7,01m development / 2,98>15,7 mph / 4,8>-25,2 km/h Speed)
Now someone told me that if you have an eccentric bottom bracket (EBB) like my bike has, those few mm in 23+24t can be adjusted for somehow? And is a 24t sprocket a good choice or is this much too low? FYI, I am 47 years old but have a very good fitness and mostly ride on flat terrain (+- 60%), but often I do slopes and/or mountains (+- 30%) and occasionally I go off road (+- 10%).

If you guys want to give me a gamble with this information (because I know it's still a gamble), I would be eternally grateful  :D

Cheers, Joseph

FTR I ride 45 x 19 on my Nomad MK2; as per Thorn Mega Brochure. Combination works well for me. Perhaps a look at the brochure might be useful for you.

Thanks, that's  a good gear ratio you've got there  :D
I already read the brochure which is a great resource but I wasn't able to get the information I needed from it as my question is very specific to the Gates Belt Drive I guess..

For heavy touring or for when I set up my Nomad Mk II with suspension front fork for mountain biking, I use a ratio of 2.25 for chainring to rear sprocket (36/16), chain drive.  This is a heavy bike, a bit over 20 kg, designed to carry a load.  With 57mm tires (26 inch wheels), I have lowest gear of 16.2 gear inches with this gearing.

But for riding around near home where I rarely have more weight on the bike than a pannier of groceries, I run a ratio of 2.75 (44/16).  That is 19.8 gear inches for unladen riding.

I have a chain drive because (1) that was the only option with that model but also (2) because I knew before I bought it that I would want different ratios for different purposes.  Thus, I can swap chainrings and with a second quick link I can add or subtract the 4 chain links to do that.  I am clueless on belt drive and choose to stay that way.  I considered buying a different model but chose not to because it was belt drive.

When touring on that bike there are times that I wish I had higher gears when riding down a shallow slope hill and I am spinning out due to lack of higher gears.  But for touring I value the lower gears more.  When riding around near home with a light load, those low gears are unnecessary so I gear it higher to obtain a couple gears that are only used on downhills.

I am clueless on belt drives and choose to stay that way.

I have three touring bikes, the other two are derailleur drive.  For lighter loads I usually use the derailleur bikes, in part because they have a wider gear range.

For what it's worth I've got an almost new 46T 104BCD CDX chainring and an almost 115T belt which came off a bike where I found the gearing too low and did a few miles while alternative parts were in the post. I've also got a 118T belt which has done about 3k miles before I dismantled the bike to use the Rohloff hub on a new build. One of those combinations might work if the chainring will fit - you would need to check the max and min chainstay lengths provided by the EBB.

The parts are gathering dust in my garage so I'm open to an offer.


[0] Message Index

[#] Next page

Go to full version