Wow, it’s been too long since I’ve written an article. I’ve been working like mad to try to stage and plant 5000 fruit and nut trees in just one year and have been grossly neglecting my faithful readers. So far I’ve gotten over 1000 trees in the ground and about 2500 trees staged, but I’ve been shoveling manure and wood chips pretty much non-stop to get to this point. In my infinite wisdom (and cheapness) I’ve decided to undertake this project without using a tractor (hey the Amish do it, I can too).
Last year I bought a Christini AWD Snowshoe 2XL fat bike to use exclusively in the winter (review here). I loved everything about this bike except the large oversized chainring in the front. Often when powering through a foot of deep snow I need the granniest of granny gears that the Ultra Max just can’t deliver with the larger 38T BCD 130 chainring. To make matters even worst the stock Ultra Max comes with a 44T steel chainring which in my opinion is completely unusable for trail riding and snow. The chainring adapter on the stock Bafang Ultra is also made of steel and is about three times as heavy as it needs to be. This article is about the custom Ultra Max BCD 104 adapter that Steve Christini from Christini Bicycles made at my urging that makes the Ultra Max a low gear, snow crawling monster that it was always meant to be. Christini Bicycles also makes a bunch of non-motorized AWD bicycles and has a BBSHD version of their AWD system which I tested about a year and a half ago.
This chainring adapter works on any Bafang Ultra Max drive unit on the market. Getting the adapter off the Ultra Max is a little tricky. You need a Park Tool BBT-69.2 adapter (cheap on ebay) to get the main ring off the adapter, and it’s reverse threaded. I also found that my crankarm puller did not work well with the ISIS crankarms because the pin that pushes against the square cranks just goes into the larger threaded hole for the ISIS bolts. I found the right sized washer and shoved it in the hole then used my standard square crankarm puller and it worked fine.
When mounting the Race Face chainring on the adapter it only works if the fancy all-logo side faces out. If you mount it the other way then the recessed chainring adapter bolt holes allow too much play and the chainring is a little loose. Expect to spend about 20 minutes swapping this chainring and adapter out.
I found that I need to pull 2 links out to go from a 38T down to a 32T. If you are going down from the stock 44T you might have to pull 4 links out to make the derailer line up right. Put the chain on the highest gear and make sure the derailer doesn’t fold over on itself. This adapter works with some 30T narrow/wide chainring adapters, but not all. The 30T BCD104 chainrings are different as they don’t have both sides of the chainring bolts, they only use the male chainring bolts and the female threads are located right on the chainring. The 30T Race face also has slightly more offset than the 32T chainring so you might want to consider it if you’re getting chain rub on the fat tire. I used the 32T chainring and with the 2XL tires I did not have any issues with chain rub on the tire. If you do have issues you can space out the chainring slightly with washers between the adapter and the chainring.
When putting the crankarm back on the drive side I found that the bolts are not really long enough and you have to gently push the crankarm onto the Isis adapter to get it to start threading. If you don’t get enough bite with the threads you’ll end up stripping out the crank which will be a problem so don’t do that.
I gotta say that the BCD104 chainring adapter is a must-have for any Ultra Max trail bike whether you’re riding in snow or just on singletrack trails. The weight loss and the ability to put on any size front chainring opens up a world of possibilities for your bike and allows you to pick the perfect chainring size for your riding style. Although a 44T will be fine for a 30mph+ commuter, it’s not going to make any singletrack trail riders happy because most of the time we spend in the 10-15mph range. You can snag the adapter on ebay right now for $95 here or just contact Christini bicycles and order it directly.
You’ll be oh-so-glad that you did.