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Wow, it’s been a long time since I wrote an article. I’ve been working like crazy trying to plant and plant 5,000 fruit and nut trees in just one year while seriously neglecting my loyal readers. I’ve planted over 1,000 trees in the ground so far and about 2,500 more have been placed on stage, but to get to this point I’ve been shoveling manure and sawdust almost non-stop. In my infinite wisdom (and cheapness), I decided to take on this project without using a tractor (hey, the Amish did it, so can I).
Last year I bought a Christini AWD Snowshoe 2XL fat bike for winter use (check it out here). I love everything about this bike except the oversized chainring up front. Usually, when I’m driving in a foot of snow, I need the oldest gears, and the Ultra Max can’t provide those with the larger 38T BCD 130 crankset. To make matters worse, the stock Ultra Max comes with 44T steel discs, which in my opinion are completely unsuitable for trail riding and snow riding. The chainring adapters on the stock Bafang Ultra are also steel and weigh about three times as much as needed.This article is about Steve Christini’s custom Ultra Max BCD 104 Adapter christini bike At my urging, the Ultra Max becomes a low-end, snow-crawling monster, which is what it is. Christini Bicycles also makes a line of non-motorized AWD bikes and has a BBSHD version of the AWD system that I tested about a year and a half ago.
Here you can see how the 32T chainring performed on my dirty snow bike
This chainring adapter will fit 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 remove the main ring from the adapter, it is reverse threaded. I also found that my crank puller didn’t work well with the ISIS cranks because the pins that push the square crank fit right into the larger threaded holes of the ISIS bolts. I found the right size washer and pushed it into the hole, then used my standard square crank puller and it worked great.
These are the tools I used to install the chainring adapter, the bolt and ring on the right are what came with the Ultra Max
When installing the Race Face chainring to the adapter it only works with the nice full logo side out. If mounted any other way, the recessed chainring adapter bolt holes would create too much play and the chainring would loosen a bit. Expect this chainring and adapter replacement to take about 20 minutes.
The stock steel ring adapter weighs 380 grams.
I found that I needed to pull 2 links to get from 38T to 32T. If you’re coming off a stock 44T, you may need to pull out 4 links to get the derailleurs aligned. Put the chain in the highest gear and make sure the derailleur doesn’t collapse on itself. This adapter will work with some 30T narrow/wide chainring adapters, but not all. 30T BCD104 chainrings are different in that they don’t have chainring bolts on both sides, they only use male chainring bolts and the female threads are on the chainring. The 30T Race chainring also has slightly more offset than the 32T chainring, so you might want to take that into account if you have chain rub on your wide tires. I use a 32T chainring with 2XL tires and I don’t have any issues with chain friction on the tires. If you do have a problem, you can use washers between the adapter and the chainring to space the chainring slightly.
Very light Christini adapters and links machined from 7075 alloy (good stuff)
When putting the crank back on the drive side, I found that the bolt wasn’t long enough, you had to gently push the crank onto the Isis adapter to start the threading. If you don’t have enough thread engagement, you’ll end up knocking out the crank, which will be a problem, so don’t do it.
Clearance is good even with 2XL tires, the fattest tires money can buy
I have to say that the BCD104 chainring adapter is a must-have for any Ultra Max trail bike, whether you’re riding in the snow or on singletrack trails. The weight reduction and the ability to fit any size front chainring opens up a world of possibilities for your bike and allows you to choose the perfect chainring size for your riding style. While the 44T is good enough for commuters at speeds over 30 mph, it won’t please any singletrack trail riders, since we spend most of our time in the 10-15 mph range.You can buy the adapter right now on eBay for $95 here or just contact christini bicycle And order directly.
You’ll be glad you did.
ride.
