Saturday, April 15, 2017

Avanti Inc 3: Dura-Ace 7900 Crankset + Gates Belt and Sprocket

In the previous post, the Bushnell Eccentric BB was used to replace the stock eccentric BB on the Avanti Inc 3. This changed the BB width from 73mm to 68mm, allowing the use of a road crankset.

The road crankset that I can use should have a 5 arm design, and 130mm BCD. I would have preferred to use the new 4 arm road crankset, but Gates does not make their belt drive sprockets in that specification. Therefore, I have to select the crankset to match the available belt drive sprocket from Gates.

The smallest 5 arm, 130mm BCD front sprocket from Gates is 46T. This is smaller than the stock 50T, but still larger than the 42T that I was previously using. Together with the 28T Alfine Di2 rear sprocket, the gear ratio will be changed again.

46T, 5 arm, 130mm BCD Gates front sprocket.

Weighs 81 grams

The road 5 arm cranksets that I can choose from are the Ultegra 6700 (on Dahon MuEX), and Dura-Ace 7900 (removed from Merida Scultura 5000). In order to maintain a full Ultegra 6700/6770 groupset on the Dahon MuEX, I decided to use the Dura-Ace 7900 crankset on the Avanti Inc 3. Only the crankarms will be used, while the chain rings will be removed.

Since the Alfine 11 Di2 hub has a blue accent line running around the hub shell, I was thinking if I should use some blue chain ring bolts to match that.

Blue accent line on the Alfine 11 Di2 hub

Blue chain ring bolts. However, too many colours on the crank arm (blue, black, dark grey, silver) makes it difficult to showcase the beauty of the Dura-Ace crankset. 

Using black chain ring bolts makes the crankset look less busy, giving a more stealthy look

Gates 46T front sprocket mounted on Dura-Ace 7900 crankarm

Front sprocket needs to be mounted behind the tab to maintain straight chain line with rear sprocket

409 grams for right side crankarm plus 46T Gates front sprocket

A comparison picture of the front single sprockets. Crankarm on the left will be installed on the Avanti Inc 3, while the Dura-Ace 9000 crankarm + Wolf Tooth chain ring on the right has already been installed on the Wheelsport Fantasy mini velo.

Next, due to the change in sprocket size, a new longer Gates belt is required. I have no choice but to order a new belt.

Gates carbon drive belts come in a large box to prevent mishandling (twisting, bending) of the belts

118T, which is the next step up in size from the previous 115T belt.

118T Gates belt weighs 90 grams

With all the components gathered, the next step is to install all of them on the Avanti Inc 3. This modification will allow the use of a road crankset, which will have a narrower Q factor for more comfortable pedaling. This is quite a lot of work and modification required just to change the Q factor! To be continued...


  1. Where do you buy your gates belt supplies?


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