Wednesday, May 3, 2017

Avanti Inc 3: Installation of 60mm FSA Stem

After completing the modification of the Avanti Inc 3 to have a narrower Q factor, it seemed that the geometry had been dialed in already. However, even after using a road crankset with road drop bars, something still did not feel right.

I found that while riding, the reach on the Avanti Inc 3 seemed longer than the Merida Scultura 5000 road bike. When holding the shifters, I felt that I had to reach further than what I am comfortable with. This is not my intention as the road bike should have the most aggressive posture out of all my bikes, since it is the fastest bike that I have.

During the previous modification to change to Alfine 11 Di2 with a drop bar setup, I used a shorter 80mm stem to compensate for the longer top tube of the Avanti Inc 3 frame. To double check my previous measurements, I measured from the saddle (area where the sit bones contact the saddle) to the centre of the handlebar.

Distance on Merida road bike is about 665mm.

Distance on Avanti Inc 3 is about 668mm.

The distance from saddle to handlebar is almost the same. Both the bikes are using a compact drop bar from FSA, which means a 80mm reach on the drop bar itself. Therefore, the different reach is not from these areas. Finally, I realised that the bracket on the shifters might be different in length.

Ultegra Di2 6770 road shifters, gripping distance is about 100mm from centre of handlebar.

ST-RS785 shifters, with a gripping distance of about 120mm from centre of handlebar.

Finally, I realised that the bracket length on the shifters are different in length, which means a different reach distance. On the Avanti Inc 3, the road hydraulic disc brake shifters ST-RS785 has a bracket that is about 20mm longer, which is probably to fit in all the hydraulic components.

This extra 20mm of reach is the difference that I feel when riding the bikes. As I ride all my bikes often, I am able to feel any subtle geometry differences.

It is easy to fix this, as I can just change to a shorter stem. There is no worry of a shorter stem making the steering less stable, as the longer shifter bracket makes up for it. As long as the overall distance from the steerer tube to the gripping area on the shifters are the same, it should feel the same.

Simple FSA stem with a 60mm reach

+/- 6 degrees of tilt, depending on which way you fix the stem

Weighs 115 grams for this 60mm length. If it was a more expensive stem, it will weigh less, probably 100 grams.

Comparing the difference in stem length. 60mm in front, 80mm behind. See how much difference it makes to the handlebar position.

New FSA 60mm stem installed! Short stem indeed.

Now the handlebar reach and height is the same as on the Merida road bike!

With this modification, both bikes will ride more similarly as the geometry is now almost the same.

The Avanti Inc 3 can now be classified as an all-weather commuting road bike

Some rearrangement of the accessories is required, due to the shorter stem. Looks rather cluttered, think it needs more work.

View of the full bike. Handlebar area looks a bit cramped due to the short 60mm stem, but it rides really nicely.

With this change of stem length, the geometry has been nicely adjusted and feels perfect. After testing the bike on a half round island ride, passing through Mandai road, I was pleased to find that the gear range is perfect. The highest gear was just sufficient for continued pedaling even when rolling down the Mandai slopes at close to 50km/h. The lowest gear has not been used yet, but it will definitely come in useful if I need to go up steeper slopes such as in NTU or Mount Faber.

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