Help me out here. I'm not understanding. If the OEM cassette specs are 42T and are you saying that 46T is what it should be, yet you are going to use a 38T?
Better or worse, benefit or detriment of 38T vs 42T vs 46T?
Reference:
http://gears.mtbcrosscountry.com
How to know without spending a fortune and swapping out over and over?
Guru,
I was talking about two different things: the largest cassette cog size; and the chainring (chainwheel) size.
The specifications of MY 2018-2021 Vado 6.0, (and of MY 2017 Vado 5.0) have been:
- Chainring (front sprocket): 48T (it is a large one!)
- Cassette (rear cogs): 11-46T (it is a wide-gear-range, expensive cogset)
- Long cage derailleur (to fit the large 46T granny gear in the cassette).
The design intentions were:
- In the top gear (48 teeth front, 11 teeth rear), you are getting the top gear ratio >4 meaning you can get at 45 km/h (28 mph) at reasonable cadence of 76-78 rpm (Turbo mode, hard pedalling)
- In the granny gear (48 teeth front, 46 teeth rear), the gear ratio is slightly above 1, which is pretty low, and it allows climbing very steep hills on road.
To summarize the design: Focused on high speed, and giving the rider a honest break in the hilly area as long as the rider takes paved roads.
If we talk about gearing in terms of
gear-inches, the granny gear of Vado 6.0 is equivalent to 30 gear-inches. The granny gear of a premium MTB should be 20 gear-inches or less. It is because a mountain bike is expected to climb extreme hills off-road, on technical single track. However, an MTB is never a speed bike (all premium e-MTBs are Class 1) because the focus is on the climbing capabilities not on speed.
My Vado was specified with the costly 11-46t cassette, and with the long cage derailleur. The mechanic cheated me by replacing that cassette with a 11-42T, and I had at least one steep road climb where I was struggling. I have restored the originally specified cassette to my Vado now.
It is never expected from the owner of a bike to change the
chainring size unless a good reason is given. For instance, you are free to swap your 40T chainring with the 48T (11-speed) Praxis one (and replace the chainguard, too) for easier getting at high speed but losing some climbing capabilities. You will also need a longer chain.
My specific need is to
temporarily improve the climbing capability of my Vado at the cost of reduced road speed. Therefore, I have bought a 38T, 11-speed, Narrow-Wide, 104 BCD Shimano chainring (SM-CRE80), and standard aluminium MTB chainring bolts with nuts. The setup required removing the motor cover and using a special wrench to keep the nut in place when tightening the chainring bolt.
The large 11-46t cassette in the rear, and the small 38T chainring in the front. I had to shorten the chain, too. See the huge Deore XT SGS (long cage) derailleur.
The outcome: The bike speed decreased to Class 1 range but its climbing capabilities increased to such level that 19-20% grade climbs could be (almost for sure) cleared. (The current granny gear is less than 24 gear-inches). After my mountain vacation is over, I'm swapping the 38T chainring for the 48T back.
See this calculator:
https://www.bikecalc.com/gear_inches