Marlin 5 diy ebike gearing questions for top speed pedalling

ManBroSON

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I'm looking to convert a Trek Marlin 5 (2022) to an ebike. The rear hub motor kit I'm using is rated to give a little over 40mph top speed, but this bike by default can only reasonably pedal up to about 26mph. I would like to still have a bit of resistance in the pedals at higher speeds. It's a 2x8 setup, so I'm wondering if it is possible to swap out the large front chain ring (30T) for maybe a 44T or 46T? Then it would have a 22T and a 44T or 46T front chainring. Is a 44T front chainring compatible with this bike? Would this be easily doable, or would it require additional modifications so that it can shift from the 22T to the 44T? Would I need a different front derailleur or chain?
See: https://99spokes.com/bikes/trek/2022/marlin-5 (can add custom gearing to see the max pedalling speed)
Thanks.
 
Possibly. What RPM do you like to pedal at? 46T front chainring might not be large enough. What is the smallest rear cog?

Might (probably will) need a longer chain, longer arm derailler. Also watch out for chainring/chainstay interference.

Also: pedaling at higher speeds might impede rather than help because of increased wind resistance drag.
 
Not sure what RPM I like to pedal at. Probably I'd guess around 60-70 when at top speed. Smallest rear cog is 12T. I think you are right. I would need more like 54T? Is it possible to run 22/54 in front and 12/32 rear?

https://www.youtube.com/watch?v=uTJAW999Ol8 This guy put a 50T front chainring on, and just removed the derailleur, which I would rather not do. He said that doing so required putting in a longer bottom bracket, but he didn't mention anything about the chain.
 
ManBroSON said:
The rear hub motor kit I'm using is rated to give a little over 40mph top speed,

Yeah... probably not. Best get it installed and test ridden before you worry about being able to pedal along. You have to feed your motor about 4000W watts to maintain 40 mph on flat ground.

In the 30s of mph, the drag increase from pedaling starts to exceed the amount of power you are likely to add by pedaling. So you'll actually be losing range and top speed if you pedal along.
 
Actually, maybe a different bike would better suit me? The 2022 Trek Dual Sport 2 seems like it has a wider range of gears, with a 2x9 setup; 46/30 front and 11-36 rear. It keeps the hydraulic disc brakes, but does have thinner tires and less suspension travel (63mm on the DS2 vs 100mm on the Marlin)
 
ManBroSON said:
Actually, maybe a different bike would better suit me? The 2022 Trek Dual Sport 2 seems like it has a wider range of gears, with a 2x9 setup; 46/30 front and 11-36 rear. It keeps the hydraulic disc brakes, but does have thinner tires and less suspension travel (63mm on the DS2 vs 100mm on the Marlin)

Which hub motor are you using that supports a 9 speed cassette?
 
This one: https://www.amazon.com/dp/B07Y1QZNKD?psc=1&ref=ppx_yo2ov_dt_b_product_details You can ask them to make a custom one with a 7, 8, or 9 speed freewheel on.
 
ManBroSON said:
This one: https://www.amazon.com/dp/B07Y1QZNKD?psc=1&ref=ppx_yo2ov_dt_b_product_details You can ask them to make a custom one with a 7, 8, or 9 speed freewheel on.

That may be a lot of washers.
 
E-HP said:
ManBroSON said:
This one: https://www.amazon.com/dp/B07Y1QZNKD?psc=1&ref=ppx_yo2ov_dt_b_product_details You can ask them to make a custom one with a 7, 8, or 9 speed freewheel on.

That may be a lot of washers.

Also maybe impossible to dish the rim to center. Hub motors already make very compromised rear wheels even before you mess with their spacing.
 
ManBroSON said:
Update: I just bought a 2021 Trek Dual Sport 2 instead. Has a wider range of gears.

That's better if you want to pedal, since the frame allows for that bigger chain ring up front, instead of a dinky one. Realistically you don't need range, you'll chuck the middle and smaller chain rings and probably only use 48/11 for riding fast and 48/13 or 48/14 for everything else in the end.

ManBroSON said:
This one: https://www.amazon.com/dp/B07Y1QZNKD?psc=1&ref=ppx_yo2ov_dt_b_product_details You can ask them to make a custom one with a 7, 8, or 9 speed freewheel on.

Do you mean supports a 7, 8, or 9 speed cassette, or freewheel? The latter limits the options.
 
It took going to a 55 tooth on mine to really have a reasonable high speed cadence for pedaling.
I don't bother with front derailleur as the motor power was high enough I only ever needed the inner ring when the motor broke down to limp home, so would just manually shift it to the inner ring when needed.
 
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