TREK Powerfly 9.7 Lt Chain ring options

[w4clm]

Hello to the group. I have a new to me 2019/2020 Trek EMTB Powerfly 9.7 Lt, with a Bosch performance line CX which also has a 15T front chain ring.
This is not my first rodeo with an E.bike I've had several Trek Police model 2015 which had the same small chain ring and I sold several years back.
I wasn't paying close attention to the front chain ring when buying the EMTB, my mistake but I couldn't afford a new Rail at the moment so I settled
for this nice second hand bike being Carbon and all I though I did well making the purchase. It has the same identical small front 15T chain ring that the my Police bike had
and I remember having to spin the daylights out of it as well. Never the less it works but my legs are fried from spinning the crank every time I ride the bike.

My question to the group is this. Has anyone had any experience changing out the front chain ring on a bike with a Bosch Performance Line CX motor from
a 15t front chain ring to that of a 34t chainring (Raceface or whatever) to some other brand. Upon close inspection of the Bosch motor case it has what I would call a
"CHAIN GUIDE" of sorts molded on the case where the chain resides and the chain runs under this guide. I'm thinking we can get another motor cover for the drive side if need be
and grind the molded chain guide off the Bosch motor cover to accommodate a 34t chain ring.

There has got to be a good reason that all the new model Trek EMTB got away from the 15t chain ring such as the Rail models all have a 34t Vs. this dang little 15t chain ring.
In my opinion you have to spin the living daylights out of the 15t chain ring when riding this thing.
Lastly I'm not sure if by doing this modification the Purion controller will get confused in some manner or another but it would
be interesting to know if anyone has done such a modification. There appears to be plenty of 34t chain rings available on the market specifically for the Bosch Performance
line CX (4th Gen) motors. I can't say for sure what generation my Bosch motor is.

The Specs for the Powerfly are here:

Powerfly LT 9.7 - Trek Bikes

Discover your next great ride with Powerfly LT 9.7 Plus. See the bike and visit your local Trek retailer. Shop now!

www.trekbikes.com

Thanking you in advance for your time and suggestions.
CLM

 

[fooferdoggie]

your mistaking a regular chainring with a older bosch chainring. that 15t is really about a 38 or so chainring because the gearing is a 2.51 ratio. you can check this just by peddling and watching the chainring spin more then the cranks. like so.

Samox Bosch GEN 2 Steel CNC Chainring with Single Chainguide - 18t, Black | eBay

Samox eBike chainrings designed for use with Bosch GEN 2 drivetrains.18t chainring with outer guide for non-boost chainlines. Item Specifications: Designed for ebike, Yes, Direct Mount Type, Direct Mount Bosch Gen 2, Tooth Count, 18, Material, Steel,.

www.ebay.com

this is the tool that removes it. its a bit of a bear to do.

https://www.ebay.com/itm/2841464688...Zugv4UXSnrxzUMkycC6b0Zog==|tkp:Bk9SR9a6hfy0Yg

 

[w4clm]

This is very interesting, I will do this and check it out. As for the 18t GEN 2 CNC do you think it will make any difference. Being it's 2.5 to 1 radio maybe that's all it needs if any is 3 more teeth. That gearing ratio must be made up in the engine gears, I did not think of that. I can see what you're saying about my mistaking this for a regular chainring. Thank you.

 

[fooferdoggie]

This is very interesting, I will do this and check it out. As for the 18t GEN 2 CNC do you think it will make any difference. Being it's 2.5 to 1 radio maybe that's all it needs if any is 3 more teeth. That gearing ratio must be made up in the engine gears, I did not think of that. I can see what you're saying about my mistaking this for a regular chainring. Thank you.

your limited to 20mph so I would think the lower the better so you climb better. are you spinning out? I have a 18 on my bulls with a 11-32 cassette and I can spin to about 30 mph.

 

[Saratoga Dave]

I could swear my XM-700 had a seventeen tooth front ring, but I’m probably wrong. John in Ct would know, he’s still got one.

 

[w4clm]

your limited to 20mph so I would think the lower the better so you climb better. are you spinning out? I have a 18 on my bulls with a 11-32 cassette and I can spin to about 30 mph.

Not sure what you mean by spinning out. If you're asking if I got it up to 20 mph, yes. I could tell the motor kicked out at 20 as it was supposed to.
I just feel like my legs are spinning so much that they are about to fall off. It's only the first time I rode this thing, any distance on a test ride.
It could just be me and I need to work with the gears a bit.
But I recall feeling the same way about my 2015 (Trek Police) bike. It too was an early PowerFly police version. I rode it clear across the USA on RT.66. It had the same dang little 15T Chainring in the front. However that police version has a Class Three Bosch motor , I only got it above 28 a few times on the entire trip. I'm looking into my options. Trek got away from using that 15T chain ring in 2021 / 2022. I've got a local friend looking into the Trek Rail 7 gen 2, it's a 12 speed with a 34T chain ring. with the Bosch Performance line CX motor, the same motor I have on the Powerfly 9.7 We are studying both rigs to see if it's possible to make the 2019 Powerfly similar to the Rail 7.

Bottom line however as you said earlier, this may not be necessary. I'm just looking at the options.
Thank you

 

[fooferdoggie]

Not sure what you mean by spinning out. If you're asking if I got it up to 20 mph, yes. I could tell the motor kicked out at 20 as it was supposed to.
I just feel like my legs are spinning so much that they are about to fall off. It's only the first time I rode this thing, any distance on a test ride.
It could just be me and I need to work with the gears a bit.
But I recall feeling the same way about my 2015 (Trek Police) bike. It too was an early PowerFly police version. I rode it clear across the USA on RT.66. It had the same dang little 15T Chainring in the front. However that police version has a Class Three Bosch motor , I only got it above 28 a few times on the entire trip. I'm looking into my options. Trek got away from using that 15T chain ring in 2021 / 2022. I've got a local friend looking into the Trek Rail 7 gen 2, it's a 12 speed with a 34T chain ring. with the Bosch Performance line CX motor, the same motor I have on the Powerfly 9.7 We are studying both rigs to see if it's possible to make the 2019 Powerfly similar to the Rail 7.

Bottom line however as you said earlier, this may not be necessary. I'm just looking at the options.
Thank you

you should not be spinning out unless your going a lot faster then 20mph. it sounds like a gearing issue. hell our tandem is geared real low only a 36t chain ring and a 11-42 cassette and we dint spin out till around 22mph. if your vacancy is really slow that may be it. my trek allant 8 has 11-36 and a 42t chainring and I can't the bike up to 28mph with a cadence not about 90 if i remember right.

 

[TrevorB]

As Fooferdoggie said the Gen2 CX motors have 2.5 internal gear ratio which makes 15t =37.5t chainring. Changing chainrings is easy with tool mention. Likes of bike24.com or bikediscount sell a range of sizes from 14-20t along with tool. Unfortunately some bike manufacturers had chainrings with 1-3mm spaces. Which was case with my Trek. Website also sell spacers(large washer) separately. If you look carefully maybe able spot it. Most aftermarket chainrings don't have a spacer. Just note how it is put together before dismantling.
Some manufacturers even had chainguard and chainring combined $$$$ Haibike, luckily my Trek had separate chainguard made by Miranda but I've never been able to source one. If running 14t will need to replace chainguard with nut which websites sell. Unfortunately didn't work for me as chain would bounce of chainring without guard when MTBing, have to stop and put it back on at bottom of every downhill section. End up keeping 15t + chain guard.

These chainrings are cheap Eur10 which is good as they need to be replaced with chain.

Being GEN2 you can fit badass dongle without any issues. If bike is 20mph version x2 will be fine, for 15mph version go for x3 as you really need to be able to do 35mph if taking lane and mixing with traffic.

I'd start with tool and find out want chainring type you have then order replacements from there. Try 17t and see how you go from there, maybe larger if using dongle.

 

[w4clm]

As Fooferdoggie said the Gen2 CX motors have 2.5 internal gear ratio which makes 15t =37.5t chainring. Changing chainrings is easy with tool mention. Likes of bike24.com or bikediscount sell a range of sizes from 14-20t along with tool. Unfortunately some bike manufacturers had chainrings with 1-3mm spaces. Which was case with my Trek. Website also sell spacers(large washer) separately. If you look carefully maybe able spot it. Most aftermarket chainrings don't have a spacer. Just note how it is put together before dismantling.
Some manufacturers even had chainguard and chainring combined $$$$ Haibike, luckily my Trek had separate chainguard made by Miranda but I've never been able to source one. If running 14t will need to replace chainguard with nut which websites sell. Unfortunately didn't work for me as chain would bounce of chainring without guard when MTBing, have to stop and put it back on at bottom of every downhill section. End up keeping 15t + chain guard.

These chainrings are cheap Eur10 which is good as they need to be replaced with chain.

Being GEN2 you can fit badass dongle without any issues. If bike is 20mph version x2 will be fine, for 15mph version go for x3 as you really need to be able to do 35mph if taking lane and mixing with traffic.

I'd start with tool and find out want chainring type you have then order replacements from there. Try 17t and see how you go from there, maybe larger if using dongle.

THANK YOU FOR THE AWESOME REPLY.
Great information. I'LL look into this.

 

[John from Connecticut]

I could swear my XM-700 had a seventeen tooth front ring, but I’m probably wrong. John in Ct would know, he’s still got one.

Hey Dave,
Great to hear from you. I can't believe I missed your post. Us Trek XM 700 guys have to stick together,
there's so few of us... : )

I was unable to physically check my front ring, but will do so tomorrow, Tuesday. In the mean
time the Trek XM 700 Specs call for a 20 T ring.

John

 

[fooferdoggie]

20 would be a 50t chain ring. I bought Sram chainrings the one I had lasted almost 10,000 miles before the last chain started jamming up. that what my performance speed motor had and it made it climb less then great.

 

[John from Connecticut]

Hey Dave,
Great to hear from you. I can't believe I missed your post. Us Trek XM 700 guys have to stick together,
there's so few of us... : )

I was unable to physically check my front ring, but will do so tomorrow, Tuesday. In the mean
time the Trek XM 700 Specs call for a 20 T ring.

John

Howdy,
I misspoke in my original chain ring size. Dummy me, 20T is the crank...
From the Trek Website, XM700 "Crank.....Miranda Delta, 20T" Duhhh.
I'll count the teeth and report back. Sorry.

John

 

[John from Connecticut]

Howdy,
I misspoke in my original chain ring size. Dummy me, 20T is the crank...
From the Trek Website, XM700 "Crank.....Miranda Delta, 20T" Duhhh.
I'll count the teeth and report back. Sorry.

John

Hi Dave, All,

I counted the teeth on my Trek XM700+ Commuter chain ring today...20t

John