Rockrider E-st 900 changes upgrades

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
I am very satisfied with my new Decathlon Rockrider e-st 900, but like everything, nothing is perfect.
In this tread I will document all changes I make to the Ebike.

I use it daily for Field roads, asphalt Work commute, twice a week for bushes or bike parks.

You will also see some "missing specs"
When ordering parts, you sometimes need dimensions that are documented nowhere.

.
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
This is a picture of the bike with rain fenders installed.
I had to drill a 5mm hole in the front fork, then tapped M6 in it.

In the back there was the possibility to mount the fender support directly.

This is the reference to the fenders. the normal size.

They are narrower than the 27.5-2.8 tires, but as these tires are "bombed", the fenders keep away 90% of the rain.

It was the only model that was:
-quick click remove
-budget
-good close following of the tire
-not too much destroying the looks, no side supports etc.

118419983_10157944584034132_1031125038046264988_o.jpg


20200819_184837.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
I wanted a dropping post, so had to check dimensions to see if it would fit.
The tube is 31.6, but is it deep enough ?

I ended up buying the KS E20 125mm, mid cable

20200806_202348.jpg


Kindshock e20 A.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
I need a kickstand, but Decathlon forgot to weld a support for that.
So I ordered and "oval mount" Aliexpress Kickstand.

It isn't the right "kind" of oval. You see a plastic insert between kickstand and frame.
I grinded away some aluminium from the kickstand, the plastic will deform so it fits better without damaging the bike frame.

20200817_120005.jpg


20200817_120130.jpg


20200817_121330.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
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Belgium
In the previous image above you see the rectangle thing on the central wheel bolt.
It is a children trailer hitch. I just had to drill the hole in the hitch somewhat bigger to accept the big though-hole bolt.
There is still enough tread on the bolt to stay in place in the frame

20200729_215014rs.jpg


20200729_215159rs.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
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Belgium
Here you see the connections of the Brose-T engine.
2-pin wheel sensor below.
5-pin for HMI somewhat higher.

Anybody knows what the other connections are for ?
It think, the 2 above are 6V for front- and back light, but there seems to be another 5-pin (?) below.

20200811_173043.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
The Rockrider e-st 900 has a 34t chainring and a 11-42t cassette.

This 34t is much too short.
(Official: I drive sometimes very long asphalt downhill where electrical assistance isn't needed but where I drive faster than 27 km/h)

I measured around somewhat. The original 34t chainring has long teeth, so the new longer will have that too.
It seemed a 42t could fit.

The 34t came off without dismanteling something else.
It needs some positioning and some minor force, but it works.

The 42t is a cheapo Aliexpress thing. I prefered to spend 6eur instead of 50eur for this compatibility test.
You see the result: 1mm clearance.
The plastic chain guide doesn't fit anymore. I will have to 3D-print a similar one.

The 114link chain is too short now. I will not use the biggest ring of the cassette till the new E10 - X10E 136link chain arrives.

20200817_122741.jpg


20200817_124035.jpg


20200817_160925.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
The Rockrider E-st 900 comes with "tubeless ready" tires.
But are the rims also tubeless ready ?
Here an image when I put Maxxis tires on it, and in the same time drilling to 8mm for Schrader valves.

20200819_172854.jpg
 
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BeBiker

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Aug 26, 2020
661
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Belgium
Next I will post about installing the seatpost.

Changing the angle doesn't work like described in the manual, the 4mm cable is 10cm too short, and there are some other minor issues.
But it will work.

20200826_175202[1].jpg
 
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Zimmerframe

MUPPET
Subscriber
Jun 12, 2019
13,786
20,478
Brittany, France
Looks like you bought the wrong bike for the purpose...
As he said in his other thread, he was limited in choice :


@BeBiker thanks for all the detailed updates.
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
In an ideal world, I would have bought:

- +8000euro full suspension E-mtb
- "ladies" model E-bike for work commute
- a trashbike to go drinking some beers, go get some food.
- "Amish" lightweight mtb for bike park, bush, downhill, jump

I think I made a good choice, as a beginner, a relative "cheap" mix to satisfy most of the needs.

"beginner" points to the MTB- and EMTB world.
I am a full skilled technician who drove Motocross, Oldtimer races with access to a complete machining shop.
 
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freaks

New Member
Jun 6, 2020
8
5
Bangor
Thanks for sharing your upgrades. How do you find the 42T chain ring? Are you using more of the rear cassette? I am thinking about a 40T for my e-st900. Do you think I would still need to change to a longer chain?
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
with 42t chainring the chain goes over the 42t in the bacķ, but with the derailleur completely at the end. That's why I don't use that shortest gear at the moment.
Up to the tech-pro's to decide if the 40t with 2t chain-reserve is allowed.
 
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BeBiker

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Aug 26, 2020
661
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Belgium
Before I was only using the longest gears, never needed to go to the shortest 3 gears.
This is much better now.

The cassette is 11-13-15-18-21-24-28-32-37-42
You see the third shortest gear(32t) is approximately the same as the original chainring(34t)
So now I will have approximately the same ratio with the new chainring(42t) in the shortest gear (42t)
I "win" two gears.
With a 38t chainring you will win one gear.
 
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luckyOne

Member
Sep 1, 2020
8
6
Europe
Thanks a lot for this thread! Very useful information.
Can you please share which chainring have you ordered? It should be model "104BCD"? I see there are round and oval ones (whatever that means). Which one is correct?

Another question, have you found out anything about pins on the motor? I think about unlocking mine too, but paying almost 2 hundred euros looks too much. So I'm thinking about making a DIY solution. The simplest one would be to send two times less signals from the wheel, but that would make speedometer and (most importantly) odometer show wrong info. From what I understand some of those "tuning" boxes manage to unlock brose motors and still have correct speedometer. Any ideas how this is done?
 

BeBiker

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Aug 26, 2020
661
404
Belgium
For the last question, IIRC, the management here forbid to talk about this, except in the closed tuning-section.

86bcd and 104bcd exist. That's the spread between the mounting bolts. The e-st900 is 104bcd.
Do attention that chainrings are standard short tooth, ours have long tooth, option "narrow-wide".
This is mine: Link to aliexpress article 32938764549

Oval is for Phd professors who calculated you can win 0.05% on road races with that. A funny concept, a lot of videos on Youtube about this.
 
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BeBiker

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Aug 26, 2020
661
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Belgium
First thing, I mounted the Dropper Post KindShock E20.

I'm not completely (completely not) satisfied.
The marketing and manual say you can adjust the angle between cable attachment and saddle position.
This is not the case for that model, and they admitted it.

I wanted to pass the cable on the back,between the tubes.
This is not possible now.

But it works.

20200829_124739rs.jpg
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
The cables were too short. As this is an E-MTB, they have to pass under the electric motor.
So I bought a shimano 4mm derailleur cable-hose set.

In the cover there is no reserved place for this dropper post option, but some spare place so I could put the new cable.

20200829_110800rs.jpg
 

BeBiker

Active member
Aug 26, 2020
661
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Belgium
This is the "spare" chain length with the 42t instead of the 34t.

I consider this not enough, so I had the choice:
-passing to 38t
-longer chain, 4 extra links

20200905_145202rs.jpg
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
Changing the chainring (again)
Original it comes with 34t, then I changed to 42t, here a pic with the new 38t.

The chain guide goes back on, and I have enough spare chain length now.
The guide is now at maximum height in the guide-travel into the plastic cover.

First driving impressions are good.
Compared to the 42t, I have to pedal faster to go top-speed at full electric power (don't need that often)
I have more choice in the shortest gears, useful to climb without elec assistance.

20200905_150845rs.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
Now I know why "everybody" buys a full suspension :)

I installed this little accessory. It gives me 2cm suspension travel.
With the correct mounting the total height was too big, and the dropper post can't be installed lower, so I mounted the suspension-saddle bars and connector upside down.

With bolt emplacement optimization I can get some more suspension travel, but it is good for now.
I will put the connectors closer to the corner to get a somewhat harder result.

The saddle angle looks weird, but with my weight on it, it gets the correct angle.

Waiting for my new Taillight now. One that is compatible with Bike, Dropper post, Suspension and Saddle :)

20200906_161423rs.jpg
 
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BeBiker

Active member
Aug 26, 2020
661
404
Belgium
An image of the dropper-Post lever.
I think I prefer the angle mounted levers, but this one was included in the set.
It looks rigid, works well enough and it was possible to mount it under the HMI.

20200906_161428rs.jpg
 
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luckyOne

Member
Sep 1, 2020
8
6
Europe
Do you have a link for the mirror? And does it require cutting the handle to fit it?

edit: Now on the bigger image looks like it's fitted over the handle, so no cutting involved? :)
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
Here you go: aliexpress.com/item/4001042158136.html
Option "8mm pair convex"

I noted that for the work commute and between tracks, I do regulary a lot of asphalt.
But I was a bit afraid it would look too stupid and get in the way.

As you see in the article, it stretches around whatever you choose.

So this is my compromise :)
 
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luckyOne

Member
Sep 1, 2020
8
6
Europe
Yes, it doesn't look bad at all! I'll order one for myself :D

About the taillight - I've fitted a cateye orb (CATEYE [ORB] ) on the back of the frame. Looks good, and battery lasts quite long, it's now about two months and it's still holding. But would be cool to have something that could be switched from the button on the speedo, bacause I often forget to turn the light on before the ride :)

PS. And thanks one more time for your thread! After reading it, I also bought a wheelchair for kids and just widened the hole to 12mm :D Before that I hesitated because I had to find a special axle, then wait for it to ship... looked like too much time and hustle for me :)
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
I also bought a wheelchair for kids and just widened the hole to 12mm :D Before that I hesitated because I had to find a special axle, then wait for it to ship... looked like too much time and hustle for me :)
That's the reason why I started this tread. There are a lot of missing specifications and details.
You really have to take those things in hand and look.
A bit difficult when you have to order online...

This forum helped me a lot for general things, I'm completing it now for specific e-st 900 stuff.
 

BeBiker

Active member
Aug 26, 2020
661
404
Belgium
Yes, it doesn't look bad at all! I'll order one for myself :D

About the taillight - I've fitted a cateye orb (CATEYE [ORB] ) on the back of the frame. Looks good, and battery lasts quite long, it's now about two months and it's still holding. But would be cool to have something that could be switched from the button on the speedo, bacause I often forget to turn the light on before the ride :)

With the dropper post completely shifting in, I'm looking for a saddle-double-bars mounted taillight on battery.
Something like this: www.aliexpress.com/item/33044217963.html
There is Rockbros, Newboiler, Xlite, Meroca, Cubelite,... they have auto-on, auto-off, brake light,...

For a system-powered HMI-commanded taillight it should be able to operate on 6V (I think) and without internal battery.
I still have to buy the (expensive) 2-pin Brose-T taillight-cable, and figure out how the signal behaves.
Very sad there is zero specifications and manuals for this.

Is yours mounted on the side ?
 
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