longpete

An E-tandem makes a lot of sense but not for everyone. And riding a E-tandem is a completly different experience than riding two Ebikes.
My partner and me each on a E-mountainbike? That would be a long walk not a long ride. On a E-tandem by the end of the summer we will ride everything I Used to ride alone
except for the singletracks with hairpins where u have to turn by lifting the rear wheel.
End of 2020 our fullsuspension foldable custom sized E-tandem frame was finally delivered. It had to be a fullsuspension because the extra comfort and safety for the stoker.
It had to be a mountainbike while I prefer offroad. It had to be a 27.5 inch because a 29 rim wit 1.5 trekking tyres has about the same diameter as a 27.5 rim wit 2.6 tyres.
I chose 148 and 110 mm boost because the extra comfort, grip, brake traction that comes with that comes with 2.6 tires and 35 mm rims.
27.5 wheels are also stronger than 29 wheels.
Because of the difficulty to find tandem cranksets and the exagerated price of tandem cranks I wanted all chainwheels on the right side so normal Shimano cranksets and BSA brackets could be used.
No pressfit bracket.
The bike had to be foldable for easier transport. The old tandem I could transport in our car without disassembling anything, the new one was going to be longer and would not fit.
The tandem had to be custom sized because I'm 198 cm tall and my partner only 153cm. The old tandem frame fitted her ok, but was too small for me.
With the old tandem the fun for her ended with rides over three hours (where I live there's a lot of strong wind) or with over 1000 altimeters. Ofroad even with a suspended seatpost was for her not very pleasant because of the narrow tyre 1.6 tyres.
This meant reduced speed and mostly gravel roads. The geometry of the old tandem was not suited for front suspension.
I have over 45 years of bike experience she never rode a bicycle before we met.
I wanted to start riding more again(the last 10 years I did not do a lot of cycling(too much work), before at least 10 hours a week) If I want to ride that much again this means that
in the weekend we would not be doing much together. I like long rides because it frees my mind.
The solution for all these things was an E-bike. Speed pedelec or normal restricted Ebike? Speed pedelec choice meant a lot of paper work for me and the frame builder who lives in
another country. So it was resttricted to 25km/an hour. Normally we do an average of 19 tot 23 km/h.
Beacause of the reliability of Shimano and the fact that the frame builder had very goods contacts with the shimano importer
I chose Shimano. Came along corona. The waiting had one advantage I got the now EP 8 motor and 2 630 watt batteries for the same price.
Intended use was on the flat eco support mode in a low level, uphil trail in a low level. That way the batteries would last longer. No need for boost i thought.
A tandem brings extra weight and a lot more rolling resistance especially on the front wheel. So it takes more power out of the battery.
The weight distrubution with a reach of 50 and a stem of 9cm with 17 degree rise surprised me : 53% on the rearwheel and 47% on the frontwheel.
Uphilll the total weight of riders+bike+clothes+gear is 185. With two batteries the bike weighs a bit less then32 kilos.(one batterie+holder +- 3.5 kg).
One batterie with a combination of eco and trail modus offroad is good for about 75km, when flat country around 100km.(temperature between 0 and 13°Celsius).
Charging one batterie takes over 4 hours. So until now we did not need the second batterie. When we ride with luggage and in the mountains we will need the
batterie.
Narrow offroad curvy singletrack : low level trail modus is the best choice, when trail modus level 4 the bike goes too fast and u have to use the brakes a lot instead of ging with the flow
and freewheeling. Really steep not too long uphill we manage easily in low trail level.
Our weight distribution with 47% on the frontwheel makes a hard to find a fork without exceeding the maximal allowed pressure.
A solution is to ride a fork with more travel than 120mm with 40% sag. The fork rolls very easily over everything lower than 22 cm without to much change in weight distribution.
The rear RS Monarch RT (165*38) shock performs very well with 140 PSI and the rebound a bit over the middle probably also because only 53% of the weight is in the back.
In steep uphill the traction is fantastic even with continental mountain king. When muddy and flat the 2.6 tyre has it difficult to find traction in the mud, he spins easily.
Uphill this is less. I keep the tyre because the rolling resistance is very good. Probably because of the 49cm long rear stays and the bit of motor help the tandem can can easily climb real steep slopes without body -English.
Just stay seated and push.
The rear tyre needs 1.8 bar the front tyre 1.9 or more to be stable in tubeless set up .
One more advantage of the motor : I don't have switch the wheels, most of the time I ride 27.5 with 2.6. Switching tandem discbrake wheels is because of the weight of
the tandem and the big rotors not so easy as on a single mountainbike. What surprised me is that a 22 cm rotor on the rear wheel(18 up front) on long singletrack downhills where u're using the brakes
almost the whole time really works a lot better in avoiding overheating and fading.
The motor also solved another problem : the 11/12 speed off today. With a long tandem rear derailleur cable the rear derailleur with 11 and 12 speed is very sensible to cable stretching.
DI2 solved this. For the moment DI2 mountainbikparts are cheap.
The biggest added value was the rear suspension (we keep on using codes for the obstacles that are coming) but for her it's like she's on a flying carpet.
The motor makes it possible to ride longer and in more difficult terrain.
Simplified the motor makes us 10% to 15% faster and we can ride much longer wirthout feeling overtired. So the next day we can do the same etc......
If u're both young, very fit, have the same level and low weight u don't need the motor.
The motor 2.7, the batteries 3.2 each the holders and the cables weigh +10kg. But when I did competition my weight was 78 k for 1m98. Now it is 98 but lowering.
That weight difference is the same as the weight of my first tandem.
One more advantage of the new tandem : very stiff . This makes it easy to accelerate and climb me not seated, my wife seated.
I cut her handlebar down to 58cm, when the bar was 66 her bar touched to much trese and other things in sharp singletrack turns.
I think that smaller than 58cm would even be bettter offroad.
We're spinners never lower 85 rpm, I think this has a big influence on batterie reach. The gaps on standard 11 speed cassettes 11-40/42/46 are too big.
So I made my own cassette combining Ultegra+105+slx sprockets +a hg 1700: 13-15-16-17-18-19-21-24-27-30-34. On longer climbs in the mountains we will need 11-46.
II use wipperman chains 9 speed for the timing chain, 11 speed for the the rear. Normally i use cheaper chains.(Deore : 3 chains changed when cleaned and oiled and one cassette wear out together
and shimano chain wheels good for at least one other set when changed around 0.75mm. I think with wipperman chains the combination of 2 chains with one cassette wil give the same results.
For the moment (after 2000k) with our riding style I see not much difference in chain and cassette wear Etandem compaired with non Ebike.
The chain was never covered with mud.
The timing chain fell of the rearchainwheel three times because of branches who got stuck between the chain and the chainwheel.
Chainwheels timing chain have 34 teeth, reardrive chainwheel 38. For the Alps that's too much. So in the alps Iwill have to switch: 38 timing chain, 34 reardrive chainwheel.