My review of Haibike SDURO HardFour 4.0


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Recorded a video on Haibike HardFour, one of the few kids' ebikes out there. With some upgrades (as always)!



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Dude, I have a Bosch and pedal it without power just fine!
Err, Bosch is terrible to pedal. Don't take my word for it, here's what Bosch themselves say about the crank:

For 2018 the Bosch Active Line gets re-worked, with a new motor designed to deliver moderately dosed support for riders. The new motor design has reduced the overall size by 25% by going back to a big sprocket externally compared to being internally geared.
This allows less resistance and brings the size of the unit down for better integration.
(Emphasis mine). Later, Bosch mentions that:

The motor noise and resistance are also significantly reduced too, due to the new gearing set-up.
So Bosch themselves acknowledge that there's more resistance on a small crank. Of course, they are talking about electrical operation, but on mechanical, it's even worse. On a Rohloff, with a 27kg bike, that problem is compounded even more.


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I'll take my word for it; the resistance is insignificant, that or I'm in incredible shape.

P.S.: I'm not in incredible shape.


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The crappy Suntour fork on this bike gave out, oil leaked everywhere, it was rather unpleasant. And now Suntour is resisting on the warranty. Hey I know it's a $100 fork, but I want to think they'll honor their international warranty without claiming "you did it".

Meanwhile, I replaced the Suntour fork with RST F1RST. Dirt cheap (EUR150), oil/air, who knows how long it will last.

Some info for people wanting to upgrade:
  • The frame actually accepts a conical (1 1/2-1 1/8) fork, so you can install that instead of a straight one.
  • Removal of the straight-to-cone adapter required the use of an industrial fan. That's because the adapter is made of steel and wouldn't come off with just hammer&chisel. In fact, I broke the chisel.
  • You won't find any 24" forks apart from Suntour and RST.
  • A 26" fork with small travel distance would go well here.
  • You need 9mm QR unless you decide to rebuild the wheel with a TA hub.
Overall, looks pretty good. And btw those decals are not stickers, they are painted.

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