Electric Bikes – Yuba Mundo eV4 – first rides

So, the build was finished at 6.00 on Friday, and Saturday morning I took it for a first ride, into Porirua to take my wife a coffee at work, and to buy some mudguards.

Obviously this was to be a shakedown trip, and a trial of the bikes performance. Despite choosing the Lekkie 300w kit, and knowing that it was probably programmed by Paul at EM3EV, I didn’t realise some of its features.

The ride over into Porirua didn’t seem too bad, a good 100+ metres of climb at first, followed by lots of downhill and another sharp climb. The Pedelec system seemed to work great, but at times I felt I was putting too much effort in. A coffee was bought, delivered and shared, and I set off for the local bike shop (Pack and Pedal in Porirua) to look for some fat mudguards to cover the 26 by 2.125 tyres. On the way there some peculiar things started to be felt, and it appeared the left crank wanted to get off! Fortunately, I could throttle my way the last 500m to the LBS. I found some ludicrously expensive mudguards, and borrowed an 8mm allan key to tighten up the cranks – good and proper!

On the way home I started to get very frustrated with the bike, some very unusual things were happening. I am used to a 350w hub motor, which is a little under powered, so I have developed quite a high cadence in order to help it out up the hills. The Lekkie system came with a 46tooth chain ring, which is possibly a little big for the bike.

Anyway, the main issue was that it seemed to be easier to pedal in high gears than low gears. Whenever I changed down a gear to go up hills etc, it got harder to pedal up the hill. When going along straight flat roads in 7th gear, changing down to 6th gear felt like I had thrown an anchor off the back! This is a summary based on what I know now, but at the time I was frustrated and annoyed that getting home was very hard on me and the battery (I used the throttle to overcome some of the hills and head winds etc).

A bit despondent, I fitted the mudguards. By chance I had picked up a set for an ATB, which fitted using rubber bungees and cable ties – no bolts, nuts or anything else mechanical. At first I found this annoying, and while I got the front guard to fit as per the instructions, the back was not going anywhere near it. A quick rethink at the back and I realised that the Yuba has so many supports, cross bars and stays, that the whole mudguard could be attached to the stays and frame directly. When I looked closer at the front forks I realised that if it had needed lugs to bolt to, I would have been in trouble as there are no lugs other than for disc brakes on the front forks. I need to look for some normal stays to replace the bungee attached ones that came with the front guards, there are threaded mounting holes at the bottom of the forks.  Anyway, the guards are fitted and look great.

I also changed the height and angle of the handlebars, using the adjustable angle thing between the stem and the bars. The bike now fits a lot better! I did a retighten of everything I had fitted just to make sure.

So – what about the main issue? At first I thought something was faulty, so I started looking on the web for the same symptoms, searching for “bbs01 bafang low power in low gears”. A fortunate search choice, nothing that matched my problem came up, but a lot of links to pages about programming the Bafang mid drive hubs, including this one on Electricbike-blog.com.

Without reading too deeply I realised that the Bafang cuts off the power gradually as your cadence increases, so low gears and fast cadence means little assistance. While I didn’t think my cadence was high, the description matched my experience exactly.

So on Sunday we did another bike ride to our favourite cafe (a 23km circular route) and I changed my riding style to suit what I had read. What a change, I went from hating the damn bike to loving it in about 5km! I explored exactly what was happening in various power settings, gears and amounts of effort, and it all started to make sense. I was still working hard going up hill, but 103kg on a 30kg fat wheeled bike is always going to be hard work even with 300 watts of assist.

I am now using the watt meter to learn how and when to change gear. When the watts starts to rise over the norm for the PAS setting, change down a gear. When the watts drop down below about half of that change up a gear, and feel the push of that motor!

I checked out the settings in the above article for the EM3EV version of the motor, and found the offending item. The current decay setting which controls how high the cadence is allowed to get before power is reduced is in a range of 1-8, and of the 5 example of settings, the setting on my motor is the lowest, a 4 where others are at least 6 and usually an 8. This explains a lot. A programming cable is not expensive, so I have one on order, and when it comes I will check out the motors parameters, and fiddle just one or two of them. Hopefully I will be able to retain my faster cadence, because slogging up hills with a cadence of 60 or so is killing my old knees!

I also need a lower gear, 1st gear is just a bit hard on the hills I ride regularly, but there are some tougher hills in the area which will need something a bit lower. The 38tooth ring that came with the bike is probably a little low, so I thought I would swap the 46 tooth ring for a 42 tooth. What I lose in top speed will be made up for in hill climbing ability!

Posted in Electric Bikes, Yuba Mundo eV4

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