Changing gears/chainring on Swagtron EB7+

nj1266

New Member
Region
USA
I purchased a cheap ($700) Swagtron EB7+ about a month or so ago. I got it because it was the only folding bike that would easily fit in the trunk of a Tesla Model 3. The Tesla design language makes the trunk opening small. Any bike thicker than 18 inches will be hard to pass through the trunk opening. For a cheap bike, it had good components: Shimano 7-speed gears, 3 electric modes, disk brakes, 350 W motor, 16 inch mag wheels, rear suspension.

The problem with the bike was the gearing was all messed up. The bike had a 7 cog rear gear cassette. The top gear (7th) had 14 teeth and the 1st gear had 28 teeth. 7th gear is for top speed and 1st gear is for climbing steep hills. The chainring had 44 teeth. The bike should have had a bigger chainring and a smaller rear cassette.

This set-up is extremely poor for an electric bike on 16 inch wheels. When in top gear (7th), I was limited to using mode 1 only. If I put the bike in mode 2 and 3, I couldn’t pedal fast enough to keep up with the speed of the electric motor. Pedaling in Mode 2 and 3 was useless in 7th gear. Top speed suffered and average speed when pedaling was 10-12 mph in mode 1 and 7th gear.

After asking around on this forum, a person suggested swapping the rear cassette and possibly the chainring. My brother and I replaced the rear cassette that had a 14 tooth 7th gear with an 11 tooth one for the same gear. 3rd through 6th gear also had cogs with fewer teeth, but the most important one was 7th gear. We also replaced the chainring with a 48 tooth larger one. This gave the bike a gear ratio of 4.36:1. So in 7th gear every time the crank/pedal had a full rotation, the rear 16 inch wheel turned 4.36 times. The stock 7th gear had a ratio of 3.14:1. Every full crank rotation turned the rear wheel 3.14 times. So every full rotation of the pedals the bike moved further than before.

The impact was amazing. Below are two before and after screenshots from rides on the same stretch of bike paths. For that 3 mile section the stock gearing allowed me an average speed of 12 mph which I covered in 15 minutes.

With the modified gearing, I was able to cover the same 3 mile stretch in 11 minutes at an average speed of 17.3 mph. That is a stunning 5.3 miles faster and 4 minutes quicker than stock. Moreover, i can now use mode 2 and 3 while pedaling, something I couldn’t do with the stock gearing. Finally, 5th and 6th gear are now usable when I encounter the occasional hill to climb.

Lastly, we added a driveline chainring protector to complete the new look. The look is so much better than stock.
 

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