Polini E-P3 mid drive, dual chainrings and ISIS cranks

December 27, 2016

There is a new player in the very large European mid drive ebike market. Polini is designed and made in Italy, and the only mystery is why this hasn’t happened sooner. Northern Italy is connected to the Alps, so Italians in the north are very fond of off-road riding.


Who is Polini?

To be honest, I didn’t know who Polini was until just now (December of 2016). In simplified terms, they are a company from Italy that makes hot rod parts for scooters. It was started just after WWII by Battista Polini, and is now run by his three sons, Carlo, Franco, and Piero.




A well-known classic Vespa Scooter, using Polini upgraded performance parts. It may “look” stock to the Polizia, but…it’s not!


The pic above shows two things that are very popular with young Italian men…a scooter, and Polini hot rod parts. North American 2-wheeled riders may scoff at scooters, but the price of gasoline in Italy is artificially high due to government contraints. It has been this way for decades, so several generations have grown up with the venerable scooter being a viable option for young adults.

The two features that are characteristic for this style of transportation is the lack of a top-bar (which European governments have identified as a safety feature, when a scooter is struck on the side by a car). Adding a top-bar would make the resulting injuries more severe.

The second feature is that…scooters do not use a common clutch (with a manually shifting transmission), and instead they use a type of automatic transmission called a variator. Once a government defines what a legal class of vehicle entails, they also identify those areas where a “legal” scooter can maybe…bend the rules?

The licensing, insurance, and registration for scooters is easier to get and costs less, depending on the size of the engine (compared to a true motorcycle). This makes it easier for a young adult to acquire affordable transportation, but of course…as soon as a young man gets a scooter, they often want to find some way to get a couple more horsepower…without needing to pay the extra cost for the licensing and registration of a larger engine.



A Yamaha T-Max 530cc 2-cylinder scooter using Polini hot rod parts. After this rider won the race, he couldn’t help show-boating a little for the fans…


In 2014, Polini partnered with Yamaha for their maxi-scooter racing series. Many famous racers (and some “rising stars”) won prizes for racing Polini hot-rodded Yamaha scooters against each other. A few decades ago, I doubt many observers could have predicted that young adults in the EU would pay significant prices for an upscale and more powerful scooter, but…the “maxi scooter” market is now very large and growing.


Polini, and the Yamaha connection

Yamaha is a global company, but…in the EU they are primarily regarded as a Japanese company. Their scooter partnership has proven to be very mutually beneficial, and I am pleased to see that Polini has now decided to enter the competitive ebike mid-drive arena. Yamaha had already been retailing a well-regarded factory mid drive under their own banner, but I think this partnership will expand business for both of them.

The headquarters for Ferrari is in Modena, Ducati motorcycles is in Bologna, in fact…the entire northern Italian region is a fertile ground for performance-minded enthusiasts of all types. In March of 2016, we wrote about the Mekkanobike, a fat-tire off-roader from northern Italy. Polini is in Bergamo, a few kilometers east of Milan (in Northern Italy), and they have developed an expertise for designing and marketing products in the EU.

In April of 2014, we wrote about the Yamaha YPJ-01 mid drive that had been seen at a PR showing. That was about the same time that Yamaha had partnered with Polini in their scooter racing series, and also when Yamaha introduced several models of electric scooter.

I don’t think the new Polini drive is simply a re-branded Yamaha, but…I am sure that this new drive does share some DNA. Lets just say that the it is very likely that the Polini design engineers and the Yamaha engineers probably know each other?


So, whats new here?

Two things jumped out at me as soon as I saw the youtube PR video. First, it uses the ISIS-interface for the crank-arms. The more common square-taper interface is likely strong enough, but…many off-road customers prefer the stronger ISIS splines.



ISIS-splines are obviously on the left, and the common square taper spindle is on the right. Pic courtesy of bikeman.com


Second, it has two chainrings right from the factory. The video shows a 34T chainring, and that particular chainring shown is as small in diameter as will fit. The spider has 5 arms, and those facts add up to the interface using a 110-BCD pattern (Bolt Center Diameter). The larger chainring in their PR video has 46T.

I have long contended that the more power you have available, the fewer gears you need. In spite of that, many customers still want a lot of gears to choose from. Cassette freehubs on the rear wheel have been made with anywhere from 8-sprockets, up to 11. The Polini drive then has a theoretical option of having 22-gears to choose from. (although, due to the limits of how far a chain can deflect to the side, two of the possible gears might not be useable)


An integrated downtube battery

In keeping with modern trends, the Polini system locates their battery in the downtube. I noticed that the plug interface was located at the top, and I like that. Although it may seem to be more awkward than the battery packs that plug-in at the bottom, doing this makes it easier to swap-in a larger battery pack that has a triangular shape (which obviously would be fatter at the rear).



The Polini downtube battery pack. The logo reads “Polini Motori”


Whether such a triangle pack is ever produced by Polini (or a third party), I think it is a useful option, as opposed to carrying a second battery when you want to go on a longer ride. The stock unit is listed as 500-WH. Since it is a 36V pack, this suggests that the size of the battery is approximately 13.8-Ah.



The 136mm Q-factor of the Polini drive


The distance between your knees when you are pedaling is called the Q-factor. The “Q” comes from quadriceps (the front thigh muscle), but it is an important factor for long-range cycling. If your body posture is off a little, it can actually lead to chronic pain and inflammation. You can add “bent” crank-arms to widen the bikes’ Q-factor, but you can only make them so narrow. The Polini drive uses a narrow 136mm Q-factor, so it can fit the widest variety of body types. Although female riders typically have wider hips than men, this is a useful feature for any rider, in order to obtain the best possible fit.



This motor is rated to provide a respectable 70-Nm of torque. And although it has a continuous rating of only 250W, it is capable of drawing a max of 500W peaks, which is the power limit in the nearby mountainous Austria and Switzerland.

This may seem to be a little mild for a company that prides itself in making hot-rod parts, but Polini is also known for something else in the EU ebike world. They make the most popular hot rod module that converts the popular Bosch and Panasonic mod-drives to having a 50-km/h (31-MPH) top speed. “Ben fatto, i miei amici!”


Written by Ron/spinningmagnets, December 2016

Grew up in Los Angeles California, US Navy submarine mechanic from 1977-81/SanDiego. Hydraulic mechanic in the 1980's/Los Angeles. Heavy equipment operator in the 1990's/traveled to various locations. Dump truck driver in the 2000's/SW Utah. Currently a water plant operator since 2010/NW Kansas


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