Firefox Avatar MTB Review - CVT Magic?

Photography: Vikrant Date

I must admit that I’ve had quite a blast reviewing bicycles at ZigWheels for the past couple of years. The reviews I’ve done till date have included e-bikes such as the Decathalon e-ST100 and Hero Lectro C5X, among others. So when Firefox sent over a mountain bike with a CVT (Continuously Variable Transmission), I was quite excited to give it a whirl. Honestly, I wasn’t sure what to expect. Would it be like pedaling a scooter? Would a CVT completely revolutionise the way one rides a bicycle? So I spent a couple of weeks riding around my home and occasionally commuting to work to find out.

What is it?

As mentioned earlier, the Avatar is a mountain bike from Firefox (Hero Cycle’s premium bicycle brand). It’s an alloy frame MTB running on 27.5-inch wheels, which features a Suntour XCT hydraulic suspension at the front with 100mm of travel that’s preload adjustable and features a fork lockout as well. In terms of braking hardware, it gets a mechanical disc brake at the front wheel and a V-brake at the rear. While the drivetrain looks quite conventional with a 40-tooth crankset and an 18-tooth rear sprocket, the Avatar’s claim to fame is Enviolo’s patented CVT hub for the rear wheel in place of a standard hub-mounted gear set a derailleur. And for changing the ratios on this CVT hub, it gets Enviolo’s stepless Revo shifter. With a total weight of 18.5kg, the Avatar isn’t a light mountain bike by any means, but it’s not too heavy either. So lugging it up and down a couple of flights of stairs is no problem at all.

How does the CVT system work?

The CVT mechanism employs a series of planets (metal balls) positioned between an input ring (controlled by the pedals) and an output ring (responsible for propelling the rear wheel). Power transmission from the input ring to the planets and then to the output ring is facilitated by a unique oil. This oil, under compressive forces between the planets and rings, transforms into a nearly solid state. This innovative design ensures power transfer without any internal hub wear and tear. Adjusting the planets’ tilt on their horizontal axis alters the surface contact with each ring, thus modifying the drive ratio.

What’s the riding experience like?

Honestly, when I first hopped on the bike, I was expecting the CVT hub to handle changing ratios all by itself, depending on the load on the system (going uphill, downhill, etc). But this is not the case. The stepless shifter is a ring on the right handlebar which changes the ratio when twisted back and forth. So the riding experience isn’t that much different from a regular geared bicycle apart from the fact that you don’t have to shift the transmission into pre-set ratios. Depending on the setting of the shifter, you get a smooth transition between various gear ratios. So while the ratios are infinitely variable between the highest and lowest ratios, and can be finely adjusted depending on how much you turn the shifter, there’s no automatic shifting happening here. 

Riding it everyday

Now my office commute is a little under 19km one way. On an e-cycle, I can usually complete this journey in under 45 minutes. But since the riding experience of the Avatar is quite similar to a conventional cycle (for the most part), I would end up taking an hour to get to the office. And the effort required would be equivalent to a regular geared cycle in any case.

Where the Avatar would make a difference is in the gear shifting experience. The fine control the Revo shifter allows, would let me set the exact ratio I would require for any given incline… in theory at least. In reality, I could only quickly choose between 6-7 positions on the shifter, so the riding experience would be akin to riding a 7-speed bicycle. But I’m guessing over time, it would be possible to be more precise with the shifter, giving you a wider selection of gear ratios to choose from.

But where this Enviolo CVT hub really shines is the actual way it goes from one ratio to the next. Since there is no derailleur to move the chain up and down a gear set (like on conventional geared cycles), the transition between ratios is incredibly smooth. And since the chain doesn’t move, there’s no sudden change in chain tension when you do change ratios. This would also mean significantly longer life for your chain and sprockets, and also no chance of the chain slipping off the sprockets.

The Revo shifter has a little analogue display on it with a band that can go from flat to quite curved, along with a tiny representation of a bicycle on it. This lets you know whether you’re on a higher or lower ratio, for flatter or steeper inclines, respectively. It’s a very cute display, but our test cycle had a very funny glitch. Instead of showing a steeper incline as you selected lower ratios and a flatter one for higher ones, our bicycle showed the exact opposite - most likely caused by crossed up cables connecting the shifter to the hub. But this, we’re sure, can be easily remedied and is far from a deal breaker.

What was a bit of a deal breaker for me was the rear brake. After having experienced mostly disc brakes on modern bicycles, the V-brake setup at the rear simply felt too underpowered. And no matter how much I adjusted the cable, the rear brake would start losing bite after a few kilometers of riding through our traffic-ridden roads in Pune. While this might be forgivable on cheaper bicycles, this simply won’t fly for an MTB that costs over Rs 40,000.

Verdict

Priced at Rs 41,475, the Avatar is a pretty decent offering in the mid-priced MTB space. It rides well, features decent components (except for the lacklustre rear brake) and is well built too. But apart from the novelty of its CVT hub, it’s not doing anything too different from more budget MTBs with conventional transmissions. If, though, you are enamored by the thought of an infinitely variable transmission that offers super smooth ratio changes, then the Firefox Avatar might just be worth a dekko.