Technical FAQ: Motorized cheating, roller tires

Lennard Zinn answers questions about motorized cheating and follows up on his advice for indoor roller-specific tires.

Dear Lennard,
With the first confirmed electric cheating case, I was wondering what you could tell us about these systems? I would have thought the noise alone would give them away, and what about the drag from the gears when it’s not in use? And I wonder just how much battery one can reasonably hide.

When it comes to catching cheaters, I wonder if the bike manufactures will end up putting little portals on the downtube, for easy inspection. This came to mind after seeing the little portal Trek puts on its new Madone (pic #12). With carbon frames, it seems like an easy thing to do. Any thoughts on where this is all heading?
— Steve

Dear Steve,
Good question. I watched this entire race closely to look for any evidence that Femke van den Driessche was using a motor. It didn’t seem like it to me.

Given that the Vivax Assist looks like a direct worm-gear connection to the crank spindle, I don’t know what happens when freewheeling, but it seems that if you don’t switch it off, you might have to resist its forward motion. That said, I’ve ridden a lot of e-bikes, and they generally only assist in the pedaling; when you stop pedaling, they stop driving, too.

Greg LeMond has one of these systems, and his motor is probably quiet enough not to be heard in ‘cross. It does clearly have the capability to run without the rider pedaling, though I don’t know if it still would strictly be a pedal-assist, once there is resistance against it. LeMond has a huge water-bottle battery, but in ‘cross, you could probably get away with a much smaller one hidden somewhere in the frame, since I would think that the maximum time the rider could have it turned on in a 40-minute race would be under 20 minutes. LeMond says his puts out 200 watts for half an hour. This test uses a battery in a saddle bag and says it puts out 200W for 70 minutes.

It sure seems like all of that mechanism inside the seat tube would offer some resistance when you’re pedaling with the motor off. Most e-bikes I’ve pedaled certainly are hard to move along when the motor is off, and not just because they are so heavy.

I have picked up carbon racing bikes with Vivax motors in them at European bike shows. While they’re certainly lighter than any other e-bike, the weight is quite noticeable. To refute van den Driessche’s alibi, there is no way a mechanic could unknowingly prepare that bike and not wonder why it was so heavy. This says the system weighs 3.2kg (7 pounds).

With a carbon bike (and probably with non-ferrous bikes, like aluminum and titanium), the sensor in the UCI tablet can detect a motor. I doubt it could sense it inside a steel bike.
― Lennard

Dear Lennard,
I recently received the March issue and have a question about the Bianchi bike ad that immediately greets the reader. The ad shows a rider with white bar tape that also shows a black button on the inside of the handlebar just down from the left hood. Is this a button for a motor? I can not find this image on Bianchi’s web page.
— Gary

Dear Gary,
That is clearly the button for a Shimano Di2 sprint shifter.
― Lennard

More on tires for riding rollers:
I forgot to mention the high rate of tire wear when riding on rollers; thankfully, a couple of you pointed that out.
― Lennard

Dear Lennard,
Since the resistance from rollers comes from the tire flexing around the drum diameter, tires play a role in resistance levels/performance of riding rollers.

What we recommend:

1.) Tire type: It generally does not matter, but a couple of things to keep in mind, which may impact the tire choice you make:
– Rollers wear a tire faster than normal road riding (generally less than a trainer but more than normal riding). A softer tire will wear faster and will generally increase the level of resistance slightly. A firmer tire will last longer and reduce the resistance slightly.
– Due to the wear, we recommend a lower-end (lower TPI) tire for roller riding. If you are switching tires between riding on the road and the rollers.
– Honestly, tire pressure probably has more impact on how the tire performs on rollers than the type of tire.

2.) I have not seen bumpiness, generally caused by the conditions of the tire, although I am sure it is possible. In most cases, it is tied to the trueness of the wheels or the rollers. The user can swap out tires, and it may be the issue, but that would not be the first item I would look at if a customer were having this issue.

We see most of our customers go back and forth between riding on the road and the rollers. So they use the same tires. But if they ask for a tire recommendation, we steer them toward a lower-end/stiffer-wall tire, due to wear and cost.
– Tim Fry
President/CEO MRP, Kreitler

Dear Lennard,
I think there is a simpler answer to Adam’s questions about which tires to ride on rollers: A few manufacturers (including Vittoria) make roller/turbo trainer specific tires. They actually have lower TPI, a rubber compound made to resist heat buildup, are thicker, and some have specific grooves intended to keep the noise down. I know besides Vittoria, Elite and Conti are also making these in various sizes.

From personal experience on rollers, I don’t recommend at all using new ‘regular’ tires because of the high wear. Besides the inconvenience of the ‘black dust’ from the tire going everywhere, it is not as safe as a roller-specific tire – I have seen a friend fall off rollers as the tube exploded after poking through the thin casing of his regular road tire. I have had Vittoria Zaffiro Home Trainer tires for well over eight years (long before I started working in the bike industry), and they are still nowhere near being worn. It is definitely also cheaper than getting regular tires.

Final comment: Most of these home trainer/roller specific tires require at least 100 PSI minimum for 700×23/25. I have experimented a bit with pressures and lower pressures (80-90) have given me flats, probably due to the bouncing. Very high pressures (120-130) have not given me enough resistance on my simple CycleOps rollers, but have given relatively smooth rides. Now I tend to stick to 100 PSI with the Vittoria Zaffiro Home Trainer 700×23.
— Cassio

Dear Lennard,
I’m expecting the arrival of my first set of rollers in a few days. I just read your response to a reader question about what tires to use on rollers. My question is similar. I have a set of used Conti Grand Prix tires. However, one has a pretty decent cut in it and the other was pierced by a thorn. I no longer use them on the road, and would have simply recycled them, but your article got me wondering if it would be safe to use them on rollers, where I don’t need to worry about additional punctures or road damage/debris. As long as I used a boot, could these tires safely be used on the rollers?
— Kevin

Dear Kevin,
I guess the question of “safe” is an individual one. Once one gets used to riding them, when you come off of the rollers (which can certainly happen if you blow a tire), you can usually put a foot down and not end up sprawled across the floor. Also, you can put the rollers between, say, a wall and the back of a couch to prevent tipping over. It is certainly safer to ride a booted tire indoors on rollers than out on the road!
― Lennard