Turbo Trainer - Rolling Resistance

This guide relates to setting the rolling resistance on your turbo trainer (referred to as trainer from her on in) for those trainers where your rear wheel presses onto a roller to create resistance.  This guide is not applicable to direct drive trainers.

Setting the rolling resistance is particular important if are using a software platform that calculates a power figure using speed and cadence data but is just as important in using the trainer in standalone mode to give consistency between gear selection.

Turbo sessions cab be prescribed through a variety of methods: using instructional videos e.g. Spinervals, paper based workouts or through the preferred method of TrainerRoad and utilising VirtualPower.

VirtualPower Accuracy

When using VirtualPower, at some point you’re bound to ask yourself: Is this accurate compared to a power meter? Consistency is the most important factor when using VirtualPower to become a better cyclist. While VirtualPower data may vary between power-meter data, training with a consistent setup still gives you consistent data.

That being said, there is one factor that can cause your VirtualPower data to be inconsistent from one ride to the next – rolling resistance. Rolling resistance has two components: Trainer Pressure and Tire Pressure. By keeping these consistent and using the same power curve from workout to workout, your results will be comparable. Plus, you’ll be able to track your results as you improve.

Trainer Pressure

Trainer Pressure The term Trainer Pressure refers to the pressure between your trainer and the rear tire. When that pressure changes between workouts while using the same power curve, power readings become inconsistent.

Tyre Pressure

When your tyre pressure fluctuates, the resistance between your trainer and rear tyre changes. Thus, any variation in tyre pressure affects VirtualPower readings.



Rolling Resistance - Setup

When setting up the turbo for normal workouts you want to get to as near to “road feel” as you can. If you are using VirtualPower then you always want to set it up as near the same every time.

If the turbo has variable resistance then you are likely to get the best “road feel” by setting it to the lowest resistance and using the gears to get the load you want. The only time you wouldn’t do this is if you wanted to do specific hill training on the turbo trainer and your range of gears didn’t go high enough to generate that sort of resistance at your hill climb cadence.

Step 1 - Tyre Pressure

At room temperature inflate the tyre to the desired pressure.  Do this before you apply any press on force with the trainer's roller. This pressure is defined by two factors:
Trainer recommended tyre pressure (see trainer user guide) – a good rule of thumb is to use the tyre’s maximum pressure
Tyre maximum pressure (see the sidewall of tyre)

Whatever pressure you select make sure it the same everytime to take out the variability of random tyre pressure.

Step 2 - Clean Tyre

If you have used the bike out on the road it is prudent to clean the tyre first use water and a cloth and then something like an alcohol wipe and and to remove any grease from the tyre that may cause slippage.

Step 3 - Roller Pressure / Press on Force

Next you need to set the roller pressure. This needs to be just enough to avoid wheel slippage when you put the power down on the pedals, but no more than that. You don’t want too much tyre deformation or the turbo trainer will feel like you are on a hill all the time. If you are planning on doing a hill simulation session (higher resistance to achieve a low cadence) you may need a higher amount of press on force.

Most trainers vary the amount of press on force by turning a knob. To set this consistently every time get the trainer roller to lightly touch the rear wheel and then turn the knob a specific number of times that correlates with avoiding wheel slippage for the session you are doing e.g. 3 turns for a normal session but 4 turns for a hill session.

Step 4 - Roll Down Test

A final steup check you can do is a roll down test. Once you have set the rolling resistance you can check it is similar to the previous time you used the trainer.  The process is as follows:

  1. You will need a timer e.g. a stopwatch.
  2. Set the turbo trainer up as described above, get on the bike and pedal up to above 25mph / 40kph – use the gearing so that it only takes a few spins of the cranks to get up to speed.
  3. Stop pedalling completely.
  4. Watch the speed.
  5. When the speed hits 25mph / 40kph start the stop watch.
  6. Stop the stop watch when the wheel stops rotating.
  7. For more accuracy you could repeat the roll down test 2-3 times and calculate an average roll down time.
  8. The time it takes for the wheel to roll down to stationary should be similar each time you use the trainer.
  9. If the time is not similar assuming then assuming tyre pressure is correct adjust the roller pressure / press on force and repeat the the roll down test.