Fluid Trainer Resistance

[jsmith123]

Hi, I'm using a Elite TurboMuin Smart B+ trainer. I notice however that the fluid resistance seems really high. It's been like that since the day I bought it. I can barely ride anything past 39x17 for a long duration as the resistance is too high. I have never been able to use my 52 chain ring on this trainer. This trainer has no controllable resistance. Also I realize when I'm coasting it can only freewheel for a few seconds before the resistance stops the flywheel. Whereas I've noticed in some videos online, people using other trainers can coast for pretty long and the flywheel keeps spinning. Because of this I'm unable to coast too long on rides which can get a bit uncomfortable on longer rides as I virtually have to pedal non stop to prevent getting dropped from the group. Is this normal for this trainer and how is the effect on those trainers that allow you to coast longer. Does the speed drop much? Or can you still coast and stay in the group because the flywheel is still moving?

Secondly I just want to roughly make sure that my power output is right. At 39x19 around 70rpm I'm putting out around 130W or so on Zwift? I'm 62kg btw. Does this sound right?

Thanks for the help!

 

[jmdirt]

I know people who used to use different viscosity oils to get the feel they wanted, but what you are describing is the nature of fluid trainers. Be aware not to put the drum against the tire too hard/tight. If you have tire spin/slip on the drum try lower tire psi instead of just cranking on the drum adjuster. You don't want to deform the tire. I used to run 80 psi in 23 mm tires, and old, flat-top, bald tires work best. Don't clean the drum either unless it gets oil on it, because it will actually build up tire dust in the metal, and create more friction (less slip).

Please don't take this as me being a smart ars, but who cares what gear combo you are in if you get the desired workout.

Your 'coasting' sounds correct because the wheel doesn't have enough force (weight/mass) to overcome the fluid resistance. Really its a benefit to pedal the entire time. One of the training 'gurus', Joel Friel maybe, did a quick observation study about the average number of pedal strokes per hour of riding on a trainer vs. riding a typical road loop (at 100 rpm that's obviously 6,000 in an hour, but on the road it was much less (can't remember the number) because of all of the coasting. Much less workout if that's why you're doing it.

I'm not sure what other trainers you are seeing people use, but some have a decoupler type mechanism, air trainers require much less force to overcome at low speeds....

Now I'm going to have nightmares about my old Cyclops Fluid! I sure don't miss the days when I 'had' to ride a trainer!

 

[jsmith123]

Hi Jm, thanks for your reply and feedback. I'm so sorry I forgot to mention that this is a direct drive trainer so the tire isn't an issue. Yeah I mean it definitely is giving me more of a workout but I'm just wondering why it's virtually impossible for me to use my big ring because there's simply too much resistance. This definitely can't be the way that the trainer was designed. The ones that I've seen that can free wheel easily are mostly the newer ones like Tacx Neo and Wahoo Kickr core.

Any idea about the power numbers that I'm putting out? Do they sound right?

 

[JayKosta]

...
Secondly I just want to roughly make sure that my power output is right. At 39x19 around 70rpm I'm putting out around 130W or so on Zwift? I'm 62kg btw. Does this sound right? ...

Your power output greatly depends on your condition. Age can be a big factor. What distance and time on flat not windy road is a hard ride for you?
What time duration on the trainer can you maintain the 130W before you can't prevent going slower?

Jay

 

[jsmith123]

Hi Jay. Well maintaining that 130w is no problem more than an hour. Most of my rides are around an hour so I don't know how long more I can go but its not pushing definitely.

 

[King Boonen]

Hi @jsmith123 , welcome to the forums. What you describe is to be expected from this turbo. The power curve associated with it goes into high wattages pretty quickly. For reference, a speed of ~20kph requires ~200w, ~30kph requires ~400w, ~40kph requires 1000w and ~50kph requires 2000w.

39/19 at 70 rpm is around 18.5kph, so 130w sounds reasonable. If you were to ride in the 52/19 ratio at 85rpm, you be doing 30kph. This would need 400w or, based on your weight, 6.45w/kg. As such, you’ll be in the small ring most of the time.


In terms of coasting, many of the videos you will see are of true smart trainers. Many of these contain a motor that will assist when the gradient on any connected program, like Zwift, is negative. Other dumb trainers with lower power curves will be running at higher speeds for the same watts so will also take longer to slow down.


Hope that helps. I do a lot my my training on a fixed gear on rollers, continuous pedalling is a good thing, you get a much more consistent workout.

 

[jsmith123]

Hi King Boonen. Thanks for the welcome and the info. 6.45w on the big ring for 30kph? Ugh there is no way I can hold that for long. So is it fair to say that this is because of the resistance on this specific turbo?

 

[King Boonen]

Yes, it designed that way to allow anyone from beginners and skinny climbers up to massive sprinters to be able to use it. Sounds like it’s working as it should.

 

[jsmith123]

Alright then. Thanks so much for all the help.

 

[King Boonen]

No problem, hope you enjoy it. I’ve really got into riding in Zwift, it’s been a great distraction while I can’t get outside for long rides.

 

[jsmith123]

Yeah same here. Only used my trainer a couple of times long time ago when I bought it. Now it's getting a real workout. And so am I!

 

[King Boonen]

My rollers have been taking an absolute hammering and, to be honest, I’m probably the fittest I’ve been in a long time!

 

[del1962]

Out of interest how long do you spend on the rollers each day?

 

[King Boonen]

Out of interest how long do you spend on the rollers each day?

Depends on the planned session but usually anywhere from 45 minutes to 2 hours. I’m planning to do some longer rides if this lockdown continues but fitting them around other things is tricky at the moment.