I hate to tell you but I think that might just be the way it is. One day last spring I wanted to ride outside but didn't want to get on the roads so I set up my trainer in the backyard directly in the sun and my normal speeds of 18-19 mph was slowed to 14-15 due to the overheating. I also notice inside that my CycleOps 2 allows me to ride around 21-22 mph for the first 15 minutes until the unit heats up and then it slows down to it's 18-19 mph with the same effort. Once it's warmed up it stays consistent for hours as I've done numerous 100+ mile rides on it.

It used to drive me crazy but now I just accept it for what it is. The only workaround I could/can think of was to buy a different trainer.

I started a thread about exactly the same thing a few weeks ago, in fact I see you posted at the end of it!

My experience was exactly the same, doing any kind of structured workout using TR's Virtual Power was just impossible because of the massive increase in resistance as it heats up.

I hope you find an acceptable solution but I didn't have the patience any more; my solution was to sell it and buy a Kurt Kinetic Road Machine.

1. Ride it for 10 minutes to get it heated up so it presents the problem.
2. Carefully thread a rope through the cooling apparatus.
3. Tie off the rope in a bowline (preferred) or a taughtline hitch.
4. Pull firmly to ensure the knot is engaged properly.
5. Gently push it off the stern of your bass boat to not scare the fish and use as an anchor.

---

----------------------------------------------------------
Zen and the Art of Triathlon. Strava Workout Log
Interviews with Chris McCormack, Helle Frederikson, Angela Naeth, and many more.
http://www.zentriathlon.com

Same issue. I really don't like this trainer. TR with virtual power is impossible. I ended up buying a power meter.... but I'm still not a fan of the trainer.

Not the answer you're looking for but the trainer isn't the problem. Trying to guesstimate power from wheel speed and some approximate resistance load ramp for the trainer is causing the issue. The resistance for my Fluid II increases significantly over the first 10-15min even in my cold garage. That's what happens when fluid heats up and expands. Get a real power meter or a "smart" trainer - I'd vote for an actual power meter. I totally understand TR trying to provide some sort of virtual "power" metric to expand the audience for their product but you are bound to have these kind of issues.

Hello, Eric here from CycleOps.

Heat is definitely something that can effect a fluid trainer, more than a magnetic trainer which is quite minimally heat sensitive. As heat increases the dynamics of the fluid change and this can be amplified by direct heat or sunlight if you were riding outdoors. Generally we consider the warm-up period of a fluid trainer 5-10 minutes. Meaning after this time the power curve will settle and should be consistent as user SwiftRunner has mentioned.

If you are riding with a power meter it would be interesting to me to see the power to speed values that you are getting during your workouts. Otherwise, things to lookout for are any signs of wear on the trainer if it's older, or possible leaking fluid that would effect the intended resistance. Lastly, is this a new phenomenon or has it worked properly in the past and this being something new that you are experiencing?

I would like to hear more from you or anybody else having troubles so we can find out more on whats going on and help resolve it.

Feel free to reach out to me directly anytime, ealbers@saris.com

.

What's annoying to me is that it goes through the warm up period during every interval. During a 5+ minute interval, I would have to gradually lower my cadence by 10+ rpm to maintain the same power and gear. Every time. Even if the rest interval is only 2 minutes. I just find that annoying but I guess it's how it is.

This is fine if you're planning on doing all of your rides at a constant effort for sure, after 5-10 mins the fluid unit will reach a temperature equilibrium where the rate of heat generation is equal to the rate of heat dissipation. However, this is absolutely no help if you're trying to do interval workouts where your effort level is frequently changing. The major issue is that the delta of the resistance change over this lag period is particularly harsh on the Fluid 2 compared to other trainers I've used and it means your wheel-speed and cadence has to shift massively to accommodate. It doesn't matter if you're using a real power meter, Virtual Power or even just RPE, it's going to be disruptive to a structured workout.

My 10 year old Cycleops Fluid 2 instantly went from being a total piece of junk to a perfectly acceptable trainer with the addition of a Powertap ;-)

From the respondents to my thread above and some enquiries I made elsewhere, I personally concluded that the design or the manufacturing (e.g. the fluid used inside) of the Cycleops Fluid 2 has changed significantly over time.

It seems that some people, seemingly those with older units, see a reasonably stable correlation between power output and wheel speed. However, a lot of users also report these large swings in resistance over the temperature equilibration period, in my case with a very recent model.

The Cycleops Fluid 2 has been on the market for over a decade with numerous revisions to it's design and I don't think it's inconceivable that the functionality of different people's units out there is wildly discordant.

FWIW, I have a well used 10 year old Fluid 2 that is pretty inconsistent. I'm sure it is just "worn out" after years of heavy use so I have no beef with it but thought I would describe what mine is doing.

I get the warm up spike in resistance constantly at about 2-3 minutes into a ride. I know now that I have a power meter that this is about 20-30 watts and generally happens quickly like a switch going off over about 10 seconds or so. That basic affect has consistently been there since day 1 although of late it appears the power jump is greater. I presume it is an expected effect of the fluid reaching a critical temperature (I don't know anything about fluid mechanics but it is actually pretty interesting how the fluid and/or power unit seems to function like a switch).

Where my trainer has seemed to change over time as its gotten older is that once it is up to temperature, it has become more variable during rides. I will pedal at a fixed cadence without changing gears and once I get above about 220 watts, it will swing 10-15 watts at seemingly random intervals. Once I get up to around 270+ watts, the unit is actually showing more variation in power than I see when I am riding outside on the road out in the elements. I also get an affect where I speed up substantially, the power goes up, then over time will settle back over time. This shows up most doing intervals. At times it seems to behave almost erg like where I can shift a gear or two either way and at the same cadence will get the same power/resistance.

I'm a glass half full kind of guy so I just look at this like I am getting an incredible "road like" ride as in shifting head winds and small undulating elevation changes ;-)

Agreed. I know my 10 year old unit had almost no correlation tot he power curve TrainerRoad uses which I presume is from a newer unit.

Mine is maybe 5 yrs old, but after 10 or so minutes the resistance feels consistent even with intervals. Using Sufferfest and cadence/RPE though not power.

I have a 6-7 year old Fluid-2. I just started using it with a Power2Max crank based power meter and Trainer Road.

As others have experienced, it does increase in resistance quite significantly after about 10-15 minutes of warming. In my experience it is consistent after that but since my watts come from the crank based meter and not virtual power via the TR estimate it does not effect me.

Have you thought about a portable room air conditioner? Not the ones that sit in a window, but a stand alone unit like a space heater or a dehumidifier and such. Otherwise, I've got no other suggestions. (Or you could do the cheaps mans A/C, ice packs behind the cooling fan ).

Just curious - how old is your Fluid2?

I had one purchased in 2009, and it was rock-solid even in various temperatures, and I didn't have any big changes in resistance. I would definitely have noticed - I used it with TR with both HR and virtualpower, and on every single one of my graphs, the HR and virtualpower are almost lockstep perfect, with no early or late swings. I did every sort of TR workout from the <1 minute anaerobic sprints to the long intervals, and I never had any strange decoupling of virtualpower and heart rate for the several years I used it.

I experienced the same problem, LBS sent it back for replacement and new one works much better.

Yeah at that stage my exasperation wasnt full blown yet as it is now. No solution yet - torn between a Kickr and Powertap peddles (I should be able to get a good deal on the Kickr which is the only reason I'm debating between the two - otherwise would definitely be the PM).

At least then it doesnt matter what the unit does with resistance - PM would tell me correct power. Dont have the cash right now though to spend

Hi Eric,

Thanks - unfortunately I dont have a PM so can't provide you with the data.

I bought the unit in 2012 I think (end 2012) so it really isnt that old, no signs of wear, and its done this since I first got it. I understand that the fluid needs time to warm up but I'm taking about vast differences in resistance when working above threshold, even if I've been warming up for 20min.

The unit itself will be extremely hot to the touch, even with the fan directed at it

Bought mine end of 2012. Change in resistance is so big that for example last week I tried a 20min FTP test. The 5min clearing effort almost killed me (way way way harder than it should be), and then by the time the 20min test came I couldnt even hold 20watts below my current FTP.

I have this trainer and have been in the middle of a TR plan, and as my FTP increased, and I started doing more short high intensity intervals, I was totally confounded, because I was having incredible difficulty holding onto the end of each of them - seemingly out of nowhere I would suddenly fail.

So I googled and found this thread. I have the same trainer and was wondering if there was some weird reaction happening. It may be that I am just terrible at these types of intervals, but a resistance jump fits what I am feeling.

If I picked up a power meter, would I simply pair TR to the power meter, and if my trainer’s resistance is fluctuating, it would not matter, because I would just my effort accordingly based on the reading from my power meter?

Yes a PM would solve your problem as you would just ride according to that. Any change in the resistance curve of the fluid 2 wouldn't matter because your PM would be the source of the truth

Same for me as well. Although I’ve moved on to a smart trainer. But initially I used the fluid 2 using virtual power and it seemed fine for me. Eventually I got a PM so obviously it wouldn’t effect me. I still have the fluid 2 sitting around as a backup

Try staying in the small ring. You'll still get a similar amount of resistance, but you wont be making the thing turn at 25MPH. I've also pointed a small fan at mine before which definitely helps.