# What kind of oil in a fluid trainer?



## Italophile (Jun 11, 2004)

Hey!

Does anyone know what type of oil is generally used in fluid trainers? I bought a Performance one, which is also sold under other brand names as a base model fluid trainer, and its resistance is ...OK, as long as I am in the highest gear and cranking hard, but that is a bit limiting and generates a lot of heat. No, I am not going to buy a better one, as this was a steal on eBay, brand new, and I am only trying to stay in some kind of off-season shape, and build a little leg strength for climbing.

Anyhoo, I was thinking of cracking it open and putting in some heavier oil for greater resistance at lower speeds, you know? I am guessing it is something automotive that won't foam, like ATF or hypoid gear oil.

Anybody know this? Ever try it? Should work, right? :thumbsup: 

Thanks for the help!

_Dino_
Fondriest/Campagnolo/Barbaresco


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## Speedi Pig (Apr 18, 2004)

I've never heard of anyone trying to open a fluid trainer. I do know that many models will eventually leak as their o-rings start to age, dry-up, and crack.

Given that, I'd have to bet you'd have a real hard time ever getting it closed back up so that it would not leak.

If your model offers less resistance than you like, it may be because the unit has fewer blades moving through the fluid than other models.

I'm just theorizing since I don't know much about the inner workings of a trainer, but it seems like your best (read that, least frustrating) option would be to buy another trainer.

Of course, if you can get your HR up high enough (I could do that on the worn-out mag trainer I threw out recently), that's good enough.

Good Luck!!


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## Kerry Irons (Feb 25, 2002)

*Power = heat*



Italophile said:


> OK, as long as I am in the highest gear and cranking hard, but that is a bit limiting and generates a lot of heat. _Dino_
> Fondriest/Campagnolo/Barbaresco


It won't make any difference what gear you are in, how fast you're pedaling, or what oil you have in the trainer. Your power will be converted into heat. Changing oil will not affect this, unless the new oil has a higher specific heat capacity, which is hugely unlikely. If you get enough resistance from your current unit, as you say, then there is no point in trying to change the resistance. 

Not sure what you mean by "highest gear and cranking hard, but that is a bit limiting"


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## Italophile (Jun 11, 2004)

*Yeah, but...*

Thanks for the input, Kerry and Speedi ...sounds like a cartoon!

Opening and closing the unit should be easy, since it has six screws that hold what effectively is a cylinder head onto the resistance cylinder, and I'm a fair mechanic. Leaks are no reason to toss away and otherwise good fluid trainer! Just replace the oil and reseal the head with gasket goop or gasket material and new O-rings where necessary. I guess I will find out what is inside when I open it up!  

Heart rate is the thing for aerobic conditioning, but it would help with leg strength if I could get more resistance at various cadences with the thicker oil. I could get a more varied workout, like we get on real roads. This is my thought process. :idea:



> It won't make any difference what gear you are in, how fast you're pedaling, or what oil you have in the trainer. Your power will be converted into heat. Changing oil will not affect this, unless the new oil has a higher specific heat capacity, which is hugely unlikely. If you get enough resistance from your current unit, as you say, then there is no point in trying to change the resistance.


Actually, since the power applied to the unit is neither electrical nor chemical nor nuclear, the heat comes solely from the kinetic energy of the resistance blades within the oil (and the bearings, etc.). Thus, if the blades turn more slowly, there will be less heat generated in the unit.

_"Wait!"_, I hear you saying, _"what about Newton's laws?"_ They haven't been repealed, Kerry, though I am sure the Bush Administration is working on that; the difference is that there would be more heat generated in my leg muscles and less in the resistance unit. The heat would come from internal muscle energy, kinetic and chemical, not expressed in rotational speed, even if the aggregate workload were the same.

I think this is correct. Whether the result will be what I hope, I will have to find out. Anyway, it seems nobody knows the oil type, and it is entirely possible that different manufacturers use different oils. Some day when I feel adventurous, I may do this experiment. I will report the results here, if anyone is interested.


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## imetis (Jul 5, 2005)

Personally I just tighten the cylinder tighter to the tire to increase resistance. Wears tires faster, but I use retired road tires on the trainer anyway. Bad idea???


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## beantownbiker (May 30, 2002)

oddly enough I know what you mean when you talk about being in the highest gear and still spinning. I am able to do that on the performance trainer (and I am not that strong of a rider.)

I guess you could always put some extremely heavy weight oil in there, just make sure you get the proper type of oil so that it wont degrade the o rings and won't bubble up. 

Either way, keep us apprised to what you do.


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## Kerry Irons (Feb 25, 2002)

*Bad thinking*



Italophile said:


> there would be more heat generated in my leg muscles and less in the resistance unit. The heat would come from internal muscle energy, kinetic and chemical, not expressed in rotational speed, even if the aggregate workload were the same.
> 
> I think this is correct.


Well, you're just plain wrong. You generate the power, and the hydraulic unit dissipates it (as heat). The more power you generate, the hotter the unit gets, regardless of the speed of the rotors in the oil, the viscosity of the oil, or anything else. It is (extremely) simple thermodynamics. There are (very) slight differences in calorie expenditure due to leg speed differences, but the VAST majority of any power you generate turns into heat in the hydraulic unit. Changing what gear you ride in to make this happen doesn't change the power you generate. Simple as that.


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## Prolene (Jul 30, 2006)

Kurt Kinetic uses a silicone fluid which according to the manufacturer maintains consistent viscosity over the temperature ranges. Performance... silicone as well?


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## Italophile (Jun 11, 2004)

*Silicone has no appeal for me!*

I like it natural, Prolene.

Sounds like DOT 5 brake fluid, though, which is thin, thin, thin.

Jeez, I hope beantownbiker is a woman, because I am in love with her avatar.

Kerry, _you_ are just plain wrong: the bike and the trainer are not a closed system; my legs are an equal part of the thermodynamic difference between the two very complex setups. I may be only a poet, but I know enough biophysics to hack this simple problem. ...And different viscosity oils do have different heat carrying properties.  You must also believe that flexy Ti frames miraculously conserve energy on big climbs. How childish.

OK, just kidding around, man! ...But I am still convinced ...about the fluid and the stiff BB thing. I'm a stubborn poet, and that is a tough, chewy piece of gristle. Spit me out, before you choke!

...beantown? ...beantown???


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## Italophile (Jun 11, 2004)

imetis said:


> Personally I just tighten the cylinder tighter to the tire to increase resistance. Wears tires faster, but I use retired road tires on the trainer anyway. Bad idea???


No, not a bad idea. I have even considered tightening my brake cable 'til I get rub! This is my retired bike, after all, which I no longer ride. I will try this before I will crack open the unit. The old Vittoria Techno Twin Treads are showing fabric anyway.

Peace.


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## Kerry Irons (Feb 25, 2002)

*Living in confusion*

I hope it makes you happy, as a poet, to be pretty much confused about things. Whether it be simple thermodynamics, or the nature of hydraulic fluids, it all must be very fuzzy to you


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## Italophile (Jun 11, 2004)

Well, you must understand that fuzz is a poet's reinforced concrete.


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