Other than the KK Rock and Roll Trainer, does a rider using their bike on their trainer harm the frame?

I don't stand on my trainer, but what i'm saying is, does stress build up on the frame because the bike is (almost) completely restricted from moving side to side? The parts of the frame that might be most effected are the dropouts, seat and chain stays.

I don't know about others, but when i pedal, especially with larger gears for intervals (on my trainer), the more intense i go, the more i can feel my bike flexing, but this might be due to the material of the frame...and i know that the bike is installed on the trainer correctly.
My frame is aluminum, but i also know that is stiff on the road.

Soo...is it harmful, and to what extent?

i've seen like 3 of these threads in the last week or two.

Your frame will be fine. Your soul and sanity, on the other hand, are in grave peril.

Oddly enough, I was just wondering this myself. I don't seem to notice any flex on my bike on the road, but on the trainer I can see the bottom bracket moving if I'm in a big enough gear. It can't be good.

It's not a problem.

Go forth and be fruitful.

Looking down at your bottom bracket while riding on the road?

Exactly. your bike is flexing the same on the road, you just don't have a fixed reference point to guage it by, and you're not staring at the bb.

In many ways, riding the trainer puts less stress on the bike, i.e. you're not hitting potholes at 25mph.

The only significant worry about the bike on the trainer is sweat. Make sure you wipe the bike off when you're done.

you're fine. HOWEVER, riding a fixed gear on a trainer can be another story. My Track Pro has a bit of chain suck (really only through the paint) on the chain stay because the chainring cuts so close to the stay... this is from just having it up on the trainer once when I sent my bike home a week early for a race and I had to get in some training miles leading up to it. It's going to flex more since it's holding the rear in one place, but for the most part, no big deal, or else you'd be seeing a lot more people warning against the dangers of the trainer!

and by that.. i mean its no big deal, you just need to be careful with it... and that bike with the 49t chainring has about 2mm of clearance.

I don't think that's correct. Is your wheel sliding laterally as you pedal down the road?

the friction between the tire and the road is holding the wheel in place laterally. So the flex between the bb and the rear axle is going to
essentially the same on the road or on the trainer.

I remember the first time I rode in a boat through a slalom course while my 215lb friend waterskiied behind it. I couldn't believe how much he was pulling the boat from side to side with every cut.

Nothing changed except there was a handy fixed reference. I thought about that the first time I looked down while riding out of the saddle on my trainer.

Not really, you're not taking into consideration flex in the wheel itself nor the body of the tire. Not a factor in a fore/aft direction but laterally certainly not easily possible in a trainer where it does exist on the road.

find a hill, where is no traffic, pound on the cranks, watch what the BB does.

The rear triangle is not held in a fixed horizontal position riding on the road. It is on a trainer. Really cranking on the trainer places considerably more stress on the frame. If you are a featherweight roadie, you won't do damage. If you are a clyde and standing, you may well damage your frame. I have seen several frames ruined on trainers. Most of them were CF/metal combinations.

Ride rollers.

This actually makes sense. It's fairly obvious that the frame is subjected to more stress on the trainer since the bike is constrained from tilting side to side. It doesn't matter that the lateral position of the wheel doesn't change on the road, it matters that the wheel (and frame) are allowed to tilt freely.

The point about the wheel being allowed to absorb some flex is good as well.

Nobody is claiming that a bike on the road isn't subjected to stress. I think the point is that the frame is probably subjected to considerably more stress while in the trainer.

Riding a trainer may well be harmful to my frame, since said activity could potentially cause me to throw my bike in front of an oncoming truck.

I hate trainers.

It's not obvious at all that a bike is subject to more stress on a trainer.

1) The stress of putting 200lbs of bike and rider into obstructions such as potholes at a considerable rate of speed is completely eliminated. While one can debate the stress from holding the rear wheel in place, my bet is road related stress is much more substantial.

2) Nothing in the warranty or Owner's manual of my bike says not to use it on a trainer. Nothing in my trainer's owner's manual says not to use a CF bike on it, and in fact the photos show a CF bike. If this were such a problem you can guarantee the lawyers would have warnings, and warranty exclusions all over the place.

3) Ever watch a TT? All sorts of folks are warming up on trainers with high dollar CF frames, yet one does not see those frames self destructing.

CF frames are a whole lot tougher than many people think, and the thought that there is undue stress from riding one on a trainer is silly.

I know a guy who once put his expensive carbon fiber frame in the same room as a trainer. Needless to say the CF bike exploded into a million pieces.

Correct

More correct

It would have exploded anyway. Was the trainer damaged?

No but it was holding a prison shank (after close forensic examination they discover trace amount of carbon fiber).

Actually, my steel road bike has sculpted dropouts. I can't - or more properly, won't - clamp them in the fluid trainer for fear that the metal clamps will chip the paint off the dropouts. Otherwise I wouldn't worry much about it.