# Scott CR1 Team Issue safe in trainer?



## B R H (Sep 9, 2004)

Is a lightweight frame like this safe to use on a trainer (Minoura 850 for example)?


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## gogogomoveit (Nov 20, 2003)

I dont know. Lets not ride it on the road.


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## orange_julius (Jan 24, 2003)

Sorry if this is stupid, but why the particular concern with using the bike, or any bike, on a trainer?


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## B R H (Sep 9, 2004)

I've noticed that some of my other bikes (all mountain bikes) have varying amounts of flex on the trainer. These bikes are all aluminum frames. One, a hardtail, is rock solid, but the others, full suspension, have a considerable amount of side to side flex.

I'm considering building a light carbon frame road bike that I would use on the same trainer during the winter months. I am wondering if a light carbon frame will flex even more and if using it on a trainer will decrease its life expectency.


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## orange_julius (Jan 24, 2003)

It seems to me that if you were rightfully concerned about your force breaking the bike while it is mounted on a trainer, then the bike shouldn't be ridden on the road. You're not applying any more force than you would when you are riding the bike, it's just more visible. Plus, hitting bumps and potholes apply quite a lot of force on your bike.

My 34 cents.


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## B R H (Sep 9, 2004)

A bike isn't held in a fixed position by the axle when riding on the road. In the trainer, the bike has to be stressed more laterally.


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## orange_julius (Jan 24, 2003)

But the source of the force (you) is not fixed by the same axle. Hence my previous comment.


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## B R H (Sep 9, 2004)

I don't see your point. If I am out of the saddle in the trainer I guarantee the stresses at the rear dropout and bottom bracket are higher than at anytime on the road. My question if whether or not they are high enough to be a concern.


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## gogogomoveit (Nov 20, 2003)

*Rest assured buddy.*

" One, a hardtail, is rock solid, but the others, full suspension, have a considerable amount of side to side flex."

If the bike is secured on the trainer, it will not be possible for it to sway from side to side since the trainer is acting as a wider base at the rear wheel. For it to flex sideways, you have to bend the axle. I think you have mistaken the vertical flex as horizontal flex.

If you go out of saddle, pump out certain amount of force and the frame does not break, it will not break no matter how long you keep pedalling constantly. Carbon fiber does not fatigue under load: either it holds up, or it bends and breaks immediately.

On the road, the bike swings from side to side to counterbalance your legs' pumping motion, therefore the "swaying", and you can stay in a relatively unchanged position to your bike. On a trainer, the bike is fixed, so you will move horizontally and vertically to counterbalance the motion instead. I dont have a good calculation on this, but there should not be significant difference in stress levels on both your legs and your frame. If it does, either your legs or the frame will break.


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## B R H (Sep 9, 2004)

For the bike to flex sideways the axle does not have to move at all. I'm talking about frame flex laterally. Put your bike in a trainer, get on the bike, and lean over to the side. The frame will be stressed and will flex. Try this on the road and you fall over... no stress on the frame (until it hits the ground).

Seemed like such a simple question.


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## gogogomoveit (Nov 20, 2003)

B R H said:


> For the bike to flex sideways the axle does not have to move at all. I'm talking about frame flex laterally. Put your bike in a trainer, get on the bike, and lean over to the side. The frame will be stressed and will flex. Try this on the road and you fall over... no stress on the frame (until it hits the ground).
> 
> Seemed like such a simple question.


The other intesting point to note is, your pedalling motion is up-down cycle, not sideways. Frame "flexes" because the pedals are offset from the center and there is a torque acting on the BB shell area, but NOT the entire frame. I highly doubt there is that much perceptible flex in the BB area, given the CR1 is a rigid frame, and the moment arm is too short to be effective in bending the frame. Your scenario of leaning the bike to the side does not happen in real life. The bike swings side to side during out-of-saddle effort, as I have said, is just the bike trying to counteract your pedalling motion so that you stay in a constant location relative to the bike (conservation of momentum). On a trainer, it is just vice versa. You go up and down rather than the bike swing sideways, as long as you pedal in a correct way. If one produce a significant lateral flex in the entire frame, there is a problem going on.


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## B R H (Sep 9, 2004)

I wasn't so much concerned with frame flex in the tubes, but rather near the dropouts and joints where things are bonded. I agree that with smooth pedaling action, it really shouldn't be an issue, but I do get a little crazy on the trainer sometimes especially when doing intervals to failure. The trainer moves around leaving black marks all over the floor. I know these stresses are higher than the bike will see otherwise. Perhaps I do need to worry more about my technique rather than the bike though! I suppose if it were an issue someone would have chimed in with an example or picture of a failure by now.


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## mark_m (Apr 24, 2003)

B R H said:


> Is a lightweight frame like this safe to use on a trainer (Minoura 850 for example)?


see newsgroup rec.bicycles.tech for discussion on this.
For example see: Google search 

Even if there wouldn't be any examples of frame failures why you would want to use your "good" bike for trainer use (except for warming up at races etc.)? Buy beater bike for trainer and set it up similarly to your main bike.


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## B R H (Sep 9, 2004)

Thanks! You know I just never seem to be able to type in the right combination of words to get many hits on searches.

Good bike vs. beater bike. That's another reason I was asking. I'd rather not have additional bikes to maintain and find room for. It's trainer-worthiness is part of the purchase decision I'm making right now.


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## CHT (Mar 1, 2001)

Why debate it, just ask Scott directly. It's their warranty, so you'll know if it'll be honored. Everyone's posts here (myself included) are only speculation. In the unlikely event you crack your frame, it's all about the warranty here. Scott either builds or designed the frame, so they'll either stand behind it for this use or not. 

p.s. Nice frame. Saw one at a local century. Very beefy tubes (I have a LOOK 381 which looked painfully thin in comparison).


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## topcarb (Aug 27, 2004)

FWIW B R H, I agree, I dont think the force distribution can be the same locked in the trainer as on the road. Contacting Scott is probably the most secure decision you can make...and I put my Al frame in my trainer just to avoid any issue that might ever happen with my carbon.

topcarb


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## 1-2win (Apr 22, 2004)

*I know what you mean...*

_


B R H said:



For the bike to flex sideways the axle does not have to move at all. I'm talking about frame flex laterally. Put your bike in a trainer, get on the bike, and lean over to the side. The frame will be stressed and will flex. Try this on the road and you fall over... no stress on the frame (until it hits the ground).

Seemed like such a simple question.

Click to expand...

_And you are right about the flex. I don´t have exactly a super light frame but a nice Trek 5500 that I have ridden in my trainer for the last couple of years and I have noticed the lateral flex you talk about, it sort of tweaks the bike from the droputs. I freaked out at first but kinda got used to it later on. Since I am no engineer i can´t tell if carbon fatigues or not but my bike is still holding on pretty well so far. Of course I can´t comment about the Scott frame but thought you may want to hear from other carbon frames used on indoor trainers, I am sure asking Scott directly can give you the piece of mind you need.

Hope I have helped.


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