question on turbos and their effect on the frame.

cyclingDoc
cyclingDoc Posts: 20
edited January 2013 in Training, fitness and health
Hi folks.

Have been using my old roadbike on a turbo this fall/winter, but decided to upgrade to a new full carbon beauty, a 2012 Cannondale Supersix Ultegra Di2.
She's a beauty and I hope she will surve me faithfully for many years.
I would like to use my new bike to train so that I get used to the position, but I was wondering if the way the turbo fixes the frame will put extra strain on it so that it will decrease the life of the frame?

Anybody have any knowledge on this?

Comments

  • neeb
    neeb Posts: 4,473
    It'll be fine. If you imagine the physics involved when climbing out of the saddle on a steep hill, you are also putting all of your power and body weight through the frame and dropouts when you are doing that. The difference is that you are leaning the bike slightly to counteract the force rather than having the turbo frame counteracting it. In both cases the lateral forces are being transmitted through the frame and dropouts. The frame is designed to put up with that. If there was less force going through the frame when you were cycling on the road you would fall over sideways.

    Admittedly the wheels absorb some of the force on the road by flexing a little, but then most turbo frames flex a little too.
  • aleslie22
    aleslie22 Posts: 26
    Don't use it on rollers though as they damage carbon frames.
  • Jauncarlos67
    Jauncarlos67 Posts: 95
    Sorry for sounding thick, but what bike would be better on a turbo trainer an alloy or carbon?
    I have just hooked up my Specialized Tarmac Comp (carbon) onto my turbo trainer, and don't wont to damage it.

    I'm beginning to sound like a t*rt, maybe my kids are right I think I love my bike to much!!!!!
    Wilier La Triestina
    Specialized Tarmac Comp
  • neeb
    neeb Posts: 4,473
    Jauncarlos67 wrote:
    Sorry for sounding thick, but what bike would be better on a turbo trainer an alloy or carbon?
    I have just hooked up my Specialized Tarmac Comp (carbon) onto my turbo trainer, and don't wont to damage it.

    I'm beginning to sound like a t*rt, maybe my kids are right I think I love my bike to much!!!!!
    Honestly, it doesn't matter, you won't damage it. I use my best bike on the trainer in the winter, and my winter bike on it during the summer.

    Of course you could always damage the frame just by bashing it hard accidentally on the turbo when trying to attach it or remove it. You are far more likely to damage a carbon frame that way than by actual use on the turbo.
  • Jauncarlos67
    Jauncarlos67 Posts: 95
    Thanks Neeb
    Wilier La Triestina
    Specialized Tarmac Comp
  • neeb
    neeb Posts: 4,473
    P.S. Another thing to possibly bear in mind is sweat - it can corrode metal bits over time although generally only stuff such as bolts and washers. It washes off carbon without problems though...
  • sadlybiggins
    sadlybiggins Posts: 158
    One thing to check is your warranty docs from Cannondale. I have a Cube Agree GTC SL and the Cube warranty states not to use it on "fixed trainers" or similar wording but that rollers are fine. I checked with Cube whether this meant a turbo and they said that it did. Obviously loads of people do use carbon bikes on turbos without any ill effects and I can't see why this would be a problem, but it might be something the manufacturer asks if you ever have a frame problem - even if totally unrelated to use on the turbo - and try to claim on the warranty.
  • wardieboy
    wardieboy Posts: 230
    I did have a vintage Raleigh 501 frame snap at the chain stay on my turbo. This was a 1986 bike and had some rust, I'm sure the frame would have snapped eventually through road use but don't think the turbo helped at all.

    I wouldn't use another steel framed bike on a turbo due to the flexibility in the frame, you could see the bottom bracket moving from left to right with each pedal stroke. I've now got an alloy bike on the trainer and the difference is huge.
  • Alex_Simmons/RST
    Alex_Simmons/RST Posts: 4,161
    wardieboy wrote:
    I wouldn't use another steel framed bike on a turbo due to the flexibility in the frame, you could see the bottom bracket moving from left to right with each pedal stroke. I've now got an alloy bike on the trainer and the difference is huge.
    What makes you think that the bike doesn't also do that when riding on the road?
    RST Sport : Coaching - Training Plans - Powermeters -- My blog -- AeroCoach Australia
  • wardieboy
    wardieboy Posts: 230
    Alex_Simmons/RST wrote:
    wardieboy wrote:
    I wouldn't use another steel framed bike on a turbo due to the flexibility in the frame, you could see the bottom bracket moving from left to right with each pedal stroke. I've now got an alloy bike on the trainer and the difference is huge.
    What makes you think that the bike doesn't also do that when riding on the road?

    I fully understand that frames also flex on the road, what I experienced was the flex was more apparent when the bike was on the turbo, to the extent that the rear wheel would rub against the chain stay when pushing really hard. I never experienced the wheel rubbing when out on the road.
  • Froomes Edgar
    Froomes Edgar Posts: 359
    wardieboy wrote:
    I did have a vintage Raleigh 501 frame snap at the chain stay on my turbo. This was a 1986 bike and had some rust, I'm sure the frame would have snapped eventually through road use but don't think the turbo helped at all.

    I wouldn't use another steel framed bike on a turbo due to the flexibility in the frame, you could see the bottom bracket moving from left to right with each pedal stroke. I've now got an alloy bike on the trainer and the difference is huge.

    Nice. I had a frame snap at the chainstay on the road whilst going up a massive hill. Also I have an alloy bike on my turbo and I can see the bottom bracket moving from side-to-side.

    I think this clears it up for the OP.
  • mamba80
    mamba80 Posts: 5,032
    Alex_Simmons/RST wrote:
    wardieboy wrote:
    I wouldn't use another steel framed bike on a turbo due to the flexibility in the frame, you could see the bottom bracket moving from left to right with each pedal stroke. I've now got an alloy bike on the trainer and the difference is huge.

    What makes you think that the bike doesn't also do that when riding on the road?

    Maybe your frame was flexing 'cause your frame was in the process of snapping?
    steel frames arnt made of pasta.

    Cube specify no turbo use, because their bikes aare xxxp
  • iPip
    iPip Posts: 90
    mamba80 wrote:
    Cube specify no turbo use, because their bikes aare xxxp
    No they're not, far from it.
    Personally, I wouldn't use a turbo for any frame. No matter what forces it comes under during normal riding it's not the same as the lateral resistance of you trying to tilt a frame that's fixed at the rear axle. Possibly, the rock and roll versions mitigate this.
    Regards
    Pip

    Cube Agree GTC Pro
    Boardman Hybrid Comp
    Voodoo Bantu
  • Froomes Edgar
    Froomes Edgar Posts: 359
    iPip wrote:
    mamba80 wrote:
    Cube specify no turbo use, because their bikes aare xxxp

    Personally, I wouldn't use a turbo for any frame. No matter what forces it comes under during normal riding it's not the same as the lateral resistance of you trying to tilt a frame that's fixed at the rear axle.

    Agreed that they're not the same. Are they worse than those encountered by hitting a pothole at 30mph? Or sprinting on the drops at 1200w rather than chugging along at 300w (not many people sprint on the turbo)?
  • mike101
    mike101 Posts: 42
    I'm not sure I'd put my best bike on the turbo. My winter bike makes some lovely creaking noises during longer threshold sessions that I don't hear on the road :D
  • neeb
    neeb Posts: 4,473
    The reason you are more aware of the frame/BB flexing on the turbo is that you have a fixed visual reference point. On the road you just have a moving blur below the BB, so you generally won't see any flexing that is occurring.

    Remember on most turbos the dropouts themselves are not directly clamped by the turbo frame, all that the turbo is doing is holding the quick release in a fixed position. So the frame is flexing against the axle and the quick release just as it is on the road. Think what you are doing when you are climbing out of the saddle on the road - you are putting all of your weight and power into pushing one pedal down, while leaning the bike the other way to maintain balance. Effectively you are angling the frame in order to exert maximum shearing force on the dropouts, as if you were trying to break the bike in half - how else would the lateral force be opposed to stop you falling over?
  • le_boss
    le_boss Posts: 183
    aleslie22 wrote:
    Don't use it on rollers though as they damage carbon frames.

    how do they???

    last year i went to watch several races, including 3 stages of the tour, every stage of the tour of britain and 2 stages of the giro. on each occasion i was surprised at how many riders (most noticeably sky) were using rollers to warm up on...on the same bikes they would be using in the race!

    So please explain your claim.
  • Tom Butcher
    Tom Butcher Posts: 3,830
    They were joking
    it's a hard life if you don't weaken.
  • thegreatdivide
    thegreatdivide Posts: 5,807
    neeb wrote:
    The reason you are more aware of the frame/BB flexing on the turbo is that you have a fixed visual reference point. On the road you just have a moving blur below the BB, so you generally won't see any flexing that is occurring.

    Remember on most turbos the dropouts themselves are not directly clamped by the turbo frame, all that the turbo is doing is holding the quick release in a fixed position. So the frame is flexing against the axle and the quick release just as it is on the road. Think what you are doing when you are climbing out of the saddle on the road - you are putting all of your weight and power into pushing one pedal down, while leaning the bike the other way to maintain balance. Effectively you are angling the frame in order to exert maximum shearing force on the dropouts, as if you were trying to break the bike in half - how else would the lateral force be opposed to stop you falling over?

    All of this.
  • mamba80
    mamba80 Posts: 5,032
    le_boss wrote:
    aleslie22 wrote:
    Don't use it on rollers though as they damage carbon frames.

    how do they???

    last year i went to watch several races, including 3 stages of the tour, every stage of the tour of britain and 2 stages of the giro. on each occasion i was surprised at how many riders (most noticeably sky) were using rollers to warm up on...on the same bikes they would be using in the race!

    So please explain your claim.
    Tom Butcher wrote:
    They were joking

    I dont believe it ! i ve just given away my Elite Arion rollers because of what i read here :(
  • iPip
    iPip Posts: 90
    thegreatdivide wrote:
    neeb wrote:
    The reason you are more aware of the frame/BB flexing on the turbo is that you have a fixed visual reference point. On the road you just have a moving blur below the BB, so you generally won't see any flexing that is occurring.

    Remember on most turbos the dropouts themselves are not directly clamped by the turbo frame, all that the turbo is doing is holding the quick release in a fixed position. So the frame is flexing against the axle and the quick release just as it is on the road. Think what you are doing when you are climbing out of the saddle on the road - you are putting all of your weight and power into pushing one pedal down, while leaning the bike the other way to maintain balance. Effectively you are angling the frame in order to exert maximum shearing force on the dropouts, as if you were trying to break the bike in half - how else would the lateral force be opposed to stop you falling over?

    All of this.
    Sorry, this is just wrong. The predominant force through the drop-outs is the linear drive from the chain, which will try and create some twist about the axle (as the drive is one-sided), but nothing like you have described. The majority of the lateral force from your awesome sprint or uphill mash is through the cranks and bottom bracket.

    This is exactly why there are concerns on turbos.
    Regards
    Pip

    Cube Agree GTC Pro
    Boardman Hybrid Comp
    Voodoo Bantu
  • neeb
    neeb Posts: 4,473
    iPip wrote:
    Sorry, this is just wrong. The predominant force through the drop-outs is the linear drive from the chain, which will try and create some twist about the axle (as the drive is one-sided), but nothing like you have described. The majority of the lateral force from your awesome sprint or uphill mash is through the cranks and bottom bracket.

    This is exactly why there are concerns on turbos.
    What exactly do you mean by "twist about the axle"? Do you mean that the linear forces will tend to pull the driveside end of the axle forward and push the non-driveside end backwards? If so, surely it is the dropouts that are resisting and/or transmitting this force, and they are designed to do that. If the turbo frame is holding the quick release, all it is doing is opposing this "twisting". Either the turbo frame itself will flex slightly (thus absorbing some of the force that would otherwise be twisting the dropouts), or if it doesn't flex, a little more power will go towards turning the rear wheel instead of twisting the dropouts. Either way, there should be less strain on the dropouts.
  • iPip
    iPip Posts: 90
    neeb wrote:
    iPip wrote:
    Sorry, this is just wrong. The predominant force through the drop-outs is the linear drive from the chain, which will try and create some twist about the axle (as the drive is one-sided), but nothing like you have described. The majority of the lateral force from your awesome sprint or uphill mash is through the cranks and bottom bracket.

    This is exactly why there are concerns on turbos.
    What exactly do you mean by "twist about the axle"? Do you mean that the linear forces will tend to pull the driveside end of the axle forward and push the non-driveside end backwards? If so, surely it is the dropouts that are resisting and/or transmitting this force, and they are designed to do that. If the turbo frame is holding the quick release, all it is doing is opposing this "twisting". Either the turbo frame itself will flex slightly (thus absorbing some of the force that would otherwise be twisting the dropouts), or if it doesn't flex, a little more power will go towards turning the rear wheel instead of twisting the dropouts. Either way, there should be less strain on the dropouts.
    If you could apply the power perfectly, this wouldn't be far off.

    However, the problem comes from the side to side leaning of the bike that will happen, even during a relatively gentle ride. Imagine just trying to rock the bike side to side in a turbo, the turbo would resist the tilt of the rear wheel/frame because it's completely rigid. It's this force that isn't comparable to anything in normal riding and carbon may be more susceptible to damage because its very design gives it strength against quite specific directional forces. Introduce a force it hasn't been designed to cope with and it might fail.

    The real problem of course is that none of these forces act independently or as 'text book' as we all state in our arguments. You then balance that with a large number of people who claim they have no (known!) problems vs a few who think its knackered their bikes and make your own decision. Personally, mine is not to use one.
    Regards
    Pip

    Cube Agree GTC Pro
    Boardman Hybrid Comp
    Voodoo Bantu
  • Froomes Edgar
    Froomes Edgar Posts: 359
    Is there actually any evidence that turbos damage frames, or just a bunch of speculation?
  • thegreatdivide
    thegreatdivide Posts: 5,807
    Froomes Edgar wrote:
    Is there actually any evidence that turbos damage frames, or just a bunch of speculation?

    A bunch of forum speculation.
  • neeb
    neeb Posts: 4,473
    iPip wrote:
    However, the problem comes from the side to side leaning of the bike that will happen, even during a relatively gentle ride. Imagine just trying to rock the bike side to side in a turbo, the turbo would resist the tilt of the rear wheel/frame because it's completely rigid.
    Well, that's the issue I was addressing to begin with, before you started talking about linear forces and rear axle twisting... :wink:

    The side to side rocking that is resisted by the turbo is resisted by the wheels and weight distribution/balance when you are on the road. When you are following someone's wheel, do you see it rock from side to side when they are in the saddle? And when they are out of the saddle, is the rocking from side to side actually being caused by the pedalling forces? No, it's a result of reorientating the bike (changing centre of balance) in order to better resist the pedalling forces.
  • Froomes Edgar
    Froomes Edgar Posts: 359
    thegreatdivide wrote:
    Froomes Edgar wrote:
    Is there actually any evidence that turbos damage frames, or just a bunch of speculation?

    A bunch of forum speculation.

    I KNEW it.

    A quick google reveals hundreds of people asking if you should use a (carbon mostly) bike in a turbo, but no actual instances of frame damage. Not that such instances would be conclusive of course - frames break on the road too.

    I'll file this right next to all the things which sound plausible but for which no evidence exists, like overgeared training and religion.

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