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PostPosted: Thu Mar 07, 2013 4:36 pm 
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Joined: Thu Mar 07, 2013 4:23 pm
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I'm new to training with power (new enve wheelset with g3 hub), and have been riding indoors for the past month or so on the trainer. My power readings on a ride last night were low, and I had a hard time keeping the wattage up during what should have been an relatively easy intensity ride. I hoped off half way through and loosened the trainer clamp, and the ride got immediately easier and my wattage went up by 30-40 watts using the same effort.

Has anyone else had this experience? Is it a common phenomenon with an indoor trainer? If so, how do you know how tight to clamp the rear wheel in the trainer?

Thanks in advance!

Matt P


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PostPosted: Thu Mar 07, 2013 4:55 pm 
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Posts: 136
Less inertia when the roller is tighter. It gets more difficult on dead spot. Per your experience, keep it as light as possible without any wheel slippage. I think I was using 2 full turns when I had a KK. Experiment setups and try to keep it consistent.

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PostPosted: Thu Mar 07, 2013 5:09 pm 
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Sorry. It was the clamp on the rear hub that I loosened. Not the roller. But thanks for the suggestion. I think I am at around 3 turns, which may be tighter than it needs to be ...


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PostPosted: Thu Mar 07, 2013 5:33 pm 
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Joined: Mon Feb 19, 2007 3:44 am
Posts: 2015
Location: Canada
Doesn't matter with a real PM. Maybe your head unit has the "smoothing" option and it felt easier though, from the direct reading on the screen.
We're not talking about speed, are we ? The thing is, even if you crank the resistance unit to squeeze the tire, well, maybe you won't be able to use the same gears, maybe the trainer won't have the same inertia, but a Watt is a Watt, and if you target an intensty level with a Power meter, it should end up the same, at 20 km/h, or at 55 km/h.

It would matter with the KK power estimator device though, since it measures the rear wheel RPM to estimate power...

I used it last year. Good trainer.

Tough days can happen. Make shure you get proper ventilation to avoid over heating (a huge fan close to the core is the way I do). Training indoors is a different sport. You have to get used to it. Us canadians become experts at this, and bring our indoors numbers close to our best outdoors ones.

Louis :)


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PostPosted: Thu Mar 07, 2013 7:01 pm 
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I don't know Louis. Squeeze the tire 2-3 more turns and go do an FTP test with 90-95 cadence. Let me know how it feels :), I think you should see a difference, even more with a high cadence. I agree with all the other tips... I've had different PE with just slight changes in room temperature or using 2 fans instead of 1. I think you also get used to your setup after a while, but like you said, it does feel like a different sport in the first weeks.

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PostPosted: Thu Mar 07, 2013 7:34 pm 
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Any FTP test I'll do, will be by looking at my Power Meter head unit screen. So if I do it outdoors, while climbing a 10% hill, I'll adjust...I certainly won't try to reach a pre estimated RPM, or speed...


If you can only manage 20 km/h (for example) and use a smaller gearing and still put out 270 Watts with 3 more turns on the resistance unit at 90 rpm, it would be the same as using a bigger gearing at 55 km/h and 90 RPM, with less pressure on the tire, IF the Power output is 270 Watts, it's 270 Watts.
If you stop pedalling half a second, that half a second, you're producing 0 Watts, even if the screen on the head unit tells you otherwise, nothing to relate to the speed, or the rear wheel RPM.

Since the OP has a (otherwise very nice ) real Power meter, my take is he "feels" more resistance (wich I understand, and agree as long as we're talking same gearing, same rear wheel RPM).
And his readings are smoothened by the head unit device he uses.

I would also add this question to the OP: Check if the problematic training session was done with same cranks RPM than usual, or less ?
If the session was an easy ride, low effort, then maybe check for this:
If you have eliminated the zero on your PM calibration, this also will change your real work data. When "cruising", or when you stop pedalling, your PM should record 0 Watts (include the "0" when setting).
You won't "cheat" the real numbers this way, when spinning a low gear or resistance, and high cadence on the trainer.

Louis :)


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PostPosted: Thu Mar 07, 2013 8:36 pm 
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MAPhillips wrote:
Sorry. It was the clamp on the rear hub that I loosened. Not the roller. But thanks for the suggestion. I think I am at around 3 turns, which may be tighter than it needs to be ...


With the roller disengaged and the clamp tight can the wheel still coast?

Are you saying the hub body was getting squeezed?

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PostPosted: Thu Mar 07, 2013 9:19 pm 
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Thanks for the feedback. I don't recall if I spun the rear wheel after I tightened the knob/clamp on the rear skewer. I know that the wheel was coasting fine after I originally put it in the trainer, but I went back (I think) to tighten the knob/clamp on the skewer after I spun the wheel. I suspect that, after I adjusted the clamp tightness, the clamp or the frame was was exerting some pressure on the hub that was throwing of the power readings. I did zero out the PT before I started the workout, and the calibration reading was in spec (506).

I originally thought that I was just having a tough day and might have been fatigued. But the numbers just didn't seem right. I have a FTP of 212, and was having difficulty keeping my wattage at 160. I also noticed that my HR was elevated (close to 160) versus the 135-40 to normally keep my power in the 160-170 range.

After 55 minutes of torture, I decided to get off the bike and loosen the rear skewer knob on the KK trainer. That was all I did. I didn't adjust the roller tension. I got back on the bike and it felt immediately easier and I was able to easily bring the power up to 170-190 range.


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PostPosted: Thu Mar 07, 2013 9:46 pm 
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Posts: 2015
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Hum. Okayyyyy...

Now I understand (I think).

Seems like a hub tightening problem. Maybe you squeezed the bearings with too much pressure. I'm not shure, but the Powertap hub doesn't have bearing preload adjustment (!?!). Check those bearings to make shure everything is OK.

And the Kurt Kinetic holds the bike very well usually, without having to overtighten the knob.

My 2 cents...

Louis :)


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PostPosted: Thu Mar 07, 2013 10:25 pm 
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Thanks, Louis. I have always been concerned about the bike having too much play in the trainer, but I now see the error in my ways. Think I also need to go easy on the roller tension on the wheel, just enough so that it rolls smoothly and doesn't skip ...


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PostPosted: Fri Apr 05, 2013 9:15 pm 
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Joined: Sat May 22, 2010 2:42 pm
Posts: 59
Location: Wiltshire, UK
My Power2max matches the KK published speed/power curve when I have 4 full turns on the roller (from it just touching hte tire) and 110psi in the tire.

Its much easier with between 2.5 & 3 full turns, but I get a good amount wheel slippage with any short intense intervals.


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