AeroPod, PowerPod and Newton

I rode the trainer over the weekend due to weather. Got on, put the iBike in Trainer mode, warmed up, putting out pretty good numbers with less-than-expected effort, felt really good. Training DVD starts ramping up, so I'm shifting and getting into it. My 1 hour power is approx 295w, so I was surprised when I was putting out 350w at a low HR. Started breaking a sweat at 400w. I was having an amazing day! At some point I finally caved in to the reality of "too good to be true" and stopped. Turns out my rear tire was flat. I fixed that and suddenly 300w took a LOT of effort once again.

But I've been kind of noodling on this -- when the tire was flat, it was still turning the roller on the trainer and therefore should have been providing the normal resistance, right? I looked at it pretty carefully while pedaling and the trainer was engaged, the roller was rolling, and the cooling fins on the resistance unit was getting pretty warm.

This isn't an iBike problem. Not really a problem at all since everything went back to normal after I fixed the flat. I just can't come up with an explanation on why riding the trainer with a flat tire was so easy since I was still spinning the resistance unit by pedaling.

I felt a little slippage when stomping up to the next power level while doing ladders per the training DVD which is what tipped me off to the flat, but it was not slipping constantly, the tire was engaged pretty much all the time.

So I'm still wondering why this might be. Any ideas?

I don't know, but I'm lowering my pressures with one hand as I type with the other

Seriously though, on a trainer the only way to create more wattage is to go faster. So on your first spinup did you spin out in whatever gear you were in?

Yeah, if your tire goes flat then there's not as much contact with the trainer drum and it spins much easier/faster. On the trainer faster speed = faster watts.

We kind of did the same thing at Interbike when we were debuting the fitness test feature. John had me come up with a three minute test with w/kg fitness values for 1-10. Well, I did that but it was based on an all out effort on the road, the kind of effort where you pretty much fall off your bike afterwards. Needless to say, the people that were hoping on my bike at Interbike in gym shoes and jeans (riding my Speedplay pedals) were not really pushing any power so everybody was getting a fitness ranking 1.

So I took all pressure off the back tire so it was spinning about 28 mph with me just moving the pedals around so we could prove to people that there was more than one number for a fitness level.

Check out the graph -- I did a laddered warm-up that usually results in me going up to about 325w and getting my HR into the high 160s, but with a flat tire I was doing 375-400w and my HR was around 145bpm. I did not know I had a flat; I was thinking "wow, I'm having a great day!". Then did a rest (not really necessary since I hardly broke a sweat), thought maybe I had not tightened the roller onto the tire, watched everything spinning correctly in the back, figured I was truly having a good day. So I ramped it up per the DVD and started hitting it harder about 16 minutes into the ride and was putting out 425-450w with my HR at 130bpm. That's when "wow I'm having a great day" turned into "too good to be true, something is not right".

As you can see from the graph, after fixing the flat at approx 17 minutes into the session, putting out 275-300w had my heart pumping to a much different level than with the flat -- into the 170s.

So, seriously, would this have any relationship to why tubulars have an advantage? Less deformation of the tire or something? I'm wondering if there is any lesson to be applied to real outdoor riding so I can get more watts for less effort. Probably not, but it continues to simmer on the backburner of my brain.

The tire was turning the drum and therefore engaging the resistance unit, so it seems like the same speed would produce the same resistance which would take the same effort.