Kurt Kinetic tension setting

I have a KK trainer and have been cranking down the tension as the manual directs until the tire barely or doesn't slip when I grab the wheel and give it a good 1/4 rotation. This results in noticable tire deformation at the roller. Doing this I've gotten my apparent FTP from 230 to about 280* since last October. This last weekend while warming up for a race in Phoenix, a teamate told me I was nuts and to just give it tension but without any real tie deformation (from cranking down). So I come home and try it and suddenly my power numbers are way up and my apparent FTP is now 310-325* or so. The tire slips easily by hand, but not noticable while peddaling, except possibly at the first strokes of a 1 minute max pwer interval.

Which is the best way to tension the trainer and should I belive the numbers with less tension or crank it down and keep working?


*power I can hold for a 5 minutes interval without major difficulty.

 

I assume you're using the KK power computer to determine power? If so, then your body's output is probably the same in either case, however with the higher tension, more energy is being absorbed to squash the tire and so less left to spin the wheel.

Personally, I'd use as little tension as needed to prevent the tire from slipping during workouts. If you're wanting to use the computer to track progress, then you should make an effort to keep the tension constant from ride to ride so that it doesn't change what you're seeing on the display.

 

I haven't noticed big changes in power readings unless the tire is slipping I try to stay consistant with the way I tension the knob and the air pressure of the tire. If I am planning on doing a sprint at the end of my 3x20s I make sure the wheel is not slipping before I start.

 

I do try to keep the tension similar from work out to work out and the watt numbers on my KK meter (forget to mention this is what I'm using) are always fairly predictable. Not having tried less or more tension before, I was surprised to see such a noticable increase in power. It does make me wonder how much tension, or tire deformation, correlates with speed on the road for the same wattage. It certainly explains the lower constant speed I was able to acheive on the KK.

 

Talk to the KK men...

2 to 5 full turns of the knob mean next to nothing re: power differences.

To be super accurate....calibrate it like this.....

stop pedaling from 20 mph and time the wheel roll down...until it stops. Use a stop watch.
Adjust the tensioning knob until is takes about 13.4 seconds for the wheel to come to a complete stop.

This makes the KK computer DEAD ON with my power tap with wattage above 100.

With my tire that's about 2.5 turns of the knob...after the tire just comes in contact with the roller.

 

I just went UP on my tension by a half turn (from 2 turns to 2.5) because the squeeking of my tires was driving me nuts. Now i get no squeek at all, even on a 600 watt out of saddle spin up for an interval and I didnt notice much difference between my wattage last time I did the same workout. Like this I get quite a bit of tire deformation, but no slipping is always better for your tire (and roller).

I'd like to hear if anyone else saw chnages so dramatic in wattage between tension adjustements or maybe a power tap file.

One ride afew weeks agao something odd did happen which I am at a loss to explain. I did 3x7 leg tensions. 50 cadence in a 53/12 all three times. For some reason on the third set my wattage went down 30 watts compared to the first two-I never got off the bike-didnt touch a thing. THat was weird and I am still stumped. I dont think the fluid unit took a dump because I am of the belief that when the fluid part fails you can spin easily in a 53/12. Also-my power numbers during Tempo and such remains the same from ride to ride.

Ray

 

I just tried the coast down test and 13.4 seconds might be to slippery for my tire but I will use a coast down of 10 to 11 seconds for better consistency in my rides that's a great idea....Thanks.....We are talking about the Kurt Kinetic Road Machine correct?

 

To help minimize the slipping, I tried frenchyge's tire cleaning tips. I noticed a significant decrease in slippage afterwards, so I incorporated it in my pre-ride routine. Good stuff!

 

Yep, the Road Machine. Go here:

http://www.planet-x-bikes.com/triat...pagemaster&PAGE_user_op=view_page&PAGE_id=189

As you can see, when the roll down is set to 13.4 seconds the power computer is calibrated properly. If you don't care what the wattage reading is, you can just choose an arbitrary roll-down like 10 seconds. The only problem is that you won't be able to determine your actual FTP, just a relative number that would only matter to you; still good enough to track progress of course.

 

The temperature has gone up a bit around here and in my basement where the KK is and now I can get the coast down between 12 and 13 seconds. If it warms up some more I might hit the 13.4 second accuracy target.

 

I tighten mine as hard as I can when doing LT's and VO2 Max efforts. I've even sprayed Super77 spray glue on the tire to keep it from slipping. I usually do my LT's at 300-350w and my VO2's at 375-425w, depending on the time of year. I try hard to pedal evenly, but I'm sure most will think I just have a crappy pedal stroke.

BTW, my left leg gets the squeek at the bottom of the stroke, but if I pull back and over the top before I hit bottom it goes away. Of course just holding wattage during an interval makes it tough to pedal perfect circles!

 

Glue?....Why? After I put silicon where the knob makes contact with the risistance unit I can tighten it down to stop slipping even while sprinting at 37mph without glue. Glue must leave residue on the tire and wheel that would be a mess.

 

Because it was sitting there and it's sticky! It worked too, plus I don't really care if my road bike gets dirty. I do care when I'm trying to crank out the watts and my tire slips every pedal stroke!