The Cadence Chasm - how best to cross it?

kmepham

Now that I'm indoors on the trainer and can keep my cadence and power steady, I'm suddenly acutely aware of the cadence chasm between 4th and 5th gears on my 12-25 cassette.  The jump from 19 to 17 is the largest gain ratio on a 12-25, and at 90RPM seems to require a huge 45W jump from about 190W to 235W.  I managed to achieve 207W for my FTP test in 4th gear by increasing cadence to 94RPM, but where should I go from here?  My thought is to just suck it up and start doing the workouts in 5th gear, in the hopes that by the time the next FTP test comes around, I will have developed, if not the strength, at least the mental six-pack to endure the test in that gear.  But based on today's 6' intervals, I'm not so sure I can pull it off.

For those of you who are either currently stuck in the middle of the largest gain ratio on your cassettes, or have made it successfully to the other side, what is your experience and what approach would you recommend?  

Chris G

 Have you looked for a cass with closer gears?  I do not know off the top of my head but maybe a 11-21 or 12-21 might have less of a gap.  You can also make a franken cass putting cogs from several together.  Would work fine on the trainer when you do not care abou the high or low range.  Have you tried the little ring and smaller cog on the back?  

kmepham

Chris, you're right, a 12-21 in back would give me the missing 18 and 20 gears, maybe that's what I'll have to resort to if the 17 proves to be too much for me as the intervals get longer. The only way I can get an in-between gearing with my current setup is to go small gear up front and 10th gear in the back, but are there any downsides to cross-chaining like that, especially for extended periods?

William Jenks

Kevin-

Another cassette is certainly a good solution, but can you also do this by going to the other chain ring? Sometimes the other chain ring will end up giving you the "in between" gear. I know that you're not "supposed" to use the big chain ring up front and the ~2nd or 3rd gear in the back, but that might give you the spot you need. Chains are consumables in the long run anyway. :-)

kmepham

William, I'd have to go to small chain ring, and 10th gear in back, to get the gear that's in between 4th and 5th with the big chain ring in front. Just wondering if that's too extreme a cross-chain.

chris malone

Why not use both gears? Go to the lighter gear for longer intervals.
Everyone has their sweet spot cadence. There's not that big a difference betwen your cadences now. If you got a closer gear, would you be at 92? I would say when in doubt, getting your watts from the higher cadence is advisable. As you get stronger my guess is that you will find yourself being able to push the bigger gear at 94 versus 90- then you'll really be pushing mo watts, which is basically what this is all about. So you might consider just hanging in for a bit to see which gear/cadence gets you the best results. You can also jump between the two, training both cadences. Longer intervals you're probably also going to be more comfortable deriving watts from a higher cadence/lighter gear.
2 cents.
Good luck.

William Jenks

Well, it's not good for your chain or gear rings and it may be noisy. That's the worst case of all of them, obviously.

Cassettes can be had for $60-75...and no harm in getting a lower grade one (105 instead of Ultegra?) if you only intend to use it on the trainer... I dunno.

I'll confess that I just deal with having a lower cadence on the bike in the trainer than outside...from high side of normal to low side of normal.

kmepham

I checked - to buy a Shimano cassette with an 18, I have to go Ultegra (12-23) or Dura Ace (choice of 12-21 or 12-23). But the prices on eBay aren't too bad. There's even a new Dura Ace 12-21 going for $50 right now. Looks like that's my fallback plan if I'm unable to stay on the 17 as the intervals get longer. Personally I don't do so well with low cadences - my sweet spot is probably around 95, and dropping from 95 to 85 (which is what going from 19 to 17 equates to) will probably cause my power output to drop, which is where my concern is coming from. We'll just have to see what happens in the next few weeks.

There must be others who've faced this. That 19-17 gap exists in most cassettes, and it's a doozy. Did everyone else simply accept the big cadence drop and gut it out until their power went up enough to get back to a sweet spot cadence on the 17?

Dave Campbell

How do you get the resistance from your trainer? Some have adjustable resistance. I ride a Cyclops fluid and can adjust resistance by changing the pressure the resistance unit puts on the tire and tire pressure. Might find a no cost solution there as well.

 

William Jenks

Good idea Dave! Presumably you'll lessen the resistance with higher tire pressure and less "indentation" with the tire.

Chris G

To be honest i never really thought about it that much. There is kind of a big gap for me on the trainer holding the hard intervals. I have a bunch of cassettes but have been too lazy to switch it up for the trainer. Not a bad idea. I tend to train with an 11-23 and race with the 11-26 if it is hilly. I know that i do not need the 11 but kinda like it.

Chris G

To be honest i never really thought about it that much. There is kind of a big gap for me on the trainer holding the hard intervals. I have a bunch of cassettes but have been too lazy to switch it up for the trainer. Not a bad idea. I tend to train with an 11-23 and race with the 11-26 if it is hilly. I know that i do not need the 11 but kinda like it.

kmepham

Dave's idea sounded like a good one, so I pumped up the tire to max recommended pressure (it was way low so thanks for the reminder), and adjusted the roller pressure on the tire until it was just enough to prevent slippage. Didn't make a difference: same wattage for the same gear and RPM. My KK Road Machine doesn't seem to have adjustable resistance; resistance is just a factor of how fast the back wheel is spinning. I'll hang onto 5th gear as long as I can, and if ultimately I can't then I'll probably end up rush-ordering a 12-23 cassette or something LOL. Thanks to everyone for your advice, much appreciated!

timdawg7

It's a great idea to change roller pressure on the tire. I've done it in the past on my Blackburn trainer and it really works. The only problem I ran into is how it affected my tires. It caused a dramatic decrease in the tire life and left a skid mark on the floor. Taught me a great lesson that a mat or towel under the trainer is a necessity. Hopefully you don't have the same problem.

Dave Campbell

For trainer season, I just went to Performance bike and told the sales guy I wanted a bullet proof in-expensive trainer tire. Don't remember the model right off the top of my ead, can look tonght. Its a hard, heavy, wire beaded thing. I actually ride it outside this time of year because it works fine and I'm too lazy to change it every time I go outside. When I first got the trainer, I messed around with varying the tire pressure and the amount of compression the resistance unit put on the tire to vary the power at a given cadence. I found a combination at about 110lbs and the 3rd cog off the bottom that would give me 230 watts @90rpm. Thats how I set it up.

@William, If I remember correctly, more tire pressure ended up giving me more watts at given cadence. Unlike on the road, where the contact patch of the tire/road gets smaller with more pressure, I think on the trainer, it actually add to the deformation. This is due to the tire wanting to increase in diameter, but the resistance surface isn't going anywhere, thus more "indentation". Since tonight is an off night, I'll do some more experimentation and record the results.

Anyway, get a cheap tough tire for this OS!

William Jenks

Yeah, I may have it backwards.

I know that on rollers, if you have higher tire pressure, you go "faster" for a given wattage, but that's more like the road prescription.

They do make trainer tires, but I've never bothered. I just use my old almost-worn-out ones.

Dave Campbell

OK, the trainer tire I'm using is a Continental Gatorskin. I messed with the pressure the resistance unit puts on the tire by screwing in the camming handle 1/2 turn and it added 5 watts at 85 rpm. So, I think if you experiment with tire pressure and the pressure, you can find a combination that hits the cadence/power number you want. I start there then shift up and down a couple cogs from this "center" position to break the monotony. I usually hold power constant and vary the cadence. 1 cog equals about 10 rpm's with a 50 tooth compact up front.

Carl

Okay since I'm so new to this PM thing. I seem to be able to go at a lower cadence and get my % of power for the workout and over. Like today I was easily in the 70's for rpm and hitting my % of power. So would the recommendation be not to do that and shift into a lower gear and crank up the rpm's to 85-90 to hit my % of power. I did notice shitting into number 5 I can only hold that for a short time but played with it today and enjoyed burning a "match". Learned that word today in the book I'm reading "Training and Racing with a Power Meter" 2nd addition. Great book......but for a laugh I have to tell you these quadrant graphs have me more and more confused than ever that I had to close the book and laugh.

Dave Campbell

Others may chime in, but I find it best to aim for 85-90rpm. Thats what I see as a minimum cadence to be able to run afterwards. I'll do some time over 100, and some at 70, but the bulk of the time is 85-90. I'm not a masher, even though I can hold a little higher wattage for a short time.

Chris G

You will eventually self select the best cadence for you on when doing intervals. I am not sure it really matters that much. It will work itself out. Its not like it is going to be easy no matter what or that you are going to run great after if you pedal 90 rpm but not be able to at all if you ride 80.

Gordon Cherwoniak

Kevin,

I did last year's OS on an 8 speed and found that I was utilitzing cadnece's between 80-100, mostly 85-95.  I just did the workouts and never worried about the cadence too much.  I looked at it as an opportunity to expand my comfort zone for my cadence.  It did have some effects on the legs and HR depending upon 80 rpm vs 100.

Gordon