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TT Crank Length

Old 01-19-18, 10:33 AM
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TT Crank Length

Year 2 of the TT transformation is off to a pretty good start. All my interval time & testing has been in the Aero position, very close now to my Road bike PD numbers (1 min actually passed my road bike). The fitter I work with has suggested trying out 165's, thinks I may benefit from opening the hip angle up a bit more. I'm currently on 172.5 (for about the last 100 years). I've always ridden 165 on the track and never had an issue jumping back and forth. Seems like a worth while experiment.

Anybody else make this change? Adaptation time? Did you notice an immediate impact?
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Old 01-19-18, 11:48 AM
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Originally Posted by Voodoo76 View Post
Year 2 of the TT transformation is off to a pretty good start. All my interval time & testing has been in the Aero position, very close now to my Road bike PD numbers (1 min actually passed my road bike). The fitter I work with has suggested trying out 165's, thinks I may benefit from opening the hip angle up a bit more. I'm currently on 172.5 (for about the last 100 years). I've always ridden 165 on the track and never had an issue jumping back and forth. Seems like a worth while experiment.

Anybody else make this change? Adaptation time? Did you notice an immediate impact?
I made the change to 165's. Not sure if it made a difference but I've learned when you don't succeed listen to your coach.
I did and they are on two of the bikes now.

Can't put them on the @sarals red tt bike all I could do to get compact gearing on that.
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Old 01-19-18, 01:29 PM
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I've been riding 165MM cranks on my TT bike for years, and the track bike (only a year) also has 165's. To be honest, when I went from 170's to 165's on the TT bike, I don't recall feeling a difference. Apparently there was one, though, because my times over a 12 or 20K course started to improve. My cadence also came up a bit, too, but I don't know that I'd attribute that directly to the cranks.
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Old 01-19-18, 09:19 PM
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I switched from 170 to 165s on my road bikes a few years ago upon the advice of my fitter. For me, the difference was a marginally better power output with the shorter cranks. When my foot got to the top of the pedal stroke with the 170s, I had a small “dead spot” in which my power dropped off, I just needed to lift my leg a little too high.

I don’t like the feel that of 170s on the road bikes, I just feel like my pedal stroke if off, a little jerky-feeling. So when I got the TT bike, I went with 165s too.

As weird as the 170s feel to me on the road bikes, the mountain bike came with 170s and that feels totally fine.
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Old 01-20-18, 10:29 AM
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I use 165 mm on my track bike and 172.5 on my TT bike. If I get a new power meter for my TT bike, I would switch to 165 cranks.

I have tight hamstrings and a bad back. Shorter cranks are better for me when riding with a reduced hip angle.

Having said that, old school thinking was longer cranks and bigger gears for time trials and pursuit.
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Old 01-20-18, 12:44 PM
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Originally Posted by Hermes View Post
I use 165 mm on my track bike and 172.5 on my TT bike. If I get a new power meter for my TT bike, I would switch to 165 cranks.

I have tight hamstrings and a bad back. Shorter cranks are better for me when riding with a reduced hip angle.

Having said that, old school thinking was longer cranks and bigger gears for time trials and pursuit.
Hermes, were you Pursuiting on 165's?

Fortunately I'm running Hollowgram cranks & a P2Max meter. I picked up a set of 165mm arms on eBay and per P2Max support there is no recalibration needed with the arm change (I have the necessary tools). Very easy swap, don't even need to pull the BB.

I put off trying this for quite a while due to the remnants of that old school thinking. I'm in full on experiment mode this winter.
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Old 01-20-18, 08:14 PM
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When I started to ride track, I used 172.5 cranks for pursuit. I switched to 165 a couple of years ago.
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Old 01-21-18, 09:09 PM
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I switched to 165 mm cranks on my TT bike a 4(?) years ago. Was using 172.5 mm cranks but switched to try to open my hip angle and to allow for a slightly lower front end. Always used 165 mm cranks on the track and as others have said, I never had trouble switching back and forth. One of the few position differences that I don't feel. for reference, my road bikes have 170 mm cranks.
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Old 01-22-18, 11:55 AM
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Appreciate all the feedback. Making the change this week, I'm on an easy week. Some testing late week/weekend to set up my next training cycle. I'll do that with the change.
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Old 01-22-18, 01:01 PM
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Not just a masters question. I'm a decent TTer, son and wife are outstanding. I've been playing with this 30 years.
Net is, it depends.

Of course your setup on the bike matters. Part of this is the fore/aft seat position. In a more roadie position longer cranks can really close that hip angle (not wanted for a long power stroke). On the TT/seat forward, if the rider also uses a higher seat (they should) than road, the hips can be as open with longer cranks in the power area. And if they have a shorter power-on stroke, that matters even less.

I have a smoother stroke and am fine with shorter cranks. Wife likes a bit longer cranks. Son longer cranks yet.

For junior, we subscribe to the stomp theory for TTs - power comes in a staccato stomp/tic tic tic tic from 3-oclock to 5-oclock. So the "longer" 172.5, or 175 work well. As there is no more requirement for junior gears and higher cadence might go to the 175mm. I had a similar discussion yesterday with another ex-junior/pro who has decreased cadence. This is in contrast to a track-like spinner (or me) who is putting power over longer arc.

So while I (a smooth circle peddler) would notice a dead spot near the top, a stomper would not.
Masters tend to have lower cadence. I think that is due to lower cardio top end (max HR) that the higher cadence takes, or maybe it is that 11T, but masters are lower based on observation.

I'm not convinced someone should change pedaling styles, or not. But the position, crank length and style should be taken together.

If you are playing around with things also try changing the power arc - so smooth power on/spin vs the stomp.

Last edited by Doge; 01-22-18 at 03:21 PM.
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Old 01-22-18, 06:35 PM
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Doge some good points, thoughts. My tendency is to spin, that style is heavily ingrained. I'm currently faster at 90-100 rpm over 20K than at 80-85. Ask me to do a 5m max and I'll self select closer to 105-110 rpm. That has not changed from my 20's. I've always felt very strong on 165's on the Track. Add to that a fitter I trust observing that I'm smoother over the top on my road bike & suggesting the change.

Worked a bit with stomping the pedals more last summer. I could make it work (better with Q-rings) but was marginally slower testing & had some knee discomfort. Not sure if that's something I would have worked through but did not want to take the risk for what seemed like little to no gain. That kind of a style change may be tougher for an older rider than younger. So much adaptation has take place.

Should be interesting either way.
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Old 01-22-18, 08:13 PM
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I went to 165 arms on my TT bike several years ago. For most folks the trade-off of being able to get somewhat lower with the same hip angle generates more speed, especially true on longer TTs.

With that my best TTs and track Pursuits were on 172 cranks. But those were also my absolute peak all time fitness and power periods as well. The reduced flexibility because of age and injury made turning over the longer cranks more problematic. But if I over laid my mass start track stuff over my road stuff which would be a 165 to 172 5 comparison, I never saw any significant differences.

What I did notice was the slightly shorter cranks were easier on my knees overall. I run 170's on the road for what it's worth.
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Old 01-23-18, 10:19 AM
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Commenting on spin and cadence. Here are my observations:

In the hour record successes I have witnessed by masters men, the cadence was 100 rpm or greater that corresponds with pro / elites. And of course, him, our Lord Voldemort, Kevin, did 108 rpm at Aguascalientes Mex for his 50-54 his hour record last year.

In 2014, I was training with Dmitry, who was also advising Costa, Froome's training partner. Team Sky wanted Froome to lower his cadence during time trials to the 80 to 90 range.

I have to train to spin faster but I can always elect to spin slower. And it is only in the beginning that cadence affects my aerobic system. As I adapt, my aerobic system returns to normal for the power produced. And I know this because I measure power, cadence and HR.

Also, if I train at the track in the drops at higher cadence, my power riding on the hoods or tops on my road bike climbing is lower (or harder to make) at lower cadence.

I think it is easier to spin shorter cranks fasters.

So experimentation is key with the proviso that we as athletes are highly adaptive and through training and practice can have success across a large range of technology modalities.
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Old 01-23-18, 11:02 AM
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Originally Posted by Hermes View Post
I think it is easier to spin shorter cranks fasters.
Pretty true. And for most people riding higher cadence produces better efficiency and lessens fatigue. All my TT's come in around 100-101 RPM, I started out in the 90's and put in a lot of time self selecting that up.

FWIW Chris Hoy, who's got fairly long legs, runs 170's. Wiggans at 6'2" did his hour on 170's as well.

There are exceptions though. I raced against a two time track Olympian at the Tour of Gila, and I swear the guy climbed at 70 RPM. Know of a couple of other Nats/World level TT guys who are high 80's low 90's. They tend to be "thicker" all slow twitch folks.
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Old 01-25-18, 07:46 AM
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My track sprint bike and pursuit bike both have 167.5 cranks. Both sets are Dura Ace and I have a Stages power meter on a crank arm that I switch between bikes. My road bike is set up with 172.5 cranks. Without looking I don't know what the mtb, cross bikes and SS/fixie cross bike crank arms are. I really don't feel a difference when riding them.

Recently I found out something about my pedal stroke that is good news for me. I have two fused ankles with only limited motion in my foot. While getting a professional fitting on the bike that I will use for the pursuit and team pursuit the fitter found that I have no dead spot in my pedal stroke and both sides are with 2% of each other. At first he didn't believe his machine was recording correctly and had me move to one side of the saddle and ride only pushing down. That showed showed dead spots and inequities in leg strength.
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Old 02-01-18, 12:38 PM
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A couple of rides in on the trainer, including some Tempo to SS. My initial impression is positive. I raised my seat about 8mm, no change in the pads yet. I feel a little looser over the top, even with more pad drop. Sweet Spot targeting 95-100 rpm was not an issue and I was more comfortable at the end of 2x20 in the drops. If this is the real gain it's big. Time in zone on the pads was lacking a little last year.

Doing a longer Tempo session tonight. Going to do a quick video check on position Friday. Hopefully can get this setup change outside over the weekend.
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Old 02-28-18, 07:08 AM
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My initial observation was that I seemed a little better over the top as you would expect. On the down side when gassed late in longer intervals I didn't feel like I could grind out finishes as well as the 172's.

My current work & home schedule leaves me training indoors till the days get longer. So I can't get at the real question, does the shorter crank allow a setup that is faster? Some racing in March/April and State TT Championship is May, so I switched back to 172's. Promptly set a 20m power best in TT position, higher than my 2017 best on the Road bike.

I'll come back to this change again over the summer. When I can better test it.
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Old 02-28-18, 09:46 AM
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Check this out. https://cyclingtips.com/2013/09/clim...-are-affected/

I have always been intrigued by the differences of perceived effort between climbing, flat riding, time trialing and the trainer. According to the article it is about the way muscles are recruited on the different types of terrain and the trainer.

On the track and time trialing at higher speeds one is constantly topping up the energy to maintain speed where as when climbing or on the trainer, one recruits muscles differently to overcome a more constant force such as gravity.

There is no bad news here. My interpretation is that practice makes perfect and different muscle compositions will favor different situations. The only wild card is interpreting test data i.e. comparing riding the trainer versus riding on the track or the road.
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Old 03-06-18, 06:55 AM
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Similar to my n=1 observation over the years. 400W up a hill is mentally "easier" than 400W on the flat. Maintaining speed on the flat requires relentless focus.

The difference in feel from trainer to road for me is much less pronounced with some trainers. Kickr > Cyclops Fluid > Old school wheel on w fan. It seems like this ranking order follows flywheel inertia.
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