Bike Fit... sweet spot or ever evolving? (Page 5)

Exactly!
Hopefully they are both, but we both know that those kind of results don't prove that.


So now we're back to Marc's suggestion

Thanks Tom,

What is the discrepancy now between road and tri ?

Do you think there is a tipping point where you lose the most power ....in your case somewhere between 4 and 5.25".

That's only 1.25" or say 3cm.According to cervelo, that 3 cm is worth 4.5watts. Sounds like you gave up 4.5 watts of aero for many more watts of power.

Well, I only figured this out this summer after I purchased the SHIV and had about 1 week with the previous bike side by side, Valdora PHX2. I looked at my fitting paper by a FIST certified fitter, and simultaneously measuring the angles on the road bike, the Valdora and the SHIV. On my road bike I was powerful, but there was a loss of power on the Valdora.

I'll try to make this short...

My Valdora angles were off of what my original FIST settings on paper. I had fidgeted with my bike so much to get aero as possible, thinking that was the avenue to speed. I knew that I was getting more speed and power, b/c when I road my road bike... I was producing good numbers and turning the same gears that I was turning on the Valdora despite being up on the hoods and less aero.

So, anyways, I discovered 2 things during this measuring process... to get aero on the Valdora, not only did I lower the bars and everything else, got a negative stem, BUT I also had raised the seat about 1 cm, and of course way forward. BUT, I was not getting any faster, just more aero and more uncomfortable. So, I put the SHIV together with the original FIST settings and put a GENOMONITER (sic?) app on my ipad and measured my angles again, then measured my Valdora angles... I was WAY off the mark on the Valdora. I dialed in my SHIV and no prior rides (I bought it and got it about 2 weeks before my Aug 11th HIM), no time on it, except in the house to make sure all my measurements were good. I went to the race and won, with the 4th fastest bike split. This convinced right there that it wasn't about going low as possible, since my power was always there, I couldn't access it.

Then, on Sept 15th, I did the 40k TT and got a new wattage PR of 315w / 320 np, then 1 week later I got 300w / 312 np at the Oly race with the fastest bike split,

To answer your question... my delta between the road and tri bike is now about 10 watts from around 35 watts. In this case, I gladly gave up a few percentage points of aero for watts. I just wish I had a better wheelset.

Another thing that I've worked on too is my back position and turtling better... I noticed that in the Oly race that when I concentrated on a flat back and turtling... my speed jumped higher by about 1/4 to 1/3 mph. But as you probably know... when you get tired, you scrunch up, so I've got to concentrate more and that's tiring, but I'm still learning and practicing.

I could experiment with going lower on the SHIV with 165mm crank arms from 170mm, that'd get me lower by another cm (or higher in the saddle by 1 cm), but that's an expensive experiment. You did that... what was your results? and what is your opinion about the crank arms?

Edited by tomspharmacy 2013-10-08 2:47 PM

woah! by a Centimeter??

Well, a mm here and a mm there and you end up way off. I guess that's the moral of the story... should have said this earlier, trying to pass along some experience with the mindset of going low...spared you of all the gory details.

Edited by tomspharmacy 2013-10-08 2:57 PM

I went from 172.5 to 165 cranks, so 7.5mm. I raised the seat by 7.5mm. But it's the equivalent of going up by 1.5cm at the top of the pedal cycle.

It mad no difference to me. I am not even sure I could feel the difference.

The fact it made no difference in my ability to generate power leads me to believe it's not my closed hip angle that is my limiter.

I also have a 10watts road to tri bike difference.

What is your "closed" hip angle? Have you measured it? I believe in the no lower than 90 degrees rule.

From what I've read from scientific study and now Cervelo, is that a shorter crank doesn't make you more powerful and neither less, but should open up the hip angle... and make the rider inturn more aero because of the higher seat. It sounds logical. But not from a power standpoint, did you get a bump in speed, that would determine whether you became more aero?

On a side note... I'm getting more interested in lowering my crr... that's less expensive and could have just as good a benefit as spending uber $$$ on cranks and bars. Again, I wish that I had a better wheelset so that I could experiment with 25's on wide aero wheels vs. my skinny chinese aluminum clinchers with 23's.





Edited by tomspharmacy 2013-10-08 3:13 PM

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sort of. You raise your seat because you lowered your cockpit, you go to shorter crankarms because once you do those two things you have pinched your hip angle.

on CRR you are still better off with 23's than 25's due to the aerodynamic hit you take from the wide shape. Even though Zipp says FC wheels were made to be used with 25mm tires, they don't claim they are optimal with them.

In 0 / low yaw situations, even narrower tires / rims generally hold up well / exceed their bigger brethren. Sweeps get iffy though.

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That's what everyone says...

I use michelin pro 4 service course with basic kenda tubes, would I see an improvement with the gp 4000s? and what if I used them with the michelin latex tubes that I have but never used yet?

I'm kind of timid to change b/c I like the michelin's for the durability and grip... knock on wood.

What about the new s-works turbo 23's or 24's?

Now, Schwalbe has a new Ironman tire that shows good results, acc. to crr master Tom A.?

I have an A race in 2 weeks, should I convert now?

the 23mm 4000s' have "magic" aero properties with wider (and by wider I mean sweeping generalization of non 19mm wide HED/ZIPP/etc wheels.) wheels. Nobody's 100% sure why, but they are fast.

If you install latex correctly, there is some evidence that they are MORE durable than butyl tubes (small % less chance of pinch flats) and they are definitely faster. 99.9% of the issues people have with latex is getting in a hurry when you are installing them.

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SNAP!!!

I guess that I'll pick up a pair of contis and carefully install the latex. At least I have 4 latex tubes, so I can mess up at least one or two.

It has no impact on my power. Speed is another beast. I think raising my butt 1.5 cm will have very little impact on my cda. Without a tunnel, I don't think it's even measurable given all the 'noise' during field testing



Hard work :-)

Seriously, I think more time riding hard is what I need most. Many people have a lot of optimization they can do ALONG WITH hard work. I think I am somewhat optimized and just need to work harder. Problem is I need to do this across 3 sports (and nutrition and weight and.....). So little time, so much to do.

Definitely do it!  Below is from Tom Anhalt's Blather 'bout Bikes site. The GP4000s w/latex measured ~9W per pair less than the Mich Pro4 SC with Latex, ~7W less than the Mich Pro4 Comp SC.  The GP4000s with butyl tubes measured 8W more than the latex tubes.  If the Mic Pro4 SC with butyl tubes are ~8W more than that's in the neighborhood of 16W (+/-) coming your way.

The Tubular was a top tire, the tubeless was on pair with the GP4000S/latex and the clincher was about as good as GP4000s with butyl.

I'd say even replace it.  In my last race I came back to T to get my bike after the race and my front tire was flat.  Later inspected it and found a tiny hole on the rim tape side. Lined it up again in the wheel and there was the tiniest pin hole in the tape over a spoke hole that the tube found its way into.  I swear it wasn't there when I last inspected the tape!

DOUBLE SNAP!!!

What kind of rim tape do you all recommend? I think that it's got ritchey tape from the purchase 2 years ago, never payed attention... got no problems with it currently.

always use velox cloth rim tape. It's the best by far.
If you ever get nervous, you can run a layer of packing tape over top of your rim tape so you know things are smooth. I've done that before on wheels that don't need/use rim tape (non-spoked discs / H3's)

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I'll admit that I didn't give the tires too much serious thought. I was more interested in durability and reliability. Since the wheelset came with Michelin, I stuck with them. I had read about faster tires but just went about my business.

I had rented Zipp 606 combo for St. George that came with Michelin Pro 4 SC tires, I didn't feel that it made a difference, except being more stable than my wheels.

I'll know if the tires had any effect since I plan to ride at a specific power range and a hit the expected speed, if I go that speed on less watts, it'll be b/c of tires, if I go faster on the specified watts then I'll know it's b/c of the tires. I know this course like the back of my hand, so I'll have my power meter and my butt meter to assess. I'll report back.

Edited by tomspharmacy 2013-10-09 9:35 AM

What tire pressure?

I'm 173-174 with bike in race setup. I've always run about 100 with the michelins.

A complicated question, there is no one universal answer. Different days, weather, roads, conditions, speeds, temps require different pressures. But if you run the same width tire front and rear, you want at least a 7-10 lb psi difference between front and rear wheels.

My race weights about the same. The local sprint races have had most of the roads repaved in recent years and I ride with 105ish. On the rougher roads that I train on I ride with 90ish. I should add I usually put an extra pump or two in the rear tire.

Edited by Donto 2013-10-09 3:22 PM