RPE (+HR?) vs Power for TTs - Page 2

i believe that Roadie_scum is trying to find some good evidence one way or another about TT/power pacing efforts. however, i think R_S is convinced of the benefits in regards to training by power.

My own personal view (even if i no longer ride officially sanctioned TTs that aren't part of stage races) is that for most TTs i would use a power meter on something like a deep dish carbon aero rim. However, on a couple occasions i may be tempted to use a disc to see if i can note a difference.

Of course, i have 21 years of experience so my pacing isn't too bad when i do a TT (or TT training), but when i've been blinded to power it's been more up and down than i'd like (and i don't mean because of changes in terrain -- just i tend to slack off without the power meter to cajoule me on -- TTpower less 10% hurts me just as much as TTpower -- so i have slacked off).

Ric

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I don't think the value of a PM is limited to courses that lend themselves to a VP pacing strategy. A PM has value whenever you are trying to manage output with precision. In a TT, that is precisely the challenge -- to manage your limited resource (your maximum sustainable power over the duration of the event) to your maximum benefit (lowest time). This is hard to do without a PM on even a flat course with no wind when we're trying to maintain absolutely constant power. If the course is variable grade and there's some wind (when's the last time you rode a TT that wasn't variable grade with wind?), it becomes many times harder. The net result of managing output less precisely is that you will produce less power for the duration of the event because of the 4th power penalty you pay when you inadvertently put out more than your sustainable power. The VP pacing strategy says, "Yes, I know there is a price to be paid for putting out more watts for a short period of time, but the gain (time) is worth the price because I am cherry-picking where to put out more watts." To produce more watts unintentionally is to pay the price but not collect the benefit.

I would probably put my money on the rider using a PM and standard wheels vs. the rider with no PM but the best discs money can buy, especially if the course is rolling with wind. But, who says that is the choice? As beerco said, you can invest $50 in aero covers. So, to compare a disc to standard wheels is to tee up a straw man to beat up on. How about the disc/no PM vs. aero covers/PM?

I think this is precisely the issue -- your pacing is more up and down or, i.e., less precise. If we accept Andy's normalized power algorithm, this up and down pacing must, by definition, result in less average power due to the 4th order "penalty" you pay for the ups.

Hi Rap,

I'm not working hard to convince myself of anything. I'd be asking similarly skeptical questions if the answers were flowing in the other direction. I'm never going to buy race wheels as I've always been able to borrow them when it matters and I couldn't afford it anyway, whereas I'm almost definitely going to buy a powermeter for training and use in secondary races. Just trying to get a handle on how to intelligently manage equipment choices for target TT's. Or to put it another way - what Ric said.

As far as the wheel covers, I've always found it bizarre that UCI rules aren't followed in the US. Is this the case in the UK and elsewhere also? When I head home that won't be an option for me - every race requires UCI legal equipment from club level to nationals. That makes the equipment choice for me Disk vs PM on standard wheels - until I can afford or convince my rich friends to buy a new Zipp 808 w Powertap SL wheelset, by which time I may have retired from cycling.

I agree that aero covers would be the best solution for a dedicated PM user and occasional TT-er in terms of cost, pacing and aero benefit. Still, Roadie says he borrows disc wheels so maybe there's something else in the decision for him that we don't know about.

I wasn't comparing a disc to a standard wheel, but rather a disc to the high end carbon spoked aero wheels that will support a SL hub. The spoked wheels (w/ SL hub) are significantly more expensive than a disc and give up some aero to the disc. Certainly the pacing benefit favors the SL wheel. All I was saying is the optimal choice is not a clear-cut one since it depends on the rider's budget and how confident they are with their pacing by feel (and in Roadie's case, the fact that he can occasionally borrow a disc for *free*).

*free* = Lots of phone calls and grovelling + years of building contacts + establishing a reputation as a reliable guy + promising to pay for any damage + some luck

(Jumping in late...) RS: have you seen this link?

http://freespace.virgin.net/martin.shakeshaft/10tt.htm

It discusses pacing in a 10-mile TT and notes a 1 minute improvement from proper pacing. While the data presented is for a single rider it claims that this is about average.

Lanier

Okay, I retract my comment. It just seemed to me that you were leaning toward the aero wheels and wanted the facts to support what you wanted to do anyway. Either way, I enjoy the dialogue. It's an interesting question that raises the classic cost/benefit analysis of any economic decision. And, I think those who haven't trained and ridden with a PM can find it hard to believe it is of much value in TT pacing. I think their logic goes something like this: "In a TT, I need to go as hard as possible and I can manage my pacing pretty well with my HRM. How much better can I manage it with a PM?" I'm not suggesting you look at it like this, but I have seen similar comments from others.

Well, I'd be interested in seeing an analysis of the time savings at different power levels comparing good, deep dish aero wheels with discs. Have you seen that analysis?

Not that this has anything to do with anything but I'm quite happy that we don't follow many of the UCI's rules, especially the moronic ones like no wheel covers. Rather ironic that a Euro based organization fixes their rules to favor big $$ over ingenuity and strength.

Unfortunately I believe that the US is switching to full UCI rules next year, but I still doubt that anyone would put up a fight about using wheel covers.

This is an interesting study, one I have not seen before. Thanks for the link. I think the result is exactly as I would have predicted, that the ability to precisely manage power at the sustainable level would beat by a considerable margin the over/under pacing that results from trying to "find" the maximum pace by "feel." And, for most TT courses, the optimal pacing strategy is not constant power. The selective use of an over/under pacing strategy precisely managed with a PM would even beat by a considerable margin the constant power strategy. And, this was only a 10 mile TT. Extrapolate to 40K and VP/PM rules. No contest!

Except for states and nationals. Thanks a lot -- you've just cost me a bunch of money for a disc with an SL hub. Seriously, I didn't know about the change and I'm planning to build up a TT bike next Spring. Now I know what I need to do about wheels. $$Ugh!

Zipp themselves suggest that their 404 and 808 rears are reasonably competitive with their Disc for wind angles less than 15 degrees. Check out table 1 at the bottom of this page: http://www.bicycling.com/tourdefranc...ategory_id=527

Well, I assume it is info from Zipp, anyway, as Allen Lim is connected to Phonak who are sponsored by Zipp.

Also worth noting that Steve Hed seems to be a fan of tri-spoke rears and some of the Disco boys were using them in the last TT of the tour.

My impression is that Discs have a clear but marginal advantage over deep dish wheels. Tri-spokes are a whole other question I don't quite have a handle on, but that doesn't really matter as you can't run a PT on them either. Once you consider pacing strategy and cost (compared to SRM + disc) the deep rear w SL hub starts to look good - if you can afford it.

I hadn't seen that link. It is quite a simple analysis, but interesting to me to note the similarity in the HR data between each ride. Seems to confirm my basic thinking about TT pacing. Cheers.

Although Graham O'Bree is the obvious exception in terms of innovation on a budget, my inclination would be to expect money to play a much bigger role if the UCI hadn't put a brake on technological development. Ambivalent about whether or not they do this, but I really don't see how they favour money over ingenuity.

As far as the US switching - I won't be racing here forever so it doesn't worry me so much either way, but it does seem to me that it makes sense to race on equipment that is legal the world over. If you want to race on the big stage, you have to play by the rules. It also makes economic sense - if riders are going to compete o/s they don't want to suddenly find their equipment is not legal. And some of the rules are based around safety concerns which seem legitimate to me.

Zipp seems to have some form of partnership with Saris, as evidenced by their overt promotion of PT hubs with their wheels. I would expect Zipp to offer their discs with PT SL hubs as an option in the future. Is there any technical reason why they wouldn't? Of course, cost will be high. Which brings us full circle to your original question -- cost/benefit.

What's the first thing the UCI do to Graham? - ban his gear. If you look at the wheel cover thing - wheel covers are cheap and smart. They allow cheap SOBs such as myself to run a PT during a time trial without sacrificing aero. UCI would force me to run a disk in which case to use power I'd need to run an SRM or ergomo, both choices I wouldn't make, specifically because it costs more money.

Here's another interesting take on the "safety" aspect of UCI - http://www.biketechreview.com/archive/uci_n_me.htm

If you believe Kraig, the UCI certainly favors the Euro wheel maker's money over the little US wheel maker's innovation.


To boil it down though, I don't see any reason why pro rules should apply to we hobbyists (Not to say we shouldn't have any rules). We do this for fun, I'm not going to protest someone for having their saddle too far forward and I hope that next year during our state TT nobody protests me for using wheel covers, because I most certainly will regardless of what the UCI says.

Assuming, of course, that such flucuations last long enough to not be obliterated by the 30 s rolling average smoothing that is applied, i.e., longer than ~15 s.

I guess another comment I'd make would be that the normalized power algorithm is simply a way of attempting to quantify what we, as cyclists, all already know. IOW, you don't really have to buy into the math to accept that a constant effort is generally easier than a non-constant one.