P3C Dimensions: An interesting difference between the "name" of the size and the actual measurements of the frame (photos)

Triathlon Forum
41

Thanks Slowman for your response, however, this still begs the question of what difference is there really between a 54 and 56 bike for a tweener person. First, my bike background is a bit sparse. I haven’t ridden too many different model bikes. However, from a physics point of view and actually efficiency point of view. How much of a handling issue is there between a 54 and 56 bike for a person who is 5’10". In both cases I feel that that person could be properly fit on each bike (with a steep angle, aero position and comfortable), with the former the stem might be a bit longer, etc. This in theory may alter the person’s center of mass versus the head tube and hence steering, but I don’t think appreciably.

Also in the end, handling is an acquired skill. So I don’t believe that there would be significant difference. Already, one gives up some handling ability by riding aero, but most IM courses and other tri courses are technically demanding.

42

This is very intriguing. I did not know this was cervelo’s design philosophy. Assuming it is, can I ask this ?:

You say the talon has its two-headed seatpost to allow people who want to ride that frame to ride it in a way for which it’s not optimized. And the talon is optimized for road geometry riding as it’s a road bike. but it’s got a facility allowing it to be ridden steep for tri racing.

And that generally makes some sense. Kestrel thought that by including this (you say non-optimal) option, it could capture some of the triathlon racing market with the talon, right?

But then would you also say “that cervelo P2/P3s have their reversible seatpost heads to allow people who want to ride those frames to ride them in a way for which they are not optimized. And the P2/P3 are optimized for tri riding as they are TT bikes. but they’ve got a facility allowing then to be ridden slacker for road racing” ???

Was cervelo also including this (you say non-optimal) option to also capture some of the road racing market with the P2/P3? I’ve never seen a P3 in a crit, at least not yet …

?

43

Your website is cool, photos current, color scheme nice. Thanks for the link.

44

maybe not as relevant in tri set up but stem length makes a huge difference in handling uin the case of a road bike. It also makes a difference in where your knee is in relation to the pedal axle (I gues you could change crank length to some extent)

45

The real answer to all these questions…

get a Kestrel airfoil!

Brother Bonk (with tongue implanted in cheek)

46

First, I meant to say IM course and most tri courses are NOT technically demanding.

As to knee versus pedal axle, this is not necessarily related to the size of the bike, meaning I can adjust the crank length, the seat height to BB length, the fore-aft position of the bike and maintain a constant knee to pedal axle distance and angle. Although, I think as others have pointed out that Knee Over Pedal (KOPS) is not the proper way to fit your tri bike.

I still think that at the margin there is no real difference in bike fit between two consecutively sized bikes. Certainly a person who is 6’2" won’t ride a 52 sized bike, or a 5’6" ride a 58 sized bike but there is an arbitrariness for each of those persons between the two consecutively sized bikes that are close to their “true” size. For instance, a 5"10" person, could be fit equally properly (aero, comfortable, etc.) on a 54 or 56 sized bike. There is not one correct size. Maybe the correct size for this person is 55 or “54.76” or “55.6”, the choice is somewhat dependent on the size of bike the manufacture offered. If instead of sizing their P3C bikes as 54, 56 but instead 53, 55, etc. maybe that person is a 55. All I am saying that at the margin their is no real difference in handling, or ability to be properly fit.

Every bike is custom to the extent that the various aspects of the bike can be adjusted such as seat height, stem length, drop, angle, etc.

It always pisses me off that people say you are definitely a size X. That is BS. It is especially BS when their basis is on an inseam measurement, or even worse by just looking at you. The person may be right especially if they have a lot of experience (read the book BLINK by Malcolm Gladwell, BTW). But, the size X they tell you is a starting point, at the margin a size up or size down probably will not make a difference to that individual, as long as the other aspects are fit properly such as stem, crank length, seat heigh etc.

47

I agree with you completely. Half of the guys at the LBS no crap about bike fit, sizing, geometry etc.

48

As Dan said, slowman and I have been philosophizing about bike positioning and geometry for years and years. Forthe most part, we appear to be on the same page, he’ll say something like “you ought to try this” and I’ll answer we already do that, or I will think out loud that it would be nice to try something, and he’ll tell me he;s already tried it and it doesn’t work.

Bike handling is obviously not an open and shut characteristics, there are many shades of grey. Even in the most advantageous set-up, bike A may not handle as well as bike B. As I have said many times and will continue to do, we feel that most people are better off riding steep. So in that sense our tri bikes are designed around that philosophy and by all accounts handling in that position is good (I’ll leave the judgement of “optimized” to others). At the same time, we recognized that there are triathletes and even more time trialists who prefer or need to ride a bit shallower. This does not mean they will ride a P3 in a crit, but rather that they would like to ride at 75-76 degrees. So we worked hard to make sure the bike handles very well in that regard. This was actually one of the most rewarding aspects of working with Ivan Basso last year. Aside from how much he liked his position, he really liked how his P3 handled in this supposedly less-than-optimal (for handling) slack position (this was even before we moved him forward to his 77 degree effective seattube angle). He said a lot of the road bikes he had used in the past didn’t handle as nicely as his new TT bike, and he was quite surprised about that.

So yes, Dan is absolutely right that our first focus was to get the handling right for the steep seattube angle, but with the work we’ve done for the handling in the slacker configuration it seems we have achieved a pretty good result in that set-up as well.

49

I wouldnt care what the seat tube measures, the important dimension for ANY frame measurement is ONLY the top tube. The seat tube is highly adjustable by moving the post up and down, but the top tube is only adjustable by moving the seat on the rails or changing out the stem to a different length. So the measurement of the P3 is close enough.
As with all bikes we sell we measure the frames, preferably in each frame size, precisely using our measurement protocol to compare the actual dimensions to the size name designated by the company selling the bike.

In the case of the Cervelo P3C, these are our findings:

This is for a 56cm frame size (see box photo below as labeled):

Frame seat tube, total seat tube length as measured precisely from center of bottom bracket spindle to top of seat tube: 53.4 cm.

Effective top tube length measured as shown in below photo: 55cm. (note: this measurement is highly subjective- please look carefully at the photo of us measuring to determine if our technique is relevant to how you are sizing your bike).

As with many manufacturers, the dimensions of the bike are significantly different than the actual dimensions. This may be a very easy bike to get the wrong size in. The “56cm” actually has a 53.4 cm seat tube. See photos: http://images.snapfish.com/3436%3B69523232fp46%3Dot>2337%3D736%3D376%3DXROQDF>2323833%3A2%3B3%3B%3Bot1lsi http://images.snapfish.com/3436%3B69523232fp46%3Dot>2337%3D736%3D376%3DXROQDF>2323833%3A353<7ot1lsi http://images.snapfish.com/3436%3B69523232fp4>nu%3D3246>645>285>WSNRCG%3D32329249444%3B4nu0mrj http://images.snapfish.com/3436%3B69523232fp58%3Dot>2337%3D736%3D376%3DXROQDF>2323833%3A353<6ot1lsi http://images.snapfish.com/3436%3B69523232fp47%3Dot>2337%3D736%3D376%3DXROQDF>2323833%3A353<4ot1lsi

50

“I wouldnt care what the seat tube measures, the important dimension for ANY frame measurement is ONLY the top tube. The seat tube is highly adjustable by moving the post up and down, but the top tube is only adjustable by moving the seat on the rails or changing out the stem to a different length. So the measurement of the P3 is close enough”

That isn’t exactly true. There are 2 important measurements for any give frame, stack and reach. Those concepts are explained on this site and on the cervelo site. Unfortunately, very few manufacturers publish that information, so it is up to the consumer (or a knowledgable bike shop) to do those calculations so that frames can be compared.

51

Thanks. Very interesting. I think I am one of those who also likes to ride at about 75-76 degrees.

And I have no complaints about my P2. The only thing I sometimes wish Cervelo had was another seatpost head option, one that basically clamped the saddle’s rails, not behind or ahead of the seatpost (depending on which position it was in) like the current head, but directly above the seatpost (similiar to a straight thomson post). This would easily allow a 75-76 degree position without the necessity of sliding the saddle most of the way forward or most of the way back. And such a seatpost head could potentially be far simpler (and far lighter) than the current head, as it would not have to support a rider’s weight cantilevered so far forward or backward, which obviously requires an immensely strong seatpost head.

There you go, a free product idea. If you ever made one, believe me, you would sell many of these as an accessory upgrade…

52

Just post more Pictures for us to see.

53

We’re so swamped with sold bikes we haven’t even finished building the P3C’s. Austin Tri Cyclist beat us to the punch by weeks.

Most big Cervelo dealers have P3C’s now.

54

this was a great thread.

I ride a 55cm lemond road bike - which means a 56.5cm top tube and a 55 cm seat tube - c-c, 56 c-t. I replaced the 110mm stem with a 100, and it fits great. I 've still got all the spacers it came with maybe 3 cm, but the stem is flat , so it doesn’t look like a 5 a.m. woody …LOL.

I have 56 cm dual. In the aero position, the only way i can ride it, using AERO bars, the effective top tube is 530mm I think,and I’ve got a flat 110mm stem on it - an old 3TTT Mutant, a stem that would truly look stupid flipped up.

I had a 54 delivered first, but I felt like the drop from seat to stem was too much, even with the stem turned up, so had a 56 sent instead.

now I’m in a good position, and have a lot of room to improve as I get more used to the position.

that’s a lot to look forward to , and one reason I think it’s great the bike is delivered the way it is.

If the steerer had been hacked off so that only 1 or 2 cm of spacers could fit, I’d probably have to go to a 58, and then i’d be too high.

or maybe it would work , I don’t know , but I know this , the better I get , the lower i’mm going…

i’ve always loved the traditional road position, but I’m really starting to dig my dual…