I have been lusting for a Cervelo P3 for quite some time now. I had the opportunity to borrow a friends 2002, 55cm which is currenly what size I ride in a Blade. I am 5’11" 160 #'s with a 32.5" inseam.
I ride with seat height of 77cm measured from the center of the bb to the top, of the seat, which was easily obtainable and very close to where he rode it. I had the seat post flipped forward with seat back most of the way. I also used a 110mm stem that seemed to be a fairly good fit for me. The problem I had was how low the front end was. I can ride pretty well with a 10cm drop from the top of the seat to the top of the elbow pads on the aero bars. To acheive this I had to use a ridiculous amount of spacers. In essence making it look silly having that tall stack. I realize this is not the most aggressive drop, however this is what I find comfortable and still allows me to breath good without wrenching my neck.
Is it just that the front end of a P3 is too aggressive for me. Would it be possible to acheive this poisition on a different size maybe?
This is where a good fitter comes into play. You seem to have found a position that you are happy with, now you have to find a bike that suits that position.
Specifically, the P3 is reputed to allow a low front end. If you like a low front great, if not bad (or at least not good). You can go with a lot of spacers, a stem with more rise or a handlebar/aerobar configuration which gives more height.
Or a bigger size bike will (or should) have a higher headtube.
The way you need to decide is from my afor mentioned choices which configuration results in a bike that handles properly? Only a experienced fitter or extensive test rides can answer this for you.
Just be aware that two different size bikes (or the exact same model) with the same rider in the same position will handle radically different.
Simple solution – buy a 57. It’s 2cm taller. All you have to do is run a shorter stem, say a 90. I personally feel that a tri-bike rider should always buy the largest frame that will still allow them to dial in their fit. That means a shorter stem than most people are used to. The big benefit is that you get a longer, more stable wheelbase.
BTW – I would ride a 55 P3. I’m 5’11.5", and my saddle is at 80cm. I like my arm pads 17-19cm below the saddle. The only reason I don’t ride a P3 is that the wheelbase is too short for my taste in that size. While it might appear (from my height) that I would ride a 57, I can’t get the bars low enough and close enough to me on a 57. Hence, the 55 is the largest P3 frame that will fit me.
The largest size possible is also the heaviest. I have the opposite view, always buy the smallest possible. Also the shorter the stem, the worse is the handling.
I agree with smartasscoach. Buy the smallest frame that will fit you. A smaller frame is stiffer, lighter, and usually more responsive. I ride a 51cm P2K, but have ridden a 54cm with no problem. I think you’ll find the general consensus to be buy the smallest frame that will fit you.
I think you’ll find the general consensus to be buy the smallest frame that will fit you.
~AB~
Thanks for your reply’s gentlemen. Both points make sense. The problem I have with buying the smaller bike, is the tall stack needed to achive my position. About as 10 cm drop is all I can ride comfortably. The 57cm makes sense, but do not want an ill handling bike. I looked at cervelo.com and see they don’t make the 57 any longer but have a 58. The top tube may be a bit long. As much as I hate to think it, the p3 may not work for me. I may need something with a longer head tube.
How old are you? Do you have any medical condition that prevents you from riding lower?
42 yrs old with no problems. I have ridden my current bike lower but my neck gets sore fairly quickly and I seem to be less powerful, although I have never raced that way to prove it. I’m definatly not the most flexible of people. I may just need to work on stengthening my neck to ride lower. I consider myself a fair rider, did a 23 mph average 40k this summer. I just can’t seem to get comfortable real low.
Rider - You bring up a good point and a topic of discussion I had last week at the local guru tri shop…
With all of Dan’s revolutionary work, it appears some companies have taken it to an extreme as some headtubes are waaaaaay short.
I’m 5’11" (long femur) and in love with short top tubes. (54.5cm please) But, most bikes with this top tube, coupled with my 76cm seat height are simply too low in front.
I suppose I could use spacers and a riser stem, but it looks really funny…
Not exactly related…saw it on ebay a few weeks ago. LOL
Smitty, that picture is exactly what I want to avoid. I refuse to ride like that. I am able to ride my Blade fine with the above measurements because it has a long headtube, and I think a slightly sloping top tube. I’ve been riding it for 3 years and thought it would be nice to have something else (P3), but not if I have to have a huge stack of spacers or a quill stem.
I tend to ride low in the front on my tri bike but have seen no evidence that this is any faster than being bit more upright. It almost seems like what I may gain in aerodynamics is lost in power production in this position. This may not be so for everyone, but it seems so for me.
Do also consider the Cervelo Dual. Yes, it’s not as high end sexy as the P3 but it has a longer head tube that might be much more suited for you. And with the money you save purchase some reall good wheels or take a Caribbean vacation.
The smallest bike that fits you is the 48cm. 18cm stem, extra-long seatpost and off you go. Ridiculous? Then so is the notion to buy the smallest bike that fits you. Fit is not a fail/pass system, there are shades of grey. don’t buy a size that fits, buy the size that fits best. And what size that is depends on body position and wheel position considerations. You’re a bit lucky in that the P3 is fairly immune to positioning changes when it comes to its handling, so the 55cm and the 58cm will in all likelihood both handle well. That means it would be a choice of which frame best enables your body to get into the right position (they both will be able to get you there, the question is which one does it the best/easiest). And don’t worry about the 30g weight difference between the two, half of that you’ll get back with the shorter stem and the shorter seatpost anyway. Not worth buying the wrong frame for.
Common misconception: Smaller frames are stiffer. They are not. torsional stillness is virtually constant as frame size increases, while bb stiffness is governed more by chainstay design than by the front triangle.
If you don’t have any cervical problems, your neck will eventually adapt to that position. Just go lower cm by cm, 10cm doesn’t seem like a big drop, you’re probably too high up front.
klehner is about your age I think, since the begining of the season he’s dropped the front end quite a bit, and with good results I think. Just pm him, or wait until he posts here or seache for T-Rex, you can’t go wrong with that keyword :-)))
“Common misconception: Smaller frames are stiffer. They are not.”
Hmm. I just learned something then. Logically, you would think the overall stiffness of a 48cm frame would be greater than a 58cm frame – shorter pipes = stiffer frame. Gerard, could you elaborate on this? I have been incorrect for years then and feel like an idiot. I’d like to be educated on this.
The tubes are longer on a bigger frame, but they are also further apart. Similar effect as with oversized tubes, the further apart the material is, the stiffer the structure. Also, you need to turn that longer headtube a bigger distance to get the same angle change as on a smaller frame (if we’re talking about torsional stiffness).
So when you test frame vs. frame, there is little difference (there is always some difference depending on the particular frame model, as the stiffness also depends on tube overlaps, tube shape changes, etc).
If you were to test bike vs. bike, there is no doubt that the bigger framed bike is stiffer (if they are set up for the same rider. A frame is much stiffer than a stem, so when you pull on the handlebars most of the flex will come from the bars and the stem and relatively little from the frame. Make the frame smaller (and thus the stem longer) and you will see more flex in torsion. For bb stiffness, the components you add to the frame wouldn’t change from size to size so it would not have an effect.
I pretty much agree with Gerard’s response, but would like to add the following.
A stiffer frame is, engineering wise pretty vague. What most people mean is a bike which handles well, ie goes where you aim it consistently. Certainly a frame made of very flexible tubing is going to handle like crap. But when we look at a given rider deciding on two frames, say a 50cm X4 and a 58 cm X4 it gets more complicated. The important things to consider are:
Did the designer use bigger diameter or thicker walled tubes in the bigger frame.
Did the designer tweak the frame construction in the bigger frame.
The smaller frame will need more fork spacers and a taller seatpost. These longer unsupported tubes will flex more than shorter lengths, giving the feeling of more flex.
Finally, not all flex is bad, if it were softrides, titanflexes, slingshots etc, would be all but unrideable.
The largest size possible is also the heaviest. I have the opposite view, always buy the smallest possible. Also the shorter the stem, the worse is the handling.
A 57 versus a 55 is the difference in weight of a Gu packet. ie, meaningless.
Au contraire about the stem. On road bikes, one might say that. On tri bikes, we steer with our arms on pads, and leaning down onto the front wheel a lot harder. It’s not the shorter stem that improves the handling, it’s the longer front-center. The longer top tube keeps the front wheel farther out in front of our weight. In order to have the longest front-center you can get, you need to buy a long frame and a compensate with a short stem. And that is the main problem with draping a big rider on a small frame – the rider’s weight ends up too far out over the front of the bike. Works on road bikes, but not on a TT bike.
We steer bikes with our weight. The handlebars/stem/hands setup just fine-tunes the arc and keeps the front wheel under our effective COG. Bike handling (like car handling) is firstly about weight distribution. Secondly about trail and head tube angle, and lastly about handlebars and stems.
The smallest bike that fits you is the 48cm. 18cm stem, extra-long seatpost and off you go. Ridiculous? Then so is the notion to buy the smallest bike that fits you. Fit is not a fail/pass system, there are shades of grey. don’t buy a size that fits, buy the size that fits best. And what size that is depends on body position and wheel position considerations. You’re a bit lucky in that the P3 is fairly immune to positioning changes when it comes to its handling, so the 55cm and the 58cm will in all likelihood both handle well. That means it would be a choice of which frame best enables your body to get into the right position (they both will be able to get you there, the question is which one does it the best/easiest). And don’t worry about the 30g weight difference between the two, half of that you’ll get back with the shorter stem and the shorter seatpost anyway. Not worth buying the wrong frame for.
Common misconception: Smaller frames are stiffer. They are not. torsional stillness is virtually constant as frame size increases, while bb stiffness is governed more by chainstay design than by the front triangle.
Exactly.
Ves Mandaric puts in another way. It’s not enough that the saddle/bars/bb triangle fits the rider. The machine still has to work. That means it has to steer well, and handle well, etc. In my view (which Ves shares) that means that a too-small frame will do all the wrong things for a triathlon racer. Short wheel base, with too much weight on the front wheel.
And, when are folks going to stop with the “smaller frames are lighter and stiffer” stuff!!! By the time you put a long seatpost and a long stem on the thing, it weighs more than the bigger frame! Which weighs less per inch – frame tubing or seatpost tubing? Gerard also has enough experience to know that the lateral “stiffness” of the bb with respect to the rear wheel is determined by the part of the frame that connects the bb to the rear wheel – ie, the chainstays. It has virtually zero to do with the seat/top/down/headtubes. Since the chainstays stay the same as frames get bigger, the stiffness does not change.
