"After reading about how Cervelo is designed to be able to be ridden in a variety of seat angles without compromise"

Actually everything is a bit of a compromise. What Cervelo has done is minimize it. These guys are engineers, not just theory boys, but also have practical common hands on sense as well as the initials behind their names.

I realize that... my question is how did they minimize the compromise...

and I have to admit that I am not really sure what the compromise is... is it handling/stability, weight, durability,

" my question is how did they minimize the compromise"


Better talk to Gerard about this one. A lot of their design theory philosphy is on their website.

I'm only a consumer of their product but as I see it, basically you take two guys who are into bikes and have engineering degrees and can differentiate between a screwdriver from a socket wrench. ie. they've actually done practical work and not just read theory. One guy has a background in aerodynamics and the other in materials. So they get get together to design race bicycles instead of formula cars. Can it get any better than this for us tri-geeks. My dad is a retired university engineer prof with academic qualifications but was a "hands on guy" who always fixed everything at home himself and always complained that too many of his students could get A's in theory but if they couldn't change the spark plugs on their cars or fix the plumbing then they weren't true engineers. These are two guys that actually hand built their first bikes by themselves. My dad would have called them "engineers".

The old Italian guy named Luigi with the bike shop in his garage is also damn good, but in a much different way.

This is an excellent set of questions. I don't want to answer for Gerard so hopefully he will chime in here, but here are my responses: Regarding the Soloist's capability to change between 73.5 degree to 76 degree seat tube angles- Using Cervelo's "Variable Geometry" (my phrase, borrowed from General Dynamics); I have ridden the previous Soloist model (the black and blue one) for a review I did on our website at bikesportmichigan.com. In the review I tried the bike both in the 73.5 degree configuration and the 76 degree seat post orinetation (by rotating the head forward). I found that something about the bike- by design or by coincidence- resulted in very good performance in the 76 degree orientation (not too responsive, reasonably balanced and stable, very confident)using Syntace C-2 aerobars. In the 73.5 (standard road) orientation I found it was even better. An excellent standard road bike. The unusual feature of this is that very few road geometry capable bikes have good handling qualities when ridden at steeper seat tube angles. Gerard contends that a 51cm frame can be made to fit (or more correctly, "position" ) a rider just like a 58cm frame: i.e., the points in space where the rider contacts the bike can be arranged in the identical proximity to each other on both bikes. Given the correct seatpost, stem and cranks, they probably can. However, this will effect handling, especially at speed and on technical courses at maximal efforts. Have you ever gone so hard in a race you realized you had very little energy left to control your bike? That is what I mean by confident, stable handling. The bike does what you want it to almost telepathically. That has more to do with the bike and rider's center of gravity, weight distribution over the wheels, wheelbase, fork rake and trail, front center measurement and head tube angle. My feeling is the Soloist has some subtle qualities (at least in my size, 51cm) that contribute to this handling confidence. I feel it IS better at 73.5 degrees than at 76, when compared to other bikes (such as my Yaqui Carbo- built at 76 degrees) but it is more than serviceable at 76 degrees, actually more than serviceable- its pretty darn good. Again, I can't tell you right now what causes this- maybe Gerard knows. I can tell you there are some really weird things going on at the rear end of this bike: The chainstays have the strangest bend I've ever seen on a modern bike. The seat tube does some very subtle, but very weird things as it approaches the bottom bracket. There is a comlex "curve" as it blends into the bottom bracket shell. My guess is this construction affects rider weight distribution somehow. Maybe it enables the rear wheel to sit farther under the rider so the bike does not get the "front end twitchies" that a normal road bike gets with aerobars. This bike rides great with aerobars . Also, the bottom bracket is farther back due to the weird little curve. The tubing here is very complex. I see why it took some time to make these bikes. Nice workmanship too. In general the Soloist offers a degree of capabilities I haven't found on any other bike. Oops, I am so out of time. I have to do something constructive. Bye bye.

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Tom Demerly
The Tri Shop.com

just bumping it back to the top to get a response from gerard

Ok Taku helping you out here. Great question, but I too have no idea. Sorry. But what I can tell you is I could not get my Trek 5500 to work comfortably as a steep angle bike and I tried, raced it three times at IM races, I have no idea how the Soloist manages its dual roles. Aside from Tom, I know of only one other rider who has one and its her only ride. She raves about it.

I gave up and got a P2K recently and I am still shaking my head at how much faster I am on it, it is shocking actually, cant tell if it is the position or the bike's aeroness or what. I converted the Trek back to a full time road bike and low and behold its a great road bike, comfortable and handles great.

Told you I was no help!

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Simple Simon
Where's the Fried Chicken??

No worries, Taku, I will respknd to this question but it's been rather busy these past few days so it may not be until next week. But I won't forget (and if I do, remind me).

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Gerard Vroomen
3T.bike
OPEN cycle

Bump!

Hi Taku,

After some crazy days I finally decided to sit down and answer your questions, only to find out that a lot of this stuff I don't really want to disclose. No point in telling other bike companies how to make a road bike that DOES work with a moderately forward seat position. But I'll gived some general observations.

First of, I don't think it is rocket science. It all comes down to common sense, unfortunately there isn't enough of that in the bike industry. I remember that ten years ago a magazine had a few pages full of drawings, and each drawing showed a bike with one change compared to the previous bike, and how that change affected the properties of that bike. So it would show a longer chainstay, and it would note that this increases the weight on the front wheel and reduces the bb and torsional stiffness. And it would do that with all sorts of variations. Unfortunately some of the conclusions were wrong but I believe this is the type of understanding that a bike designer needs to have. Yet if you were to walk around at Interbike and ask people what effect a longer chainstay has, very, very few people would be able to tell you.

And since you cannot rely on anybody to get this right, as a designer you basically have to figure out all these possibilities for yourself. Not terribly hard, it's more an approach to thinking you have to get used to.

So to use that knowledge to the Soloist, the starting point was that we wanted this bike to be a 100% road bike. We have our ideas on what that means to weight distribution, and handling quickness, but we also know we can achieve these goals several different ways. For example, Andrea Tafi likes the Colnago C-40 but also the Cervelo Soloist, even though both bikes have completely different geometries. But they are the same where it matters to him.

The thing is, the C-40 wouldn't be worth anything with a forward seatpost, yet the Soloist rides very well in that position. That is because out of all the options we had, we chose the road geometry that achieved all our road handling goals and was the least susceptible to problems when the center of gravity of the rider is shifted forward.

It's not perfect, it can't be, the Soloist will always be 100% road bike and 50% tri bike, but that's better than the 100% road bike 20% tri bike that most other road bikes are. It's just a matter of finding the proper geometry to accomplish that without losing any of its road capabilities. Luckily our philosophies for road geometry already incorporated many details that made them less susceptible to weight shifts, it's just that before the Soloist this feature was not that important while now it is.

I have a feeling I'm straying from the issue, but maybe this gives you some insight. If you have some more focussed questions I'll gladly try to answer them, and I won't take as long.

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Gerard Vroomen
3T.bike
OPEN cycle

Your post really gets at many of the issues I was wondering about...

I was trying to get a better understanding of how bike design effects the properties of a bike... I can easily understand how a beefy BB area or thick chain stays are better for power transmission.. but how do the other things start to effect the characteristics of the bike... It was more of a philosophical question.

I totally respect your need to keep your ideas to yourself... I'm sure the answere is one that is so fundamental that when another bike designer figures it out they would just smack them selves in the head

The question kind of popped into my head becuase I was thinkign about retrofitting road bikes The often quoted reason for not retrofitting a road bike is that there is too much weight on the front wheel... If you then wanted to compensate for this could you put a fork with a longer rake to extend the front end of the bike... would that be the equivalent thing to shortening the rear end? How about if you had a bike that was just flat out longer... Shifting your weight foward would only change the distribution a smaller percentage... could that be a solution...

I guess there is so much talk about bike fitting I thought that I would like to know mre about bike design

I do really wonder about what a difference chain stay length makes, as well as top tube design... these are things that do not effect how a bike fits but they must have an effect on the way the bike handles.

I guess I don't really have any specific questions... just a desire to know more about bikes themselves... so much talk about people on bikes these days

So you guys must move the "centre" of the whole bike forward a little - shorter chainstays and a longer front-centre?

Shifting the center of gravity toward the front or back to accomodate the seat tube angle (or vice versa) is important but not the only issue when it comes to handling capabilities. If it was, then bike geomotry could be simply duplicated and all bikes would handle pretty much the same.

Instead, what seems to complicate the matter is that the center of gravity varies relative to where the weight (force) is applied and/or shifted during the ride. In simplier terms, (IMHO) where the bottom bracket is located can make as big a difference in handling capabilities as seat post angle (and, these difference are also reflected in the rear chain stay, forward rake or top tube designs).

It seems that it is the perfect combination of geometric issues that generate the best design. Those combinations can change dramatically from rider to rider and bike to bike (not to mention changes caused by riding course and rider skills). Finding the right combination is the "holy grail" of bike fit and riding comfort.

I think Cervelo is attempting to find a bike that has the greatest options to provide such variance. Sometimes they succeed and sometimes they don't. Success begins with the rider. Then, fitting the rider to the bike. A bike that has wide range of adjustments provides the greatest chance of getting it right the first time. But, the odds of getting it in the long run assumes your body, riding skills and riding environment remains constant.

What would be interesting and very useful would be a reference manual showing all bike frame geometries from a constant reference point (say, the rear axel). Then, show the comparitive differences between frame designs from a top view as well as side view. A reference like that would visually show the differences between bike designs. And if you really want to do it right, do a study of what particular design most commonly fits what general body types. Then, associate that design with riding style and specific course preference. I figure if someone started woarking full time on creating such a reference book today, they would have the definative bike design reference book done in about 2-3 yrs. (of course, you would be broke trying to create such a reference - or need a research grant to create such a reference source).

Until then, we as bikers (and the bike industry) just plods along into the dark depending upon trial and error and good LBS judgement.

FWIW Joe Moya

Well put... The reason I was thinking about this is that there is so much talk about fit and positioning however there is very little being talked about with bike design.

The majority of the discussion about bike design has been within the realm of whether or not a bike design can accomadate a certain position. However there isn't much talk about how a bikes gemoetry (not just seat angle and head tube length) effects its characteristics.

I jus think that this is an area of biking that really isn't talked about and I think that if we started throwing our theories out there we can all get a better understanding of bike design and perhaps make better decisions...

As per your BB comment I think that is a very good point... it would be easy to track straight and smooth if we never pedaled... however we are putting huge forces onto the frame at the BB... It would only make sense that its characteristics and position in space relative to the other points on teh bike would make a huge difference

There are so many variables in bike design. Look at the wheel base for example: too long for the size and handling is ponderous and slow, too short can be twitchy and unnerving. I can think of a GT that I had for a short while. It was very twitchy, and the geometry was great for a crit bike. Slap on a forward post and aero bars and it was a nightmare to handle. Also, the centre of gravity was fully optimised with a typical seat post. The geometry of that bike was a dual 73.5 (head and seat), and it steered with nary a thought of the rider. The rear wheel was not underneath my bum when in the tuck, and the quick steering was scary.

I could see that if one were to build a bike with a very neutral geometry, it could be done forward and backward. But, the forward seating would only be a semi-aggressive forward position. I think of a KHS aero turbo I had. It was very nice at a 75 degree angle, and I could have manipulated it to about a 74. I got to be quite nicely positioned at about 76-77-ish with a Control Tech seat post. A forward post would have made it too steep. It had very short chainstays, a curved seat tube that kept the rear wheel in quite nicely. I could tuck quite nicely once I was shown how to properly sit onto it.

I am a student of bike geometries. I know what I like, and I certainly know what I don't. Convertible bike geometries fascinate me.

[reply]There are so many variables in bike design. Look at the wheel base for example: too long for the size and handling is ponderous and slow, too short can be twitchy and unnerving.[/reply]

Can be, but doesn't have to be. And THAT's what makes it so interesting, for example our Baracchi and Iridato models both had very, very short wheelbases (the Baracchi was 89cm) yet they were very stable.

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Gerard Vroomen
3T.bike
OPEN cycle

doesn't that come down to headtube angle, fork offset and trail ?

[reply]doesn't that come down to headtube angle, fork offset and trail ?[/reply]

Yes, for any given wheelsize two of these parameters lock in the third. But it is the combination of headtube angle and fork offset with the wheelbase, wheelsize, weight distribution that make up the overall handling characteristic of the bike.

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Gerard Vroomen
3T.bike
OPEN cycle