I am thinking about starting a time trial bike build over the winter, and I am wondering if weight really matters that much on a flat, or moderately rolling time trial. Should I go with Record or Chorus, or does the weight reduction only matter in my wallet?

What about a frame. Should I go with a carbon fiber frame, or will aluminum be just fine?

Weight is very insignificant compared to aerodynamics. Read this article
http://home.hia.no/~stephens/aero.htm

thanks for the link - great info. I bookmarked it for reference.

Take a look at this article too http://www.byrn.org/gtips/cobb_fit.htm

Aerodynamics is not the ultimate goal. You need a balance. Bike weight is pretty far down the list unless you've done everything else to maximize your performance.

Also consider the amount of time you'll use the bike. If you're a tri guy and train and race on the bike it's definitely worth spending money on a comfortable and fast bike. If you only intend to use it for an occasional TT and a few training rides why spend the money (that is, unless you're loaded, then buy what you want) on a fancy rig. Get a good fitting but inexpensive frame and equip it with decent parts but why blow the wad on something if it isn't going to see a lot of use?

Agree with the above posts. But, regarding your qn, well, aero qualities definitely outweigh bike weight.. Of course don't get a 30 pounder !! :D

Carbon is stiffer, lighter but more expensive. Also damps vibrations actually.

Good luck

The simple answer is: "how many feet of elevation gain does the TT have?"

The REAL WORLD simple answer, with no offense: if you're at a place where you're asking "do I need Record, or should I go with Chorus," you're at a place where you "need" the aluminum bike with chorus or centaur. If you've got money burning a hole in your pocket and want the fancier bike because it's fancy and you like it, fine...

The simple answer is: "how many feet of elevation gain does the TT have?"

The REAL WORLD simple answer, with no offense: if you're at a place where you're asking "do I need Record, or should I go with Chorus," you're at a place where you "need" the aluminum bike with chorus or centaur. If you've got money burning a hole in your pocket and want the fancier bike because it's fancy and you like it, fine...


He always gives top advice.. Take it from the expert. I second the aluminium bike.:thumbsup:

To be a little more specific to your question, on a flat or moderately rolling TT weight is not very important as long as you're in a reasonable ball park weight. Any frame material will get you into a reasonable ball park. The weight difference between Record and Chorus will not affect your time trial times at all. If you like and can afford Record, go for it. If Chorus is more in your price range, go for it. Doesn't matter as far as performance is concerned. Get some aero wheels (high profile, bladed spokes, maybe a rear cover), aero clip ons or bullhorns with clip ons (bar end or down tube shifters needed) and most importantly an aero helmet (MIT tests say this is THE most important aerodynamic aid).

and most importantly an aero helmet (MIT tests say this is THE most important aerodynamic aid).

Really? I thought in some other test it was stated that aerobars are most important, followed by bike or sth...

From an 11/05 Pez article on the Liberty Seguros wind tunnel tests at MIT.

2. Equipment
A common misconception about equipment is that of the order of aerodynamic importance for aero-gear. Most think that the frame matters the most, wheels next, and helmet last. Some even think that the components come before the helmet. In reality, a well designed aero-helmet will save you more time (power) than anything else. The drag difference between a vented road helmet and an aero-helmet is 2-4 times larger than the difference between a good aero-wheelset and a 32-spoked wheels

As far as aero bars are concerned, they are absolutely necessary to get the rider in the best aero/power position. You gotta have them as part of positioning which is THE most important factor.

I am building up a TT bike this winter myself and do like the campy setup I have on my regular bike so I was thinking I would go with Campy on the TT bike but once I started shopping around I decided it just didn't make sense. Of the two things I really like about the campy gear I don't think either applies to a TT bike and those are the shape of the ergo levers and the ability to shift well under load. Now that is kinda of assuming you are going to use bar end shifters but even if you aren't you probably are not going to be on the hoods much. And I could only find campy bar ends at the record level for much much more than Shimano Dura Ace bar ends. Once I priced the whole setup as campy vs. Shimano the money and the weight just didn't make sense to me so I went with shimano. Now I don't know the Campy setup might shift better or something else as I have never had a campy tt rig, but in the end I doubted it would be enough of a difference to justify the extra cost.

And one final note on using bar end shifters, when you don't have to buy ergo levers, or STI for your group, the cost of the group goes down quite a bit. Aero brake levers are comparatively cheap and I would say you could get the bar ends and levers for just over $100 total which is a drop in the bucket compared to either the ergo or sti type.

None of this is to in any way imply that I needed a TT rig of any type or cost. But I have never let reason get in the way of a good bike build. You know what they say n+1.

Really? I thought in some other test it was stated that aerobars are most important, followed by bike or sth...


i thought so too, with the helmet in 2nd

Yeah, I do one team time trial a year. It's a long one, 50 miles, and a little hilly but not bad. I'm building a TT bike this winter from stuff I had on hand. I needed to buy some clip ons, bar end shifters, a derailleur and a cassette, otherwise I've go the rest. Might get a different seat post depending on positioning requirements. Total out of pocket will be less than $150. Now, all I have to do is convince my team mates to do the same or at least get clip on bars. Gives me a good excuse for a winter project.

Weight doesn't matter a lot for any bike.

Does weight matter a lot for a time trial bike? Unless you're riding up a mountain, no it doesn't.

Thanks for the replies guys.

Oh, I'll agree that weight doesn't matter a lot for any bike, and it is mostly about the rider, but having been beat at the line by a couple of inches, I always wonder if lighter wheels would have helped me accelerate better and win that sprint. Having been dropped at the crest of the second mountain, in a two mountain race, I sometimes wonder if I would have been able to keep up if my bike were just a little lighter.

Then again, I might have won the sprint and stayed with the group over that climb if I had just trained a little more.

I read a couple of articles, and it appears that weight only really matters when the road turns uphill. If a road is completely flat, the weight of the bike doesn't matter at all. I also read that light wheels only help with acceleration, and they really do not matter if you are just trying to keep a steady speed in a time trial, unless of course the time trial is a mountain course. Then, the light wheels come in handy.

All things being equal, a light wheel accelerates marginally faster compared with a heavy wheel. The corollary of that argument applies when wheels decelerate; light wheels decelerate marginally slower than heavy ones. These differences are marginal though.
Aerodynamics is another thing altogether, especially given that up to 70% of the energy we expend in turning the pedals around is taken up by moving the bike and rider through the air. The rest propels the rider forward (I'm sure Kerry Irons or C40 have the exact figures, which I know vary considerably according to how fast you are moving through the air).

Check out the link below to the Cervelo website (data seems to come from independent sources). Record or Chorus? If you have to ask, get Chorus.

Get a frame that will allow you to maximize your body's aerodynamics. Over a 40km TT, a Cat. 3 racer can save almost 6 minutes in an "excellent" aero position versus a "typical" aero position. Wow. Aero wheels (full disc) can save you another 1:32, aero frame can save you another 1:01. A 5-pound-lighter bike will save you 36 seconds.

http://www.cervelo.com/content.aspx?m=Engineering&i=Aerodynamics

The Cervelo discussion was very informative. However, I think they underestimate the affect of an aero position on cycling power. Here's what they say:

Is there a trade-off between position and power output? If done badly, maybe, but if done well, no. Recently, Heil et al., (MSSE, May 1995) have investigated this question, and the results tend to show that your cardiovascular stress for a given power is increased by decreasing the trunk to femur angle. Therefore, if you lower your elbow position, you may need to move the saddle forward to maintain your trunk to femur angle while getting a lower, more nearly horizontal torso position.

Two things stand out. First he says "recently" then points to a 1995 study. When was the Cervelo aero discussion formulated? If it was in the mid '90's there's been a lot learned since then. Second he doesn't really account for the change in aero position as it affects watts. He assumes the change in aero position will not affect watts generated in his calculations. John Cobb has demonstrated significant negative affects on watts generated for relatively small changes in aero position. Without a wind tunnel and a watts meter it's really hard to come up with real numbers. No doubt, aero position is the most important factor but it can be a trade off for power and you need to find the right balance point.

Oh, I'll agree that weight doesn't matter a lot for any bike, and it is mostly about the rider, but having been beat at the line by a couple of inches, I always wonder if lighter wheels would have helped me accelerate better and win that sprint. Having been dropped at the crest of the second mountain, in a two mountain race, I sometimes wonder if I would have been able to keep up if my bike were just a little lighter.
You're asking the wrong questions. In both cases, lower drag or rolling resistance would have had a much larger effect than weight in improving your position,

I don't know about drag having a larger effect on my climb issue because both climbs that day were pretty tough. They weren't just hills, but mountains in Olean, New York. We drove the course the day before after a mountain time trial, and on the descent the car was still accelerating even though we were down shifting it. I think weight might have mattered on that one.