chuck1sd

I am putting together a set of lightweight race wheels. My question is as follows: Which way do I go? Extremely light tubulars(Nisi box rims, King hubs- 1100gm wheelset) or a heavier aero wheelset like Zipp 440. I race on varying terrain. Does aerodynamics outweigh light wheels? Any info will be appeciated!!

easyrider

Well, I believe that aerodynamics and weight of moving parts are both crucial factors in determining the efficiency of a bike. So you might actually need a physics expert to crunch specific numbers to answer that part of your question.

It's like the issue with disk wheels. When they were first developed the riders all got on them and were willing to accept the heavier weight for the aerodynamic benefit. But then we found that a lighter version that is less aerodynamic could be superior. for example, you don't see anyone with the solid front wheel anymore. :confused:

Maurizio

Aerodynamics will outweigh weight-savings in all but the most extreme cases -- obviously losing a few spokes and adding four pounds won't make you faster.

Those Nisi rims you talk about are totally box shaped and are single cavity rims to achieve their weight. They won't only be incredibly un-aero with 32 spokes front and rear, but not nearly as strong as a deeper rim -- deeper tends to equate to a stronger rim via vertical stiffness, which is why manufacturers can get away with fewer spokes. Bear in mind that deep rims also have shorter spokes.

If you don't race, then considering lightweight over aerodynamics is stupid. All those non-competitive riders with Ksyrium SSL's should ditch those things and get something seriously aero if they really care about their performance.

Weight starts to matter more than aerodynamics when your speed dips below about 14mph and you're going up at least a 5% grade. At around that speed, the aeroness and lightness will offer equivalent perfomance. If a given race is 80 miles and has four ten mile climbs including a summit finish, and you know you're going to be grovelling at 5mph at the end, then get the lightweights.

I would say that unless you are RACING up climbs that are not only STEEP but also TWO OR MORE miles long, the advantage will always lie with the aero wheels assuming that you're not talking about more than a few hundred grams difference.

BTW: These days, with money, you can have both incredibly light AND incredibly aero. Zipp 404 rims laced to American Classic Hubs will tip the scales at aroung 1150 grams -- and be super aero for those times when you want to go for a 50 mile solo escape.

- Maurizio

Maurizio

Easyrider:

In terms of that disc wheel thing. A front disc is very very very tough to control as long as there is any wind. Also understand that sponsors dictate oftentimes the exact equipment that a rider must use. Note however that sometimes you do still see dual discs: Cipo and Danilo Di Luca were doing it in last years Giro.

Note: On outdoor velodromes (where there is wind) Pursuit riders will never use a front disc, only a rear. On indoor velodromes (no wind) all Pursuit riders will adopt dual discs. Since there is obviously no climbing in a Pursuit track race, the issue here is obviously the negative handling characteristics.

A lot of Pro's porbably realized that they were wasting more energy trying to keep their bikes going in the right direction to justify the aero advantage they got. I doubt it was ever an issue of weight. Corima and Zipp discs are around 900 grams, which is light to the point of no excuses on the climbs.

- Maurizio

Maurizio

Another thing:

Some riders will say that a lighter wheel will "spin-up" or accelerate faster than a heavier one.

This is kind of true.

But what REALLY MATTERS in a wheel's acceleration properties is torsional sitffness NOT lightness. Torsional stiffness is a function of spoke tension, lacing patern (3x will be better than 2X and much better than radial), hub flange spacing, and factors of build quality.

Have you ever accelerated hard and broken spokes? I have. That wheel had crappy torsional stiffness and broke.

Torsional stiffness (and also lateral stiffness) are factors that are WAY more important in wheels to almost any racing cyclist than weight should be.

Too many people just get WAY too wrapped up in weight.

- Maurizio

easyrider

Maurizio,

You obviously know a lot about this. I know that you are right that handling the bike was a major issue when using the front disk wheel (especially in the wind) but it still seems to me that riders are going with a lighter front wheel even on dead calm days.

What do you think?

Dutchy

I will stick with the Ksyrium SL's, there light enough to be a great wheel, but not so light that they are not robust.
If they are good enough for Pro's then they are good enough for me.

CHEERS.

Mark

RacerX

Ok, first of all if you are non-competitive than the time savings an aero rim gives you means nothing.
Fortunately, you can have light weight and aerodynamics with Zipps or whatever. The downside is that they are harder to control in crosswinds but if you are going for one race wheelset, I would go for 303's, 404's, reynolds carbon, etc.

Overall wheel performance is much more important than the aero benefit. This is the reason Ksyriums or custom laced "box" section rims like a mavic reflex is popular in the peloton. Especially in road races.
The number one factor is the rider preference in wheels. To say someone is stupid or wasting energy for riding non-aero wheels is really ignorant. Take a look at any recent road race and see how many of the top riders are on carbon aero wheels and how many are on standard wheels.
In theory, aero carbons are great and I love them. I also love those campagnolo hyperions. INcredible wheels! They are carbon rim, but not aero. They are beautiful and fast.