Carbon aero wheels questions

[mtechnica]

Aero wheels are faster by all accounts so there’s that.

[Schredder]

Originally Posted by Mark McM

When you ask, "do aero wheels make a difference", you first have to define what "make a difference" means. In racing, the difference between 1st and 2nd are often separated by fractions of a percent, so any improvement, even small ones, "make a difference". Even the difference between barely-hanging-on and just-losing-contact can be quite small. But in other cases, such as when you're just out riding for fun, in differences in many percentage points hardly matters.

The original poster asked if his speed difference between two different pairs of wheels could be quantified (riding solo at speeds in the low 20s mph). While we can only make loose estimations, It's a good bet that it would be just a fraction of 1 mph. Does that "make a difference"? That's up to him to decide.

OP here
First, thanks everyone for sharing their knowledge and experience!

Lots of information to digest and think about.

Another quantitative aero question. Probably harder to answer, but what average speed improvement might I realize over a ride that I currently average 20 mph for 26 miles 1100 feet of climbing. The ride is a loop with wind often 10 to 20 mph?

Chris

[FriarQuade]

Wheels in this era don't go out of true all that often so I see the internal nipples as a pretty small concession to speed. Is it harder to true internal nipple wheels, absolutely. But if you only have to do it once a year does it really matter? If you're running discs then it's non issue.

[Mark McM]

Originally Posted by Schredder

OP here
First, thanks everyone for sharing their knowledge and experience!

Lots of information to digest and think about.

Another quantitative aero question. Probably harder to answer, but what average speed improvement might I realize over a ride that I currently average 20 mph for 26 miles 1100 feet of climbing. The ride is a loop with wind often 10 to 20 mph?

There's a whole lot of variables here, involving the rider, the bike, and the course, so it's hard to give even a rough estimate based on the information known. However, others have attempted to model specific courses under specific conditions, which might be interesting to look at. For example, the folks over at FLO Cycling, a maker of aero wheels, have modeled time savings over specfic Ironman triathlon cycling courses:

https://flocycling.com/blogs/blog/fl...ight-follow-up

The most interesting one here is the Ironman Coeur d'Alene course, which has 4612 feet of elevation gain over 112 miles (close to the same elevation gain per mile as your course). They modeled it with their sample cyclist using a pair of FLO 30 wheels (30mm deep aluminum rim) vs. using a FLO 90 (90mm deep carbon rim) front wheel and FLO DISC disc rear wheel. At an average 250 Watts power, their example cyclist completed the course in 6 hr, 1 min, 36 sec (18.58 mph Avg) with the FLO 30s, and 5 hr, 55 min, 46 sec (18.88 mph Avg) with the FLO 90/Disc wheels. You asked about 50mm deep carbon rims, which are apt to be less aerodynamic than a 90mm rim plus disc wheel, so I'd expect the time savings/speed increase to be less as well.

[benb]

The Ironman test data is no drafting on a closed course though right?

6 minutes over 6 hours would completely be in the noise if you were riding with other riders or in real world events. Unless you're P/1/2 you're probably not even going to be in a 6 hour race and it seems like a closed course race is the only case where real world variances don't dwarf the savings. Even a Gran Fondo type ride you can get caught up at stop lights or a train crossing and all this stuff instantly vanishes into the noise.

To me it's all about whether the real world makes these gains imperceptible.

6 minutes over 6 hours is lost if you have to take an extra bathroom break. It's lower than the variance over a real world course if you rode the same course 2x and one of the times you got lucky and got more green lights.

If you take it down to 1 hour in a naive way they're saying 1 minute saved over an hour.. think how easy it is to lose or gain 1 minute due to external things.

You'll never be able to tell.. either just buy them and be fine with that or decide they're not worth it.

This is just me.. I'm practical enough I kind of regret having a bike with internal cable routing for supposed aero benefits just cause of the extra maintenance inconvenience.

About the only aero things I don't think are a big inconvenience are an aero helmet and a better fitting jersey.

[Mark McM]

Originally Posted by benb

The Ironman test data is no drafting on a closed course though right?.

Yes, but that helps in limiting variables. If you try to add in drafting and group dynamics, you've got too many factors to consider. I've been racing on some of the same courses here in New England for years, and the racing speeds can vary widely, depending on who's in the field and how they want to race. If there are a few teams that want to work to keep the group together until the final sprint, then riding in the pack can be relatively easy even though the average speeds are high. Or, if there are several teams that are relying on getting one or more of their riders away in a small break, there could be many attacks & chases, and the race could be very hard even if the average speed is lower.

[benb]

Having been to Kona several times and watching the way people ride there and talking to them it could not be a further planet from roadies in New England or Europe. It's a completely different sport. This stuff makes sense to them.

Everybody riding by themself even "training" in full aero kit + TT helmet + aero/TT/Tri bike riding down the side of the highway 25-50 miles in one direction and then taking a U-turn and going back along the side of the same highway.

One rider I talked to there had been doing that on the same stretch of the highway (part of the course) for decades 2-3 times a week.

Just totally different kind of riding.

There's just no way I'll ever ride in a way that limits the variables that much where I'd ever be able to quantify my equipment.

We have these debates about whether or not these parts help X amount and we're mostly talking about performance in a wind tunnel.

All I'm getting at here is unless you ride on a trainer in a wind tunnel you might never even know if it's doing anything for you.

The best way to use these wheels is to borrow them from your friend who buys everything in sight the week before a big race.

[robertbb]

Originally Posted by benb

About the only aero things I don't think are a big inconvenience are an aero helmet and a better fitting jersey.

And they also happen to be the cheapest AND with the biggest impact.

[martl]

Originally Posted by Mark McM

Yes, but that helps in limiting variables. If you try to add in drafting and group dynamics, you've got too many factors to consider. I've been racing on some of the same courses here in New England for years, and the racing speeds can vary widely, depending on who's in the field and how they want to race. If there are a few teams that want to work to keep the group together until the final sprint, then riding in the pack can be relatively easy even though the average speeds are high. Or, if there are several teams that are relying on getting one or more of their riders away in a small break, there could be many attacks & chases, and the race could be very hard even if the average speed is lower.

Flo Cycling is trying to sell aero wheels. They also have in the past not exactly excelled with their understanding of technology. I would take their calculations with several grains of salt.

[mcteague]

Originally Posted by martl

Flo Cycling is trying to sell aero wheels. They also have in the past not exactly excelled with their understanding of technology. I would take their calculations with several grains of salt.

Yeah, I take ANY claims that result from wind tunnel tests with large grains of salt. The real world does not come close to behaving like a wind tunnel at bike speeds as they all seem to test at steady state.

Transient vs Steady State drag

The concept of transient drag effects have been well noted in low speed Aerospace applications such as military reconnaissance drones. This transient concept has not been applied to bicycle related products despite the overwhelming sensitivity of the velocity vectors involved. As an example the crosswind velocity on a bike often exceeds the forward velocity (Ratio > 1). A comparison for a car would yield a forward to crosswind ratio of 0.25 at 100km/h typical cruising speed.

https://www.hambini.com/testing-to-f...icycle-wheels/

Tim