Wheel combinations for aerodynamics?
 

I was thinking about get an aero wheelset, but then I thought, what if I just got a front wheel only that was 2x as deep as one of the wheels in the wheelset and then keep the rear wheel?

For example, my wheels right now are about 25mm deep and I want to upgrade to a 40mm deep wheelset. Would my bike be just as aero just I just got a 80mm deep front wheel?

This would save money and I wouldn't have to switch out my back wheel for a trainer. (For those of you who switch between an on-road wheel and trainer wheel)

The front wheel has about 2/3 of the total wheel drag, and the rear 1/3

So if the front wheel has a bigger impact on aerodynamics than the rear wheel. Having an 80mm front would be even MORE aero than two 40mm deep wheels??

It could work, but it would be basically impossible to actually quantify and still depend on the specific wheels. Not all 80mm (or 25mm) wheels are equally aero.

And I am hoping you are also aware that an 80mm front can be a handful in a cross wind.

Depends what your riding goals are. Time Trials ? Road Racing ? Hilly ? Flat ?

bottle on the seat tube and aero helmet

Well, money is actually my goal. Buying one wheel (especially the front) is usually %50 the wheelset if not more. I am just looking for a wheel upgrade (aerodynamic and/or light) from the stock ones that came with my road bike. Most of my rides are climbing and descending so a light weight wheel or aero wheel would work.

Any gains you'll see will be so small you'll need a flat windless stretch of road, a power meter, and a ton of free time to quantify them.

Unless your current set is broken don't waste your money.

For various reasons I've raced with just a front aero wheel, usually a TriSpoke (aka HED3).

This was the track but I've also done it on the road. Found it:


You can see my setup in the very beginning of the clip. In this case I had a Powertap rear wheel so I used just the front aero wheel, and it was the most aero wheel I owned. It didn't help me in that race but I ran a setup like it for years, the Specialized Trispoke up front and a less aero but much lighter wheel in the rear.

As far as you're concerned going from a ~25mm rim to a 40mm rim won't be significant. In fact, if I did it, I wouldn't be able to tell the difference. For me I need to go 58/60mm or taller to be able to tell if I have a more aero wheel. I was just telling a relatively new racer (also a teammate) today that he shouldn't look at normal width rims 46mm or shorter. I had an unfortunate opportunity to ride two wheels back to back, a 60mm modern aero wheel and a 46mm not-so-modern shaped wheel. I flatted the tire on the first and grabbed the second wheel from a teammate. After I got the 46mm rimmed wheel I actually checked my bike a bunch of times, during the race, because I thought my brakes were rubbing. It felt so slow I couldn't believe it. We run the same tires (I glued them for him) so it was the wheel. It's not like I didn't know the 46mm wheel either - it's mine. I permanently lent it to him, a different teammate, in 2010 when I got the 60mm tall wheels.

The problem with a tall front wheel is the control thing, as pointed out above. You can't go fast if you can't control the bike. If I'm doing any really fast descents (50+ mph) I put the shortest wheel I can up front. Gusty winds can wreak havoc with bike control, like when trucks pass you or if you ride past a building on a windy day.

You never stated your budget but you can probably get a pair of used wheels, 58mm or taller, pretty inexpensively. If you want to get just the front then you need to take into account the control thing. I haven't ridden with a rim taller than 60mm up front but I'm going to be running a 75mm rim in the front this year. It ought to be interesting.

One thing that you can do is to try and get a pair of tall wheels, like a pair of 80s or something like that. If it's not too windy you have a blazing set of wheels. If it's really windy just use the front wheel you have now, the 25mm one. I did this for stability and speed, i.e. stable at speed and the tall rear wheel helps a bit.

http://2.bp.blogspot.com/_TbmplkIYLx...10202_Bike.jpg

yeah.

best you can do aero-wise is a disk front and back. anything else is a compromise of some kind. Plus a disk won't make up for a mediocre position on the bike. an aggressive position and a 'Properly*' matched aero helmet will impact Cda far more than a different set of wheels.

That being said, for about $100 the Wheelbuilder Aero Jackets are almost identical to disks in wind tunnel tests.
I'd start there. if you don't really notice a speed difference, don't spend $3k on 'aero wheels'.

T

*testing required

Good new aero wheels for $1000 for a front deep and disc rear if you can wait for the orders to come in since they arrive in batches.

http://www.flocycling.com/store/index.php

Actually with R. Chung's Virtual Elevation (VE) method, you don't need a flat road. Don't want a flat road, actually. Power meter - yes / very helpful. Windless - yes. Low traffic - yes. One where you don't need to brake at all - definitely desirable. (Out and backs work for this where the turn-arounds are both on hills. Make sure the turnarounds have good (safe) lines of sight.) Tons of free time - no. (Perhaps 60 to 90 minutes for field testing. Once you know what you are doing a little bit, perhaps 30 minutes of time playing around in the Aerolab of Golden Cheetah.)

http://rothrockcyrcle.wordpress.com/...-my-aerolab-2/

Edited to add: One trusted (by me) source of aero info suggested that reducing spoke count matters more than using deep rims. IOW, you'd get more bang for your aero buck by going with a 20 bladed spoke wheel with a low profile (say, 25mm) rim than using a 32 round spoke wheel with a 60mm rim. You'd obviously save weight with the former approach too. And you can get pre-fab'ed wheels like this for cheap.

ONe example: http://www.neuvationcycling.com/prod...black-1237.htm

well, if saving money is the goal, ride more, ride smarter (train, ride properly in the draft, etc.) and ride in the drops more.

It is true that the majority of aerodynamic gains come from the front wheel. The rear wheel is tucked behind a couple of churning legs and tubes so the air is very turbulent back there. On the front wheel you are seeing good clean wind, however your weight is over the rear wheel which adds stability (which is why you see riders using a full disc on the back but rarely on the front).

Staggering wheels (using a deeper one on the rear and shallower on the front) is a possibility but until you start going to big depths (80mm+ on the rear) you aren't making that big of a difference. Having a really deep wheel on the front could give you handling issues depending on the crosswind situation.

A lot of this will depend on the type of riding you are doing too. If you are just looking for an everyday wheel to train on then you shouldn't be looking at super deep as crosswind handling could be an issue. If you are spending all your time fighting crosswinds it's going to take away from the fun of riding deeper wheels and you won't see the benefit. For doing a lot of faster group rides, some events, some races I usually recommend to go with something in the mid depth range (40-60mm). You'll still have a very aerodynamic wheelset but it will be a little easier to control. It'll also be lighter for spin up when you are in a group ride and it will still be a decent climbing option.

If you are just solo training and doing a lot of climbing and descending, sticking with a good alloy clincher is still the best option in my opinion. At the slower speeds of climbing aerodynamics will not be an issue. Plus descending long steep roads with an alloy rim is a lot better as carbon may not be the best option for those situations (especially in the wet).

Can anyone here honestly say that they got significantly faster by getting aero wheels? No placebo, no manufacturer's advertising statistics...just plain old hard evidence.

While I don't dispute the reality that carbon wheels will give you a tiny (<1 min per hour) speed advantage, I wish I could start an 'over-rated' thread.

#1 would be:
Posters saying "I got new carbon wheels and they're SO much faster - I can really tell the difference by riding them!"

Pretty hard to believe when the difference is <0.5mph at speed of 25mph. Go at the more realistic 20-22 mph and it's less than 0.25mph of an advantage.

I believe the wind tunnel numbers, so I use 50mm carbon tubulars for racing. I've always liked the way tubulars feel, but other than races, I would not bother. I got a used Zipp 404 front, and built my own rear for about $450 total. I definately would not blow big bucks on non-race wheels, but that's just me.

Why don't you check for yourself first, then decide? Temporarily put a plastic or even cardboard spokes cover on your front wheel, ride it and see what if any speed increase you get. The disc will be equally or more aerodynamic than the deep wheel of any dimension of depth.

Bear in mind that a covered wheel would feel like a zero-trail wheel for handling at high speeds, and additionally the effect of side gusts are amplified against the pivot of the whole bike + rider further degrading stability. Those effects are still there but to proportionally less degree with deep wheels. This is just "theory" ;) if you're disposed against that, plus a little bit of testing.

I am asking about real-world significance to 99.99% of cyclists who ride recreationally. I can see it making a difference to a professional at the highest leves of ability and fitness, but for the rest of us high-end areo wheels just seem like a tremendous waste of money and mostly simply for bragging rights.

Perhaps a pro-level rider in top condition hammering away can achieve that kind of difference, but for the rest of us snuffys it is likely just placebo.

Sure. Just like BMWs, Volkl skis, G Loomis rods, etc.

yes.

So... You're looking for aerodynamics that are cheap? You're not gonna pick up branded aero stuff cheap. You could go and look at Chinese stuff that has no brand, poor warranties and most likely, poor quality or pick up some wheel covers (Thin, plastic covers that go over your spokes). They will somewhat give a disc effect. I think they may be banned for use in racing though, not sure. (Might depend on the race holder).