Are expensive carbon wheels worth it? Testing deep carbon rims vs classic aluminium

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We're often told that "aero is king" and that "wheels are one of the biggest upgrades you can make to your bike". Well, we set out to find out how much faster deep wheels make you before deciding whether deep rims are worth it. Aluminum Extrusion Cnc

To find out we've taken the fastest wheels from Pt.1 of our wheels testing (recap available below) and pitted them against the new Roval Alpinist SLXs, an aluminium shallow section wheelset designed to be a more cost-conscious upgrade, at £650 they're a whole, £1,900 cheaper than our carbon deep section winner.

> Are expensive carbon road bike wheels worth the money?

If you cast your mind back to last autumn then you’ll remember that deserter Liam and I put a whole host of carbon wheels through their paces to find out if spending more resulted in going faster. SPOILER ALERT: The answer was...kind of...up to a point...

Given the small margins between those wheels, we thought it would be interesting to see how much of a difference deep carbon wheels actually make out on the road when compared to a more traditional aluminium shallow rim.

> Specialized Allez Sprint vs Trek Emonda ALR — which aluminium race bike will win this epic showdown?

Aluminium bikes are having a bit of a resurgence at the moment, could we be about to see the same when it comes to wheels? Or does carbon still rule the roost? To find out, we're putting t he pinnacle of carbon up against the wheels that claim to be the pinnacle of alloy, place your bets below!

The Roval Rapide CLXs ar e still my go-to race wheelset thanks to being stable, pretty light and most importantly, fast! But how much difference can a set of super-wheels like these actually make in the real world?

One thing that the Rapide's ain't is cheap! (The current second generation of the wheels have an RRP of £2,550!). Well, now Roval reckons they’ve got the perfect wheelset upgrade for riders on a smaller budget and the 24mm deep aluminium Alpinist SLXs (£650) claim to be “the pinnacle of what can be achieved with alloy”.

> Roval says new Alpinist SLX wheels are “the pinnacle of what can be achieved with alloy”

You'll be able to find our full review of the Alpinist SLX wheelset to independently verify (or squash) those claims up on the site soon but in the meantime, it seemed like the perfect excuse to try and answer the many of you in the comments who asked how much faster carbon deeps really are... Let’s see how much speed you can really buy!

> Best road bike wheels 2023 — transform your road bike with some shiny new hoops

We’ll be running three tests, one up a hill, one on the flat and you guessed it one going downhill. Obviously being quite deep, I think we can expect the Rapide wheelset to be quicker on most terrains - but by how much?

Oh and one other interesting thing to note is that despite clearly being quite different in just about every way, the two wheelsets are actually quite a similar weight, 1,485g for the Alpinist SLX and just 20g heavier for the 1505g Roval Rapide CLX II’s.

> road.cc Recommends Wheels of the Year 2022/23

Obviously, we want to try and make this as fair as possible so without a wind tunnel we’re left having to rely on a nice still day for consistent conditions, my trusty Quarq power meter, the same tyres and tubes and of course the same tyre pressures as well.

Then, to get both the most reliable results possible and because people seem to like watching me suffer, each test was conducted three times on each wheelset to try and weed out any anomalies and get a more reliable average. Oh, and of course I also wore the same clothing and held the same position for each run.

We kicked off with the descending test, which my legs definitely regretted later when having to do back-to-back flat and uphill tests. The descent in question was around 1.2km long and physics tells us that this is technically where we should see the biggest difference in the wheelsets as aero becomes ever more important at higher speeds thanks to the drag force being proportional to the square of the rider's velocity.

As always with real-world tests it is worth noting that there are always going to be factors out of our control, the real world is after all an uncontrolled environment. However, we hope you agree it’s still worth doing these tests as it is where we ride and if we can’t find a difference in a range of conditions then it’s unlikely you'll be able to either.

To make sure that it was in fact the wheels that were the variable and not my bravery, the descent in question had no corners that required braking and on each of the six runs I didn't pedal, kept my legs in the same position and set off from a standing start, again, without pedalling.

As we’d expect, the carbon deeps were indeed faster at descending and whilst that difference might look small, this was of course only a very small descent. If you look at some of the proper mountain descents in Europe then you can quite easily be descending for 20 minutes plus.

On average, the much shallower Alpinist wheels were 1.8 seconds slower over our 1 minute 20 or so descent, that's a difference of around 2.2%. Perhaps more interesting, is the fact that I held an average speed of around 52 kph on each run, so using the data from all the runs I put my aerospace degree and some CDA estimates to good use and calculated that this 1.8-second saving equates to around 16w at 52kph.

Now, I’ll be the first to hold my hand up and pick faults in this test but that figure is in keeping with what wheel brands regularly tell us, While researching this test I’ve read from multiple sources that a set of 50mm deep wheels can save 10w at 40kph so it’s not unreasonable to assume that some of the fastest deeps out there can save you this pretty tidy figure that we've come to.

As an add-on - Yes, saving 16 watts is certainly worth writing home about but we do also know that the vast majority of drag comes from you, not your bike or equipment. Having finished the runs, I made one final attempt no longer holding the same position on the drops and instead did an illegal super tuck, that run took me 1:15 and I had a max speed of 3kph faster, a far bigger difference than swapping out the wheelset!

> Why riders like you need to get more aero and wheel weight doesn't matter

Unless you’re very lucky…or lazy…most of us don’t do rides just downhill, this next test was along an 11km section of road with just a few rollers to test the performance of the wheels on more typical riding terrain. Again, we’d expect the deeps to be faster and here’s what we found…

On the full six attempts I road at a constant 275 watts and managed to average within +/- 1 watt of the target each time. Even so, our results are far from conclusive. On one run for example I was 20 seconds faster with the deeps on and on others only 10. We should therefore take the final figures with a pinch of salt but we can conclude that the deeps were faster on each and every run than when the shallow alloy hoops were fitted which surely cannot be down to pure chance.

On average I was 13 seconds faster on the Rapides, that’s a difference of around 1.2%, again, body position or pushing harder on the small rises is likely to have a far greater impact on time. We found that swapping out the wheels, a change that in this case represents spending an additional £1,900 resulted in a speed advantage of about half a kilometre per hour, whether that’s worth it is up to you to decide.

It’s also worth noting that I completed all the runs solo, if I was able to share turns, draft someone, or even better hide in a bunch then we’re looking at minuscule advantages even smaller than the 10 watts that I predict the deeps saved me.

So far, in every test we’ve expected the deeps to be faster and indeed they have been, however, there’s one area that we see pro and amateur riders ditching the deep sections - we are, of course, talking about on climbs.

However, the two wheelsets we have here are more similar in weight than you might expect, whereas usually, you can expect a significant weight penalty by switching to deeper wheels, the Alpinist SLXs weigh in at 1,485g on our scales and at 1505g the Roval Rapide CLX II’s are just 20g heavier.

As the graph below shows, when travelling at slower speeds, rolling resistance makes up a far larger proportion of the forces slowing you down and so as with all the tests, we’ll once again be using the same tyres, latex inner tubes and tyre pressures to ensure that it stays as consistent as possible.

Having ridden up the hill at 275 watts on the deep wheels I switched them out for the shallow aluminium wheels, to be honest, they sounded nowhere near as good, felt less stiff and felt slower as well. I was therefore pretty surprised when I crossed the line at exactly the same time as on the deeps.

The climb in question was around 1.35km long, had an average gradient of 9.5% and I averaged 12.2kph, it’s therefore safe to assume that aero played a fairly insignificant role in the climbing times. Was one set of wheels faster on it? It’s hard to say, having clocked exactly the same time on the first run the wheels then traded blows with differences far smaller than the margin of error.

As a reminder, I rode to a set power on each of the runs so the order in which the wheels were tested or fatigue should have no affec

If the climb had had a gradient of less than say, around 5% or I was a world tour pro climbing at much faster speeds then arguably the aero wheels would have been beneficial.

In general deeper rims are stiffer radially and laterally. This was in keeping with my ride impressions from the back-to-back runs although this clearly didn’t have a huge impact on the overall speed of the wheels.

So, in conclusion, the deeps were indeed faster, on the flats and downhills at least and then no slower than the shallower wheels on the steep climb. Obviously, if you were looking to spend the same amount of money on a set of shallower wheels then you could find something a fair bit lighter - maybe that’s a test for another day!

Of course, when deciding on a wheelset upgrade there’s far more to consider than just pure speed, for example, price - there’s a vast difference between these two wheelsets, the type of riding you do - speed freaks will gain more from a set of deeps than someone who’d rather meander up climbs and of course stability. The super-wide Rapide’s are in my experience some of the most stable wheels out there but they’re no match in crosswinds for a shallow rim like this that simply doesn’t have the surface area to be affected by crosswinds as much.

Want to know how these Roval Alpinist SLXs stack up against other aluminium wheels - that video will be coming soon!

> Lighter, wider, more aero: which wheels work best for your type of riding?

So in conclusion, unless the margins are very small then a set of deeps is not going to win you that race, body position, mental strength and of course the power in your legs are going to make a far bigger difference. Of course, that by no means means that there isn’t a place for deeps, if you’re looking for marginal gains then as they come this is quite a sizeable one.

Let us know if you think a set of deep carbon wheels are worth it in the comments section below...

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Jamie has been riding bikes since a tender age but really caught the bug for racing and reviewing whilst studying towards a master's in Mechanical engineering at Swansea University. Having graduated, he decided he really quite liked working with bikes and is now a full-time addition to the road.cc team. When not writing about tech news or working on the Youtube channel, you can still find him racing local crits trying to cling on to his cat 2 licence...and missing every break going...

For the cash strapped roadie, there is another consideration - weather conditions. You can ride shallow rim all year round, but on a gusty day, your average cyclist is put at risk by deep section rims. If you've only got the one set, chances are you are going to risk coming a cropper at some field gate in a hedge.

Deep section rims are the domain of competitive cyclists who invest in having the choice of appropriate wheels for the conditions, they are not an either one or the other choice of a leisure roadie.

Seems I now count as above average, because i ride "deep" setions all year round. 45mm as a minimum.

Maybe my large mass reduces the risk from cross winds. similar area, but much more mass to move.

YMMV always applies to these discussions but I think it was remiss of the writer not to raise the potential issue. I know of a couple of people who have bought deep section rims because they are a relatively cheap carbon rims (I suspect they are easier to make strong) and were caught out by their effect on handling - though any cyclist will be affected to some extent by an unfortunate gust.

I think the main conclusion is not; deep sections are only a little bit quicker than shallow rims, but that the Alpinest SLXs are bloody good wheels.

Not sure we know anything of the kind until they are tested against similar Alu wheels.

as soon as you're in a 5-15 degree crosswind the aero wheels will spank the shallow wheels, you might even get done sailing effect if the wheels are well designed enough and 50+min deep.

deep wheels are not really any faster at 0-5 yaw but faster at all other yaw angles

as soon as you're in a 5-15 degree crosswind the aero wheels will spank the shallow wheels, you might even get done sailing effect if the wheels are well designed enough and 50+min deep.

deep wheels are not really any faster at 0-5 yaw but faster at all other yaw angles

Here we might ask: are the deep wheelers wanting to be cyclists or sailors? Why not just buy a dinghy?

Coz we don't like getting our feet wet...

I think Dr Hutch and Sean Yates have both been keen sailors?

Coz we don't like getting our feet wet...

feet stay inside the boat, water stays outside the boat. surely?

This is more about feel and a psychological sense of speed for most people. I know my tcr is only slightly quicker than stock because of my wheels but they make me feel quicker and so i want to ride more. In actual fact the thing that makes them feel so good is really good hubs with really good bearings. I reckon thats the best real world upgrade.

Go-faster stripes do have the effect that you mention - observe boy-racers in their murderous stink bombs, for example.

Myself, I rely on the go-faster stripe of a retro racing jersey as worn by a Merckx or even a Poulidor. (It must one in 100% merino, though). Also, there is the "another cyclist up the road" go-faster effect. Perhaps it should be possible to buy an up-the-road-cyclist from Amazon, just for that purpose?

But how much would such a slave cost!?

On the other hand, after decades of hooting about as fast as possible, I are lately been mostly pootling, with only the odd burst of eyeballs-out. It's very pretty out here in The Hinterland, especially down the turfed-bank lanes awash with every wild flower you can imagine (and some you can't).

Would Jamie (or someone else) by able to shared the "multiple sources that a set of 50mm deep wheels can save 10w at 40kph"?

Where are the error bars, confidence intervals and inferential tests? I know such mathematical things are "boring" and "complicated", but without them your descriptive data is meaningless and uninterpretable. Thanks.

That's untrue and unkind and just a little curmudgeonly.

Whilst all those things would be nice an attempt to apply something vaguely scientific shouldn't be moaned at.

Error bars and confidence intervals are statistical methods which can be applied to raw data. If you want them, calculate them yourself. Of course, with such small sample sizes it will be pointless, so you'll have to go out yourself and, say, reproduce the tests 97 more times.

That was my first thought. Variation between runs on the same wheel was about the same order as differences between wheels. That means many more replicates required to have a chance of rejecting the null hypothesis (no difference).

Does it matter? Maybe not for wheels, where the choice is between round ones, or bling round ones. Apply this to any other question where someone is trying to sell you something, or ask for your vote, and the confidence interval is a powerful BS detector.

First, nice test. Second, that was a lot of riding/testing, so thanks for your efforts. That shows a lot of commitment. Third, there are faster and maybe easier ways to do real world comparisons like that.

says the poster who then doesn't go on to name any of these "faster ways".

Perhaps he was being modest?

Silca blog post describing the Chung Method

(the interview in the youtube video at the bottom is worth a watch if you are interested in actually doing some tests yourself

PDF going into a lot of detail of how it works

says the poster who then doesn't go on to name any of these "faster ways".

says the brave poster who goes by the name "Secret_squirrel."

says the poster who then doesn't go on to name any of these "faster ways".

says the brave poster who goes by the name "Secret_squirrel."

I like this article. Slightly disappointed that it wasnt comparing a set of old school deep aluminiums against modern carbon though....

Ahh yes, the forever ongoing debate about whether that £1000 or £10,000 makes you into a TdF rider. As is always the case, the person on the bike makes up about 98% of the equation.

Not sure why people have such strong opinions on it though. This is a hobby. That overweight guy on a £7000 bike hasn't bought it because he thinks it will turn him into an athlete. Hes bought it because he has the money and wants it.

Same reason people spend silly money on cars, holidays, coffee machines, houses etc etc. I have carbon rims and I love them. They make me faster but negligably so. I love the sound of them, they look cool and I can afford them. I, like most people I imagine, don't think they are going to make me a better cyclist. I just like them.

Do what makes you happy. There are millions of videos showing how little difference every upgrade to your bike makes but people still spend thousands. Its almost like people do it because it makes them happy...

More like people do it because they were Svengalied by an advert.

I suppose consuming pretty things does make one happy - for the day or three until "an even better one" gets advertised into your eye-brain. The happy fades back into the nagging-want.

Soon the bike and its spares box starts to become more like a-one o' them wardrobes full of shoes and handbags; or my tool collection.

But thanks to the authors of the article revealing the more objective stuff concerning, in this case, the actual data around expensive "cool" wheels. Always sobering to know the truth; even the buyers who thought they were getting some important faster-magic get a lesson in why one should generally eschew impulse buying for a considered decision and the pleasures of delayed gratification in a truly useful purchase.

For those of us who don't race, the only reason to have aero wheels is to beat our mates, but most of the advantage is negated by riding in a group, so what's the point?

that sounds suspicously like racing to me.

Isn't the reason for aero wheels

For those of us who don't race, the only reason to have aero wheels is to beat our mates, but most of the advantage is negated by riding in a group, so what's the point?

that sounds suspicously like racing to me.

Isn't the reason for aero wheels

Ha ha. Faux-racing, surely - aka not-racing-at-all but trying to look like it and failing.

Energy saved? Just eat a bigger bit of cake at the cafe and try a teeny bit harder when pedalling.

Looks cool? Shurely shome mishtake as (i) they are also described as "hot" and (ii) they make most riders look like fashion victim wanabees when ridden along at their usual 17.2mph maximum.

As to the "beating our mates" - this is presumably at "having a bigger wallet so able to buy the tech" rather than at being faster on a bike due to superior ability at cycling?

Still, promenading in one's best & latest gubbins-clobber on a bike is no dafter than doing it on an actual promenade whilst dressed in the latest frock & teeter-shoes or oddly-shaped trews & toe-distorters.

Yeah but your group blasts to pieces on the hills? Or is that just every group I've ridden in ?

Very interesting real world test Jamie!

But possibly you off your advertisers' Christmas card list

I definitely ride my 50mms faster but that may be a placebo effect. As I've no power meter I've no way of knowing.

Well, make your mind up. Either it is or it isn't legal advice, it can't be both. It isn't Schrödinger’s cat.

In my bit of the South west, anyone who appears on the road in the pink stripe, never waves. Is this true of the rest of the country? ...

Any way you like, provided its legal and doesn't endanger other road users.

One for the wait 'til he hears about cars folder...

No. That pothole is on the sunlit uphill direction. Once you crest the hill and come down the other side it gets more exciting - there are shoals...

When these people get tracked down and arrested, they'd better be facing attempted murder charges. It'd be no less if they used any other offensive...

I've got an Orro Terra C which was great value and I used for a long distance cycling tour over a mixture of roads, bike paths and rough forest...

Well, a GP5K lists at the same price so other tyres can also make your wallet shudder....

I wish bans from driving were not seen as a punishment! Making this more "administrative" might help make this less "drama" - although this relies...

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Are expensive carbon wheels worth it? Testing deep carbon rims vs classic aluminium | road.cc