The real deal with deep rims

by GoodOldFashionedLoverBoy   February 26, 2014  

Hi,

I upgraded the poor stock wheels that came with my CAAD 10 race bike to DuraAce C24-CL wheels.
These have as shallow rims as the stock one but weigh 500g less.
The change in handling is huge, and the bike feels way faster in climbs or flat, or in starting.
So from my point of view, it is really just the weight that changed (possibly better bearings in the hubs?) everything.

Now I wonder, when I look at most wheelsets with deep rims, those often start at 1500g and are sometimes as heavy as 1900g and still being considered top notch wheels.
There has to be something about that rim height I am missing.
Could someone explain what really rim depth changes?

From my research, shallow rims work well in climbs, when there is little or no crosswind and with many restarts, many directions changes while deep work on windless long straight flat roads.
But won't that extra weight be a handicap either way?

I understand why crosswind is deep rims' enemy so I understand why no wind is ok to ride deep rims, but what is the real advantadge about deep rims? why should one consider them against shallow rims?

Also, what is the deal with carbon and the overall rigidity of a wheel? I hear everywhere about wheelsets being or not extra rigid, but what is the effect on the ride?

Thank you!

13 user comments

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Rigid wheels give better feedback and also the bike reacts to smaller inputs through the bars and pedals. They will also take more of a pounding on the roads. I run a very stiff set and love the feel of them, I also feel I can lean the bike over more as I have more feeling through the bars.

Deep rims are meant to be aero (cut through the air more) but how much this is compared to a normal rim I don't know. I did hear well known tour rider say that the differences between the two types of rims is not as big as it used to be. Whether that is fact or not I wouldn't like to say.

Weight is ok if it is in the hub, my custom set are not much lighter than my OEM wheels but they are lighter at the rim so spin up quicker, it is noticeable as well but you lose the inertia you would gain from a heavy wheel on a descent so you will be slightly slower on downhills. This could be compensated by the hubs/bearings or peddling like f..Smile

As a side note I run Hope RS mono hubs, Mavic Open Pro rims, DT swiss Spokes 28 frt, 32 RR.

posted by Shep73 [137 posts]
26th February 2014 - 14:10

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The theory is that the aero drag of a wheel is caused not by the front of the tyre pushing through the air, but by the low-pressure area 'behind' the rim (caused by the air having been pushed out of the way). The deeper the rim, the more gradually the air flows back 'together' and less vacuum is created.

Boardman CX Team '14 | Cannondale CAAD8 '12 (written off, SMIDSY) | Scott Sportster '08

Gizmo_'s picture

posted by Gizmo_ [904 posts]
26th February 2014 - 15:12

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Deep rims make any bike look fast. FACT!
I use detec m-58 carbon tubulars. They weigh just under 1500g and are beautiful to ride without being mental money.

posted by Craig0605 [10 posts]
26th February 2014 - 17:00

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The stiffer the wheel, the less it flexes under hard pedalling
and so the less energy you lose that way. Also flexi wheels may end up rubbing on your brake pad. I hear deep rims only become more efficient than shallow runs after 25mph or there abouts, as that's when aero dynamics really come into play.

Canyon Roadlite Centaur/ Veloce groupset, Shamal wheels

Miles253's picture

posted by Miles253 [205 posts]
26th February 2014 - 21:48

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Craig0605 wrote:
Deep rims make any bike look fast. FACT!

^ this is the reason lots of people buy deep (carbon) rimmed wheels. Appearance, wanting to look 'pro'. Many owners can't or won't be objective about their fancy hoops, purchase justification gets in the way.

In terms of performance AFAIK a deeper rim only really affects aerodynamics. It's why time triallists and sprinters are the ones most likely to benefit from it.

Planet-X claim their fat 45mm rims, their "fastest ever", will save 3 mins over an Ironman bike leg compared to a trad shallow rim. That equates to 40 seconds in a 25 mile TT compared to the classic profiled Mavic Open Pro (32 spokes). That's £10 per second. I reckon that reducing the front wheel spoke count from 32 to 20 would account for a fair proportion of the time gained, as at speed the turbulence produced from each spoke becomes significant.

FLO Wheels also used the 32-spoke Open Pro as their baseline. The biggest improvement is for 30mm while their 60 and 90mm rims show little further gain. But to muddy the waters, they found that the aero gains varied with tyre choice:
http://flocycling.blogspot.co.uk/2013/04/flo-cycling-flo-30-wind-tunnel-...

An article about wheel stiffness:
http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html

Simon E's picture

posted by Simon E [2007 posts]
26th February 2014 - 23:23

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I have Shimano Dura Ace C24's and Zipp 404's. They are both excellent wheelsets, but here is my take on the differences.

1. The C24's are fantastic for climbing. They are lightweight and reasonably stiff and respond well to rider demands. I prefer these over the deep section Zipp's when climbing because I don't have to worry about crosswinds when descending. Where I ride, it can get pretty windy (especially in the afternoon), and I can remember more than one occasion where a stiff crosswind pushed me off my intended line with the deeper wheel set in the hills.

2. The Zipp's are great for sprints and time trials. They are very stiff, light and respond extremely well with hard, out of the saddle efforts. They also get up to speed quickly and hold speed well. They also look bad ass.

I love both wheels. It all depends on what you are using them for.

regman

rnarito's picture

posted by rnarito [31 posts]
27th February 2014 - 0:55

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40 seconds over 25 miles, yet folk still bang on about how they can feel how much faster their wheels are when pulling away, climbing or whatever.

Hilarious.

ColT's picture

posted by ColT [218 posts]
27th February 2014 - 9:24

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ColT wrote:
40 seconds over 25 miles, yet folk still bang on about how they can feel how much faster their wheels are when pulling away, climbing or whatever.

Hilarious.

....well yes, if they're using well built & designed wheels they will feel the difference. Usually expensive deep rimmed wheels are quite well build so if someone is banging on about how they feel faster it's probably because they've upgraded to a better wheel in the first place.

A stiffer wheel will help when "pulling away" as your power transfer is more effectively managed by the components you're pushing. A better quality wheel will help your overall efficiency as everything from the spoke tension to the bearing quality in the hub will simply work better.

While 40seconds over 25 miles at a certain speed may not help 50% of club riders in a local handicap, the benefits from using a better quality wheel will - in both physical advantage and the mental benefit gained from knowing you can rely on your kit - knowing only you are to blame when **** hits the fan.

If you do a bad sprint while wearing quality deeps, you need to look at your sprint.

I might be completely wrong here of course...so please do correct me if I'm wrong! Smile

Merlin Cycles women's race team ~ http://www.merlincycles.com
Manx nerd peddler ~ http://mooleur.blogspot.com

mooleur's picture

posted by mooleur [542 posts]
27th February 2014 - 9:46

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I have a set of Shimano RS80 C24s (~1500g), and a set of RS80 C50s (~1750g I think) - and I think rnarito hit the nail on the head really.

The C50s give me around 1mph increased average speed over a ~40-60 mile ride on flat or rolling terrain, but can be a bit of a handful at times when windy.

One point not mentioned above is the flywheel/gyroscope effect of a deep section wheel. As more rotating weight is closer to the edge, it has more ability to store kinetic energy than a shallow-profiled equivalent. This is useful on undulating or lumpy terrain, as the energy helps carry you up the rises a little. It does affect handling though - stabilising the steering at higher speeds, although some regard this as making the bike less responsive and don't like it.

The added rotating weight of a mid-range deep section wheel has it's drawbacks of course. They are not as immediately responsive to acceleration efforts as their traditional profiled cousins (or a lighter high-spec deep section wheelset), and on climbs over a certain length/gradient the drawback of the added weight negates any aero or flywheel type of benefit.

On a week-long trip down the Route des grandes Alpes I had both wheelsets. I ran the C24s for the first 4 days over traditional alpine roads, mostly having 7-8% gradients. On day 5, over the shallower slopes through the Mercantour national park (4-5% grades) I swapped to the C50s and they were superb. However, on the final day where the terrain reverted to the traditional alpine gradients, interspersed with frequent steeper sections over 10% I suffered on the C50s as the day wore on. For me personally, the benefit of the C50's disappears at about 6%.

In comfort terms, the Shimano C24 rims tend to give quite a nice forgiving ride. Deeper rims are not necessarily uncomfortable, but do transmit more road feel up to the rider.

A final usage example, I rode the Ride London-Surrey 100 on the C50s. Only 3 climbs of note and major roads most of the way. I was pretty pleased with my average speed and not too beaten up at the end - it was the right choice. However, a month or two previously I rode the Chiltern 100 on the C24s. A greater variety of road surfaces, more climbs (most shorter, but some steeper), and more total elevation gained/lost. I suspect I would have struggled a little on the C50s and think I picked correctly. Most other riders on that sportive were also on shallow rimmed wheelsets.

Next time I buy a bike and go 11-speed, I'll probably aim for a single set of good wheels, around 35-40mm depth.

andyspaceman's picture

posted by andyspaceman [229 posts]
27th February 2014 - 10:30

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Craig0605 wrote:
I use detec m-58 carbon tubulars. They weigh just under 1500g and are beautiful to ride without being mental money.

^^
This. I also wanted lighter wheels when I upgraded. I got deep rim (50mm )carbons, with seemingly very nice bearings, which *I think* Smile make me go faster (I have absolutely no indisputable scientific evidence for this), ~1400g wheelset for ~£400 (tubulars). Planet X R50.

If I'm really giving it some up the hills when out of the saddle, I can feel they are not laterally super stiff (I'm ~80kg), but actually, that is encouraging me to be much more subtle and efficient in my climbing style, rather than just mashing the power into the pedals and handlebars. I do not feel any lack of responsiveness when sprinting - getting from a ~22mph cruising speed to >30mph feels very rapid indeed.

The right wheels for you will depend on the type of riding you do. Lots of hills/mountains, or lots of bunch riding, deep rims will bring you no real value. Lots of solo riding with extended periods at fairly flattish gradients, at 20mph+, you'll probably get some benefit from deep rims.

I've never yet found crosswinds to be a big problem with my deep rims.

posted by Tjuice [121 posts]
27th February 2014 - 15:43

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One of the Cycling Internet's most useful rules of thumb is that unless someone actually makes their living designing, manufacturing and wind-tunnel-testing wheels, everything they write on the subject will be complete crap.

This thread demonstrates that perfectly.

MiserableBastard's picture

posted by MiserableBastard [6 posts]
27th February 2014 - 17:22

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MiserableBastard wrote:
One of the Cycling Internet's most useful rules of thumb is that unless someone actually makes their living designing, manufacturing and wind-tunnel-testing wheels, everything they write on the subject will be complete crap.

This thread demonstrates that perfectly.

Another of the internet's rules of thumb is that there will always be a few lazy, unimaginative, negative individuals who don't really know very much at all about the threads they're commenting on, but like to try to sound superior by trashing other people's valid experience.

andyspaceman's picture

posted by andyspaceman [229 posts]
27th February 2014 - 18:28

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Troll aside, there's some reasonable points on here.

You can't really consider rim depth in isolation, and manufacturer claims such as those made by Planet X, should be taken with a pinch of salt.

But combine each element of a quality wheel, (stiff, light, smooth rolling, 'aero' rim and spokes, quality tyres whose profile doesn't bulge over the rim), and I'm certain most riders will feel the benefit over a cheaper factory offering.

It's important to use the right wheel for the job though, so having winter /deep /shallow options is useful. Your Zipp 808'a aren't gong to be much help when it's blowing a gale outside..

posted by 700c [567 posts]
27th February 2014 - 18:42

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