whats the advantages of deep carbon rims?

ianbar

i know its probably a really dumb question but what are the advantages if using deep carbon rims? is it simply that they cut through the air better? and of course look ace!

ilovebigwig

ianbar wrote:

i know its probably a really dumb question but what are the advantages if using deep carbon rims? is it simply that they cut through the air better? and of course look ace!

Is this the correct forum for a deep rim debate? :shock:

MattC59

Don't forget, they sound ace too !!!

I believe that they have aerodynamic benefits, however I've got a set of Aeolus 5.0 ACC, 50mm carbon wheels, and the only reason I have them is that they look ace.

As far as I'm concerned, they're like a go faster stripe

MattC59

ilovebigwig wrote:

ianbar wrote:

i know its probably a really dumb question but what are the advantages if using deep carbon rims? is it simply that they cut through the air better? and of course look ace!

Is this the correct forum for a deep rim debate? :shock:

it is if you're a beginner !

ianbar

well i think its a beginners question if you don't know the answer and have never ridden with deep rims.

ilovebigwig

So if you're new to deep rims, just dive in and get involved?

okgo

Yes, they are more aerodynamic, however their benefits only really make themselves known at higher speed, so if you're riding is on the slower side, then they offer very little outside of looks.

jonomc4

deep rims = slower acceleration (over a lighter wheel I.e. less rim) and more hassle from side winds - but for keeping on going they are better, and more aerodynamic (less use if you ride in a bunch though but still a little). Maybe just go for a 40 rim - less of the above problems but still look ace

Is that a reasonable summary?

Im Bald Ok

I read somewhere that deep rims start making a difference at 13.5mph. I don't remember where I saw that so take it with a pinch of salt. Maybe someone will come along and elaborate.

Their purpose is to better your aerodynamics. I find as previously said that they spin up slower but will hold a higher speed much better than shallow rims.

They do make a difference in a bunch as you're still taking wind but will obviously make less of an impact compared to riding a TT for example. There's not some magical vacuum pack in bunch racing.

Down the Road

Im Bald Ok wrote:

I read somewhere that deep rims start making a difference at 13.5mph. I don't remember where I saw that so take it with a pinch of salt. Maybe someone will come along and elaborate.

Their purpose is to better your aerodynamics. I find as previously said that they spin up slower but will hold a higher speed much better than shallow rims.

They do make a difference in a bunch as you're still taking wind but will obviously make less of an impact compared to riding a TT for example. There's not some magical vacuum pack in bunch racing.

They make a diffierence at over 22 -25 mph. That's why they are used for racing. Other uses are for posing!

ianbar

hmmm thin i would come in the posing category then lol just as thought since I'm a bigger chap is there any other benefits/concerns for being heavier? as in wear and tare? the other thing is overall i goes they make it harder for climbing then but better on decent and flats? so guess i am saying not good if you struggle like me as should save lighter wheels for climbing easier or go with rims which would allow me to make the most of my power on the flat...sorry my post turned onto a bit of rant!

jgsi

Im Bald Ok wrote:

I read somewhere that deep rims start making a difference at 13.5mph. I don't remember where I saw that so take it with a pinch of salt. Maybe someone will come along and elaborate.

Their purpose is to better your aerodynamics. I find as previously said that they spin up slower but will hold a higher speed much better than shallow rims.

They do make a difference in a bunch as you're still taking wind but will obviously make less of an impact compared to riding a TT for example. There's not some magical vacuum pack in bunch racing.

I have never felt at a disadvantage riding with shallow rims in the bunch.
Heart likes the idea of 42mm full carbon tubualars but head says Racing Zeros for me.

Wirral_paul

jonomc4 wrote:

deep rims = slower acceleration (over a lighter wheel I.e. less rim) and more hassle from side winds - but for keeping on going they are better, and more aerodynamic (less use if you ride in a bunch though). Maybe just go for a 40 rim - less of the above problems but still look ace

Is that a reasonable summary?

Thats a pretty good assessment although the shape of the rim has a significant effect on how a particular rim performs in crosswinds. I've seen many struggle on 30mm ali rims more than i did on 58mm carbon rims in the same group ride, but as a generalisation its true.

Also i'd have to add, a lighter rim will spin up quicker, so a full carbon rim will be closer to a lightweight ali rim in this respect than a ali / carbon rim. Downside is the braking performance isnt as good.

Swings and roundabouts really. Go for carbon wheels if you want them, if not then dont.

ianbar

as usual it seems more complicated than just numbers and is a lot about quality of design.i currently have magic aksiums which i like a lot so won't be looking really for a while but you never know if the urge strikes!!!

oldwelshman

5 or 6 pair of ultegra wheels or 4 pair dura ace CL clinchers compared to one pair corima or zipp deep section ? no contest with respect to performance and value for money, IMO

Wirral_paul

Its a good job there's sometimes more to our purchases than value for money. Life would be dull if we stuck to that!

oldwelshman

Wirral_Paul wrote:

Its a good job there's sometimes more to our purchases than value for money. Life would be dull if we stuck to that!

Ah but I said with respect to performance and value for money.
If you pay, or a beginner pays around £1k to £2k for deep section rims will they see a four fold increase in performance? no. Especially on crap UK roads and oiur weather for breaking crap in rain.

Cubic

Couldn't some company start fashioning some sort of plastic, clip-on 50mm rim that you could attach to a normal shallow rimmed wheel as and when needed?

I'm sure there's an obvious reason why this isn't done, but wouldn't that give you the aero advantage with a relatively small weight increase and be cheap?

cougie

People do something similar. Some of the deep carbon rims aren't structural. Theyre just shells over a real wheel. You wouldn't want them removable though. Imagine something going wrong on a fast descent ?

jonomc4

Cubic wrote:

Couldn't some company start fashioning some sort of plastic, clip-on 50mm rim that you could attach to a normal shallow rimmed wheel as and when needed?

I'm sure there's an obvious reason why this isn't done, but wouldn't that give you the aero advantage with a relatively small weight increase and be cheap?

I am sure I have seen fixies with something like this - not sure what it is.

For me, I need to upgrade my Ksyrium Equipe to Elites (which I think look better than a lot of Carbon wheels - understated class as it were) at least I will also be using a wheel that is equivalent to my abilities and needs as well.

Tom Dean

Wirral_Paul wrote:

a lighter rim will spin up quicker

Always struck me as a strange expression - obviously a lighter wheel is easier to move than a heavy one. You roll along on your wheels. Since when did they 'spin'?

See also 'these wheels hold their speed well'.

cougie

Deep rims are good for Time Trials - once you start - you don't stop (unless traffic balks you).

They'd be of little use say commuting through traffic - any aero benefits are spoilt by the slower time it takes them to 'spin up' after all of the stopping.

DavidJB

I love a deep rim.

pilot_pete

I've got both. Handbuilt 50mm carbon clinchers and 30mm alloy clinchers. The carbon wheels are lighter and stiffer (much better quality build with Sapim CX Rays on Superlight hubs). They made a huge immediate difference to the feel of the bike over the standard (cheap) alloy wheels. They also look the mutts nuts!

However, it's not all good news. Supposedly being a 'heavier' rider (currently 82kg) I have had real problems with the braking of these carbon clinchers. I fitted Swissstop Yellow carbon specific pads, but both rims are now ruined. The problem is the braking surface starting to delaminate after changes to the resin. It would appear this is due to heat generated when braking. It happened after hilly rides and downhill braking. Somehow the heat generated is absorbed into the resin causing it to change its structure. This lead to patches of the braking surface becoming harder than other areas, presumably the resin cooling again and re-setting into this hardened form. This then started to excessively wear the pad material on these hard areas, I'm talking half a brake pad worn out over one ride. This caused the braking to become 'grabby' and left yellow deposits around the brake track.

Having cleaned all this material off the rim (interestingly it was only one side of the front rim) I tried again, but immediately the same thing happened again. I sent the wheel back to the builder who said it was something to do with my braking technique (which is the same with carbon or alloy rims, but only causes a problem on carbon rims!) and replaced the rim a cost price. Several weeks later on another hilly ride the rear carbon rim has done exactly the same, only the carbon fibre is starting to delaminate on this rim too. These wheels are 1 year and approximately 5000miles old.

My conclusion is that for flat rides high speed carbon deep section rims are good, but for downhill braking they can develop problems quickly. Also, in the wet, even with very expensive carbon specific pads the braking is far, far inferior to an alloy rim, even with cheap pads fitted.

I will be looking for some handbuilt alloy rimmed wheels for my hilly rides in future.

PP

giropaul

Cubic wrote:

Couldn't some company start fashioning some sort of plastic, clip-on 50mm rim that you could attach to a normal shallow rimmed wheel as and when needed?

I'm sure there's an obvious reason why this isn't done, but wouldn't that give you the aero advantage with a relatively small weight increase and be cheap?

They did at one time, at least "disc" type covers, but as anything like this isn't race-legal (Non structural aerodynamic aid) there wasn't a big enough market.

Bar Shaker

They work by replacing spoke material at the point where the spokes are travelling at their fastest... at the outer most edge of the wheel. At the top of wheel, the spokes are hitting the air at twice the speed you are riding at and this is a major source of aero drag.

The point about using them on flat rides is very valid. Heat build up will boil the resin out of the fibres and will damage the wheel. They also aren't as stiff as a good alloy wheel so climbing uses more energy (you are losing power to wheel flex - this is why the pros ditch them when in the mountains).

On the flat, cruising at mid twenties or higher, they are a revelation. This isn't my sort of riding though so I use Elites.

RowCycle

Down the Road wrote:

They make a diffierence at over 22 -25 mph. That's why they are used for racing. Other uses are for posing!

I reckon that they'd make a difference no matter what speed you're at, but that as the speed goes faster you notice the difference more.

oldwelshman

RowCycle wrote:

Down the Road wrote:

They make a diffierence at over 22 -25 mph. That's why they are used for racing. Other uses are for posing!

I reckon that they'd make a difference no matter what speed you're at, but that as the speed goes faster you notice the difference more.

nope, only benefit at higher speeds.

Millerman007

So would a wheel like the fast forward F4R with 40mm carbon dish but alloy braking surface be a good all rounder for the flats and hilly rides I do ?

ugo.santalucia

Millerman007 wrote:

So would a wheel like the fast forward F4R with 40mm carbon dish but alloy braking surface be a good all rounder for the flats and hilly rides I do ?

No, just a very expensive wheelset with no merit. They are not light wheels, they are not aero wheels, they are not reliable wheels for all roads... the question is: at that price WTF are they good for? with the same money you can buy a light set for all rides, a set of chinese carbon tubulars for TT and racing, new tyres and a flight to Geneva to ride some decent mountain... and I am not joking!

richh

Bar Shaker wrote:

They work by replacing spoke material at the point where the spokes are travelling at their fastest... at the outer most edge of the wheel. At the top of wheel, the spokes are hitting the air at twice the speed you are riding at and this is a major source of aero drag.
.

Maybe my physics head isn't working this morning but how is that possible? The edge of the wheel is traveling at exactly the same speed as you (unless you are wheel spinning down the road!), so anything further towards the centre for the wheel is going to be travelling slower than the speed at which you are moving.

Yes the end of the spoke at edge of the wheel is travelling faster than the end of the spoke near the hub, therefore causes more air resitance so using a thicker rim would reduce that drag, but I just can't see how what you've written makes sense.