roughly what speed does having deep rims take effect?

ianbar

as far as i undertsand it is only any real use having deeper rims once you get to a certain speed, i know these things are not exact but roughly what point is it? the wife is quite understanding and seems to think i need them!!! but i am not getting any until i know i actually require them...i have all the gear no idea as it is!

danlikesbikes

Seem to recall it was 20mph+ but depends on what reviews you read I think

ianbar

Danlikesbikes wrote:

Seem to recall it was 20mph+

i will stop saving then lol

danlikesbikes

Did say that it depends as some manufactures do testing at several speeds & there have been quite a few changes in design so is open to interpretation.

Wirral_paul

I've got both for my good bike - a pair of 58mm carbons and a set of very light aluminium wheels with DT Swiss 415 rims. I'd say 23 - 25mph before i start noticing the difference on holding a constant speed (gets progressively less hard on the deep rims) - but to be honest - there isnt much in it now that i've got decent aluminium wheels too.

The carbons sound awesome though - so worth it just for the noise! The bike equivalent of a V8 engine burble!!

ellj22

There are so many variables that it would be very hard to get a true answer that makes any real sense. You may also want to take into account handling, weight and wheel stiffness not just how aero. The faster you ride the more stable an aero wheel may become as your apparent wind will cause the yaw angle to become far more acute.

amaferanga

What sort of racing are you doing?

Wirral_paul

amaferanga wrote:

What sort of racing are you doing?

The one to the front of the queue in the cafe is the most important - well worth any small advantages if it means getting to the last bit of cake!! My money is Ian is in this race

pkripper

The correct answer is any speed. However, that has to be weighed up against possible additional weight and handling issues which come more into play as the gradients become more apparent.

So, the reality is that for any given wheels, if the rotating weight, stiffness, bearing friction is identical, the more aero wheel will be quicker. However, this is usually not the case as there is additional material in the rims, which weigh them down a bit (particularly at the lower end of the market), so when it's not flat, or when there are regular speed changes / accelerations, the lighter wheel claws back some, all, or more than all of that advantage.

But, if weights were identical, it's the aero wheel every time, regardless of speed.

JayKosta

For recreational/exercise/commute riding, deep aero wheels won't make much difference - except they are more affected by side wind....

For competition, they can be important.

In general, wind resistance increase geometrically with speed, 2x speed causes 4x increase in resistance. I think the effect gets most noticeable when approaching 20 mph.

A concern with deep wheels is possible difficultly / expense replacing or adjusting a spoke.

Jay Kosta
Endwell NY USA

slam that stem

Cervelo says aero is always on. Yeah, but so is rotating mass... As a regular racer I've held off on aero wheels forever, until last week when I purchased a 303 front 404 rear in clinchers and will see how it goes tomorrow. I was swayed by riding an older set ot toroidal shaped 404s for several 100+ km rides and loved the feel on the flats.

If you're riding 4-5-6 hour sportives and spend a lot of time on your own and are closer to 30 km/h than to 23 km/h average it's worth it. Don't let comments about side winds dissuade you: deep wheels are in fact more superior to box-section wheels at a 10-20 degree wind angle then they are if you have a perfect head wind.

Check out some of the calculations/graphs on the websites of Hed or Zipp. You can be cynical and say it's all marketing sheit but people spend a lot of money on them and some hours in the saddle on 404s helped me decide to part with my pretty green.

ianbar

Wirral_Paul wrote:

amaferanga wrote:

What sort of racing are you doing?

well worth any small advantages if it means getting to the last bit of cake!!

excuse me i take offence to that! i only take racing seriously and that means when theres cake...and coffee on offer! i dont race and dont envisage doing so although have a dip at time trials may happen. in a way its just lining up what my next purchase could be and weather to save.

thegreatdivide

slam that stem wrote:

Cervelo says aero is always on. Yeah, but so is rotating mass... As a regular racer I've held off on aero wheels forever, until last week when I purchased a 303 front 404 rear in clinchers and will see how it goes tomorrow. I was swayed by riding an older set ot toroidal shaped 404s for several 100+ km rides and loved the feel on the flats.

If you're riding 4-5-6 hour sportives and spend a lot of time on your own and are closer to 30 km/h than to 23 km/h average it's worth it. Don't let comments about side winds dissuade you: deep wheels are in fact more superior to box-section wheels at a 10-20 degree wind angle then they are if you have a perfect head wind.

Check out some of the calculations/graphs on the websites of Hed or Zipp. You can be cynical and say it's all marketing sheit but people spend a lot of money on them and some hours in the saddle on 404s helped me decide to part with my pretty green.

This is true, and in the case of the Zipp Firecrest series* you get the 'shopping trolley' effect where the bike/wheel will move a little with the wind but correct itself - a reassuring feeling. However if you get hit by a gust of wind side on you will be blown about.

*It's worth noting that companies like Zipp, Enve and some of the other big guns put a LOT of R&D into their wheels. Lower end deep section rims and Chinese weekend specials have had zero R&D and are essentially sails for side winds that you stick on your bike.

ugo.santalucia

slam that stem wrote:

Don't let comments about side winds dissuade you: deep wheels are in fact more superior to box-section wheels at a 10-20 degree wind angle then they are if you have a perfect head wind.

Check out some of the calculations/graphs on the websites of Hed or Zipp. You can be cynical and say it's all marketing sheit but people spend a lot of money on them and some hours in the saddle on 404s helped me decide to part with my pretty green.

How about the 70 and the 90 degree wind angle... we do get those too outside the wind tunnel. Any number that say that actually they handle better in lateral wind too?

markos1963

Deep sections only weigh so much because of all of the manufacturers stickers on them.

sloppyschleckonds

24.654321 mph

gsk82

To me the aero or not debate is exactly the same as the legs shaved or not debate. After all of the reasons to or not all it really comes down to is that aero and shaved looks better.

slam that stem

ugo.santalucia wrote:

slam that stem wrote:

Don't let comments about side winds dissuade you: deep wheels are in fact more superior to box-section wheels at a 10-20 degree wind angle then they are if you have a perfect head wind.

Check out some of the calculations/graphs on the websites of Hed or Zipp. You can be cynical and say it's all marketing sheit but people spend a lot of money on them and some hours in the saddle on 404s helped me decide to part with my pretty green.

How about the 70 and the 90 degree wind angle... we do get those too outside the wind tunnel. Any number that say that actually they handle better in lateral wind too?

I looked on Roues Artisinales, Tour Magazin, Hed and Zipp but can't find any of the graphs with their "yaw" angles. 90 degree apparent winds are called gusts and are temporary but can be dangerous. There was a painful incident at the windiest spot in the UK (btw it's the Start Finish line at the Cyclopark in Kent, check out this fact on Wikipaedia) where the winner of a E/1/2 race threw his hands in the air and promptly crashed. Ouch.

If your wind angles are 70 degress it's time to ride faster! As any catamaran sailor knows, apparent wind comes forward the faster you go :-D

My maiden voyage of the 303/404 combo today was a success despite the rear hub developing the Zipp wiggle.

sungod

on wheel drag charts, yaw angle is the effective angle, not the absolute angle, i.e. for a rider going 40kph, with a 20kph wind at 90 degrees absolute to direction of travel, the yaw angle is c. 27 degrees and effective headwind is c. 45kph

most of the time yaw angle is well within the 20 degree range, especially for faster riders, at higher yaw angles the difference in drag between wheels often reduces and on deep rims you're left with the sideways shoving

there's a chart here from the tour magazine test, the three wheels that just keep getting better at steeper angles and create negative resistance (i.e. forward thrust) are disks, the zipp 808 also manages it for some angles...

Monty Dog

Wind tunnel tests are all conducted n 'clean' air - unless you are spending a lot of time riding alone at high speed e.g. time trialling, then the benefits elsewhere are far less.

term1te

I've got some 50mm deep rim carbon wheels, and they go fast. I suspect most of the extra speed is psychological, I have fast wheels, therefore I will have to try harder to match the wheels, hence I go faster. They use tubular tyres and I suspect they tubs offer as much of a performance gain as the depth of the rim. Look good too, so even when I'm stationary, or not even on the bike, I look faster than I would with a pair of open pros.

They are twitchy in the wind though. I had one real scare descending fast when a gust of wind caught the front wheel and sent me 3 or 4 foot towards the centre of the road just as a car was trying to overtake me. fortunately the driver had good enough reactions to move even further over just in time. Even more fortunate that nothing was coming the other way. somewhat of a heart stopping moment. Never happened with the 32mm rims I normally use.

Mettan

Bontranger has got a reasonably 'up to date' look at this area (aelous .pdf) - worth a look. Depending on how deep you go at the front (and how windy it is), any potential gains can be somewhat nulified time-wise from poorer handling (in particular if you have less experience riding a deep front wheel) - if you're thinking of starting TT'ing? always bring two front wheels (deep and shallow) and way it up when you get out of the car.