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Lightweight or deep rimmed?

lbmxj560lbmxj560 Posts: 51
edited August 2013 in Road buying advice
Hello all

I have just come into a bit of money having sold my motorbike (sad times) and want to get a new set of wheels for my bike. I ride a Sensa Romagna Special and use it for everything from gentle rides to triathlons. The stock wheels are mighty heavy (over 3.5kg with tyres, cassette and skewers) so this is a primary concern.

The real thing I want advice on is whether I am best going lightweight or deep rimmed? I don't want to spend a lot (no more than 400-500) and tend to average around 19mph on a sprint tri. I weigh 78kg but am getting lighter by the week!

I have just missed the planet x wheel sale, which I am a bit annoyed about, so any advice (constructive please) is greatly welcomed.

Thanks all

Matt
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Posts

  • cougiecougie Posts: 22,512
    I'd say deep rims especially if you race tris.
    Planet X sales come round pretty often so they may be back on sale soon.
  • mrolimroli Posts: 3,622
    I think Sports Pursuit may still have a planet x deal going on if you are that keen.
  • Wirral_paulWirral_paul Posts: 2,476
    mroli wrote:
    I think Sports Pursuit may still have a planet x deal going on if you are that keen.

    Indeed - they are doing the CT45 wheels at £495 at the moment
  • sungodsungod Posts: 14,365
    low weight is an advantage when climbing or accelerating, otherwise it makes little difference

    at 19mph you'll get some benefit from improved aerodynamics, but it won't be a huge amount

    for tri, aside from rims, fit tyres with low rolling resistance (of the widely available tyres, a corsa cx for instance) and, assuming you want clinchers, use latex tubes rather than butyl, overall it'll save you a few more watts (if there's a tubeless with known low crr that could be good too, but i've not seen figures on any)
    my bike - faster than god's and twice as shiny
  • meesterbondmeesterbond Posts: 1,240
    Or get tubs and have the best of both worlds, keeping the heavyweight ones for training.
  • iPeteiPete Posts: 6,076
    I would get the Race 23 or [email protected] ~450, do like a wide rim.
    http://www.wheelsmith.co.uk/road-wheels-prices

    p.s. Did Ironman @ 19.7mph on shallow rims, try not to get suckered into the 'triathletes must buy X & X & X' products to compete camp, especially if you are using one wheelset for all types of riding.
  • passoutpassout Posts: 4,425
    Weight is more important to me but if TT is your focus then the other.
    'Happiness serves hardly any other purpose than to make unhappiness possible' Marcel Proust.
  • bianchiboybianchiboy Posts: 13
    I'd go for some of these:
    http://www.lead-out.co.uk/stilletto

    Clinchers and only 1270g a pair, so I use mine for training and racing including TT. In my opinion low rolling resistance, weight and stiffness are more important than deep section. Particularly when you look at how inefficient deep section rims are in cross/tail winds which we do get a fair amount of here!
  • johncpjohncp Posts: 302
    sungod wrote:
    low weight is an advantage when climbing or accelerating, otherwise it makes little difference

    at 19mph you'll get some benefit from improved aerodynamics, but it won't be a huge amount

    for tri, aside from rims, fit tyres with low rolling resistance (of the widely available tyres, a corsa cx for instance) and, assuming you want clinchers, use latex tubes rather than butyl, overall it'll save you a few more watts (if there's a tubeless with known low crr that could be good too, but i've not seen figures on any)

    Not true. Slower riders benefit more. From Alex Simmons blog
    "The largest absolute time savings from a given aerodynamic improvement are made by the least powerful/slowest riders"
    Full article here http://alex-cycle.blogspot.co.uk/2013/0 ... iders.html
    If you haven't got a headwind you're not trying hard enough
  • ugo.santaluciaugo.santalucia Posts: 26,786
    Johncp wrote:
    sungod wrote:
    low weight is an advantage when climbing or accelerating, otherwise it makes little difference

    at 19mph you'll get some benefit from improved aerodynamics, but it won't be a huge amount

    for tri, aside from rims, fit tyres with low rolling resistance (of the widely available tyres, a corsa cx for instance) and, assuming you want clinchers, use latex tubes rather than butyl, overall it'll save you a few more watts (if there's a tubeless with known low crr that could be good too, but i've not seen figures on any)

    Not true. Slower riders benefit more. From Alex Simmons blog
    "The largest absolute time savings from a given aerodynamic improvement are made by the least powerful/slowest riders"
    Full article here http://alex-cycle.blogspot.co.uk/2013/0 ... iders.html

    May I sugegst that I still believe physics over this Alex Simmons guy?
    You see, the man has a blog, but the blog supports an activity of cycling coaching if I understand correctly. He clearly has any interest in making sure his customers have the fastest equipment to benefit the most from the coaching. You can fit some 80 mm aero rims to a lady on a Pashley but I suspect she won't go much faster
  • imposter2.0imposter2.0 Posts: 11,738
    May I sugegst that I still believe physics over this Alex Simmons guy?
    You see, the man has a blog, but the blog supports an activity of cycling coaching if I understand correctly. He clearly has any interest in making sure his customers have the fastest equipment to benefit the most from the coaching. You can fit some 80 mm aero rims to a lady on a Pashley but I suspect she won't go much faster

    There's a bit more to coaching than just telling people to get more aero - otherwise, we would all be doing it.
  • ugo.santaluciaugo.santalucia Posts: 26,786
    Imposter wrote:
    May I sugegst that I still believe physics over this Alex Simmons guy?
    You see, the man has a blog, but the blog supports an activity of cycling coaching if I understand correctly. He clearly has any interest in making sure his customers have the fastest equipment to benefit the most from the coaching. You can fit some 80 mm aero rims to a lady on a Pashley but I suspect she won't go much faster

    There's a bit more to coaching than just telling people to get more aero - otherwise, we would all be doing it.

    Who says there isn't?
    Just better aerodynamics works better at low speed than high is simply not true. You can plot your car fuel consumption vs speed and you will see that the curve is not linear... there is point where your car will use a lot of fuel to go just a tad faster... that's where you would like your car to have the shape of a rocket... while at 40 mph it won't make pretty much any difference in the fuel consumption.
    My car is shaped like a brick and it is incredibly fuel efficient up to 60 mph, pass that and it becomes among the worst in its range of engines
  • petemadocpetemadoc Posts: 2,667
    Yep

    I call Bullpoo on that blog post. The faster you go the more aerodynamics matter, simple.
  • imposter2.0imposter2.0 Posts: 11,738
    PeteMadoc wrote:
    Yep

    I call Bullpoo on that blog post. The faster you go the more aerodynamics matter, simple.

    I love the way nobody actually bothers to read/understand the blog post before declaring it as nonsense. There is no dispute that aero equipment benefits faster riders. The contention is that aero equipment can also benefit you even if you ride at slower speeds (although not by very much).
  • petemadocpetemadoc Posts: 2,667
    The largest absolute time savings from a given aerodynamic improvement are made by the least powerful/slowest riders.

    I know what he's trying to say but it comes across wrong
  • meesterbondmeesterbond Posts: 1,240
    I thought it came across pretty clearly to be honest.

    Particularly:
    If you are a back/middle of pack rider, then some bling wheels are not going to make you the next world champion, so some perspective here is warranted but the rationale for why you are looking to improve your performance is a matter of personal choice. If you want to be faster, then you do all the things you can given the constraints you have (time, money, knowledge, rest of life factors etc). And we are talking about people riding in competition-like events, not your cruiser to pick up some milk at the local shops (let's be sensible here).
  • ugo.santaluciaugo.santalucia Posts: 26,786
    Imposter wrote:
    PeteMadoc wrote:
    Yep

    I call Bullpoo on that blog post. The faster you go the more aerodynamics matter, simple.

    I love the way nobody actually bothers to read/understand the blog post before declaring it as nonsense. There is no dispute that aero equipment benefits faster riders. The contention is that aero equipment can also benefit you even if you ride at slower speeds (although not by very much).

    There is no explanation on how these numbers are calculated, as they are clearly not measured... per se the graph doesn't make any sense, without taking into account which equations were used and which approximations were used. To be honest, It seems to me a bit strange that with 150 Watt you can go at over 30 Kmh (which is less than 20 minutes for 10Km). I find it a bit harder than 150 Watt, which is little more than tottering around
  • cougiecougie Posts: 22,512
    A lot of courses will have downhill bits or tailwind bits - so the speed there would be higher than this average 19mph anyway.
  • Monty DogMonty Dog Posts: 20,614
    Judging by the mamils I see riding on tri-bars and deep-rim wheels barely struggling to maintain 30kph on the flat, the biggest performance factor is going to be through decent training, weight-loss and position - an 80mm deep front wheel is going to help diddly unless you lose the 50mm of spacers and riser stem. People were riding 20 minute 10 mile TTs without aero bars, helmets and wheels, so this notion that you need fancy wheels to go fast is pure nonsense propogated by wheel companies.
    Make mine an Italian, with Campagnolo on the side..
  • CrimmeyCrimmey Posts: 207
    C'mon guys...CONTEXT and interpretation! Everyone is twisting it to fit their own ideas. Im no expert but i'd love to see data where a wheelset can change cdA by 0.03m^2 of the total rider, maybe 0.003m^2? No wheels? I do believe cdA changes with velocity too, no ideahow much. Lowering cdA via position change is very feasable in order of that magnitude and should not be used to compare to wheels.
  • ugo.santaluciaugo.santalucia Posts: 26,786
    Monty Dog wrote:
    Judging by the mamils I see riding on tri-bars and deep-rim wheels barely struggling to maintain 30kph on the flat, the biggest performance factor is going to be through decent training, weight-loss and position - an 80mm deep front wheel is going to help diddly unless you lose the 50mm of spacers and riser stem. People were riding 20 minute 10 mile TTs without aero bars, helmets and wheels, so this notion that you need fancy wheels to go fast is pure nonsense propogated by wheel companies.

    And let's not forget the fastest Paris-Roubaix ever in 1964!
    http://paolocoppo.drupalgardens.com/con ... ics-really
  • cyclecliniccycleclinic Posts: 6,865
    Power comsumed = 0.5* cda* frontal area * air density*(velocity)^3. Ugo makes a good point above. My 10 mile TT time is 27:15 on a standard road bike with no aero aids so I have a long way to go Monty dog.

    Power consumed is proportional to velocity cubed. Siimple as that there for the power required to over come aerodynamaic drag on the flat is 8 times that at 15mph. At 15 mph aerodymanic drag and rolling resitance are roughly equal expecept for very draggy tyres but at 30 mph aerodynamic drag is much bigger.

    I have shallow rims on my light bike and they do not stop charging down the road at 30 mph but I can't hold it for too long. Aero wheels Power savings for good aero wheels will be about 20W at 30mph compared to a 32 spoke count shallow rimmed wheelset so you really have to be going some for a long time to get any real benefit. So for a rider that sustain 30mph over 100 miles which is not possible the energy saving would be 240kJ ((100/30)*3600*20) that not even a Mars bar. O.K that a very rough calculation but you get the point.

    Light wheels will change the way the bike feels. It will make some difference (not much though) on climbs and when accelerating but only if the rims are light. Hub weight make little difference to acceleration.

    Light weight higher (24F/28R or 28F/28R even 32 spoke couts wheels) spoke count wheels can be built and I think that is a better solution to heavier rimmed low spoke count wheels unless low spoke count is the look you want. wheels in 1360g-1600g are easily built for a 80kg rider depending on what the rider requires.

    However if you want the look of deep V rims then go ahead with a pair of Planet X rims or buy the rims and a get a local trusted wheelbuilder to build them for you. There is also the Kinlin XR-380 for a deep alloy rim but it is not light.

    Or keep the wheels you have. 19mph average is not slow and if there is nothing wrong with them then the benefits will be marginal.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • CrimmeyCrimmey Posts: 207
    Light weight wheels make little difference too, just as negligable as wheel 'aeroness'
  • johncpjohncp Posts: 302
    Ok, just supposing Alex Simmons is pulling a fast one to make sure his clients get the best bang per his coaching buck (which I don't believe for a minute), try this http://www.tritalk.co.uk/forums/viewtop ... 3&start=21

    "Drag force Fd = ½ ρ v² Cd A ; where ρ is air density, v is air velocity, Cd is your drag coefficient, A is your frontal area.
    So you can see that drag ∝ velocity squared, like you said.
    Now, power is force * velocity so drag power Pd = Fd * road speed
    If we assume still air, then we can combine to give Pd = ½ ρ v³ Cd A
    Neglecting other losses such as rolling resistance, we can re-arrange to solve for velocity from rider power output (P) : v = ³√(2P / ρCdA)

    So we can see that regardless of your fitness P (watts) if we reduce the drag characteristic CdA by 15% through a more aero setup then velocity increases by the cube-root of 15%, which is 4.7%, also reducing your time over a given distance by 4.7%. Since a slower rider spends longer covering a given distance, any given reduction is drag characteristic is worth more time for a slower rider.

    Here's a complete worked example for two aero setups (CdA's of 0.28 and 0.33) and two power outputs (180 and 400W):
    http://www.bornskinny.com/TT/aero_worked.gif
    Hence, aero kit is worth more time the slower you are, and every time you read something like "deep wheels are only beneficial over 20mph" you can now snigger arrogantly to yourself."

    Whether a reduction in CdA of this order is real world doesn't really matter if all we want to understand is the benefit of aero for slower vs faster riders - the principle is the same.

    Unfortunately this doesn't answer the OP question of deep or light, but we seem to have gone off-topic somewhat so maybe the OP could have a look at this http://alex-cycle.blogspot.co.uk/2013/0 ... parts.html which, again, is from AS' blog but there's a fair bit of science in there and references to other people who have done the difficult sums too, rather than just expressed an opinion :)
    If you haven't got a headwind you're not trying hard enough
  • sungodsungod Posts: 14,365
    i doubt is accusing alex simmons of anything underhand, but you seem to be interpreting things in a way that creates disagreement

    earlier, you asserted that my statement was "not true"

    the statement, which in answer to the op's question was in the context of changing from a shallow rimmed wheel to a deep rimmed wheel, was that...

    'at 19mph you'll get some benefit from improved aerodynamics, but it won't be a huge amount'

    this is true, the words are precise, i'm not talking about 30mph, or how much more speed/less time is gained at a given power output, or different riders, or whether or not alex simmons coaches them

    i'm talking about the absolute benefit for a specific rider at 19mph

    this has nothing to do with rider power/weight/size, it is physics, i'm talking about changing one factor at a specified speed

    where those other factors come in is in the proportional benefit a rider can gain vs. another rider, sticking to the op's 19mph, consider two riders on identical bikes with with low rims, one built like a shed, the other a waif, both in the position that produces the minimum possible drag for their rider+bike combination

    the shed may need 200w to mantain 19mph, the waif 170w

    switch to a zipp fc 303* may save around 6w* at 19mph

    proportionately the waif is saving more, but in absolute terms both riders save 6w, which, like i said, is not huge

    this isn't a bragging thing about who rides fastest, it's how things are at 19mph, for a given rider that may be the right speed to aim at for long distances, there are an awful lot of people who couldn't maintain 19mph long term

    so, back to my statement, the true one, there is a benefit to improved wheel aerodynamics at 19mph, but it's not huge

    i hope you can now understand why what i said is true, if you still can't accept that then i'm happy to let believe what you like, overall there's a marginal gain to be had from others being wrong, so mostly i leave people to it

    in the real world, it's unlikely that the op has optimum position, and there could be other available options to reduce total drag that are far more cost effective per watt, such as helmet, clothing, tyres and tubes

    deep wheels are lovely things, i have some myself, but when looking for gains, it makes sense to go after the low hanging fruit first

    once that's done, if the purpose is tt, i'd get a disk wheel (as someone has mentioned above)

    *zipp claim 24w saving at 48kph vs. a low profile rim, the zipp's may well be the best for their depth, they are also way over the op's budget, a low-cost deep rimmed wheelset probably isn't going to be as efficient

    **yaw angle has a big impact on drag, if you were unfortunate enough to be riding on a completely still day or with a very narrow absolute yaw angle, the savings can become very small indeed
    my bike - faster than god's and twice as shiny
  • johncpjohncp Posts: 302
    @Sungod - In my last post I wasn't really quibbling with what you said, although your answer implied that 19mph isn't fast enough to benfit from aero improvements (ok, maybe I was a little black and white in my first reply to you, maybe I should have said not strictly true, or maybe "define huge" :D . Having said that the time benefit at lower speeds is greater). The long winded answer was for those who then went on to say that aero is more important at higher speeds, or unimportant at lower speeds both of which are untrue.
    As for ugo not accusing Alex of anything underhand
    "You see, the man has a blog, but the blog supports an activity of cycling coaching if I understand correctly. He clearly has any interest in making sure his customers have the fastest equipment to benefit the most from the coaching" suggests at least that Alex might twist things to make his coaching look more effective.

    Agree in general with the rest of what you say - as I said at the end of my last post, the thread went off the original topic somewhat which asked whether aero or light rimmed was best. And yes its probably more effective/cheaper to go for low hanging fruit such as fitness and position in real life, but the original question was essentially a theoretical one relating only to the benefit of one wheel type over another.
    If you haven't got a headwind you're not trying hard enough
  • cyclecliniccycleclinic Posts: 6,865
    johncp your calc are wrong for a 400W rider with CDa of 0.33 v= 12.61 m/s not 12.31 m/s
    A 400W rider with a CDa of 0.28 has a v = 13.35 m/s not 13 m/s

    A 180W rider with CDa of 0.33 has a velocity of 7.67 m/s not 9.43 m/s something.
    A 180W rider with a CDa of 0.28 has a v = 8.12 m/s.
    I though something did not smell right about your numbers.

    So a 40 km TT for the slower rider takes 86mins55sec vs 82mins 6secs
    A 40km TT for a fast rider takes 52mins52secs vs 49mins56secs.
    The result surprise slightly which is why it is important sometimes to work thing out. However rolling resitance is not included in this calculation which will reduce the time difference for the slower rider as it makes up bigger proportion of the total drag whether it remove the adavantage the slower rider has I don't know as I have not worked it out.

    I would like to point out though that my earlier statements were based on a a non TT situation were a rider is just riding a normal road bike maybe in a race. In this senario the aero benefit does not let you go faster per say as most will stick in a group but is will reduce your power output a bit which will allow you maitain the pace for longer. I was not considering TT or time saved. This is a completely different analaysis and not what the OP was talking about. If the OP even reading anymore, I doubt he/she has probably got bored and oved on.

    Aero is never unimporant it is just not the be all in riding. Wheels by themselves will make little difference but wheels combined with the pixie helmet, skinsuit, aeroframe, proper position will add up to something significant. This thread is about wheels though not a full TT set up. Saving a handful of Watts make little difference to anyone. Saving 60W on a full TT setup at 30mph is huge. However as I chopped nearly 1 minute of my TT time last night on a 8.4mile course on a road bike with no aero aids training has a very big effect too and riding more is all I have done.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • May I sugegst that I still believe physics over this Alex Simmons guy?
    You see, the man has a blog, but the blog supports an activity of cycling coaching if I understand correctly. He clearly has any interest in making sure his customers have the fastest equipment to benefit the most from the coaching. You can fit some 80 mm aero rims to a lady on a Pashley but I suspect she won't go much faster

    I have an interest in helping the riders I coach attain improvements in performance, be that via improving their power output over durations of most importance to them via training, the smart use of equipment options, dealing with psychological factors and mental approach, race strategy, tactics, guidance on diet, recovery and via other permitted, legal and ethical means. I'm a professional coach who provides an evidence based approach to performance improvement.

    Mind you, while I perform detailed aerodynamic testing for clients using leading edge technologies in the field, I do not sell nor have any pecuniary interest in an aerodynamic cycling equipment. What I do is help clients make good choices about what's best for them.

    I made it clear in that particular post that people need to have a little perspective on where they would best spend their resources and we are not talking about "a lady on a Pashley".

    As for believing in physics, well I do have a degree in physics so have a modest understanding of the subject and the modelling I use is based on the published science of the physics of cycling, specifically the model as presented in the following paper and which has been thoroughly vetted and tested with real world data:

    Validation of a Mathematical Model for Road Cycling Power
    Martin, Milliken, Cobb, McFadden, Coggan
    Journal of Applied Biomechanics, 1998, 14, 276-291

    The cubic relationship between speed and power is clearly articulated in this model. Aero improvements will make any rider faster for the same power output, and the relative improvement from the same relative reduction in CdA will be very similar whether you ride at 30km/h or 50km/h. There are some specific circumstances where there are differences due to CdA variances at caused by different yaw angles at different rider speeds.

    Given that's the model I use, all the relevant assumptions are listed in the item and on the chart. That's the physics.

    When you look at the absolute gains in time over a fixed distance, and realise the slower rider is on course for longer, you then understand why they also make slightly greater time gains than faster riders.
  • Just better aerodynamics works better at low speed than high is simply not true. You can plot your car fuel consumption vs speed and you will see that the curve is not linear... there is point where your car will use a lot of fuel to go just a tad faster... that's where you would like your car to have the shape of a rocket... while at 40 mph it won't make pretty much any difference in the fuel consumption.
    My car is shaped like a brick and it is incredibly fuel efficient up to 60 mph, pass that and it becomes among the worst in its range of engines
    You are confusing the difference in the power demand of riding at different speeds with the relative speed improvement from the same aerodynamic change (i.e. a fixed percentage reduction in CdA) a rider attains (be they riding at 30 or 50 km/h).
  • ugo.santaluciaugo.santalucia Posts: 26,786
    Just better aerodynamics works better at low speed than high is simply not true. You can plot your car fuel consumption vs speed and you will see that the curve is not linear... there is point where your car will use a lot of fuel to go just a tad faster... that's where you would like your car to have the shape of a rocket... while at 40 mph it won't make pretty much any difference in the fuel consumption.
    My car is shaped like a brick and it is incredibly fuel efficient up to 60 mph, pass that and it becomes among the worst in its range of engines
    You are confusing the difference in the power demand of riding at different speeds with the relative speed improvement from the same aerodynamic change (i.e. a fixed percentage reduction in CdA) a rider attains (be they riding at 30 or 50 km/h).

    Why my car, which is very aerodynamically inefficient has the same fuel consumption than a different model with the same engine at 60 mph, but a radically different one at 70 mph and ourageously different at 80 mph?
    I have owned both cars: they both did about 60 mpg at 60 mph, the current does about 48 at 70mph (former did 54) and about 35 at 80 mph (former did 48). Being a stingy persona, I do tend to look at these numbers.
    Am I wrong or this shows that aerodynamics is more relevant at speed? Where am I confused?

    EDIT: the understanding I have of speed and power is that to move from saying 10 to 20 mph you have invest X power, but to move from 20 to 30 mph you have to invest a lot more than X power and to move from 30 to 40 mph (on a bicycle) you have to invest a hell of a lot more than X.
    Typically sprinters use 1000-1400 Watt to go at 40-42 mph
    Time triallists use 400-450 Watt to go at 30 mph
    Amateurs need about 200-250 Watt to go at 20-22 mph
    In which way this relationship is linear? It seems to me rather exponential and it's all down to aerodynamic drag
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