[davman]

Hi

Whenever you read reviews of deep section carbon rims (say 38mm plus) the reviews quite often mention savings of such & such watts/power at an average speed of 40Km/h (as an example).

What if the average speed is significantly lower than 40Km/h, for example 27Km/h (approx 17mph) – are there still savings to be made from using deep section rims at these speeds or not?

Anyone have any examples or links to related information?

thanks

Simon Hume

 

 

Topic

[wycombewheeler]

I weigh 80kg, bike weighs 9kg

I weigh 80kg, bike weighs 9kg. add in water and tools easily north of 90kg total weight

changing wheels to save 450g would be a massive wheel upgrade, but would only be 0.5% of total weight

Aero wheels can easily gain 1km/h on the flat, so 31kmh instead of 30kmh will save about 2 minutes over an hour ride.

lightweight wheels are going to gain less than 1% of climbing speed. so even 1 hour of continuous climbing (which is steep enough to lose any aero benefit) would gain less than 20 seconds

[wycombewheeler]

I guess it depends whether

I guess it depends whether you are stronger than your friend, or he is stronger than you.

If he is easing back to ride at your pace, then you will get there faster. If you are already riding within yourself to stick together than saving energy will only reduce calcories burned, not really what anyone is after

[wycombewheeler]

Savings will be proportional

Savings will be proportional to the square of the speed, so 27/40 is roughly 2/3 and the watts will be reduced by 4/9.

Just under half the savings at 27kmh than at 40kmh

However, the increase in how good the bikes looks will be unchanged and people will be able to appreciate it for 50% longer

[Ihatecheese]

My wife and I ride pretty

My wife and I ride pretty slow with our dog. Under 15mph most of the time together. I ride faster on my own. My bike originally came with 50mm front and 60mm back prime black edition wheel. It was a positive experience when I swapped for some 36mm all round (as not many super shallow light carbon disk wheels about for the similar £), my Enve 2.2 rear doesn’ feel as fast with less wooshing but no real noticeable change in effort. 

Less wind buffeting and faster spin up. Aero wheels are great if you’re zooming, but in traffic in the city it’s just cool factor in my slow experience

[hmas1974]

I replaced my ageing 58mm
I replaced my ageing 58mm FFWDs with a set of Cero 35mm wheels. I get most of the aero benefits of running deeper sections, lighter wheels and they’re better suited to the terrain in the Surrey Hills, North Downs and Hampshire.

[Diggery]

Well, I made a purchase so if

Well, I made a purchase so if nothing else, my bike will look cool this summer!

[Diggery]

Thanks a lot for the feedback
Thanks a lot for the feedback!
I’m looking at the Prime 50mm black edition as they seem good for the money, lighter and more aero than the cheaper ones.

I’ll happily settle for slower climbing wheels in exchange for ‘flow’ and speed on rolling undulating flats and fast downhills of which there are plenty. If the wider rim gives grip and comfort too it’s a winner.

I just wanted to feel a difference for the cash!

[bozmandb9]

Effectively yes.

Effectively yes.

Your average speed is only telling half the story, the big question is how much elevation is in your ride.  If you’re riding at 35 kph on the flats, 45 on the descents, and 15 on the inclines, you’ll get lots of aero benefit on all but the inclines.  For climbing there is little to no downside, since most carbon aero wheels are not heavy nowadays.

If you’re doing 27kph on flat routes, you’ll still get plenty of benefit, less so than if you were going faster, but still worth having.

Check out GCN for links.

[bozmandb9]

You only benefit from weight

You only benefit from weight savings over aero benefit on a ride with average gradient over 6%, i.e. for most of us pretty much never.  Maybe for hill climb TT’s, that’s pretty much it.

Remember you’re talking maybe a couple of hundred grams, most of us could easily lose ten times that from our bodyweight!

Aero benefits are far more important than weight, in nearly all circumstances except for very steep climbs.  There’s loads of research out there, much of it independent, and now you can get decent aero rims which are 1,500 grams, it’s not really an either or thing.  

Finally, most contemporary aero rims are fine in cross winds.  My son is only 70kg, and is riding 55mm rims in all weathers.

[MattieKempy]

But your bike will look sooo

But your bike will look sooo much cooler!

[MattieKempy]

Hey @Davman, I’d suggest that

Hey @Davman, I’d suggest that deeper rims will make you faster. I’ve had Prime RR50s before now and the weren’t the fastest but I’d imagine they’d be faster than 38s. I’d also suggest that the more ‘modern’ shape of the Prime Black Edition rims might make them faster.

[MattieKempy]

@Diggery, having upgraded

@Diggery, having upgraded from shallow alloy rims to 50mm carbon rims my anecdotal evidence would suggest that climbing is no slower (possibly because the carbon rims are lighter; I don’t climb fast enough for aero to make any difference) and that descending and flat riding are significantly faster and that speed is easier to maintain. I’d also suggest (anecdotally) that different rims enhance different aspects of this. I’ve had narrower carbon rims and wider carbon rims, some in a more modern aero shape than others and, again anecdotally, the more modern, blunter-shaped, wider rims seem faster than the older, narrower ones. That’s just my feeling. Hope it helps! Oh, BTW, if you’re on rim-brakes, make sure to get wheels with good braking surfaces. I’ve had Token wheels before and while they felt fast, their braking performance was rubbish. I’ve also had Prime wheels and they didn’t feel as fast as the Tokens but the braking performance was significantly better.

[Diggery]

Good discussion!
Good discussion!

I’m thinking about new wheels.
I ride places like the Dales and Peak District, 1-3 hours at 15-18mph average, lots of hills >10%, often hit 40mph down and ride a 2014 carbon bike with da9000. Tight kit and spend time in the drops and tucked in. I like the feeling of speed, even though I’m not the fastest by a long stretch.

It doesn’t seem worth replacing my whole bike, but some of the more ‘affordable’ carbon 50mm rims would update the stock fulcrum 2.5’s. Frame and calipers limits tyre width too.

I’ve concluded weight is near irrelevant at the levels we’re talking about.

Aero is interesting. Gains are small but lots of evidence it affects slower riders more, due to yaw angle and time in the saddle.

I’m struggling to justify the purchase based on small performance performance gains but there are a few improvements.
Aero(ish) 50mm section
200g saving against my wheels.
19mm internal v 17 will give me a wider tyre. Tubeless will also add some comfort.
Wider brake track means tyres won’t catch the blocks in wheel removal.

I’ve had to admit that these changes are marginal for a solo rider and the biggest benefit is looks. I ride alone and fairly remote so it’s purely for me. The other intangible element is ‘feel’.

Still can’t decide if I should do it, but if I do it won’t be based on pure performance.

[Simon E]

bosskardo wrote:

I think the bigger question would be if he has hills. He may save a lot more with lighter wheels.

Very unlikely.

It has been shown over and over again that reducing wheel weight makes very little difference to climbing times – fractions of 1% of all-up weight to save a handful of theoretical seconds, which is irrelevant for recreational riders.

https://road.cc/content/feature/why-riders-you-need-get-more-aero-213876

https://road.cc/content/feature/lightweight-v-aero-which-best-227520

[bosskardo]

I think the bigger question

I think the bigger question would be if he has hills. He may save a lot more with lighter wheels.

I don’t feel the difference going at a steady training pace but do feel it in races or when doing intervals.

[Author]

Replies