Heat build up under braking in aero rims

Slimtim

I am about to spend some £££s on some 50mm aero wheels.

The preference is for a set of Shimano RS80 50mm which have rims with an aluminium brake track and a carbon faring.

My rationale being that I would like to have the aluminium section to brake onto as the reviews of all carbon rims under wet braking are mixed and (to be honest) I don't want to keep changing my brake pads.

My question is, are carbon/aluminium composite rims as described, more or less prone to heat build up than standard aluminium box section rims or full carbon aero rims?

I have quite a lot of experience of descending/braking on box section rims and never had an issue. As the shimano wheel is effectively a box section with a faring, I am hoping that the heat issue isn't one that will magically appear!

dmclite-3.0

Slimtim wrote:

I am about to spend some £££s on some 50mm aero wheels.

The preference is for a set of Shimano RS80 50mm which have rims with an aluminium brake track and a carbon faring.

My rationale being that I would like to have the aluminium section to brake onto as the reviews of all carbon rims under wet braking are mixed and (to be honest) I don't want to keep changing my brake pads.

My question is, are carbon/aluminium composite rims as described, more or less prone to heat build up than standard aluminium box section rims or full carbon aero rims?

I have quite a lot of experience of descending/braking on box section rims and never had an issue. As the shimano wheel is effectively a box section with a faring, I am hoping that the heat issue isn't one that will magically appear!

It won't be an issue if your rims have an aluminium brake track. The heat build up issue usually comes into play on full carbon rims and inexperienced riders descending for a long time, laying heavy on the brakes too often.

ugo.santalucia

Have you considered ditching the 50 mm idea altogether? Most people seem to buy them for the way they look. Aeordynamics is a word that fills the mouth but doesn't really apply to your sunday ride. It is a rather frivolous way to spend 1 K if you don't race "contre la montre".

If it's for the look just say and I won't comment...

Slimtim

Hello

Thanks for the feedback. The spur for my question is that I am planning to use them for Ironman Majorca which has a steepish descent as part of the course.

@Ugo, the wheels are for duathlon, tri and TT (only).

ugo.santalucia

Slimtim wrote:

Hello

Thanks for the feedback. The spur for my question is that I am planning to use them for Ironman Majorca which has a steepish descent as part of the course.

@Ugo, the wheels are for duathlon, tri and TT (only).

Then Get full carbon and get tubulars... heat dissipation is less of an issue in tubulars. Use glue, don't use tape for that.
It's Majorca, chances are it won't rain... if it rains use different wheels, problem solved. No point in getting a mediocre set of heavy boots just for one descent that is likely to be dry

Slimtim

Thanks for the feedback, I'm pretty happy with my approach especially as it is a conscious move away from the greater difficulties inherent in racing on tubs (e.g. massive time loss in case of puncture).

ugo.santalucia

Slimtim wrote:

Thanks for the feedback, I'm pretty happy with my approach especially as it is a conscious move away from the greater difficulties inherent in racing on tubs (e.g. massive time loss in case of puncture).

I think your approach is wrong, Ithink you are spending 3 times what is necessary and ending up with an inferior product for the application you have in mind. I think you are also wrong about the (unlikely) punctures and the time it takes to change a tub... but hey oh, it's your money, do what you think it's best

EDIT: seen they are half price, you are not spending 3 times as much, the rest applies

smidsy

What about something like Broby Carbon 40 mm 28 holes clinchers with Pillar bladed spokes?

Anonymous

I wish I knew more about wheels, it all seems a bit of a dark art. I too am after a set of middle depth wheels for around 400 but unfortunately mine need to be cross purpose, 95% road and 5% TT which I'm hoping to take up this year.
Am I barking up the wrong tree thinking of chinese carbon 50mm?

ugo.santalucia

hutchy_belfast wrote:

I wish I knew more about wheels, it all seems a bit of a dark art. I too am after a set of middle depth wheels for around 400 but unfortunately mine need to be cross purpose, 95% road and 5% TT which I'm hoping to take up this year.
Am I barking up the wrong tree thinking of chinese carbon 50mm?

No, you are not, as long as you accept that your idea of warranty and their idea of warranty might be different. Also bear in mind import tax and duties might add up to an extra 20-30%.
I would rather get the hubs and rims from the far east and get them built over here. The difference in price won't add up to much, but at least any issue related with the build can be sorted out without a two ways trip to China.

Anonymous

ugo.santalucia wrote:

hutchy_belfast wrote:

I wish I knew more about wheels, it all seems a bit of a dark art. I too am after a set of middle depth wheels for around 400 but unfortunately mine need to be cross purpose, 95% road and 5% TT which I'm hoping to take up this year.
Am I barking up the wrong tree thinking of chinese carbon 50mm?

No, you are not, as long as you accept that your idea of warranty and their idea of warranty might be different. Also bear in mind import tax and duties might add up to an extra 20-30%.
I would rather get the hubs and rims from the far east and get them built over here. The difference in price won't add up to much, but at least any issue related with the build can be sorted out without a two ways trip to China.

Thanks for the helpful post! I believe you are in this market, I may very well be in touch. Do you have more "trusted" or reliable suppliers of hubs and rims?
The problem is that everything seems so vairable, all reports are variable and include people saying "I love them, people buying zipps are mugs, I have done 5000m on them and toured Majorca with no problems" to "they are complete garbage and the spokes pulled through on the third ride"
I was considering planet x as they had promised a 10% off discount code yesterday which never materialised. I beleive they are pretty much the same as the far eastern wheels with a sticker and perhaps more accountable service?

ugo.santalucia

If you want tubulars, planet X by all means. If you want clinchers, then maybe you need to look at importing something in some way.
Beside the bulletproof claims and the various displays of apparent reliability, you have to live with the fact that they are often severely underengineered wheels and you can't expect to cope well with harsh use or high mileage

iPete

Are these wheels for one race only?

I nearly got sucked into the 'doing Ironman must buy aero stuff to save 1.3 watts' camp but glad I never bothered.

ugo.santalucia

iPete wrote:

Are these wheels for one race only?

I nearly got sucked into the 'doing Ironman must buy aero stuff to save 1.3 watts' camp but glad I never bothered.

Especially when the course is anything but flat...

cougie

Is this the 70.3 race ? The bike route looks like its over one mountain and then back down again. I think I'd probably go for lighter wheels over aero ? Especially if its a windy day ?

iPete

ugo.santalucia wrote:

iPete wrote:

Are these wheels for one race only?

I nearly got sucked into the 'doing Ironman must buy aero stuff to save 1.3 watts' camp but glad I never bothered.

Especially when the course is anything but flat...

To my untrained eye, it certainly isn't & it's only a half so there really isn't much to gain unless the OP has dog awful wheels already(?).

http://ironmanmallorca.com/files/2012/0 ... e_2012.pdf

mallorcajeff

living in mallorca i have descended the mountains hundreds of times and I have C50's S80's Planetx 82's and Ksyrium Elites and never had heat build up on any of them, although has to be said the 82 full carbon tubs were not that enjoyable on my TT bike.

smoggysteve

ugo.santalucia wrote:

Have you considered ditching the 50 mm idea altogether? Most people seem to buy them for the way they look. Aeordynamics is a word that fills the mouth but doesn't really apply to your sunday ride. It is a rather frivolous way to spend 1 K if you don't race "contre la montre".

If it's for the look just say and I won't comment...

I agree on this, I used to ride on 50mm rims and on a trek out in the countryside the side winds hitting them plays havoc with the handling, any aero perfomance you think you gain you lose just trying to keep the bike in a straight line.