Carbon rims and descending big hills………..

Hi  

Hi  

I have new Campag Bora Ones Carbon rims and Campag Neutron Ally’s.

I’m using the Neutrons for the MAratona on Saturday.

Reason being I’ve done a couple of Etapes in the past (2010/2011), the Marmotte in 2013, Challenge Vercors 2014 and Ventoux Sportive last year.

On the first three events I’ve seen puncture’s and destroyed carbon rims probably due to over braking/ dragging brakes.

I’ve done a reasonable amount of riding in France and subscribe to the descend fast and brake hard theory to allow rims time to cool. However when riding in the bigger sportives there are so many riders about the a certain amount of rim dragging is inevitable as you have to take account of other riders speeds and cornering lines.

Also the weather looks sketchy for the Maratona and the braking performance of the Neutrons is streets ahead of the Bora’s in the wet despite the “new, improved” braking surface.

Only my opinions though.

Cheers – enjoy the event!

Let’s roll this back a little

Let’s roll this back a little and forget about all the armchair engineers. Reflect and take a look at yourself, you are obviously concerned hence the questions.

I’m by no means a fast descender but enjoy a downhill and will progress through corners with as much speed as possible. I ride 45mm carbons as an everyday wheel and weigh in at 67-70 kg (time in season dependant!).

In the Alps last year the bike had alu Campag Zonda’s fitted for peace of mind. I’m sure the carbons would have been fine but i did not want to take the risk. I ride in Majorca every year so am happy with descending for a longish time (compared to UK) but alpine drops are another level.

You need to ask yourself if you will be able to dismiss this doubt you are having. Coming down large mountain passes at speed you need your whole focus to be ‘in the moment’. You need to process your speed, the feel of the road, shape of the road, oncoming dangers etc etc.

You don’t want to then have the additional variables of ‘should i brake now or later on these carbon rims?’, ‘How mush braking have i already done?’, ‘Are the rims heating up?’. Small lapses in concentration on mountain passes can result in not so small issues.

Bang a set of alu’s on the bike. Have peace of mind. Know that if you need to drag the brakes you have a little more wiggle room. At the end of the day having a great trip and having awesome stories to tell is much more important.

For the record comparing club riders to pro’s in this circumstance is a chalk and cheese approach. Pro’s have closed roads meaning that they have 50% more tarmac to play with. More tarmac, equals easier cornering, equals less braking.

madcarew wrote:

madcarew wrote:

Actually CFC has a higher specific heat capacity than alloy (1.1J /gdegC on average cf  0.9 J/gdegC for alloy).

You seem to have quoted a figure for aluminium which is not necessarily the
same as when it has been alloyed with whatever.

Ditto with CFC. The heat capacity of the fibres can vary wildly as can that of the matrix material.

Quoting average figures is completely worthless because the distribution is so wide.

madcarew wrote:

The conductivity in alloy is the key to the heat loss. Alloy will cool down
faster.

Correct. It’s why the heatsink on my GPU in this computer is made of Al alloy.

Wake me up when they make them from CFC.

madcarew wrote:

Your described result is very different to the real world experience of most people using carbon composite wheels.

Pray tell me: what percentage of these people with CFC rims ride up and down
alpine passes?

Huw Watkins wrote:

Mavic’s coments from one of their recent wheel launches:

[i]”At the 2015 Etape du Tour, for example, Mavic assisted with 100 wheels, of
which 52 were failures and 38 were carbon clinchers that had delaminated,
product manager Maxime Brunand said.”[/i]

Mavic’s real world experience seems to considerably differ from yours.

They’re busy flogging CFC wheels too, so it’s hardly in their interest to
mention such damning stats.

madcarew wrote:

The amount pros are paid has nothing to do with the likelihood their wheels will fail as you’ve described.  And they like to do it day after day, their livelihood depends on it so they’re not going to do it on something that fails with the certainty you’ve described.

You’re entirely wrong. The pro’s will do whatever is required of them if you
bung them enough money.

Shoot up with whatever the latest performance enhancing drug is without giving
a rat’s arse about the physical damage it could be doing to them?

Sure. They’re young men on the make and every man has his price.

If they were told to do Alpe D’Huez on a Raleigh Chopper having ingested a
truckload of Ritalin, they’d be more than up for it….given suitable
financial compensation and being told by the team manager that [i]”You want to
get along in the team, don’t you?”[/i]

madcarew wrote:

As for pros going down faster and not braking as much: they corner at ‘similar ‘ speeds to a good club cyclist (what you’d go round the corner at 20 mph, they’ll do at 25 mph; however they’re slowing down from 60+ mph instead of 45 – 50 mph, which means they actually do 60% more (energy loss from) braking, or allowing for your club cyclist to be 20% heavier (85kg vs 70kg) they are still doing 45 – 50% more braking; so if it can stand up to the pros, it can stand up to a club cyclist (YMMV)

You’re pulling figures out of your arse again. There is absolutely no reason
why I can’t get up to “60+ mph” coming down an alpine pass if I choose to.

At least I can stand assured that my wheels aren’t going to come apart when I
come to brake.

Sniffer wrote:

wellsprop wrote:

No real world experience, but…

Look at the speeds the pros were hitting in the Tour de Suisse, 120kph+, their wheels didn’t fail.

Not to say they don’t fail – ever seen the video of the guy riding a Canyon down Mount Ventoux and he overheats the pads?

Comes down to how heavy you are and how much breaking you are doing. Personally, I wouldn’t be too worried about using a pro level set of carbon wheels on a descent, one would hope that they have been tested and designed against failure.

Not sure Pro experience helps the OP.  Pros don’t ride clinchers, they ride tubs. 

Yeah, fair point, totally forgot to think about that!

I had a similar concern for a

I had a similar concern for a recent trip to Mallorca; ride carbon clinchers (DCR premium rims) or swap to alloy rims. Took the carbons and all turned out fine. Probably not as testing as ventoux/alps though but they survived descending Sa Calobra for 10km behind a line of cars (constant braking) with no fade at all. I’m 68kg and by no means confident going downhill; much prefer going up! 

Mind you I’ve had a cheaper set (chinese) delaminate in the past but couldn’t pin point when that happened or why…My guess would be that with half-decent rims and reasonable technique it should be ok…

There are a fair few slopes
There are a fair few slopes in the UK you can hit 50mph whilst being ‘sat up’ so that isn’t enough, you must apply some braking otherwise on slopes such as the one the OP is attempting could mean they are still going to be going faster than is safe for them or what they feel comfortable at.

As I posted previously regarding choice of descents, I agree with your ‘smaller hills’ comment. Getting into bother on high speed slopes can have horrendous outcomes and there was one here on road cc from in the UK where it seemed apparent the rider bit off more than they could chew and paid for it dearly.
A friend of mine came off badly three years ago in Spain, luckily only knckering his knee and a severe concussion..
This is part of the reason why I think cycle helmets are dumb, too many get overconfident and wouldn’t take as much risk without a helmet.
See far too many close calls in the last 10years or so, nothing like it used to be. Overtly aggressive and much higher risk too often ending in a spill is the norm these days

When I was in Tenerife on a

When I was in Tenerife on a cycling holiday one of the chaps had a lovely Pinarello Bike with some Enve carbon wheels.  After one day of descending Mt. Teide, he was down the local cycle shop to hire some basic alloy rimmed wheels.  He was very concerned how hot the rims were getting under long repeated braking periods.  He thought his rims would delaminate or tyre explode.

  I on the other hand, had carbon wheels with disc brakes and had no issues at all