6-minute read

OK, so you’ve booked your long-awaited road cycling tour in the mountains of Europe and you’re now counting down the days until you’re on that flight. Other than training, it’s time also to think about your bike and the equipment that’s essential for safe and smooth riding on your multi-day cycling holiday. In this blog, we share our experience of delamination in carbon wheels with rim brakes. When cycling in the mountains, you’re racking up metres of ascent and descent in the thousands. This has a significant influence on the wheelsets that are optimum for riding in these conditions. Read on for all you need to know!

Carbon wheels with rim brakes

At Marmot Tours, we’ve seen thousands of cyclists over the past 20 years, and an increasing number who’ve brought their own bike equipped with their prized carbon wheels. We’ve therefore got a huge amount of experience in what equipment does – and doesn’t – work well when cycling in the mountains with long climbs and descents.

The kind of climbing and descending you’ll do on a multi-day road cycling tour can be hard to simulate at home where we have limited opportunity for long climbs. Not so in the mountains of Europe! Suffice to say that if you’ve only ridden in the UK, you won’t have experienced anything near the climbs you’ll be doing on one of our holidays. As such, your rim-brake carbon wheels won’t have experienced the pressure they’ll be subjected to on long descents either!

Are rim-brake carbon wheels the best wheelset for cycling in the mountains?

That’s a good question. In our opinion and with the benefit of over 20 years’ experience, we would say NO. Unfortunately, we feel that the small but very real risk of delamination is too serious to ignore.

Several major manufacturers sell rim-brake carbon wheels and if you’ve splashed out on a fabulous carbon wheelset, you were hopefully well-advised by your local bike shop or an online store. We can totally understand their appeal and why you might want to use them on your cycling holiday. However, while these super-light wheels have multiple exceptional properties, they weren’t necessarily designed to be used in the way they would be on a multi-day cycling holiday with long and/or steep descents.

Benefits of carbon wheels

They’re lightweight

Carbon fibre is stronger and lighter than metal, which allows the wheel to be made much lighter than if it were aluminium, for example. Carbon rims make for a great hill-climbing wheel.

They’re aerodynamic

Carbon fibre can be shaped into more complex forms, perfect for deeper section aerodynamic rims. This yields considerable advantages over the traditional box-shaped section of metal rims. Whether road racing, time-trialling or if you just want to go faster on the flat, investing in some aero wheels will reward you with some free speed.

Ride quality and performance

A good quality carbon wheel will be stiffer laterally than its aluminium counterpart. This makes them perfect for sprinters who want every last watt of power transferred to the road.

Disadvantages of carbon wheels with rim brakes

Braking in wet conditions

Early carbon fibre wheels were known for their lack of braking response, owing mostly to excessive heat build-up as the pads try to shed water from the rim. Modern engineering techniques have helped lessen this issue. Improvements have been made with carbon, ceramic, and organic compound pads for specific rims.

However, on long mountain descents where the rider may be unfamiliar with the road and therefore more likely to be ‘riding’ the brakes, combined with braking heavily before corners, we are still asking a lot of our rims. A decent aluminium rim with a standard rubber brake block will outperform its carbon rival in wet conditions.

Carbon wheel delamination (this is where we really want you to prick up your ears …)

Unfortunately, we’ve seen too many instances of delamination of rim-brake carbon wheels. Delamination is caused by the resin between the layers of carbon heating to the point of failure. Heat build-up caused by the friction of brake pads against the rim spreads throughout the wheel. On Marmot Tours cycling holidays we’ve witnessed wheels delaminating during descents, sometimes with serious consequences. Quite simply, it’s one of the most dangerous situations a cyclist can find themself in.

The front wheel can delaminate very suddenly, effectively buckling or even exploding. It then jams completely in the fork, resulting in an extremely serious crash.

Newer wheels might be made with resins that can tolerate higher temperatures. However, one could assume that the critical temperature may still be reached in some situations.

Wheel temperature when descending is affected not only by rider weight but also by the gradient and length of descent, ambient temperature, and braking style. We’ve witnessed delamination not only on long or steep descents with heavier riders, but also on less steep descents, and on wheels ridden by even very light riders.

It’s worth pointing out that we’ve also seen serious delamination on rim-brake carbon wheels with a metal braking surface. These are still susceptible to risk, as heat is transferred from the metal braking surface to the carbon structure.

NOTE: a sensation of the wheels pulsing or throbbing during braking can indicate delamination. If you experience this, you should STOP immediately!

Daily wheel maintenance

Ultimately, whichever wheels you use, you should ensure they are straight, round and true, and that you start your cycling holiday with brand-new pads. We suggest a daily/pre-ride safety check to pick up any buckling or bulging of the carbon rim.

If you come on one of our holidays you have the option of hiring one of our titanium frame bikes with aluminium rim-brake wheels, which pose no risk of delamination. Our guides will perform a safety check on your hire bike every day.

To summarise

When planning what to ride on a multi-day cycling holiday in the mountains, we strongly advise against using rim-brake carbon wheels. In our extensive experience, delamination is a real occurrence and while it doesn’t happen very often, it is probably more likely to occur on our holidays than anywhere else, when non-professional riders are cycling in warm weather on long and/or steep descents. The risks are significant and the consequences could be fatal.

In our opinion, because of the delamination risk associated with rim-brake carbon wheels, the best rim-brake wheelset is a lightweight alloy with new and properly adjusted brake pads. This will ensure you’ve got the safest wheelset for riding in the mountains in preparation for your much-longed-for cycling holiday.