Problem with Zipp 404's!

Team Cannondale

I am just sitting in my hotel in Borg d'Osians after yesterdays La Marmotte sportive! The problem is I did not finish this event due to my new 404's blowing tubes on the front wheel 3 times within a 10 minute period of starting the decent of the Col du Glandon!!! I also blew a front tube the first time I used my new 404's on monday on the decent from Avoriaz to Morzine!!! There must be a pattern here somewhere. I have checked and double checked the michelin pro 3 tyres which are also new and they are perfect no sign of any foreign objects in sight. My concern is that the rims have become that hot due to braking that the tubes have just popped under the heat? The rim tape has also been distorted due to the heat of the rims. I had to let the rim cool down every time as I just could not physically touch the rim with the heat. Has anyone else ever had this problem? Is it just the long decents and hot weather that we have had this last week in the alps, or am I missing something completely? Any help/ advice is greatly appreciated.

Monty Dog

Another reason why pros still stick to tubs. I'd change your rim tape to a cloth-based one like Velox too and lay off the brakes.

chriskempton

I think a rim like the 404 clincher with an alu brake track joined to a carbon section is more prone to overheating than most. What you've got is a small light alu piece that's doing the braking and building up heat, that can't transmit the heat to the carbon section (not sure on the science here, but specific heat capacity, all that sort of thing). So the braking heat is concentrated in a small piece (of a bulky rim) and therefore gets very hot. It's also the bit that the tube sits on, so.....pop! With hindsight a one piece rim (be it alu or carbon) would probably have been a better choice.

Like MDog was alluding to, alpine descents are a different skill to UK ones, and managing your braking to avoid heat build up is part of that skill.

Monty Dog

The speed that you can reach on alpine descents can make a big demand on your skills and equipment - until you've experienced it, UK riders don't appreciate it. 100kph plus is possible off the Galibier and 'riding' your brakes is a recipe for disaster - the consequences of a front-wheel blow-out at that speed are very serious.

grimpeur

I was doing the Marmotte as well at the weekend, this happened to two other guys I know, both riding Zipp clinchers ( 303 or 404 ).

Both had punctures on descending the Alpe at the start, one managing to get a lift to the bike shop in Bourg for some spare tubes before the start. The other not being to ride the event at all which was very dissappointing.

Both Monty and Chris are right. The rim tap in Zipps is awful and not suitable for the wheels, furthermore carbon / alu clincher hybrids like this are simply not suitable for technical descents. Inexperienced people do ride the brakes a lot but they should still be able to get away with it on most rims. With the carbon / alu hyrid design you are building up heat on a small amount of aluminium, the heat has no where to go and worse still it is in close proximity to the vulnerable inner tube!

This if anything shows that Zipp clinchers aren't suitable for this sort of event, something Zipp should make people aware of before their equipment causes a serious accident.

ex-pat scot

Alpine descent technique.
Careful on overheating rims.
Doubly so for tandems.
Pros don't always use tubs to descent the Alps- the heat can cause the tubs to roll off the rims (melted glue / tape).

Moral: cadence braking.
Late braking
Pee on the rims if necessary
Take a few tubes.
Alternate front and rear braking (being careful of loose patches if heavy on the front brake)

Alternatively, you could always go fixed and use your legs as brakes...

Team Cannondale

Many Thanks for all of your coments regarding the 404's! I do understand that there is a big difference in the rims due to the lack of metal to dissapate the heat due to the build up of braking. I will replace the rim tape as per your comments, and try and use another type of tube as I have also been told that the tubes that I was using at the time are not the best (Bontrager Race X Lite 700x 18c-25c) is this true? And if so, can you recommened a better tube for the job? Thanks again Team Cannondale

grimpeur

... or don't use Zipps