how tyres are made
tack replied on Tue, 2016-08-23 09:08 Site Supporter
Perhaps David it would be a good time, if you have the time and resources to do an article, or get someone to do an article, on how race tyres are made.
Many years ago, I used to work for a Japanese race tyre company and back then the carcass was made first. Carcasses are important for a few reasons, first and most important is the carcass supports the tread which mostly is a slick tread but in this case is a wet patterned tread.
The carcass determines the tread shape, footprint size and controls distortion (, in conjunction with air pressure) and gives the rider feel. The other very important aspect which is either not openly revealed or understood is the carcass controls or supports heat lose or retention through the side walls and into the wheel. The compound works in conjunction with the carcass.
It used to be that once a carcass is made the tread was applied, either as a separate piece or applied like to toothpaste to the carcass to give dual compounds and then moulded to the carcass in a rather hot round press. The tread (slick or wet) is a complex mix of chemicals which all tyre companies spend time money and expertise to develop. Theylook for new materials e.g. silica to give them that compound edge and they protect compound information as proprietary information. The blend is what I would consider to be the black art of tyres and is the domain of the individual tyre manufactueres science and chemical engineers.
Anyway without going on, the thing is that the under belt (carcass), which the wet compound is moulded to, is quite often thicker (depending on the manufacturer) than ordinary slicks carcasses to help with heat retention. So for example, the exact same compound blend can be used on two different carcasses, one that retains more heat and the other that loses heat and each one could be called either a soft full wet and the other a hard full wet. This works because one tyre retains the heat and the other dissipates the heat. Thus in the race on the weekend, the bikes generating heat through load exceeded the tyres heat limits and delaminated that section of tyre from the carcass while the riders or bikes that didn’t load the tyre as much or cooled the tyres did not. Conversely, the “hard” tyres carcass disappates the heat more easily to the track and ambient and also take longer to heat and needed a drier track to maintain the heat to make the compound blend to work. (heat range)
Anyway, I don’t know what carcass construction the wet Michelins were and how they related to each other (hard to soft) nor do I know the compounding characteristics of each blend. For all I know, the same carcass design was used but a different compound blend was used on each hard or soft. I do know that from experience that Michelin have traditionally had quite soft sidewall construction but extremely good under belt footprint control and shape. This gives very good grip but takes getting used to from a “different” feel perspective as compared to the Bridgestones. Anyway, from an old bloke’s point of view the delamination of the centre tread is not a quality issue but a heat and load issue, either from the excess heat build up in the carcass or the compound blend exceeding its limits. It's not quality control but heat control and blend characteristics.
Better to ask whether the “wings” increased front end load? Or weight distribution? Or braking load? one of these factors was the cause.
I don't expect that the tyre manufacturers will tell everyone exactly what carcass design they used on the weekend and what the compound blends used were but at some stage an over view of how carcass and compound s work together and how load, ambient and track temps work in relation to each other. This might help reduce questions of quality and lead to a better understanding of the complexities that tyre negineers and technicains face with heat, load and grip on modern MotoGP bikes at different circuits with quite varying ambiant and track temps, ashalt mix pebble sizes and load.
