Which brake fluid?
Bob Owen has produced an excellent article which sets out the facts with a dispassionate assessment of the issues so fellow members can understand the DOT categories, the DOT fluid performance tests and the benefits and disadvantages of each fluid. He has also highlighted some concerns - key variables where there is uncertainty. In essence they are the lack of information on the composition of the replacement rubber seals and the effect of various formulations of glycol fluid available in the market on those different types of rubber seal - and the effect of silicone fluid on them too. They are being examined and a further report will follow. (Jan 09)

Whenever the topic of silicone brake fluid as a replacement for glycol is raised amongst classic car enthusiasts you soon see that some of the key issues and even some of the facts needed to make a balanced assessment are either not available or not sufficiently clear. So in the end each classic car owner has to make their own decision whether to change to silicone or stay with the original fluid, glycol. That decision is based on either their own view or, where they do not feel qualified or able to form a view, they will usually rely on the recommendation of the specialist who services their car.

The choice of fluid is a topic that does attract firm views from some quarters and in a few cases the assertions of the merits of silicone as a replacement brake fluid are made with a zeal that worries those who would prefer to see the issues more calmly presented and assessed. Well, when the topic reached this stage in a bulletin board thread on the V8 Register's website last November, it was felt an impartial article setting out information derived from original sources rather than hearsay would provide fellow members with the facts and other information as a basis upon which to make their own decision on "which brake fluid to use?" Bob Owen was approached by the chairman of the V8 Register to do the research and prepare the article as he had

previously contributed a number of useful workshop notes and, whilst not a brake expert, he has a good understanding of physics from his electrical engineering training and has had a love of all things mechanical since he was a boy with a father who ran an agricultural engineering business. Equally Bob can claim to be impartial as he has some personal experience of both types of fluid having a 1974 MGBGTV8 using standard DOT4 glycol and a 1949 MG TC converted to DOT5 silicone fluid some five years ago.

Bob says "this article is an attempt to provide all the information you need to enable you to make your own choice of fluid". As the article is lengthy, some six pages, it has been published on the V8 website and available as a download at:

Please note the content of this article is subject to the important caution and caveats set out at the end of the six page article
Download a copy of the brake fluids paper. More

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