My friend has left his new bike with me to bleed his elixir 1 brakes. Just finished and they work well but packing up I notice I have used dot 4 fluid. Surely they’ll be fine – or is the whole system going to explode in a ball of flames and kill him (and worse still me if i’m riding with him!).

Should be fine. Dot 5 is not compatible with Dot 5.1 though.

No should about it, its perfectly safe.

Ah don’t worry. He’ll never know…this is all cash in hand anyway right?

Cool – thought so. No cash changed hands – four bottles of Dartmoor Jail ale tho! 😀

It’ll be fine, unless he pushes them to the edge of their thermal window normally, in which case you’ve lost him a narrow margin of fluid boiling temps.

It’ll be fine, unless he pushes them to the edge of their thermal window normally, in which case you’ve lost him a narrow margin of fluid boiling temps.

Actually, he’s more likely to do that by using poorer quality dot 5.1 fluid. Actual dry boiling temperatures vary more by manufacture and quality than “dot” standard.

That’s right actually ^.

DOT 4 and 5.1 are glycol ether based and are compatible with each other, the worse thing that could happen is that you’ll reduce the overall boiling temperature by adding in the DOT 4 but fresh DOT 4 is better than old DOT 5.1 anyway so no harm done.

As previously stated the one which you definitely don’t want to use is DOT 5 which is silicone based and is not compatible with the others.