M750 Clutch Kit

[Mr Gazza]

Just going on my brother's experience after changing to DOT5.
He changed every seal except one on the brake system of his Scimitar. The only one he didn't change gave up the ghost very soon after.
He's a very thorough sort of chap and even changed all the flexible lines.
I'm told that the seals absorb some Glycol based fluid over time and then react with the Silicone.

[motomartin11]

Originally Posted by Mr Gazza

Just going on my brother's experience after changing to DOT5.
He changed every seal except one on the brake system of his Scimitar. The only one he didn't change gave up the ghost very soon after.
He's a very thorough sort of chap and even changed all the flexible lines.
I'm told that the seals absorb some Glycol based fluid over time and then react with the Silicone.

As in Reliant..............?

Well all I can say is my mate and I have been using this

https://www.ebay.co.uk/itm/301072020...r=603192971452

for some time on our bikes without any issues whatsoever.

[Luddite]

Originally Posted by Mr Gazza

Just going on my brother's experience after changing to DOT5.
He changed every seal except one on the brake system of his Scimitar. The only one he didn't change gave up the ghost very soon after.
He's a very thorough sort of chap and even changed all the flexible lines.
I'm told that the seals absorb some Glycol based fluid over time and then react with the Silicone.

I briefly considered using DOT5 some years back, tempted by the prospect of never having to change it again, which was the only thing I knew about it.

However, after further research, I quickly decided it wasn't the magic elixir that many people claim it to be.

Like you, I was concerned by its incompatibility with glycol-based fluids, (although the problem should be solvable by changing all seals and hoses).

What worried me more was the fact that, firstly, unlike glycol-based fluids, silicon fluids become compressible before they reach their boiling point, somewhere in the region of 150⁰C - 180⁰C, so giving rise to a spongy feeling during periods of prolonged heavy braking.

Secondly, silicon fluids readily trap air and so are not compatible with many ABS systems as the valving systems can cause frothing.

Lastly, while silicon fluids may not absorb water, they won't actually stop moisture from entering the system. If water does enter the system, rather than being absorbed by the brake fluid and subsequently removed when the fluid is changed, it will instead pool in the low points, possibly leading to corrosion in time.

I'm happy with my DOT5.1, which has the same high boiling point as the DOT5 but without any of the above worries.

[Mr Gazza]

You've pretty accurately echoed my thinking on brake fluid there Vince.
All these clever "fit and forget" things are fine in theory but they will inevitably save up to bite your arse when least expected.
The crucial difference is between hydrophobic and hygroscopic. I'm much happier managing a hygroscopic fluid, knowing that I remove all the moisture when changing the fluid and importantly that it can be detected accurately with one of those marvellous fluid tester pens which tell you instantly if the fluid is good or bad.
I find more often than not that the fluid is in better shape than the recommended changing time would have you believe, and that it stores in an opened bottle longer than popular mythology says. So, a very small investment in one of those pens can save a bob or two on fluid and also angst.

Maybe the aggressive incompatibility of mineral and silicone fluids is a myth too?

Oh, and my brother's Scimitar is a Supermarine. (I wish! )