I'm experimenting with some shock absorbers I resurrected from being dead :) and have like 10L of DOT 3 brake fluid I can't use in my system. In theory I can fill the abs with any viscous liquid and obviously the liquid's thickness will control the abs performance (softer or harder). And taking in mind that the rubber rings and seals should stand brake fluid without disintegrating...

Question: compared with "normal" suspension oil, how would brake fluid would behave?

2 Answers 2


Brake fluid and oil have a different chemical base

Oil is a hydrocarbon and brake fluid is a silicon.

They will not mix.

Therefore, the fluid seals are designed with that in mind. Brake fluid would break down the seals in your shocks and ruin the seals.

Additionally, beyond the issues above, brake fluid is not very viscous and you would have a very 'soft' suspension if the experiment were functional. Various shock oil viscosity would change the dampening effect of the shock.

The proper way to tune a shock would be to get one that is tuneable that has various thickness shims that would restrict oil flow based upon pressure or to have an analogue dial on the shock adjust oil restriction through various galleys within the shock to adjust dampening (rebound and compression) under varying load circumstances.

  • interesting the "tuneable" shocks, never heard of them. I know about the differences between seals for brake fluid and oil. The other experiment would be using power steering oil, which I also have plenty, the red one... Commented Dec 25, 2016 at 1:50
  • BF is a silicon - No, only DOT 5 is (ehm.. not really, it's a siliconE). But you are absolutely right not to use BF anywhere else than in the brakes. Every rubber will be three times bigger after contact with BF. (And while all DOTs including DOT5.1 can be mixed, never mix DOT5 with anything)
    – sweber
    Commented Dec 26, 2016 at 8:21

You can have fun experimenting, check out the viscosity and temperature ranges of the power steering oil compared to the oil used in shock absorbers. However, if you are going to use these on the road, then the insurance could deem your experiments as "unsafe" and not insure you in case of an accident. If you want road legal equipment here is one link - there are many : http://www.gazshocks.com/about

  • Thank you. Well, where I live, there isn't any insurances at all :) Commented Dec 25, 2016 at 17:33

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