I changed my brake fluid from Motul 5.1 to the RBF600 and noticed a difference in pedal feel. The pedal isn't really 'mushy' (although some might describe it that way) but there is more travel than with the 5.1 fluid.

I'm fairly certain that it is not a 'bleed the brakes issue' (but who knows). Will a different fluid type effect the feel through the pedal?

 

Are the brakes any worse/better?

I had mine changed a while back, although idont know what was in it and i dont know what they changed it to, but theyre highly qualified rally car builders so i figured i'd leave it up to them, i felt no difference before/after

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Flux &raquo;</TD></TR><TR><TD CLASS="quote">Will a different fluid type effect the feel through the pedal?</TD></TR></TABLE>
Absolutely not. All brake fluids would be similarly compressible (i.e. not at all).

If there really is a difference, there's air in there somewhere.

 

I went from normal brake fluid to ATE super blue; as well as pads, rotors and ss lines; and the pedal was super mushy. We bled it once more, it got better, then once more again and that fixed the problem.

I don't know too much about the brake system but bleeding it a few times really helped.

 

Bleed brakes again, you got bubbles.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITR#132 &raquo;</TD></TR><TR><TD CLASS="quote">Bleed brakes again, you got bubbles.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">Absolutely not. All brake fluids would be similarly compressible (i.e. not at all).

If there really is a difference, there's air in there somewhere.</TD></TR></TABLE>

That's not entirely correct/incorrect. All brake fluids contain air trapped between the molecules of the fluid, especially if one uses a power bleeder that pressurizes the fluid itself, forcing more air into the fluid.

Several brakefluid manufactuers advertise their fluid as having smaller molecules and thus entrapping less air (smaller the molecules the less space between them to trap air)

So while the mushiness comes from the air being compressed, it's not necesarily something that can be easily removed, although I'm not positive that may be the case here.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">That's not entirely correct/incorrect. </TD></TR></TABLE>

For the purposes of this discussion I think it's accurate enough. If YOU swapped in some RBF600, and the pedal was mushy at all, would you suspect molecule size or air in the brake lines as your first culprit?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">For the purposes of this discussion I think it's accurate enough. If YOU swapped in some RBF600, and the pedal was mushy at all, would you suspect molecule size or air in the brake lines as your first culprit? </TD></TR></TABLE>

Well, something is going on since swapping in the RBF600. I flushed the fluid and have bled them twice and I still am left with a mushy pedal. I never had this problem with the Motul 5.1.

Back to bleeding again later this week...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">For the purposes of this discussion I think it's accurate enough. If YOU swapped in some RBF600, and the pedal was mushy at all, would you suspect molecule size or air in the brake lines as your first culprit? </TD></TR></TABLE>

Depends on extent of mushines...if it was significant I'd agree, if it was minor it could be the fluid itself.

 

I'm reaching here but..

Last weekend before my track event I had the same issues. Pedal was uber-mushy and we sat and troubleshooted for about an hr. Re-bled, checked abs, brake booster etc.

Turned out my pad didnt' seat in the retaining clips properly and the piston bent/broke the pad in half .

What I'm getting at is, is there any other aspect of the brake system you changed besides the fluid?

 

is that all you changed? no new brake pads with the fluid swap?

 

I've been using Motul RBF 600 in my cars for years and have never had a mushy pedal.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">I've been using Motul RBF 600 in my cars for years and have never had a mushy pedal.
</TD></TR></TABLE>

Yeah, but have you compared the feel to Motul 5.1?

Some people swear they can feel a difference between fluids...I, personally, don't know how much of that is a placebo effect, but still...

 

i know people have suggested that the pedal may feel mushy after a changing the fluid although i have never experienced this. so, after bleeding and re-bleeding, have you been waiting a day or two for things to stiffen up? just a thought.