I have done a search and have not come to any clear conclusion (best post I found on the subject https://www.rx7club.com/showthread.p...ht=BRAKE+FLUID)

Question

In the user manual, the FD says it needs DOT3 fluid

If I put DOT 4 or 5.1 will i put stress on my braking system (pump, cylinder etc.) causing failure

I thank you all in advance

 

u will not feel any difference on daily driving stop/go,on DOT 3,4 5,.......
the difference is the heat range in fluid boiling points.
however, u should not mix the #s.You should drain and bleed out completely one # to use other DOT #.

 

I think DOT 5 is incompatible. 3, 4, and maybe 5.1 are ok.

Doesn't make much difference tho - I just used DOT 3/4 synthetic. If you think it's real imporant, check in the race forum.

Dave

 

Here is a reasonable summary: http://www.vtr.org/maintain/brake-fluids.html

This is a little more technical: http://www.rpmnet.com/techart/fluid.shtml

DOT-3 is a recommended minimum fluid. DOT-4 is a fine replacement. DOT 5.1 tends to be expensive.

You will most likely never notice the results on the street. However, if you are changing brake fluids, it is always a good thing to flush the system. Not absolutely required, but highly recommended. More important than the actual DOT rating on the fluids is to flush the system on a regular (annual) basis.

Good brands? I've used Valvoline Synthetic and Castrol LMA with good success. I use Motul RB-600 on the track, but could probably get by with either of the first two since I am not that hard on brakes.

Hope this helps,

-bill

 

DOT 3, 4, and 5.1 are compatible with each other and should be fine in your car.

DOT 3 and 4 are glycol-based fluids - I'm not sure about the chemical composition of 5.1. If you use your car only on the street, any good DOT 3 fluid, flushed at least once a year, will be fine. If you put your car on the track, you're going to want higher temperature fluids (DOT 4 or 5.1), and should probably change the fluid at least every 3 months. An alternative is the Ford Heavy Duty fluid (originally developed as part of the GT-40 project), changed before every event. I personally use Castrol LMA for the street and ATE Gold/Superblue for the track.

DOT 5 is a silicone-based fluid and not compatible with the others. It's a reasonable choice for show cars, because it does not absorb water, but I wouldn't use it on the street or track.

Nice reference: http://www.shotimes.com/SHO3brakefluid.html

 

Another nice description of the various fluid designations, pros and cons:
http://www.vtr.org/maintain/brake-fluids.html

 

I beg to differ that Dot 3 vs. 4 vs. 5.1 doesn't matter... it matters a TON if you use your brakes. I boiled the brake fluid in my FD awhile ago, and that is a SCARY venture! I replaced it with Motul 600 and the boiling never reoccurred.

You own a high-performance, crisp-handling sports car. A $20-30 brake upgrade is cheap. Just my 2 cents.

 

Interesting threads
My reading is that indeed brake fluid has an important role to play, but still if lets say I upgrade from DOT 3 - to DOT 5.1 will I be stressing my brake system more

 

How, pray tell, did you manage that? I have a dollar that says something else was wrong, or that you had wet fluid. (Both preventable)

Fresh (<12months), good quality DOT 4 is more braking power than your street tires can probably keep up with. DOT 5.1 is nice, but not necessary.

Dave

 

All that the DOT rating indicates is the minimum boiling temps for both dry (new) and wet (certain % water) fluid.

Putting DOT-5.1 (or DOT-4) in your car will not make you stop any better under normal usage. Nor will it stress your brake system any more. The stock FD brakes are actually quite good. With the exception of heavy duty track usage, you will run out of tire long before you run out of brake.

Keep you fluid fresh and clean and you will *never* have any problems with "boiling". Most reports of fluid boiling are either 1) very old fluid with lots of water in it, or 2) brake pads getting too hot (brake fade). The first can be fixed by flushing out with new clean fluid. The second can be fixed by going to a higher temperature brake pad (note: true track/race pads should *not* be run on the street).

An interesting aside it that the Ford Heavy Duty brake fluid used by a lot of racers use is actually a DOT-3 fluid. The "dry" boiling point is quite high, but the "wet" boiling point doesn't meet DOT-4 standards.

Hope this helps. There are a lot of good links posted above. You should probably go and read them.

-bill

 

I have and they were very helpfull indeed
I agree, changing fluid and draining it correctly is a good way to have a good braking system

 

The Ford Heavy Duty brake fluid is a quite old standard, while haveing good dry temp level for the price, there is much better out there. DOT 5.1 a synthetic is great for very high dry temp but some of the brands are very sensitive to moisture absorbtion, thus unless you soley track your car and flush the fuild are each race or at least monthly, I would save my $$ and go with a good DOT 4 ... for street use look at the wet boiling points.. as wet means just a few percent moisture (not standing water in the system), hell air is not dry and the reserve container has an air vent.

 

I did it by lots of repeated braking on some long backroads. After storming up the hills, coming downhill (which is worse on the brakes) eventually got the fluid to boil.

I also managed to crack the Axxis front pads. They didn't have that stress-relieving radial groove in the middle of them, and I was giving them too much heat.

My solution to the problem was get better pads, better fluid, and get R1 brake ducts (had the lip, but no ductwork after the lip). It's never happened again.

BTW, I never claimed to be a really good driver. If someone around here who IS a good driver wants to accuse me of using my brakes too much, well, they're probably right :-).

Take care,
Shad

 

That's good to know. What kind of fluid was in there before, and how long had it been in there? If you know when it was changed, could it have been from a bottle that wasn't brand new?

Dave

 

Brake fluid absorbs water and as we know water is easy to boil. Any brake fluid that is not changed as often as it should be will easily boil because of the trapped water vapor. Doesn't matter if you have $75 super duper racing brake fluid in there, it still must be flushed frequently to remove water from the system.

Cheap fresh brake fluid will outperform expensive, old and wet brake fluid.

 

I don't know what was in there. I bought the car only about seven months before the incident, and hadn't yet bled the brakes myself. It's very likely that it had a good bit of moisture in it. When I drained the fluid, it wasn't *that* dark of a brown (I've seen much worse!), but it also wasn't new.

There's no argument that a decent dry DOT 4 will outperform most everything else wet. Then again, upgrading to Motul 600 was CHEAP. It's a $30 upgrade. Regular brake fluid would have been $5. That's $25 more spent with the exact same amount of labor. To me, there was no reason not to upgrade... too easy and too cheap to risk boiling again. Besides, even the wet boiling point of Motul is pretty danged high :-).

Take care,
Shad

 

So really I think best is to get good DOT 4 and change on regular basis