I'm leaning towards using the DOT 5 brake fluid in the system on the Charger. I'm looking for some feedback from some of you guys that are running it. I know what the pros are, what are the cons? I've heard the pedal can become a little more spongy than with the typical DOT 3 fluid. For those that have not been following the restoration of it, I junked the manual drums and put 12" power discs up front, all stainless lines, the whole system is brand new and still dry. Yes the headers are going to be close to the distribution block just like a Chevelle.

I think the spongy feeling is contributed to its ability to trap air easily. If properly bled I think it works well. I still dont really see why DOT 3 isnt good enough though? Why you want to make the change? Im not arguing, DOT5 is out there for a reason.

Good info here: http://www.chevelles.com/forums/showthread.php?t=94515

There's no good reason to use it, other than the fact it doesn't eat paint. I recently switched back to DOT 3, and couldn't believe the difference!

Good info here: http://www.chevelles.com/forums/showthread.php?t=94515

There's no good reason to use it, other than the fact it doesn't eat paint. I recently switched back to DOT 3, and couldn't believe the difference!

What difference did you experience?

What difference did you experience?Firmer pedal with a better feel of the road. With the silicone, it was mushy and didn't give any feedback.

What I didn't see in all these previous discussions was any mention of brake fluid that has the best of both worlds (Dot 3/4 vs Dot 5) in terms of performance - leaving the silicone/paint removal issue out of the equation.

Synthetic Dot 3/4 fluid gives all the performance benefits of the Dot 5 in terms of > 500° dry boiling point, and > 343° wet boiling point. From just this viewpoint, the synthetic formulas meet the dry boiling point of Dot 5, and greatly exceed the wet boiling point, since the silicone based Dot 5 fluid doesn't absorb the water. I really don't understand how it gets "wet" in the first place in a closed system, but I'll leave that issue for someone else.

The synthetic formula is just a superior form of the same Dot 3/4 fluids, and is compatible (can be mixed) with all Dot 3 & Dot 4 fluids.

In my case, I used Valvoline's SynPower Synthetic Formula brake fluid. In fact, I double-checked what I put in because of this topic and have the bottle in front of me. You didn't think I remembered all that stuff, did you? I was reading it off the specs on the bottle....

I have a fresh bottle of Prestone Synthetic Brake Fluid in the garage sitting on the shelf that I bought about 3 months ago when I originally intended on bleeding the system. I think I'll go get another quart of that and finish the job on Monday. Thanks for the info!

Firmer pedal with a better feel of the road. With the silicone, it was mushy and didn't give any feedback.

That's really odd, I've had silicone in the coupe since day one and I've never had a soft pedal or lack of feedback. It was hard to bleed the rear brakes but once I got them bled the system has been great. The system has been no maintenence for 6 years now.

I switched to Dot5 in my old car, same problem bleeding the rears but felt no difference at all. I also use it in my bike clutches and works great.

That's really odd, I've had silicone in the coupe since day one and I've never had a soft pedal or lack of feedback. It was hard to bleed the rear brakes but once I got them bled the system has been great. The system has been no maintenence for 6 years now.I thought mine was fine too, until I switched back and noticed how much better it felt. :eek: I had blamed my soft pedal on my 1" bore M.C. being too small, but after the fluid swap, it feels good now.

I would have happily kept using DOT 5, but with intentions of hitting the road-course, I didn't want to lose my brakes. Now, I'm glad I've changed, and have no intention of putting it in any of my cars.

With DOT 5, any moisture that gets into the system pools at the lowest point, your calipers, dropping the boiling point in your system to that of water. Boiling fluid = no brakes.

I thought mine was fine too, until I switched back and noticed how much better it felt. :eek: I had blamed my soft pedal on my 1" bore M.C. being too small, but after the fluid swap, it feels good now.

I would have happily kept using DOT 5, but with intentions of hitting the road-course, I didn't want to lose my brakes. Now, I'm glad I've changed, and have no intention of putting it in any of my cars.

With DOT 5, any moisture that gets into the system pools at the lowest point, your calipers, dropping the boiling point in your system to that of water. Boiling fluid = no brakes.

No calipers in my coupe. ;) But I get your point. Actually in the coupe the lowest point would be the rear brake lines since the lines go up to connect to the wheel cylinders. The front cylinders would be the lowest point in that end of the system.

I had DOT 3 previously and saw no improvement or loss of performance with the switch to DOT 5 other than I don't have to be concerned about getting it on the paint. I installed an entire new system including wheel cylinders, master cylinder, hard and soft lines before I switched to DOT 5. NEVER should you mix DOT 3/4 with 5 in a system.

DOT 5 is a good choice for a seldom driven car that doesn't see road course time, otherwise it seems best to stick with DOT 3 or 4. I haven't heard of DOT 3/4 synthetic before, I might have to read up on that.

I'm guessing the Dot3/4 synthetic is safe on the paint???

Dot 3/4 Synthetic is NOT safe on the paint!

That's really odd, I've had silicone in the coupe since day one and I've never had a soft pedal or lack of feedback. It was hard to bleed the rear brakes but once I got them bled the system has been great. The system has been no maintenence for 6 years now.

Same here. I have had it in my 66SS since 99 and havent even had to take the lid off the master cylinder since. Havent had any air problems, and pedal problems what so ever. Its really not necessary but I like it also.

DOT 5 here in all stainless lines. No Leaks, no mushy pedal (in fact it is as firm as a rock!), street driven regularly. When bleeding the lines, I removed the master cylinder cap to check the level and then forgot to put it back on before bleeding again. one push of the pedal and there was fluid all over the inside of the hood on a freshly painted car. That was worth all the indecision right there!!!

Mike

I thought mine was fine too, until I switched back and noticed how much better it felt. :eek: I had blamed my soft pedal on my 1" bore M.C. being too small, but after the fluid swap, it feels good now.

I would have happily kept using DOT 5, but with intentions of hitting the road-course, I didn't want to lose my brakes. Now, I'm glad I've changed, and have no intention of putting it in any of my cars.

With DOT 5, any moisture that gets into the system pools at the lowest point, your calipers, dropping the boiling point in your system to that of water. Boiling fluid = no brakes.

While theoretically true, I doubt (based on my experience) that this is going to happen. When I swapped brakes this past summer, one of my rear wheel cylinders had began to stick, but upon disassembly there wasn't noticible corrosion.

I have been running Dot5 for 12+ years, with the first 5+ the car was stored in a carport and a drafty old garage near the ocean, where the car did and still does sit for several months at a time. I pull the cap after each storage period to check the fluid level... If anywhere is going to accumulate moisure, it would be those situations...

I never replaced the fluid, except when I swapped to a disc/disc master cylinder in anticipation of rear discs (but not a complete flush)... Even so, after 12-years the fluid was still clean.

The seals didn't leak, the fluid didn't boil. Never had a spongy pedal (my other Chevelle with the same brake setup had 'regular Dot 3 and there was no difference in feel). Not proud of my lack of maintenance, but I think it does point out that alot of the problems "reported" might not actually be attributed to Dot 5...

How many "race" car owners are going to leave the same old fluid in the car long enough to accumulate moisure???

Granted, I never took it on a "road course", but did do some very spirited driving in the mountains here, 7000+ feet to near Sea Level in an hour or so. With my 2.73 gears, I was on the brakes quite a bit...).

There's no good reason to use it, other than the fact it doesn't eat paint. There's no good reason NOT to use it :D ...

Even in a link to that other link posted earlier:
DOT 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition [possible brake failure -ed.]. Thats IF water got in the system, and enough of it to cause failure... Thats a maintenance issue. If someone is NOT going to check and change fluid or repair the reason while water is entering, then how can that be entirely blamed on the fluid???

. Silicone fluids also exhibit a 3 times greater propensity to dissolve air and other gasses which can lead to a "spongy pedal" and reduced braking at high altitudes.
Thats right, CAN lead (not necessarily going to happen)...

From a lubricity standpoint, neither fluids are outstanding, though silicones will exhibit a more stable viscosity index in extreme temperatures. Neither fluids will reduce stopping distances. Whats more extreme than the temps caused by road course racing?

Brake system contamination
The single most common brake system failure caused by a contaminant is swelling of the rubber components (piston seals etc.) due to the introduction of petroleum based products (motor oil, power steering fluid, mineral oil etc.) A small amount is enough to do major damage. Flushing with mineral spirits is enough to cause a complete system failure in a short time. I suspect this is what has happened when some BMW owners changed to DOT 5 (and then assumed that silicone caused the problem). Flushing with alcohol also causes problems. Even this guy (link to support NOT using DOT5) seems to implie that alot of failures were NOT due to the DOT5 fluid, but rather faulty maintenance issues...

Out of all the people that complain about Dot5, Derek is one of the few that I have heard actually "personally" experienced problems... Denny mentioned seeing lots of calipers with problems, but I doubt he really knows the maintenance history of all those vehicles (or any)... Did some owners use an old bottle of fluid with the cap off? or let some other contamination get in the system prior to Denny looking at them? I doubt anyone knows...

Most others "against" seem to be "I read it here" or "I heard it there"...

Funny that some people had a noticibly "spongy" pedal, while many others did not... To me that would imply that the fluid is NOT really the problem.

Not saying its the best, and not saying that maybe a "road course" or racing might expose the problems... But for probably 98%+ of the Classic car owners/drivers (who don't drive their cars daily or don't "race" them) DOT5 is probably a better choice...

Because DOt3/DOT4 loose their corrosion inhibitors they need to be flushed ever few years. If the same flushing "schedule" is kept for DOT5, then there shouldn't be an issue with Water and corrosion... Unless you have other problems, the DOT5 should "last" longer between maintenance/flushing...

Those that drive our cars periodically (parked in winter, etc), those that spend thousands on paint, those that like to keep up on maintenance and periodically have the system flushed (and those that don't;) DOT definitely has advantages...


This will probably (it is already) like the "Tall" spindle issue... True, for Hard-core racers, the DOT5 might not be the best choice, but for the majority that don't race regularly and drive on the street, there isn't going to be a big difference...

You cannot flog the bejesus out of the brake pedal when you bleed the brakes or you will suffer the entrained air problem with the system. IIRC, they no longer use it in Corvettes because of ABS.

No sense arguing with some of you. If you want that brake fluid in your cars,knock yourself out.
Sheesh!

I don't think anyone is arguing. Just stating facts, people who have used the Dot5 are sharing their experiences. When the time comes to redo mine this winter I might stick with the Dot 5.

Tony wants to argue about it. Look at his deleted posts. :D :D
Lighten up,friend.

I thought mine was fine too, until I switched back and noticed how much better it felt. :eek: I had blamed my soft pedal on my 1" bore M.C. being too small, but after the fluid swap, it feels good now.


So if you had no air in the system, you're saying that DOT5 fluid is more comressible than DOT3 fluid? (waiting patiently with physics book in hand...)

DOT 5 is prone to aeration, which is why it has the big warning "Not for use in Anti-Lock Brake Systems"

Is aeration really a problem in a standard brake system? How would it occur?

Flogging the heck out of the brake pedal while bleeding the system will do that.

Flogging the heck out of the brake pedal while bleeding the system will do that.

That's kinda what I was getting at... will it really happen if you fill and bleed as normal people do it? :)

Mine was almost entirely gravity bled.

I've bled brakes a few times, I know how it's done...

Because DOt3/DOT4 loose their corrosion inhibitors they need to be flushed ever few years. If the same flushing "schedule" is kept for DOT5, then there shouldn't be an issue with Water and corrosion... Unless you have other problems, the DOT5 should "last" longer between maintenance/flushing...
You simply cannot flush the water out of a DOT 5 brake system. The water pools at the bottom of the calipers; the bleeders are at the top of the calipers. The heavier water will not come out the bleeder, unless you turn the calipers upside-down.

Every time you open up the system, you introduce moisture/humidity to the fluid, and through gravity, that moisture goes to the calipers. Bleeding doesn't help.

Like I said earlier, there is no benefit to DOT 5 other than that it doesn't harm paint.

That's kinda what I was getting at... will it really happen if you fill and bleed as normal people do it? :)Normal people can also pour a bottle of fluid without spilling too. ;)

Firmer pedal with a better feel of the road. With the silicone, it was mushy and didn't give any feedback.

Ah ha, I've wondered why the brakes on my 90 GMC pickup have always felt spongy.
Now I know.

I wonder how hard it is to flush it ALL out.
not that I pobably ever will, I drive it slow anyway.

You simply cannot flush the water out of a DOT 5 brake system. The water pools at the bottom of the calipers; the bleeders are at the top of the calipers. The heavier water will not come out the bleeder, unless you turn the calipers upside-down.

Every time you open up the system, you introduce moisture/humidity to the fluid, and through gravity, that moisture goes to the calipers. Bleeding doesn't help.

Like I said earlier, there is no benefit to DOT 5 other than that it doesn't harm paint.

Normal people can also pour a bottle of fluid without spilling too. ;)

Derek, anyone who insists on living in Minnesota is bound to have brake problems anyway so its no surprise that you did. :D

I lived there for 45 years so I know about these things.

Mine was almost entirely gravity bled.

I've bled brakes a few times, I know how it's done...

I would certainly assume that you do, that's why I was wondering how the fluid got aerated?


Normal people can also pour a bottle of fluid without spilling too. ;)

I never said that I am normal, did I? :)

So if you had no air in the system, you're saying that DOT5 fluid is more comressible than DOT3 fluid? (waiting patiently with physics book in hand...)

Yes it is! Put away that physics book and whip out your fluid dynamics textbook, because fluid is indeed compressable. Some more than others...

DOT5 silicone is a great brake fluid, EXCEPT it will COMPRESS when hot! That makes it fine for everyday, or even somewhat hard street driving, but don't use it at the track...your pedal will be soft. It does a great job at protecting components by the lack of water, but just doesn't do the job in high heat situations (which includes ABS).

Along with professional expenience with this stuff, I also have personal experience. When I switched from the usual glycol fluid to silicone, I noticed no difference...absolutely none. For those who did, you had air in the system whenever it felt spongy, I garauntee it. When I took the car to the track and got the brakes hot, it made me pretty nervous when approaching a turn...it was that bad. It just feld like there was air in the system. Switching to Wilwood EXP fluid, the problem went away.

Tony wants to argue about it. Look at his deleted posts. :D :D
Lighten up,friend.

Thats why I deleted those posts... I am generally easy going, but do tend to get a bit heated in these discussions and search through all the rhetoric for the truth and real experiences. I truly hope to remain a "friend" to all my TC Breatheren, and didn't want anyone, especially Clint to take it the wrong way...

If you read my post (or the deleted posts), you will see that I did (Pretty sure) mentioned that DOT5 wasn't necessarily the BEST choice in all situations (esspecially the track), and that many of the "problems" (except the ABS issue and Track use) have NOT been founded... They are just hypothetical or based on contaminated systems...

But Clint, you implied by your previous post that you are correct and everyone else is wrongNo sense arguing with some of you. If you want that brake fluid in your cars,knock yourself out.
Sheesh!... Yet you are one of the few that did NOT (that I recall) post ANY personal experience with Dot5... Please share with us...

That "BMW" link that Troy posted (and I linked in the deleted post) mentioned many of the "potential" problems (even implying that they were potential and not definite) were likely caused by improper cleaning/contamination and bleeding...

Again, I restate what I mentioned earlier (maybe in the deleted post), that for the majority of car owners here on TC (and other classic cars) that have sporadically driven cars (parked in winter, etc), and not regularly or competitively flogged on the race course, DOT5 does appear to be a great choice...

Derek states that the ONLY reason is NOT eating the paint. But thats not true. Now, I don't believe everything I read, but most of the places I searched on the web (at least 20 articles I read) almost ALL came to the conclusion that for a classic that gets stored for longer periods, DOT5 IS a better choice...
For an ABS equipped car, it is NOT a good choice and for a racecar not so good...

I even read several articles about Harley Davidson not using DOT5, and they were NOT because of safety or performance issues, but mostly a cost (why else didn't Harley do a recall or immediately stop DOT5 usage is ALL their lines at once???)... There was one mention of the Air entranement, but that was to the effect that if a customer puts a bottle in their saddlebag and drives home, they should let it sit for a while to let the air bubble out, and they weren't sure cutomers would all do this. So it comes down to proper handling and bleeding. If it was a safety issue, you can be sure Harley would have had a full immediate recall to avoid any potential future litigation...


With the exception of some racers "loosing" their brakes, without similar problems switching back to 3/4, almost nothing could be attributed directly back to DOT5...

Some people complained of sludge (common with neglected 3/4 and moreso after the addition of 5 if not thoroughly cleaned), but that can't be attributed to the fluid alone (and based on how "
clean" silicone appears even when older it more unlikely).

there were several stories of masters faliing and leaking with DOT5, but thats always the case and can't be attributed to the fluid either (I have had several masters leak over the years, and ALL were with 3/4)... And these leaks ALL ate the paint on the inner fender and frame, despite being careful NOT to spill any...

My position hasn't changed, and is supported by those with actual experience, even this guy Matt (seems to have some good experience that bridges the two sides...):
DOT5 silicone is a great brake fluid, EXCEPT it will COMPRESS when hot! That makes it fine for everyday, or even somewhat hard street driving, but don't use it at the track...your pedal will be soft. It does a great job at protecting components by the lack of water, but just doesn't do the job in high heat situations (which includes ABS).

Along with professional expenience with this stuff, I also have personal experience. When I switched from the usual glycol fluid to silicone, I noticed no difference...absolutely none. For those who did, you had air in the system whenever it felt spongy, I garauntee it. When I took the car to the track and got the brakes hot, it made me pretty nervous when approaching a turn...it was that bad. It just feld like there was air in the system. Switching to Wilwood EXP fluid, the problem went away.

Pretty much summarizes what I have read elsewhere and what I and MOST others have experienced, with the added "track" experience...


Personally, I tend to agree that there isn't much reason to switch to DOT5 given the expense and hassle (unless the system in new and clean), but short of a track car (or ABS, etc), its NOT a bad choice, just a personal choice...

No offense taken here,Tony,and I hope you and I are cool with this discussion. Not worth losing friends over,for sure.

My experiences with Dot5 has been less than stellar. My last experience with it was in my Harley Road King. That bike had the worst brakes of any m/c I've ever owned. I'm no novice with bikes,having owned & built more rad rides than probably anyone on this board. Flushing the system and converting to Dot4 solved 99% of its brake problems. The majority of my bike builds have been prostreet or roadrace stuff and max effort brakes are mandatory,IMO. The possibility of a brake fluid spill is much greater on a bike than a car but Dot5 works so poorly,only show bikes ever had it added.
No way I would run it in any of my cars and I've built almost as many cars as I have bikes. IMO,Dot5's minuses outweigh its plusses.
Like I said before,use what you want. If the stuff works for you,that's great.