So my C4 is going in the shop next week for new tires and some brake work. Putting on SS hoses on all 4 corners, and the bias spring. Also having the lines all flushed out and new fluid loaded. So should i just put in the best DOT3 i can get, or upgrade to some DOT4? Will it be compatible with my stock calipers? I read that Motul 665 DOT4 is a good choice? Car is obviously a street car, and i hit the autocross 2-3 times per year. Have new Hawk pads waiting, till current pads/rotors wear down. Thanks!

 

DOT4 has a higher temp capability. That's about the best upgrade you can do. DOT5 is silicone based and I'm not sure you could use that. Maybe you can if you start with an empty system. Maybe someone else will chime in to help.

 

DOT3 and 4 are compatible/mixable. Your calipers won't care which you use.


The combination of that fluid and those pads will be way better than good enough, for what you are looking to do w/the car.

 

I use dot 4 now and seems no more drips from master cylinder. Since I needed it in the range rover (1997) I decided to go to the corvette , I read bad things about anything higher.

 

My FSM specifically says NO silicone brake fluid. Apparently it's not compatible with ABS.

 

OK, thanks for all the replies. Looks like DOT4 is a go, and avoid DOT5 fluid. There are many choices out there for brake fluid. Having the higher temp DOT4 is a bonus. I was just wondering if it would affect the calipers/seals.

I am trying to do the brake upgrades in stages, and see what the results are. I am expecting the new Nitto tires to have the biggest affect at the track. I was using the brakes hard, but i think the old, dry cracked tires were really holding me back. So maybe after the next track session, i look into rotors and load up my Hawk HPS pads.....
Cant wait to test her out!

 

I typically go with a Valvoline synthetic, Motul and PFC make good ones too, whatever you pick just don't use DOT5.

 

Copy that. Not sure i will be able to get Motul in time for next week, so i will just tell my mechanic to load up his best syn DOT4 fluid that he can get........

 

Motul RBF 600 will cover you. There is a 660 also, but its wet boiling point is lower than the 600 so I stick with 600. If you take the car to an actual track and run 20minute sessions, you will boil the fluid if you dont use a high temp fluid such as Motul 600 or Castrol SKF.

 

I will just see what my mechanic has. Had one track day this year so far. Low turnout, so we had longer sessions. first one was like 40 min. then we had 30 min after that. Brakes held up fine, but my tires were limiting me. 2.1 mile course, with 18 turns, up/down hills, only 1 long strait. should go back after the upgrade.

 

I was recently reading about DOT 5.1 fluid which is compatible with DOT 3 and 4 fluids. It's more prevalent in Europe however.

Here's a good read on it -
http://www.sector111.com/images/prod...ke%20Fluid.pdf

Here in the US, Amazon carries it -
https://www.amazon.com/Motul-DOT-5-1.../dp/B0022ZFWMM

Expensive but it can also be purchased in a two pack for $18 with free shipping -
https://www.amazon.com/Motul-Temp-Br...CPZQ278NF0XF1K

 

How about changing the brake fluid in the resevior with a turkey syringe once or twice a year rather than flushing the whole system?

 

That won't do a whole lot for the fluid that is down in the calipers. Better than nothing...but not good enough, IMO. How hard is it to bleed brakes?

 

I have run Motul RBF600 for probably 7 seasons now, really good stuff. ATE 200 is about half the price and is almost as good, but I like the extra temp protection from the Motul. The BIGGEST relatively cheap improvement I ever did was adding 3" cooling hoses with spindle ducts. I literally went from using a brake pad set every two events on my DRM upgraded brakes to this last set of my Raybestos ST43s lasting me 13 track days!!!! Astonishing improvement for under $200 and some time. I have pics I can share or you can look up the thread I posted a few years ago that has the pics. Also, I have run NT05's for about 5 years and just stepped up to NT01s. Both are awesome tires and it just depends on how much road/track you do or how much you want to pay per day

 

Hello Tom

I've heard here around, that dot3 and dot4 are not exactly the same.

A guy from a shop here told me that dot4 can makes something like corrosion on brake and clutch hidraulic rubber parts.

Anyway i'm not a chemistry expert, tough the other car i've here (dodge nitro my 2007) on brake master cap says to use dot3 only, even if dot4 was already available on market that years. Still i use dot3/4 or dot3 on my cars in place of dot4 only

What do you think about it?

Chris

 

I think I'd go fact finding further than what "a guy at a shop" said. II once had "a guy at a shop" tell me that if I put Dexcool in a Honda, it would "blow up" , so "guys at shops" opinions don't carry much weight with me.

I've never heard anything about DOT 4 being detrimental to systems in any way, but I'm not a chem E either, so perhaps some further research is in order....

Note that I didn't say that they two were "exactly the same"; I said that they're compatible, meaning you can mix them w/o issue. Unlike mixing DOT 5 (silicon) and other types, which you can not do.

 

Yes, everything you said are right, about guys shop opinion, and further reasearch would be a good idea

The only thing that support my doubt is my brake master cap.

If factory recommend to use dot 3 only, when dot4 was already available on the market and have a higher boiling point and seems to be the better one, i suspect that dot4 is at least not fully compatible IMO...

This is what I think with things i have in hand, that is just a brake cap and a FSM. (Not checked FSM yet)

 

While you can mix DOT3 and DOT4 fluids, it's not really a good idea to do so. The primary difference between the two fluids is the temperature where the fluid will boil in the system. Both DOT3 and DOT4 fluids by brand have temperature ranges for wet and dry boiling points that can vary as much as 50-100 degrees. DOT4 fluids will boil at a higher temperature compared to a DOT3 fluid. DOT4 fluids also tend to be more "hydroscopic" in that they can absorb moisture at a quicker rate.

I have been using ATE TYP200 DOT4 fluid in my autocross/track day car and it seems to work well (for me!!). This fluid has a wet boiling point of 392 degrees. By comparison, MOTUL 600 has a wet boiling point of 421 degrees (all values are Fahrenheit). A good DOT3 fluid like Castrol LMA has a wet boiling point of 311 degrees and the Ford HD Motorsports fluid has a 290 degree wet boiling point.

The factory fill for brake fluid in Corvettes has always been a DOT3 fluid. Which is fine for normal driving and even some "spirited" driving. But if the car gets aftermarket brake upgrades that will produce higher braking temps in the pads and rotors, or if the car sees a lot of autocross and track use, it's a very good idea to go with a DOT4 fluid. But that does mean a complete flush of the old DOT3 fluid and replace with a DOT4 fluid.

There are some cars that have DOT4 as a factory fill but they are typically very high performance cars like the "exotics".

 

Chances are you wont get the brakes hot enough to boil the fluid at an autox or street driving. If you do you'll want to flush the system. So why bother with expensive fluids? DOT3 is good performing fluid and cheap too.

I use a syringe to remove/replace the fluid in the reservoir at least twice a year and should the fluid look cloudy, replace it then.

 

DOT3/DOT4 actually do not mix.






DOT3 has a dry boiling point ~450F. DOT4 has a dry boiling point ~501F.










When they are mixed, the dry boiling point drops to~290F.


This boiling point is low enough to cause fluid boiling/brake loss in heavy use.




Jonathan.....