just renewed the brake fluid on my bike with dot 5 spec for a longer life,as i understand it resists hygroscopic actions for longer ,now its occured to me , are the seals compatible with dot 5[thinking it may have different ingredients]? anyone have any knowledge of specs'/fluid make up?
- Thread starter nickk
- Start date
PhillipM
Member
- Messages
- 3,051
You shouldn't mix DOT 5 with systems that have any trace of DOT 3/4/5.1 in them. Generally you'll need a lot of flushing through to get the old fluid out of the seals as they absorb some of it.
You'll also find that any water in the system will now flow straight down your lines and collect in your calipers - not generally a good thing, most systems dedicated for DOT 5 use (long distance/military stuff), usually integrate a water trap somewhere along the lines.
Oh, and the brakes will be spongier over normal stuff. It's not something I advocate using unless you have a classic with priceless paintwork or intend on driving through the amazon for years
You'll also find that any water in the system will now flow straight down your lines and collect in your calipers - not generally a good thing, most systems dedicated for DOT 5 use (long distance/military stuff), usually integrate a water trap somewhere along the lines.
Oh, and the brakes will be spongier over normal stuff. It's not something I advocate using unless you have a classic with priceless paintwork or intend on driving through the amazon for years
rikrobson
Member
- Messages
- 3,963
- Location
- Perth, Scotland
DOT 5.1 is a better grade of glycol, i.e. Higher temp and less hygroscopic. This is comaptible with DOT 4 although if your manf. says use DOT4 use DOT4. If you are worries about water change the fluid avert couple of years, like you are supposed to.
DOT5 is silicone base and is not comaptoble with DOT4. Don't get the two confused. Its for racing and military stuff not genseral road use. If it was that good we would all be using it.
DOT5 is silicone base and is not comaptoble with DOT4. Don't get the two confused. Its for racing and military stuff not genseral road use. If it was that good we would all be using it.
I'm confused ,in 1 sentence you say it is compatible,& in the next you say it isn't! the reason i changed it is 'cos the bikes nearly 3 years old & hasn't been changed yet.
zx9
Forum Supporter
- Messages
- 5,199
- Location
- South East London
pedrobedro
Man at Matalan
- Messages
- 13,099
- Location
- CX near Chesterfield
If it says Dot 4 on the master cylinder cap use Dot 4. Dot 5 silicone fluid compresses more than Dot 4 so it gives a spongy feel to the brakes.
langy
langys rodshop
- Messages
- 6,095
- Location
- London
I've seen it many times, its amazing what it does. Lots of people changed to this with all the advertising about it being miracle stuff about 20 years ago, as usual the advertising was very misleading !!!
on closer inspection the fluid the factors sent me was 5.1 even though i ordered 5,so i'll leave it in,looking on a few sites the advantage with 5.1 is higher boiling point so perhaps more hygroscopic resistance? all i was after was longer service intervals,i'll stick to dot 4.could do with more distinctive categorising-i can't be the only person who didn't notice the .1.In fact one advert even called dot 5.1 silicone based,& the label on the bottle states 5.1 is silicone based yet contains polyalkylene glycol ethers,ether esters & polyglycols & is ok with abs vehicles -completely contradictory!
Most modern dot 5 silicone systems will have a silicone diaphragm on the reservoir to allow for fluid movement in the system without getting moisture into the fluid.
Dot 5.1 is hygroscopic so that the water is bound up and does not create local pockets of material with a 100 degree boiling point.
Given the cost of the fluid I would change it at the recommended intervals, if your low mileage change on the basis of age. What's a litre of fluid and an hours effort cost compared to a problem?
Shox Dr
Chief Engineer to Carlos Fandango
- Messages
- 18,010
- Location
- East Yorkshire
I tried them all when I was racing XC and DH on MTB bikes: They all boiled in the small fluid capacities used. I found Aviation grade to be the best.
Not interested unless it has a big motor in it these days. So I find the pad/disc combos are the biggest problem with brakes
Not interested unless it has a big motor in it these days. So I find the pad/disc combos are the biggest problem with brakes
When i rebuilt my Moggie pick up i put Dot 5 silicone fluid in it. No problems as the braking system was all new pipes & parts.
I never noticed any loss of performance at all. What i did find was the brake cylinders did not seize up between Mot's, the stuff saved me a fortune!
I never noticed any loss of performance at all. What i did find was the brake cylinders did not seize up between Mot's, the stuff saved me a fortune!
Just leave it (dot5.1) in there. It's better than dot4 and no problems with mixing the two unlike dot5.
