Dot 5.1 brake fluid... any realistic gain?

[Mikey3]

As the title asks, is there any realistic gain from dot 5.1 over dot 4?
the boiling temperature's higher and it doesn't absorb water as easily but is that anything that would be noticeable on the road at all, seeing as I don't exactly boil my fluid and I don't have an issue with sponginess.
It came up in conversation the other day, and was told to just stick with dot 4, as 5.1 is more expensive and hardly any different for day to day riding.


Mike
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'04 Yamaha WR450F
'99 SV650 Streetfighter Project - mid build
'Motorcycling is about what you do; not about what you own, or how much you spend on it'

[Kickstart]

Hi

Not sure there is any benefit as far as water absorption (and it has been said on here it is worse than DOT 4). DOT 5 doesn't absorb water at all but that is very different stuff. What it does have is a higher boiling point even after absorbing a certain amount of water.

If properly bled through neither DOT 3, DOT 4 or DOT 5.1 should give any more or less spongy brakes (indeed, nor would water itself if you tried it statically, but it would boil very rapidly and give you lethally spongy brakes in real use).

But it is an extra safety margin which is only a nominal extra cost.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[map]

Agree with Kickstart's words of wisdom above.

In the real world of road riding it's not a noticeable difference. This is useful as the last set of brake pads I ordered came with a free bottle of Dot 4. That was from these people - MSA Direct.

On a side issue does anyone know how long an opened bottle (as in part used) DOT4 lasts before it's unwise to use it (i.e. goes off)?


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...and the whirlwind is in the thorn trees, it's hard for thee to kick against the pricks...
Gibbs, what did Duckie look like when he was younger?

[Budgetboy]

Dot 5.0 is silicone based.. And it can be a biatch to bleed properly.As you quite rightly state the boiling point is higher..The army use 5.0 as it does not absorb water over time which is an added benefit.Also does not damage your paintwork if spilled.


As for the open bottle someone asked... Bin it mate,, its not worth the risk for how cheap fluid is. Next time put the cap on..Dot 3/4/5.1 will absorb water as soon as its exposed to air..The longer its left in the air the worse it gets. 24hrs-48hrs i would say is ok.. But a week or more exposed tot he open elements.. then no. I would bin it if it were me but its up to you.
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[map]

[AlexW]

You will probably find changing your fluid gives you a better feel if it hasnt been changed in a few years.

I generally always change my fluid for 5, 4 would be just as good for my use but Id like to have something better. In my track car I always run dot 5.

[Hetzer]

I'm still using a can of DOT4 that's over 4 years old and it's fine (my brakes work).
____________________
"There's the horizon! Ride hard, ride fast and cut down all who stand in your way!"

[Ghost]

Can't comment on the bike but can on my car that's had a few different combinations. The brakes were fine in normal road use even after a few hard stops anyway, but before taking it on track I replaced the pads and bled the whole system through with standard Dot 4 fluid. Even with brand new clean fluid out on track I was getting bad brake fade, juddering pedal and general crap performance after a few laps. Next try I'd flushed it all through with Halfords High Performance racing 5.1 stuff and the difference is night and day!

But, the brakes on your bike will get worked nowhere near has hard as that even on a track day, let alone normal riding on the road. So realistically as long as your fluid is fresh and clean it won't make much difference what you use

[Aperf]

A higher boiling point fluid only brings a benefit if you are boiling the existing fluid. The symptoms are the brake lever coming back to the bar. Fade is due to the pads overheating and the lever will just go wooden. The bikes braking performance will drop off hugely but the lever wont go back to the bar, its just that not a lot will hapen when you pull on it. Judder is down to pad deposits on the rotors causing high spots. Brake fluid has nothing to do with fade or judder and changing the fluid has zero effect on either.

The higher the boiling point the more hydroscopic the fluid is and the more often it has to be changed. Using a 5.1 over a Dot 4 is a step backwards if you arent boiling Dot 4 as it needs changing more often.

Changing old fluid for new is worth while as all fluids absorb water over time making the brakes feel spongy. The spongyness comes on very gradually over time so you might not notice the drop in lever feel until you flush and replace the fluid. There is zero difference between the lever feel of Dot 4 or Dot 5.1.

Dot 5 isnt compatible with a lot of brake systems so I wouldnt touch it with a barge pole. Dot 5.1 = ok, Dot 5 = not ok.

Dot 5.1 isnt safer than Dot 4 unless you are braking like a hero and getting the brakes hot enough to boil Dot 4.

Halfords Dot 5.1 is inexspensive and very good.
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CRF450R supermoto, Husaberg 650 supermoto, Triumph Street Triple R

[stevo as b4]

Interesting reading in this thread!
So how many of you lot have got hot hatch's/performance car's/sportscar's that you take on track days, and how would you spend most of your available leisure budget, i.e on a high performance car or tuned car and a fairly cheap non cutting edge bike, or vice versa? I don't really do car's for mundane driving to work etc, so if i own one it has to be fun and because i want to drive it, not because i need workhorse. with bikes it a bit of both, but i'd always like to keep a cheap and cheerful 125 or something as back up transport.

And yes i know bike are more fun, but stepping away from big sportsbikes has left me cold to them now, and i don't want a 100bhp+ machine again when they are irrelavent to road use in the u.k

Also what do i buy for under £3000 as a car that i can take on as many track days as i can afford a year, but one that has to work on the street and be legal to drive to and from the circuit, if this is not an unworkable idea?

[Aperf]

[Mikey3]

Cheers guys. Question definately answered.

Another question though, how does water get into the lines if its all sealed? I was told that it heats up and creates condensation on the inside of the line, but whether that's true or not... I don't know

Mike
____________________
'04 Yamaha WR450F
'99 SV650 Streetfighter Project - mid build
'Motorcycling is about what you do; not about what you own, or how much you spend on it'

[Aperf]

Moisture can enter the system through the lines themselves unless they are teflon.
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CRF450R supermoto, Husaberg 650 supermoto, Triumph Street Triple R

[Walloper]

[Hetzer]

[Walloper]

[Aperf]

[Walloper]

[Aperf]

[map]

[Mikey3]

[Hetzer]

[Mikey3]

[Fizzer Thou]

[Walloper]