Why are most of us using Glycol Brake-fluid in clutches?
Discussion
Why are most of us using Glycol Brake-fluid in clutches? Makes no sense to me? And by this I mean...
We're not going to boil fluid like we might in brakes, and we WILL have to flush it inside 2-3 years. It's a clutch for cryin' out - what am I missing, what's wrong with DOT 5 (Purple) in there? Should outlast me, a la military practice?
I do realise the shortfalls of DOT 5, for kick-off it fails to mix with glycol, only most of the other shortfalls won't apply to a clutch.
We're not going to boil fluid like we might in brakes, and we WILL have to flush it inside 2-3 years. It's a clutch for cryin' out - what am I missing, what's wrong with DOT 5 (Purple) in there? Should outlast me, a la military practice?
I do realise the shortfalls of DOT 5, for kick-off it fails to mix with glycol, only most of the other shortfalls won't apply to a clutch.
Edited by OldDuffer on Wednesday 17th August 16:31
I realise despite DOT 5 not broadly put to use in modern cars, quite a few classics run DOT 5 in brakes. In which case, there'd be little reason not to extend the logic to the clutch.
I don't race or intend to race my classic, however it's my daily. Out in February as August, flushing glycol is not a nice job, but I do it. I'd thought to convert to DOT 5. I think I'll do the clutch and see how I go. It's claimed to be fit and forget. We'll see.
I don't race or intend to race my classic, however it's my daily. Out in February as August, flushing glycol is not a nice job, but I do it. I'd thought to convert to DOT 5. I think I'll do the clutch and see how I go. It's claimed to be fit and forget. We'll see.
Been running DOT5 for both brakes and clutch in one of my cars for over 10 years...
OldDuffer said:
I do realise the shortfalls of DOT 5, for kick-off it fails to mix with glycol, only most of the other shortfalls won't apply to a clutch.
Depends what you mean by "mix". No, DOT5 won't "mix with" (become physically inseparable from) DOT3/4 (and I [u]think[/u] 5.1 fluids but that ARE all compatible and DOT5 can be "mixed with" (used in the same hydraulic system as) DOT3/4/(5.1). That doesn't mean it's recommended to mix them - but only because you generally end up with the disadvantages of DOT5 AND the disadvantages of DOT3/4/(5.1) rather than it being unsafe. What it does mean though that if you're using DOT5 and start losing fluid in the middle of nowhere and can only get your hands on DOT3/4/(5.1) it's prefectly safe to top up with them to get you home.OldDuffer said:
I realise despite DOT 5 not broadly put to use in modern cars...
Modern's only don't use DOT5 simply because it's 5x the price of DOT4.//j17 said:
Modern's only don't use DOT5 simply because it's 5x the price of DOT4.
I did wonder why that was. I use Dot 5 in the Triumph and the correct Audi-branded fluid in the proper Audi. But the Quattro does have quite a complex Citroenesque hydraulic system so I'm a bit wary of going off-piste with my fluids.Yertis said:
//j17 said:
Modern's only don't use DOT5 simply because it's 5x the price of DOT4.
I did wonder why that was. I use Dot 5 in the Triumph and the correct Audi-branded fluid in the proper Audi. But the Quattro does have quite a complex Citroenesque hydraulic system so I'm a bit wary of going off-piste with my fluids.//j17 said:
CLX said:
BTW, whoever named 5.1 didn't think it through.
When I was looking for some DOT 5, I saw some 5.1 and assumed it was just a newer version of 5.
Should have called it DOT 6?
There's already a DOT6 fluid standard though.When I was looking for some DOT 5, I saw some 5.1 and assumed it was just a newer version of 5.
Should have called it DOT 6?
Got bored last night.
So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
//j17 said:
Got bored last night.
So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
Yes, very interesting. Thanks for that. There is some logic to it after all!So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
//j17 said:
Got bored last night.
So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
So DOT 5.1 is compatible with DOT 4 as a top up?So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
Skyedriver said:
So DOT 5.1 is compatible with DOT 4 as a top up?
Correct - although I'm sure all the DOT brake fluid standards are written to say they must be able to be mixed and most of the "No, you can't mix" advice you find online is actually people missunderstanding or dumbing down the more nuanced "They can be mixed, subject to the specifics of your motor vehicles hydraulic systems".Remember that the DOT5 standard largely came about as a US military requirement, where they wanted to be able to park up 'spare' vehicles and not have to employ teams to go around changing the brake fluid every 2 years - BUT they also didn't want a unit to be on operations and have half their vehicles out-of-action because they had lost a DOT5 brake fluid supply drop and could only buy DOT4 in the local motor factors (or trust the average squady to use the correct bottle).
For us, with the simple hydraulic systems in our cars can happily mix DOT3/4/5/5.1 - but using 5 up update a Glycol system's an expensive hobby/topping up a 5 system with Glycol gives a mix that strips paint and absorbs some water so need replacing after 2 years.
Silicon fluid is more viscous than Glycol though which means it's not compatible with most ABS systems found on modern cars so you shouldn't mix in those cars, not because the fluids themselves aren't safe to mix but because some of the cars hydraulic systems aren't designed to work with silicon fluid.
//j17 said:
Got bored last night.
So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
But they want brake fluid to be slightly hygroscopic. Any moisture, such as condensation will mix with the oil and not settle to the lowest point causing corrosion in the system.So the DOT5 standard was origonally conceived to set a standard for brake fluid with much lower hygroscopic tendencies than DOT3/4 and as only silicon fluids could achieve them at the time "silicon based" made it into the standard specification.
Roll on a couple of years and the brake fluid industry managed to develop glycol based fluids that matched all the performance side of the DOT5 standard, but because they were glycol rather than silicon based couldn't technically match the DOT5 standard. As the main difference was the chemical base that didn't warrent a new whole number, and because they had more in common with the DOT5 standard than the DOT4 one they used the DOT5.1 name for the "DOT5 but with glycol rather than silicon" standard.
Interesting to know the history. Completely pointless, but interesting.
Hence the need for regular brake fluid changes.
NMNeil said:
But they want brake fluid to be slightly hygroscopic. Any moisture, such as condensation will mix with the oil and not settle to the lowest point causing corrosion in the system.
Hence the need for regular brake fluid changes.
That sounds like flipping cause and effect to try and sell a flaw as a feature to me. You need to change the fluid because it absorbs moisture but I don't buy that the fluid was specially engineered to absorb moisture. If the issue was water collecting at the lowest point in the system why not use a non-absorbing fluid and just add a bleed nipple at the lowest point? You could then just bleed out the water till it was brake fluiid coming out and top up the master cylinder. And given the lowest point's often the brake caliper and lots of brake calipers have or could easilly be made with both top and bottom bleed nipples so they can be swapped from side-to-side and used in different applications would be straight forward to do.Hence the need for regular brake fluid changes.
//j17 said:
NMNeil said:
But they want brake fluid to be slightly hygroscopic. Any moisture, such as condensation will mix with the oil and not settle to the lowest point causing corrosion in the system.
Hence the need for regular brake fluid changes.
That sounds like flipping cause and effect to try and sell a flaw as a feature to me. You need to change the fluid because it absorbs moisture but I don't buy that the fluid was specially engineered to absorb moisture. If the issue was water collecting at the lowest point in the system why not use a non-absorbing fluid and just add a bleed nipple at the lowest point? You could then just bleed out the water till it was brake fluiid coming out and top up the master cylinder. And given the lowest point's often the brake caliper and lots of brake calipers have or could easilly be made with both top and bottom bleed nipples so they can be swapped from side-to-side and used in different applications would be straight forward to do.Hence the need for regular brake fluid changes.
And yes, it's engineered to absorb moisture.
https://www.valvoline.com/en/premium-dry-brake-flu...
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