Replacing dot 5 with dot 4?

[yorkshire_spam]

Never been totally happy with the pedal feel I get with dot 5 in the Dolomite brakes. Do I face a nightmare replacing it with dot 4? Failed seals etc?

 

[Velocita Rosso]

My thoughts are...if you have Dot 5 fluid penetration into the seals and the 4 and 5 do not mix, then all seals should be changed when changing the fluid type. I`ve never even contemplated changing to 5. To me 4 is effective enough and if maintenance is kept up then there should be no leakage to cause any damage.

[mblowing]

12 hours ago, Velocita Rosso said:

My thoughts are...if you have Dot 5 fluid penetration into the seals and the 4 and 5 do not mix, then all seals should be changed when changing the fluid type. I`ve never even contemplated changing to 5. To me 4 is effective enough and if maintenance is kept up then there should be no leakage to cause any damage.

 

[mblowing]

hi bi have a concentric clutch kit on my pi spitfire that started to leak after talking to cambridge motor sport they said they dont use dot 5 as it doesnt lubricate as well as dot 3 so im now changing my seals and an using dot 3 ,i wish theyed told me when i purchaced the kit .

 

 

 

 

 

 

 

 

mend 

[yorkshire_spam]

Previous owner put Dot 5 in it when he put the car back on the road - so brake parts were new/refurbished at that time. But as I say, I don't like the fact that it's "hard to find and expensive" dot 5 (not even 5.1) nor have I ever been totally happy with the pedal feel. (MOT tester comments on the brake feel every year)

Hmmm.... I might just ignore it for another year 😉

 

[drofgum]

Yorkshire_spam,

Although DOT 5.1 has similar temperature rating to DOT 5 it is not silicone fluid it is glycol based just as DOT 3 and DOT 4.

So adding DOT 5.1 is mixing the fluid types the same as adding DOT 3 would be.

Regards,

Paul

[yorkshire_spam]

Thanks Paul, At the moment the system is dot 5, I continue to top up with dot 5 (not 4, not 5.1) but at some point I'd rather switch to dot 4. I think I'll punt this problem do AFTER the 10CR as if I'm going to have a leaking brake system I don't want it to be during that event!

 

[Beans]

I did replace DOT5 (silicon) brake fluid many years ago when I got fed up with the soft pedal feel.
My local brake specialist advised to flush the system with methylated spirit* before filling it with DOT4.
It worked fine for me, and I didn't need to replace any seals in the years after.

* hopefully I have translated it correctly 🧐

[yorkshire_spam]

19 minutes ago, Beans said:

I did replace DOT5 (silicon) brake fluid many years ago when I got fed up with the soft pedal feel.
My local brake specialist advised to flush the system with methylated spirit* before filling it with DOT4.
It worked fine for me, and I didn't need to replace any seals in the years after.

* hopefully I have translated it correctly 🧐

Perfect translation thanks Theo! I think it's what the USA people call "Denatured Alcohol", but in the UK it's definitely methylated spirit! It's what I used to measure the volume of the combustion chambers on my cylinder head. 

Interesting, I think I'll make swapping to dot4 the job for winter after the 10cr!