yorkshire_spam Posted June 26, 2022 Share Posted June 26, 2022 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? Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted June 26, 2022 Share Posted June 26, 2022 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. Quote Link to comment Share on other sites More sharing options...
mblowing Posted June 27, 2022 Share Posted June 27, 2022 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. Quote Link to comment Share on other sites More sharing options...
mblowing Posted June 27, 2022 Share Posted June 27, 2022 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 Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted June 27, 2022 Author Share Posted June 27, 2022 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 😉 Quote Link to comment Share on other sites More sharing options...
drofgum Posted June 27, 2022 Share Posted June 27, 2022 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 1 Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted June 27, 2022 Author Share Posted June 27, 2022 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! 1 Quote Link to comment Share on other sites More sharing options...
Beans Posted June 27, 2022 Share Posted June 27, 2022 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 🧐 2 Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted June 27, 2022 Author Share Posted June 27, 2022 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! 1 Quote Link to comment Share on other sites More sharing options...
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