Brake system & proper fluid

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Jan 16, 2011 | 10:43 PM

5hands5

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Brake system & proper fluid

I am rebuilding my brake system in ny 67 electra glide & my new master cylinder says to put DOT 5 only so I cleared out my system of DOT 4 & replaced it with DOT 5. I now need to replace the rear wheel cylinder for the brake system & it says DOT 4 only. What do I do? Can I use DOT 5 with the new rear wheel brake cylinder or do I have to go back to DOT 4 & get a new master cylinder?

Last edited by 5hands5; Jan 16, 2011 at 10:51 PM.

Jan 16, 2011 | 11:02 PM

Steelhammer

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From: USA

I just asked the dealer the difference on the Dot 4 and the Dot 5. Was told the Dot 5 was for the new ABS brake systems. Dot 4 is still mostly 100% mineral oil.
Just my 2 cents
(I stand corrected on this info stated earlier) Wouldn't want anyone to read that and think it was right, so disregard it totally.The Harley parts guy didn't know the correct information obviously .Below posts have better info on the subject of Brake fluid adaptations and mixing.and chemistry, hopefully no harm taken.

Last edited by Steelhammer; Jan 22, 2011 at 12:51 PM. Reason: Correction

Jan 16, 2011 | 11:34 PM

5hands5

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Brake system & proper fluid

Thanks Hammer!

Jan 17, 2011 | 08:45 AM

panz4ever

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From: Santa Klaus County, Cali

And when you mention you "cleaned out the system", assume you know you have to take apart all brake related parts and thoroughly clean them so there is no mixing of fluids

Jan 17, 2011 | 12:36 PM

5hands5

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Yes. The whole system must be thoroughly taken apart & meticulosly cleaned. But the new master cylinder stated to use DOT 5 only for the hydrolic system but the new wheel cylinder states to use DOT 4 only. ??????

Jan 17, 2011 | 01:43 PM

B2BW

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brake fluid

i have an 74 flh with new master on rear and front with still old banana brakes and i use brake fluid no 5 i also put in new o rings and seals and it works great

Jan 17, 2011 | 03:19 PM

48pan

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From: Fort Worth, Texas

The difference is just in the make up of the fluids. The material of the o-rings is the same for both systems. You just don't want to mix them. I run a Wagner-Lockheed master with the banana clip rear and use DOT 5. Denatured alcohol is a good source to clean brake system fluid FYI.