My brother purchased a used 2005 Road King. Both his owners manual and the master cylinder caps say to use DOT 4 brake fluid and when he recently added some DOT 4 the seals started going bad in his rear master cylinder. My 2001 Road King and most others I've seen up to 2009 all use DOT 5. Could this have been an error? Do all 2005 Road Kings use DOT 4?

 

If you have seen "up to 2009" using dot 5, you might want to check again. HD switched to all dot 4 in 2006 (IIRC) since ABS was going to be introduced and dot 4 is a better fluid for that. Figured less mistakes would be made if they only used one type of brake fluid from the factory.

I guess it's possible that the previous owner swapped over to dot 5 and didn't note it anywhere....

 

To the best of my knowledge all Touring Models went to DOT4 from 05 on .. Seals may have just been going bad, if mix the 2 will get a mess of goop for Brake Fluid .. I would flush, replace the seals and be sure using the right fluid which think is DOT4..

 

'05 used DOT 4.

 

His master cylinders and manual say use DOT4. If the seals are gone replace them and use DOT4! In my bitter experience of mixing DOT5 and DOT4 it was not the seals that caused problems, but erosion in the master cylinders (plus the awful goop). Stick with the right stuff.

 

H-D used DOT 5 brake fluid for several years (2000 RG and my wife's 2001 heritage). Her 2007 Ultra and my 2008 RG with ABS went back to DOT 4. Perhaps 07RoadHawg is correct in that the transition occurred in 2006. JayStronghawk says it was 2005 (maybe when the 2006 models came out). The original poster claims all H-Ds up to 2009 use DOT 5. He is wrong.

 

Dot 5 is silicone based but there is a newer Dot 5.1 that is compatible with Dot 3 & 4.
5.1 has a higher temperature rating than Dot 4.

 

I stated all Touring Models went to DOT4 in 05 as that includes Road King consider giving it a serious check before making a sad mistake ...

 

They were using DOT5 in 1984, possibly earlier, so used it for at least 20 years.

 

Use DOT 4 only...I recently bled my brakes and my service manual for my 2005 RK Classic said to only use DOT 4