Home › Forums › Parts & Technical Info › Whats a good alternative Rear Master Cylinder
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July 18, 2016 at 3:38 pm #3525
On my 04 Raider The rear tire was locking up at 7000 miles, so we rebuilt the Accutronix Master Cylinder, well the brake stopped locking up but the seal started leaking at the plunger because the bore was shot. I ordered a New Accutronix Rear Master cylinder and it worked for one year, it has internal leaking and the pedal goes all the way down before it engages the brake 5 out of 7 times, the other times it works great. There is no external leakage. I replaced all the brake fluid with Maxima Dot5 when I got the bike and am still using it today.
Is there a Master cylinder that will bolt on that is better (reliable) than Accutronix?
It has now progressed to locking up the rear brake :blink: :pinch: after about 5 miles, I open the bleeder and fluid comes gushing out under pressure without touching the pedal. The rotor is all floppy and loose when the pressure is off so it does not look like it is rubbing on one side or the other but for some reason the rear brakes are heating up the caliper and the brake fluid is expanding causing the pucks to move in and contact the rotor, I do not see any overflow hole anywhere for the fluid to bleed off excess pressure caused by heat.
Why is this happening and other than making a mess would drilling a tiny hole through the top cover for venting fix this? :huh:
Thanksloop-single-reply.phpJuly 20, 2016 at 5:20 pm #3526I called Accutronix, they deny there is any problem with their equipment. Next I talked to a distributor for Brembo Brake systems and they informed me the problem is the accutronix stops letting fluid return to the master cylinder so pressure builds and thing get tight quick. I was told to use Performance Machine or Wilwood because they have not had any problems at all with their master cylinders. I called Wilwood and they have a bolt in perfect fit for us that they have done all the design and engineering on themselves.
http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-10377
I will be ordering this very soon. I’m taking the bike down to performance Choppers in El Cajon tomorrow to get it dyno tuned finally. It has given me 10,000 miles this last year. it has earned it.loop-single-reply.phpJuly 20, 2016 at 10:16 pm #3527Accutronix never accepts fault on any of their products and are quick to point the finger at everyone else. The Wilwood unit should work out fine for you. Tell Glen at Performance Choppers I said Hey. He does all of our dyno work as well as Solid Works drawings for the parts we design. He needs to be a little taller lol
loop-single-reply.phpJuly 21, 2016 at 11:46 am #3528Those guys at performance choppers are really really nice and helpful!
Rarely have I seen a shop with a great bunch of people in it like that shop has.
He fixed up the jetting that came out of Texas and it definitely runs smoother at low speed and has much better throttle response, he said I will probably see a little better mileage out of the tank also.
It dyno’d at 118hp and 161mph :ohmy: which is way more than it will ever see with me on it :laugh:
He must like you Vengeance folks he charged me $60 less than what we agreed on before he started the job.
It’s not a bad ride down there from Hemet so I think I might start having them do the work I can’t do in the garage were I live.
Thanks for the recommendation for Wilwood.loop-single-reply.phpJuly 25, 2016 at 11:36 pm #3529I put the new Wilwood rear brake master cylinder on, I have bled over 20oz of dot5 through the system. I tried both ways…Vacuum Bleeding and pump the pedal old style bleeding.
The pedal goes down way to far and is spongy, in no way can it lock up the rear wheel. Pumping the pedal does not do anything to harden the pedal.
I figure I will put new shoes in the caliper, maybe the old ones got glazed. Any other ideas? When I push the pedal I can hear the pucks making contact but I don’t know if it is some or all of them yet.loop-single-reply.phpJuly 26, 2016 at 12:13 am #3530The caliper needs to be removed from the bike and turned upside down to bleed completely even with a power bleeder. You’ll need to put something between the pads to mimic the rotor being in place.
loop-single-reply.phpJuly 26, 2016 at 5:16 am #3531Thanks for the Heads up, I did not know this.
READ THE EDIT ON BOTTOM OF PAGE!!!
I was doing some research about Brembo tech and ran across this article, please read it, I have learned not to trust everything on the web but in the second paragraph it says that Dot5 will mess up Brembo calipers and only Dot 3 or 4 should be used :blink:
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“B. All brembo braking products use natural-rubber base seals, and therefore are INCOMPATIBLE with DOT-5 SILICONE-based brake fluids. DOT- 5 SILICONE-based fluids react with natural-rubber seals to swell them WHICH CAN CAUSE SEVERE PISTON RETRACTION PROBLEMS. There is no cure for problems caused by DOT- 5 use other than complete seals replacement – USE ONLY DOT-3/4 NON-SILICONE TYPE FLUIDS such as CASTROLTM ‘LMA’ in your brembo components.(Yes, we know the cap on the rectangular master cylinders says “DOT 3 – 5 Fluids”-BUT PLEASE NOTE: Silicone DOT- 5 fluids are NOT generally in use in Europe, but Glycol-based “DOT-5.1” fluids ARE. Hence, the “DOT-5″ cap designation). For best braking performance, we recommend changing brake fluid twice a year. If the machine is to be stored in a damp environment (over the winter, say), we recommend installing fresh fluid before and after the storage period. At minimum service levels, glycol brake fluids MUST be completely changed at intervals not to exceed a period of 18 months.”
The full article can be viewed here…
http://cyclebrakes.com/html/brembo_tech_info.htmlEDIT: I was right not trusting the web. I called up QTI and their engineer said the paragraph is only pertaining to race products and what we have is a production based product. The paragraph does not apply to our calipers in anyway and DOT 5 is fine to use. She did strongly recommend not changing fluid types, if your using DOT 5 stay with it. …and thats the rest of the story…
Oh by the way…My brakes operate like Brand New now :cheer:
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