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Title: Rear Brakes with a HR disc brakes Post by: Flamed_FE on October 11, 2002, 08:41:01 PM I'm having troubles with my rear brakes locking up. I am running a HR disc brake front end (with booster) and a drum rear end from a HR that had drums all round.
A club member said that they thought the rear brakes from a disc brake car where different to those of a drums all round car. Can anyone confirm and give me details? Is there a mod I can do to my current rear setup to suit a disc front end? Title: Re: Rear Brakes with a HR disc brakes Post by: FC-V8 on October 11, 2002, 11:36:40 PM Hi
Your rear wheel lockup is due to the brakes being out of proportion because when you use a HR disc front end you need to use the rear drum setup that goes with it. A HR with drum brakes all round uses a different size wheel cylinder than a HR with disc's on the front. The right size wheel cylinder to suit the disc's is 9/16in. cheers Glenn Title: Re: Rear Brakes with a HR disc brakes Post by: RET on October 11, 2002, 11:41:08 PM The other alternative is to fit a proportioning valve to the rear brake line to reduce the pressure going to the drums. A competent brake place should be able to do this for you.
Title: Re: Rear Brakes with a HR disc brakes Post by: fcfromscratch on October 12, 2002, 02:44:18 AM Hey Flamed_FE,
one other thing you'll need to know if you go down the path of changing the wheel cylinders is that the two set-ups use different brake shoes. the shoes for the 9/16" wheel cylinders have short, "blunt" pushrods rather than the slotted pushrods that you would currently have and so the shoes for the 9/16" cylinders have more "meat" on the web of the shoe....the "drum brake front" rear shoes will NOT match the 9/16" wheel cylinders. (ask me how I know...... DOH!!) Brad Title: Re: Rear Brakes with a HR disc brakes Post by: Flamed_FE on October 12, 2002, 03:10:10 AM I'll start investigating the port'ing valve first then.
Until then little one's car seat will have stay in the family wagon! :'( Title: Re: Rear Brakes with a HR disc brakes Post by: Flamed_FE on October 12, 2002, 04:21:53 AM Would this work?
If I got a split system off an early Kingswood and run the front to the booster and then to the front brakes and the rear directly to the back brakes, as per the attached diagram. Would that fix the problem or would it just be opening a whole new can of worms Title: Re: Rear Brakes with a HR disc brakes Post by: gree on October 12, 2002, 05:09:02 AM as far as i am aware, and i could be wrong, but i think if you are running rear brakes that come from a non-vaccuum boosted system (that have the correct size cylinders for this purpose like yours does) you only have to boost the front circuit. that way both the discs and drums get the stopping power they were designed for.
to me your solution would work, i have a friend who is doing pretty much the same thing with a commodore booster. again - this is just from things i have heard.... Title: Re: Rear Brakes with a HR disc brakes Post by: FC2104 on October 12, 2002, 06:33:58 AM Gree,
You are right in what you said but.. the only problem is if he is running a single circuit master cylinder (standard HR) the he can not just boost the front if he changes to a dual circuit master cylinder then he can boost the front and leave the back as per standard drums. Same as was use on early model Falcons (XR XT)and Valiants A dual master cylinder like HT,HQ,XA as long it has a 1" bore the same as HR and was fitted with discs Dean :P Title: Re: Rear Brakes with a HR disc brakes Post by: mcl1959 on October 12, 2002, 07:41:45 AM Alan, you are not really fixing the problem by changing to a dual circuit brake system, you are hiding the problem by boosting the front brakes.
I would recommend you buy a pair of disc rear cylinders and shoes and the problem is solved correctly. If you contact Hoppers Stoppers and mention that you were referred by me - you will get an excellent deal. Brake cylinders and shoes are not expensive items and are easy to fit. However changing to a dual circuit system is a good move since it is much safer. But be aware that it is not just a simple bolt up deal. Ken Title: Re: Rear Brakes with a HR disc brakes Post by: Flamed_FE on October 15, 2002, 03:32:50 AM Followed Ken's advise and spoke with Peter at Hoppers Stoppers.
$95 for the cylinders and pads :D Can't complain about that!! And Peter wasn't stingy on the advise either. Would recommend him to anyone in Melb. Thanks Ken for the pointer Alan Title: Re: Rear Brakes with a HR disc brakes Post by: Flamed_FE on August 20, 2003, 07:01:58 AM refresh for vin
Title: Re: Rear Brakes with a HR disc brakes Post by: nicko on August 20, 2003, 11:38:19 AM Hi,when we used to put the volvo disc brake rear ends into fe-fc's and fx-fj's with HR disc fronts we used to take the proportioning valve from HQ's that are located on lower firewall of HQ, very easy to do with a good tool set and a flaring tool, otherwise just use the backing plates and brake shoes and drums from a HD -HR with disc front
Title: Re: Rear Brakes with a HR disc brakes Post by: fastjbav6 on August 20, 2003, 01:30:24 PM Do'nt forget to remove the residue line pressure valve in the HR brake master cylinder when fitting disc brakes. Only master cylinders for all wheel drums and for clutch have the valve fitted.
Regards Seb :) Title: Re: Rear Brakes with a HR disc brakes Post by: Dr_Terry on August 21, 2003, 06:53:45 AM Hi Guys.
Almost correct, the residual pressure valve is only fitted to the master cylinder on 4 wheel drum cars. This valve is not fitted to any clutch master cylinder or to the brake master cylinder on front disc braked cars. Regards. Dr Terry. Title: Re: Rear Brakes with a HR disc brakes Post by: fastjbav6 on August 21, 2003, 10:17:39 AM Sorry for the mis-information, ( it was late that nite), when buying new master cylinders for the HR there is a sticker on the master cylinder body advising to be used for 'DISC BRAKES & CLUTCH'. I think it was PBR that stated this.
Thanks for picking that up Dr_Terry. Regards Seb :) |