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Title: HR front disc - boosted front only? Post by: Dave_EH on March 10, 2005, 09:35:49 AM Hi guys,
I was in at the brake shop today getting some new lines made up and was told by an old school fella that HR front discs should only be boosted at the front. Have I misuderstood everyone the whole time? I was under the impression that the booster boosted all four wheels and the change in cylinder diameter and shoes at the rear would compensate for the front disc upgrade. He tells me I need to run a dual master or have a T piece that runs unassisted to the rear and assisted to the front. I'm a little confised now ??? I can't understand why the rear shoe and cylinder set up needs to be changed if the back isn't boosted anyway. Can someone set me on the right track please! Regards Dave Title: Re: HR front disc - boosted front only? Post by: Jockster on March 10, 2005, 01:34:37 PM While what he is saying is possible, the original HR brake system was boosted front and rear using a single circuit master cylinder. The advantage of what he is suggesting is that you will have a dual circuit brake system which is safer and shouldnt have to alter the rear wheel cyls providing the dual circuit master cylinder bore is the same diameter as the original master cylinder fitted to the car.
Cheers Jockster Title: Re: HR front disc - boosted front only? Post by: Fast_Eddie on March 11, 2005, 05:22:41 AM One way to do it is to run dual circuit brakes using a dual circuit master cylinder.
I am setting up my ute with such a system. It required resizing the hole in the firewall to mount the m/cyl, and two new nuts welded onto the pedalbox to allow for the different mounting holes on the m/cyl. You could get away without welding the nuts if you have a helper to work inside the car to assist in mounting the m/cyl. New brake lines for the front circuit were required from the m/cyl to the booster and then to the standard junction block on the subframe leg, which now has the rear take off blocked off. The lines to the rear brakes now bypass the junction block and join to the rear line at that point with an in line joiner. All the lines are being replaced with the smaller diametre pipe fitted to FB onwards - can't remember exactly what size it is, but most recommend it for disc brake upgrades. Hoppers Stoppers in Melbourne have been an excellent source of advice and I have purchased most of the parts through them. They can provide a far more professional assessment of the upgrade and recommendations for your application than I can. Regards Edward Title: Re: HR front disc - boosted front only? Post by: Dave_EH on March 15, 2005, 08:55:59 AM Thanks Edward and Jockster,
I shall keep the single m/cyl set up for the time being as I've just replaced everything. I shall look into the dual m/cyl set up in the future for an added piece of mind. I thought it was quite strange that only one person had ever told me that an HR came with a dual m/cyl set up! Next question: I've just picked up my new lines and for some odd reason the brake shop didn't bend them to shape like the templates I gave them - they are just straight. Do I need a special tool to bend these new lines (booster to m/cyl and booster to subframe T piece)? Regards Dave Title: Re: HR front disc - boosted front only? Post by: HARKO on March 15, 2005, 11:09:26 AM Dave ,It will bend relatively easy around a pipe or tube ,But do yourself a favour and price a pipe bending set or atleast one tool ,A four peice set cost me around $30 ...
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