Stoff Posted August 24 Share Posted August 24 For certification I've been required to retrofit a dual circuit brake master cylinder, unfortunately I don't have room for a booster between the firewall and the BMC. I do have a remote booster on the other side of the engine bay, but obviously I can only run one circuit through this. Will boosting just the front brakes result in my rear brakes doing bugger all, meaning I need two boosters? Or will it just make the pedal heavier because only half the system is boosted? Thanks in advance! Quote Link to comment Share on other sites More sharing options...
Tiger Tamer Posted August 25 Share Posted August 25 Does it have to be boosted or could you just change to a duel circuit MC with a different bore size. What make of car is it. Smaller light car shouldn't need a booster. 1 Quote Link to comment Share on other sites More sharing options...
Stoff Posted August 25 Author Share Posted August 25 It's an old Mazda B1600, about 1200kg, it's got a 4.6l Rover V8 in it, so wanting the brakes to feel good! Quote Link to comment Share on other sites More sharing options...
vk327 Posted August 25 Share Posted August 25 I've seen van master/boosters used a few times where space is an issue , hiace or L300(pic), gets the whole assembly out of the engine bay, could be an option to give dual circuit boosted 4 Quote Link to comment Share on other sites More sharing options...
Stoff Posted August 26 Author Share Posted August 26 Is this still actuated by the pedal? It wouldn't fit it under the dash, so I'd need to build a linkage to wherever it's mounted. If I was going to run a second booster I coul fit it under the deck which might be simpler. Quote Link to comment Share on other sites More sharing options...
Tiger Tamer Posted August 26 Share Posted August 26 Would something like this work for you Chase Bays Dual Piston Brake Booster Delete with Bolt-On 6:1 Pedal Rat — Speed Science I have used a hydraboost on a car before but I don't think it will take up much less space than a vacuum booster. I had a look at what guys use for the Sunbeam Tiger as well. They are a boosted single circuit system. They can fit a dual MC in the LHD cars but they seem to just boost the fronts when they do go dual circuit. 1 Quote Link to comment Share on other sites More sharing options...
Stoff Posted August 26 Author Share Posted August 26 Yea, just wondering if boosting the fronts only is a feasible option, or will it result in my rears not doing much... Hydro boost unit looks smaller, could work. Quote Link to comment Share on other sites More sharing options...
Tiger Tamer Posted August 26 Share Posted August 26 21 minutes ago, Stoff said: Yea, just wondering if boosting the fronts only is a feasible option, or will it result in my rears not doing much... Hydro boost unit looks smaller, could work. I hope I have not caused confusion. The link I provided is not a hydro boost. The hydro boost I fitted was on a Firebird. Photo attached . Quote Link to comment Share on other sites More sharing options...
Stoff Posted August 26 Author Share Posted August 26 Sorry i did look at the 6:1 unit, it unit looks cool, but getting up there price wise... Not really building a track car more of a cruiser, bit of fun. The hydro boost unit looks smaller than vacuum booster, and cheaper than the 6:1 unit so it could work. Quote Link to comment Share on other sites More sharing options...
vk327 Posted August 26 Share Posted August 26 19 hours ago, Stoff said: Is this still actuated by the pedal? It wouldn't fit it under the dash, so I'd need to build a linkage to wherever it's mounted. If I was going to run a second booster I coul fit it under the deck which might be simpler. have seen an l300 setup under dash of a mk2 escort , yeah pedal throw acts to push backwards on the booster instead of forwards, another way is to engineer a bracket with a bellcrank mechanisim and have booster sideways under dash like these https://www.rrs-online.com.au/under-dash-booster-kits Quote Link to comment Share on other sites More sharing options...
Kiwibirdman Posted August 27 Share Posted August 27 On 25/08/2024 at 09:15, Stoff said: For certification I've been required to retrofit a dual circuit brake master cylinder, unfortunately I don't have room for a booster between the firewall and the BMC. I do have a remote booster on the other side of the engine bay, but obviously I can only run one circuit through this. Will boosting just the front brakes result in my rear brakes doing bugger all, meaning I need two boosters? Or will it just make the pedal heavier because only half the system is boosted? Thanks in advance! If you have disc on the front and drums on the back boosting only the front should be fine. In most cars the front brakes do 90% of the work. Discs require higher pedal pressure to work than the old drums. It doesn't matter too much if your back brakes aren't that effective, the certifier is much more interested in will it stop up to standard and do the front brakes lock up first. Quote Link to comment Share on other sites More sharing options...
RXFORD Posted August 27 Share Posted August 27 Whats the actual issue? You said you can't fit a booster between firewall and m/c? Is that because it would hit wheel tubs or something or would the booster diam be an issue and hit the engine? If its a booster diam vs engine issue, a way I have often got around this on minitrucks with air suspension or engine swaps Is to use a old Mazda 121 or Ford Festiva booster. They are 6.5" diam and 3.5" deep. Common Nissan 2-bolt master cyls bolt to them so its easy to find a bore size to suit your needs. Can also orientate the vac barb fitting whichever way you want. 5 Quote Link to comment Share on other sites More sharing options...
sr2 Posted September 7 Share Posted September 7 On 25/08/2024 at 09:15, Stoff said: For certification I've been required to retrofit a dual circuit brake master cylinder, unfortunately I don't have room for a booster between the firewall and the BMC. I do have a remote booster on the other side of the engine bay, but obviously I can only run one circuit through this. Will boosting just the front brakes result in my rear brakes doing bugger all, meaning I need two boosters? Or will it just make the pedal heavier because only half the system is boosted? Thanks in advance! I’m presuming you’re running standard brakes with non-ventilated discs on the front, drums on the rear and, a single circuit master-cylinder and a Hydrovac (inline) booster? (From memory there were some B1600’s with front drums but please don’t quote me). Short answer is boosting the front only will result in a serious front brake bias, it won’t make the pedal heavier it will just significantly reduce braking to the rear to the point where quite possibly it becomes an issue at WOF time. My recommendation (i.e. cheapest path of least resistance) would be to go for the twin boosters option; a 2nd unit under the deck would work well – just make sure the air inlet is well shielded from water splashes. A twin circuit master-cylinder running two Hydrovacs will give you the same amount of boost and a similar pedal feel to a single Hydrovac boosting a single circuit master cylinder system, (presuming both single and dual master-cylinders have the same bore, and the Hydrovacs are the same). As an added bonus if in the future you are looking at a brake upgrade (RX7 would be an obvious choice) it’s relatively easy to adjust (or compensate) front/rear bias by changing bore and/or control sizes on the respective boosters. Hope this helps. Quote Link to comment Share on other sites More sharing options...
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