alan.gilbert_6384 Posted January 22, 2021 Report Share Posted January 22, 2021 Hi All, Hope everyone is well, safe and playing with their cars. I have searched for this idea but couldn't find anything so thought I post a new thread. Has anyone upgraded a single brake system on a spitfire, to a dual system ? Does anyone know the pros and cons of this modification (insurance issue's etc) etc ? I think (that's the best of saying "I don't really know";) the only limiting factor is the need to cut the bulk head to fit the bigger master cylinder ? Not sure if this is feasible on the pre dual system cars, mines a 76. Cheers. Link to comment Share on other sites More sharing options...
JohnD Posted January 22, 2021 Report Share Posted January 22, 2021 There are two purposes to a dual brake system. One is as an alleged safety factor, the other to allow the balance between the front and rear brakes to be altered, according to road and driving conditions. The first is borrocks. Lose the front brakes and you have only rear braking, which will precipitate a spin as soon as you turn the wheel. Lose the back brakes, and on most cars you loose very little braking ability, certainly in an emergency stop when all the weight of the car is thrown forward. Less dangerous, certainly than the first case, but ineffective. The first production car with split brake system was the Austin Princess, which was even more bizarre as while it had four-pot front calipers, each pair of pistons was on a different circuit. The two circuits went separately to the rear brakes, so if one failed, the rears failed on one side only, while the fronts were less effective on the diagonally opposite side! Trumph used a simpler system with a 'tandem' master cylinder and a front-rear split. The second demands two separate master brake cylinders, operated by a single pedal on an adjustable 'balance bar', so that the relative pressure in the front and rear circuits may be adjusted. IMHO this is only for highly skilled drivers, which of course we all are, but on the track or rally stage. On the road there should be no need for such adjustment, which can allow you to drive as near to the edge of disaster as possible, as no one should drive like that on the highway! John Link to comment Share on other sites More sharing options...
RogerH Posted January 22, 2021 Report Share Posted January 22, 2021 I thought a dual system operated diagonally opposite brakes. FNS & ROS - FOS & RNS so you have one front brake and one rear brake. Roger Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 22, 2021 Report Share Posted January 22, 2021 i guess the simplest way is to copy the late 1500 spitty .which has split line tandem master and a PWDA valve as used on later cars incl midget 1500 but its of little improvement more a sales gimmick in the day moderns are a different kettle of fish spitfire 1500 was just split front and rear one new 1500 owner locally expired on my drive , the rears leaked like a sieve the pwda valve seized so it didnt cut the rears off and he thought a pedal on the floor was normal for an old car if you need to buy a pdwa stag and late mini are far cheaper than spitfires Pete Link to comment Share on other sites More sharing options...
NonMember Posted January 22, 2021 Report Share Posted January 22, 2021 2 hours ago, RogerH said: I thought a dual system operated diagonally opposite brakes. FNS & ROS - FOS & RNS so you have one front brake and one rear brake. Modern ones are but the early ones (including anything Triumph fitted) weren't. The problem with the diagonal split is that if you do lose one circuit, you then have one front and one rear brake operational. The car still tends to spin, pulls REALLY badly, and yanks the steering wheel out of your hands. The only way this can be made safe is to adjust the suspension and steering geometry so that it's all wrong, giving horrid heavy steering with no feel. To compensate for that, modern cars all have power steering. 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 22, 2021 Report Share Posted January 22, 2021 Hi, Single system is dangerous if you have a leak at any corner. Tandem is not. Simples. Ditch the single master cylinder. Cheers, Iain. Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 22, 2021 Report Share Posted January 22, 2021 strangely the some 2000 saloons had split line but later models went back to single assume a cost driven improvement !!! Link to comment Share on other sites More sharing options...
rlubikey Posted January 23, 2021 Report Share Posted January 23, 2021 12 hours ago, SpitFire6 said: Single system is dangerous if you have a leak at any corner. Tandem is not. Agree with that! Having had this happen to me on my (dual circuit) Spit, I would also choose a dual circuit over single any time. You only find out when you're actually braking that there's a problem and if it happens, having the presence of mind to go for the handbrake is one of those things that takes a second or two to percolate through the old grey cells. The brake pedal goes further down (because you have no pressure in half the MC) but you still have some retardation. If you're driving like the road is your personal race track then that won't be enough. If you're being a bit more leisurely it probably will. I converted my 1977 Spit with bits from my '79 model when it went to that great scrap yard in the sky. You need the MC of course, plus the lower and steeper angle bracket (to hold the MC lower so it doesn't touch the bonnet) and you already know about the dish in the bulkhead so it clears there (like the one behind the battery for US models which had dual circuit years earlier). I simply declared the change to the insurance company - no problem there. Then the standard setup is front one circuit, rear the other. As has been said, less likely to spin when you panic and hit the pedal hard - which you will!!! I did not fit the PDWA (Pressure Differential Warning .... don't know what the last one is) as it only illuminates a silly little light on the dash - which you probably won't even notice. You'll know something's wrong because your foot WILL feel the difference! Cheers, Richard Link to comment Share on other sites More sharing options...
alan.gilbert_6384 Posted January 23, 2021 Author Report Share Posted January 23, 2021 Hi, thanks, I don’t suppose you have any pictures of your installation? I did think that I would have to fit the PDW thingy does it do anything else other that light up the warning lamp, reason for asking is I remover years ago my mini (when it was a bloody mini) had a pressure reducing valve one the rear circuit on the rear subframe. Only found out about it after spending days and days unsuccessfully trying to bleed the bloody thing. Found out you have to go really slowly on the down stroke to stop it locking off 😏 Link to comment Share on other sites More sharing options...
rlubikey Posted January 23, 2021 Report Share Posted January 23, 2021 Alan, I believe it's only function is as a switch for a puny little light on the dash - someone please correct me if I'm wrong. Here are some photos which may help - blue things are off the dual MC donor car. I had forgotten that the strengthening web is also different (lower) on the dual MC cars. The siamesed brake strengthening web and clutch bracket is to accommodate the 6-cylinder PI plenum. Sorry about the flash rust - that shower really caught us on the hop! Cheers, Richard 2 Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 23, 2021 Report Share Posted January 23, 2021 Any help, Alan? 2 Link to comment Share on other sites More sharing options...
alan.gilbert_6384 Posted January 23, 2021 Author Report Share Posted January 23, 2021 Brilliant thanks both, bit of long term project for when the weather gets better, and a chance to source some parts etc, Link to comment Share on other sites More sharing options...
JohnD Posted January 23, 2021 Report Share Posted January 23, 2021 Alan, My comments above were the result of fitting dual circuit to my race Vitesse, Silverback. It only needed the recess in the bulkhead to fit. I did it to enable me fitting a brake pressure valve, like this in the rear line, as an alternative way to balance the front and rear brakes. In fact, I found that I'm not that highly skilled a driver, and either it made no difference, or I couldn't adjust it in the heat of competition. The seperate rear circuit also made possible a hydraulic hand brake, which was great! No need to faff with cable tensions, and while the cable is essetail for MoT, it's mere presence was enough to satisfy the examiner, as the handbrake worked anyway. If you want to go as far as that, fine, but as I said above, there is little point in a dual system by itself. Brake failure should never happen in a well-maintained car, and is rare as a cause of incidents in cars. Tyres are far more common. Commercials suffer from brake failure but they have different brake systems. JOhn 1 Link to comment Share on other sites More sharing options...
alan.gilbert_6384 Posted January 23, 2021 Author Report Share Posted January 23, 2021 Cheers John, good to know also. Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 24, 2021 Report Share Posted January 24, 2021 If you have a single system; Fit a level switch. Mine would have given me plenty of warning if I had wired it up. Bulkhead had to be modified to fit Tandem but need to figure out how to measure both levels as a warning as do not want a PDWA. Link to comment Share on other sites More sharing options...
alan.gilbert_6384 Posted January 24, 2021 Author Report Share Posted January 24, 2021 Ah cheers that could be very good alternative. Has anybody done this already, ie is their a cap that fits with the switch in place ? Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 24, 2021 Report Share Posted January 24, 2021 there are a good few plastic res caps with switches but here is one you could have a go at fitting in any cap as an idea https://www.carbuilder.com/uk/brake-fluid-float-switch Link to comment Share on other sites More sharing options...
alan.gilbert_6384 Posted January 24, 2021 Author Report Share Posted January 24, 2021 Cheers Pete, that was quick, did you have it in back pocket 😉 Link to comment Share on other sites More sharing options...
Peter Truman Posted January 24, 2021 Report Share Posted January 24, 2021 1 hour ago, alan.gilbert_6384 said: Cheers Pete, that was quick, did you have it in back pocket 😉 He and Lindsey know everything or car find it reckon they must be on commission , bet they wish they were! Ha Link to comment Share on other sites More sharing options...
PeteH Posted January 25, 2021 Report Share Posted January 25, 2021 Taking all into account. The fitting of a reservoir float, Is likely the the better option, that and Keeping on top of Brake maintenance?. Speaking of brakes. I am "informed" that some L-R? master cylinders are a direct "swop" for the Triumph ones? Can anyone confirm. (part no`s would be nice too, especially if the L-R? part comes with a float?). I have just cleaned my extremely "grotty" O/E ones, but I am not happy with the results. Having changed the full brake pipework to Copper/Kunifer, and with New Calipers and Rear Slaves and hoses. I may as well go the "whole hog". P.s. Replacing the clutch Master is on the cards too. Pete Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 25, 2021 Report Share Posted January 25, 2021 I know that for Heralds they used to sell a similar-looking master cylinder but it was angled whereas the Herald versions were straight up when fitted - can't find any this morning, only the Clutch MCs which look the same but are listed with a 3/4 bore. Some of the later ones, seems to be late Series 3 onwards, are dual-circuit but the bracket mounting is sideways in comparison to our cars. I've looked at the larger dual circuit reservoirs on a number of sites but don't see any with any kind of float-related warning. On a slightly different point, I see a seller on eBay at present selling Triumph master cylinders with a '3/4 bore modification' but even the seller has a disclaimer to say they're sold as a modification and he cannot give any advice as to suitability. Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 25, 2021 Report Share Posted January 25, 2021 we got a Mcly and plastic reservoir form merlin motorsports larger reservoir , just change the pushrod over not angled but with far more capacity and see thro res makes checks visual and easy . just lift bonnet and peek something like these Link to comment Share on other sites More sharing options...
PeteH Posted January 25, 2021 Report Share Posted January 25, 2021 I can go out and Measure. But anyone confirm the correct dia for the Herald?. (save me unlocking and getting cold). There are similar looking M/C on offer but with 0.7 and 0.75 dia bore?. thaones I have LOOK smaller?. Pete Link to comment Share on other sites More sharing options...
Clive Posted January 25, 2021 Report Share Posted January 25, 2021 1 hour ago, PeteH said: I can go out and Measure. But anyone confirm the correct dia for the Herald?. (save me unlocking and getting cold). There are similar looking M/C on offer but with 0.7 and 0.75 dia bore?. thaones I have LOOK smaller?. Pete Do you mean bore? herald and spit are 5/8 or 0.625. A 0.7 will feel hard and a little wooden, a 0.75 rather more so. (25 and 44% respectively) 1 Link to comment Share on other sites More sharing options...
johny Posted January 25, 2021 Report Share Posted January 25, 2021 You might prefer the larger size M/C if youve got a servo fitted.... 1 Link to comment Share on other sites More sharing options...
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