falk5150 Posted November 21, 2012 Share Posted November 21, 2012 Er...as above really chaps. Just wondered how all d'guy's that have converted due to lack of space etc find the brakes to live with on the road really. Quote Link to comment Share on other sites More sharing options...
611 Posted November 21, 2012 Share Posted November 21, 2012 Will let you know when i get the car running :-) I have gone twin master cylinder, one front and one back with big wilwood fronts and ford 4x4 rear calipers so i hope this will be enough to stop it! Andy Quote Link to comment Share on other sites More sharing options...
bris jas Posted November 21, 2012 Share Posted November 21, 2012 Just took mine out the garage today for the first time after fitting bias pedal box, to be honest brakes aren't great at the moment although new disc and pads all round need bedding in (i hope). Touch a lot of time getting everything to fit propally. Quote Link to comment Share on other sites More sharing options...
Titson Posted November 21, 2012 Share Posted November 21, 2012 Twin remote servo's on rally car or one large enough on a road car, brakes are pigs without the servo assistance, unless you have legs like Popeye!! Quote Link to comment Share on other sites More sharing options...
bones Posted November 21, 2012 Share Posted November 21, 2012 My brakes are spot on with no servo, you have to fit the correct size master cylinders though. I have done a disc conversion on the rear of my car and forgot to adjust the bias, very exciting braking into a corner and have the front locking up at about 80mph. Quote Link to comment Share on other sites More sharing options...
bris jas Posted November 21, 2012 Share Posted November 21, 2012 What size master cylinders did you fit? My box came with 2x 0.70 for the rear brakes and clutch and 0.625 for the fronts I have 280mm volvo discs and calipers on the back and 280 discs with Saab 9-3 turbo calipers on the front, as mentioned b4 brakes didn't feel to good and a lot of travel on the front cylinder. Quote Link to comment Share on other sites More sharing options...
Ems Posted November 21, 2012 Share Posted November 21, 2012 If I remember correctly I've got .625 front and .70 rear. I've got wilwood midlites on the front and sierra calipers on the back and find the braking excellent, with not much pedal travel. Quote Link to comment Share on other sites More sharing options...
bones Posted November 21, 2012 Share Posted November 21, 2012 I think I was lucky with mine as I haven't had to change them they were spot on from the get go. I have 0.625 on the front and 0.750 on the rear. I'm sure there is a way to work out what size master cylinders you need by knowing the piston sizes of the callipers, not to sure to be honest as mine were bolted on and have been fine ever since. My pedal doesn't have to travel much to get the brakes working and I don't have to stand on them to stop the car. Quote Link to comment Share on other sites More sharing options...
611 Posted November 22, 2012 Share Posted November 22, 2012 As i said, not run mine yet but the guy at wilwood tech worked it out for mine (so i hope he is right ;-) 7/8 on front with wilwood dynalite 4 pots and 3/4 on rear with sierra 4x4 calipers, and im using wilwood pedals, they have a lot more throw than standard ones and you have a bias adjuster. The bigger the master cylinder internal size the more fluid you have to push through to get the brakes to work so can be soft pedal and will be less effective, the smaller internal size the less it pushes through for the same force, but can be harder pedal if too small so its getting the balance right. Im sure one of the brake suppliers must have a conversion chart so you can work it out? Andy Quote Link to comment Share on other sites More sharing options...
Retro Power Posted November 24, 2012 Share Posted November 24, 2012 Best to ask Curt himself, but I found the brakes in the Ascona 400 rep we built for him very good without servo. That has volvo 740 discs at the front (286mm IIRC) with saab 9-3 turbo calipers, and nissan 200sx rear discs with the 200sx calipers. Front master cyl is 5/8" bore, rear 3/4" bore. Yes you do have to push them, but pedal feel is excellent, very solid, progressive and easy to feel lockup onset with none of the squashy feel that modern cars have which I hate! Quote Link to comment Share on other sites More sharing options...
Retro Power Posted November 24, 2012 Share Posted November 24, 2012 As i said, not run mine yet but the guy at wilwood tech worked it out for mine (so i hope he is right ;-) 7/8 on front with wilwood dynalite 4 pots and 3/4 on rear with sierra 4x4 calipers, and im using wilwood pedals, they have a lot more throw than standard ones and you have a bias adjuster. The bigger the master cylinder internal size the more fluid you have to push through to get the brakes to work so can be soft pedal and will be less effective, the smaller internal size the less it pushes through for the same force, but can be harder pedal if too small so its getting the balance right. Im sure one of the brake suppliers must have a conversion chart so you can work it out? Andy Not sure quite what you mean, but I think you may have the wrong idea (or I have misread!) also I would say that 7/8" is too big for the fronts, you would almost certainly want smaller for the fronts than the rears (as a generalisation, it will obviously depend on caliper size, but its a pretty solid rule of thumb) For a given caliper, a smaller master cylinder will give greater brake effect, less pedal effort, longer pedal travel and less "feel". A bigger cylinder will give less brake effect (for given pedal effort obviously), more pedal effort, shorter pedal travel and more "feel" Quote Link to comment Share on other sites More sharing options...
bris jas Posted November 25, 2012 Share Posted November 25, 2012 As mentioned i do have .625 master cylinders on the front with saab 9-3 turbo calipers. The problem i've got is the front cylinder has excessive travel and the bias adjuster cable hits the accelerator pedal. I've bleed the fronts about 10 times but no difference, what i have found is the front outer pads sit about 4mm off the disc so i think this travel to the disc is what is causing the problem with the master cylinder travel, is there away i can reduce this gap as looking at the rears they sit no more than 1mm off the discs Quote Link to comment Share on other sites More sharing options...
611 Posted November 25, 2012 Share Posted November 25, 2012 (edited) Im no tech expert on brakes but this is info from wilwood. (so my post might not have been a bit muddled in the difference between hard and spongy pedal) but im not sure about the front cylinder being smaller than the back? as the fronts would be 4 pot and the rear a single pot sliding caliper? the smaller front would run out of fluid if it was to small and bottom out? and wouldnt the backs lock up before the fronts? 'Generally speaking, if the master cylinder bore is too large, the driver will feel a very hard pedal feel with minimal pedal travel, and will have a difficult time generating the necessary pressure to effectively operate the brake system. If the master cylinder bore size is too small, the driver will be able to generate a lot of pressure, but the pedal may have an excessively long stroke or a very spongy feel. And if the bore size is way too small, the pedal or master cylinder may bottom out before enough volume is pumped to operate the calipers. The best advice would be to consult with the manufacturer of the brake system you will be using and work with them to pick the right size for your application.' Edited November 25, 2012 by 611 Quote Link to comment Share on other sites More sharing options...
Retro Power Posted December 7, 2012 Share Posted December 7, 2012 Im no tech expert on brakes but this is info from wilwood. (so my post might not have been a bit muddled in the difference between hard and spongy pedal) but im not sure about the front cylinder being smaller than the back? as the fronts would be 4 pot and the rear a single pot sliding caliper? the smaller front would run out of fluid if it was to small and bottom out? and wouldnt the backs lock up before the fronts? 'Generally speaking, if the master cylinder bore is too large, the driver will feel a very hard pedal feel with minimal pedal travel, and will have a difficult time generating the necessary pressure to effectively operate the brake system. If the master cylinder bore size is too small, the driver will be able to generate a lot of pressure, but the pedal may have an excessively long stroke or a very spongy feel. And if the bore size is way too small, the pedal or master cylinder may bottom out before enough volume is pumped to operate the calipers. The best advice would be to consult with the manufacturer of the brake system you will be using and work with them to pick the right size for your application.' No the rears would be LESS inclined to lock up before the fronts if they had a BIGGER master cylinder feeding them. I agree there would be a problem if the cylinder ran out of travel before the fronts were applied, but with a 5/8" cylinder feeding a variety of 4 pot calipers and various large single piston calipers I have yet to have this problem, pedal travel on all the setups I have done this way have been fine, and have been adjustable to achieve correct front to rear balance as per VOSA calculations Quote Link to comment Share on other sites More sharing options...
Retro Power Posted December 7, 2012 Share Posted December 7, 2012 As mentioned i do have .625 master cylinders on the front with saab 9-3 turbo calipers. The problem i've got is the front cylinder has excessive travel and the bias adjuster cable hits the accelerator pedal. I've bleed the fronts about 10 times but no difference, what i have found is the front outer pads sit about 4mm off the disc so i think this travel to the disc is what is causing the problem with the master cylinder travel, is there away i can reduce this gap as looking at the rears they sit no more than 1mm off the discs bloody eck!! 4mm off the disc!!! I'm surprised you have any brakes at all!!! Yes there is a major problem there, and I have no idea what could cause that to happen!! The seal pullback, which is what is supposed to pull the brakes off after appliation, is less than 1mm, so something else is pushing them back...... You've fitted lock stops havent you? If you use those calipers then on full lock the wishbone pushes the caliper back Quote Link to comment Share on other sites More sharing options...
bris jas Posted December 7, 2012 Share Posted December 7, 2012 Found the problem why they sat off the disc 4mm, we had put the retained clip on the wrong face if you know what i mean, as this was how the calipers were set up when i bought them (second hand). So pads sit where they should now, i tested the brakes last weekend at my local mot garage and we couldn't get the fronts to lock up, the pedal felt to be honest a bit spongey although we have bleed the brakes many times with a suction pot and pumping the pedal. Any ideas? The cars ready to go apart from the brake problem Quote Link to comment Share on other sites More sharing options...
Retro Power Posted December 7, 2012 Share Posted December 7, 2012 not that it would make the brakes feel spongy, but is the bias bar set up right? i.e. with a couple of mm between the tube and the clevises each side, and wound so its 2/3 ish towards the front cylinder? Was is spongy before you used the suction pot? I ask as its quite easy to accidentally invert the master cyl seals using one of those, which if it was on one cylinder only could give a spongy feel and lack of brakes at one end of the car. beyond that it's just making sure that there are no air traps in the system (bleed nipples absolutely the highest point on the caliper where its installed, know the fronts will be ok but don't know what setup you have on the back) Certainly we've not had any sponginess issues with bias bar non servo setups, quite the opposite its normally a bit solid feeling if you are used to modern car brakes! Quote Link to comment Share on other sites More sharing options...
bris jas Posted December 8, 2012 Share Posted December 8, 2012 not that it would make the brakes feel spongy, but is the bias bar set up right? i.e. with a couple of mm between the tube and the clevises each side, and wound so its 2/3 ish towards the front cylinder? Was is spongy before you used the suction pot? I ask as its quite easy to accidentally invert the master cyl seals using one of those, which if it was on one cylinder only could give a spongy feel and lack of brakes at one end of the car. beyond that it's just making sure that there are no air traps in the system (bleed nipples absolutely the highest point on the caliper where its installed, know the fronts will be ok but don't know what setup you have on the back) Certainly we've not had any sponginess issues with bias bar non servo setups, quite the opposite its normally a bit solid feeling if you are used to modern car brakes! I think at first the gap between the tube and the clevises each side was to big, i have now reduced this to a couple of mm both sides as i was finding the pedal was trying to twist under pressure. The bias bar is cocked towards the driver on the front brake side as i've seen people do on different sites. The pedal was spongey before we used the suction pot. Im also thinking now that the spongey feel could part to do with the pedal pivot mount flexing which i have now strengthen which was happening because the gap between tube and clevises was to big allowing it to twist. All these adjustments i have done last week, so the plan is to bleed the system again this week the old fashioned way, foot on pedal tube in jar, i'll put a post up with the result. Fingers crossed! 1 Quote Link to comment Share on other sites More sharing options...
bris jas Posted February 10, 2013 Share Posted February 10, 2013 I think at first the gap between the tube and the clevises each side was to big, i have now reduced this to a couple of mm both sides as i was finding the pedal was trying to twist under pressure. The bias bar is cocked towards the driver on the front brake side as i've seen people do on different sites. The pedal was spongey before we used the suction pot. Im also thinking now that the spongey feel could part to do with the pedal pivot mount flexing which i have now strengthen which was happening because the gap between tube and clevises was to big allowing it to twist. All these adjustments i have done last week, so the plan is to bleed the system again this week the old fashioned way, foot on pedal tube in jar, i'll put a post up with the result. Fingers crossed! Been a while but found that when you pushed the brakes the front cylinder wasn't returning all the way so the pedal was slack on that side, leave it for an hour it would then return. Cylinder sticking any idea what causes this? Quote Link to comment Share on other sites More sharing options...
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