Sideways Tim Posted June 18, 2014 Share Posted June 18, 2014 I've replaced my master cylinder due to the old one sucking in air and since fitting the new one the brakes are basically a bit crap. They work, but it takes a hell of a lot of pedal pressure to stop. Could have a wrong un? I mean is there a difference between master cylinders that could cause this effect - bore or stoke or something? Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted June 18, 2014 Share Posted June 18, 2014 Yes, they come in different bore sizes. IIRC the Spitfire one would normally be 5/8" (0.625"). Fitting one with a larger bore (0.7 or 0.75" are the common alternatives) will give shorter pedal travel but need more pedal pressure. The size is normally marked on the body somewhere.Have you done anything else at the same time, like fitting different pads? That can make a huge difference.Nick Quote Link to comment Share on other sites More sharing options...
stevegt6 Posted June 18, 2014 Share Posted June 18, 2014 Obvious question :P ....Did you bleed brakes afterwards...?Does pumping the pedal once or twice give a better pedal...? if yes, then air in system most likelyIs your pedal rock hard from the start..? what pedal travel do you have.....little or lots...?Are brakes free....no sticky pistons or shoes or seized or collapsed rubber flex hoses...? or nothing hindering the travel of either pedal or mechanism..? Quote Link to comment Share on other sites More sharing options...
Sideways Tim Posted June 19, 2014 Author Share Posted June 19, 2014 Rest of the braking system is tip top. New hoses, newish pads, newish discs, new pistons and seals. It definitely stopped better before changing the master cylinder, but was proving impossible to bleed. Now the pedal feel is lovely and firm, but the actual stopping power is poor.I did cook the pads on an alpine descent last year, would that have any bearing? Quote Link to comment Share on other sites More sharing options...
stevegt6 Posted June 19, 2014 Share Posted June 19, 2014 Quote:I did cook the pads on an alpine descent last year, would that have any bearing?Depends on the pads - they may have glazed and hardened.... What pads..?MC could have wrong size (larger) seals in it - when i bought my GT6, many many moons ago, i had to really stand on the pedal to get any sort of braking (rather nervous 250 mile trip back with it) and it turned out wrong size seal kit had been put in.... Quote Link to comment Share on other sites More sharing options...
Sideways Tim Posted June 19, 2014 Author Share Posted June 19, 2014 Pads are Mintex 1144, so in theory they should be fine with the heat.M/C was a complete new unit, so seals should be correct. Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted June 19, 2014 Share Posted June 19, 2014 Nick_Jones wrote:Yes, they come in different bore sizes. IIRC the Spitfire one would normally be 5/8" (0.625"). Fitting one with a larger bore (0.7 or 0.75" are the common alternatives) will give shorter pedal travel but need more pedal pressure. The size is normally marked on the body somewhere.Have you done anything else at the same time, like fitting different pads? That can make a huge difference.NickI`d go with NickThere are a lot M/Cylinders around that are used on Land Rovers which I do believe are different in bore but look identical the Spits Quote Link to comment Share on other sites More sharing options...
Sideways Tim Posted June 19, 2014 Author Share Posted June 19, 2014 Tricky to measure the bore of the cylinders accurately, but it looks like the new one is actually slightly smaller than the old one :(I think I'll change the pads and see if that makes a difference. Quote Link to comment Share on other sites More sharing options...
.thumb.jpeg.b15b81ef10abeea1c3039ae03c4a9f3a.jpeg)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.