Ian Macquarie Posted July 17, 2002 Share Posted July 17, 2002 What diameter are the pistons in the standard brake calipers? Front Girling type 14? Rear Ford Sierra? and while we are at it the Caterham uprated rear? Thanks Ian Link to comment Share on other sites More sharing options...
philwaters Posted July 18, 2002 Share Posted July 18, 2002 Sorry I don't know the standard sizes but the uprated sizes are as follow: AP Caterham :- 41.3 & 38.1 Alcon (James Whiting) :- 38.1 & 34.9 Phil Waters Zetec is in and running wink.gif Link to comment Share on other sites More sharing options...
Graham Sewell Posted July 18, 2002 Share Posted July 18, 2002 I think AP have reconfigured their calipers as I could not see a 3mm difference in size between the pistons when I looked at them. However, they are slightly offset (front/back and distance from centre line). Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
Ian Macquarie Posted July 18, 2002 Author Share Posted July 18, 2002 Thanks Phil, that's the same info as I have (from James Whiting's site. What I was trying to find was the data for the other calipers and pistons so that I can make an informed judgement of the likely changes in brake balance / effort required with different caliper / master cylinder combinations. Whilst we are at it would someone like to confirm (or otherwise) that the master cylinder bores are.... Standard 5/8" Uprated 13/16" Ian Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted July 18, 2002 Share Posted July 18, 2002 Ian. I can't tell you the std. piston bore diameter, but the std pistons raised 'ring' (which bears against the back of the pad/shim plate) is 43mm dia. Link to comment Share on other sites More sharing options...
JAG Posted July 18, 2002 Share Posted July 18, 2002 The standard M14 Girling caliper is 48mm bore diameter and the Ford Sierra rear caliper is 43mm bore diameter. If the uprated brake sizes are correct then they will give a little bit more rear axle bias to the brake system. You would then need to be careful which pads you fitted to ensure that the rear axle doesn't lock first. Link to comment Share on other sites More sharing options...
Ian Macquarie Posted July 19, 2002 Author Share Posted July 19, 2002 JAG, Thanks for the info on piston sizes. I don’t follow your point about brake balance though – I had it as follows: Caliper Dia Total piston area Sierra rear 43 1452 M14 48 1810 Alcon front 38.1 & 34.9 2096 AP front 41.3 & 38.1 2480 I took this to give Front/rear splits of braking force (or at least force on the brake pads) to be as follows M14 / Sierra 55% / 45% Alcon / Sierra 59% / 41% AP / Sierra 63% / 37% This would mean that either of the upgrades would move the balance to more braking at the front and reduce the likelihood of locking the rears first. Is this correct or have I made some errors somewhere? Ian Link to comment Share on other sites More sharing options...
Ian Macquarie Posted July 19, 2002 Author Share Posted July 19, 2002 This was an attempt to get the spacing better - it didn't work! how do I get a "table" effect here? Edited by - Ian Macquarie on 19 Jul 2002 08:33:35 Link to comment Share on other sites More sharing options...
JAG Posted July 19, 2002 Share Posted July 19, 2002 Ian, you're dead right. I quickly ratioed the piston diameters and not resultant areas. Sorry for the misleading remarks. Link to comment Share on other sites More sharing options...
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