Toymods Car Club Inc: Tech & Conversions => JAP Brake for AE86

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dorikin
Regular

I supported Toymods

Location:
NE Melbourne
Registered:
May 2002

Re: JAP Brake for AE86	Mon, 03 June 2002 10:43

Yeeehah, a rebore is just like having you current master cylinder reconditioned, except when it comes back, it's bigger!!! quite often a reconditioned master cylinder will have been resleeved... that is the inside surface of the clyinder where the piston slides is so badly worn that a simple hone (light linish of the surface by removing only a bee's dick of material) will not adequatly clean the surface of the damage (may be damage due to water, scoring, etc) so instead they bore out the cylinder and insert a sleeve that has the same internal dimentions as the original master cylinder. the reason this is so important is that in a master cylinder it's all about the condition of the bore, not the piston as the seals actually slide and seal against the bore, not the piston (it's opposite for brake calipers, but that's a slightly different issue at the moment) now the idea a reboring the master cylinder to increase the diameter of the bore is a very good idea. as you can imagine, for a conversion, if all the external dimentions of the master cylinder remain as they were intended from the factory, there are no concerns with additional modifications when refitting the "reconditioned" master cylinder. now before the actual cylinder bore can be machined to a greater internal dimention, there first must be available an adequate piston to suit the application... without this availability a new custom piston will need to be machined - as well as the matching seals to fit the piston (this incurs further cost - and where it becomes into serious money spending) so with an adequate piston and seals available the bore is machined out and the new piston and seal fitted... it's actually a very straight forward operation otherwise. the importance of finding an appropriate piston is not just about the diameter of the piston. there are clearance dimentions associated with the back of the piston and where it meets the rod that pushes it from the booster. if the depth of the recess that this rod sits against is not exactly correct then one of two things will occur. if the recess is too shallow then the rod will always have pressure against it and may mean that the piston will not return back completely and can lead to the brakes not releasing... if the recess is too deep then there will be too much pedal travel before the piston in the master clyinder moves and braking begins... now don't ask me what 15/16' piston was used in my TA22 master cylinder as i simply don't know. they went to 15/16' size as there was a piston available to suit, not needing to custom fabricate a new piston. i sent the master cylinder off to ABS in airport west (Melbourne) and it came back the next day all new and finished (they even nickle plated the housing - looks sweet)... that's all i can think of for now... well worth it it think for $200 odd i hope i kept it simple enough, sorry if i haven't, just ask and i'll clarify. don't be afraid of brake places that don't know what this operation is about, just walk away... somone who knows what this is all about will know right away... if it comes to the point where you cannot find any help at all, i'll offer to arrange to have your master cylinder (sprinter i think???) modified where mine was and we'll arrange delivery... catch... [Report message to a moderator]

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