Ludwig Posted June 4, 2008 Share Posted June 4, 2008 Hi All,Can anyone tell me what the score is regarding the correct brake master cylinder for the Mk3 Spitfire? Am I right in thinking originally it was GMC224, but that appears to be unavailable nowadays, therefore suppliers tout the clutch master cylinder GMC205 as a direct replacement?If so, is it safe to use as a brake master cylinder? A side issue - I have an extension for the GMC205, I think it was for the overseas (Scandinavian/colder?) market. I think it increases the fluid capacity approaching that of the GMC224, is it advisable to stay clear of that?Thanks in anticipation!!Alex Link to comment Share on other sites More sharing options...
Clive Posted June 5, 2008 Share Posted June 5, 2008 the extension was used on herald too, it provides the extra fluid capacity for disc brakes (as opposed to drums). So if you use clutch master, you need the extension. But there are new brake masters out there, guess they may have the plastic resevoir? Better quality ones (willwood) are available too as a direct replacement from motorsport suppliers. Not used those myself, but if I do need a new one, thats where I will go. They are cheaper too.Std bore is 0.65 or 5/8"Clive Link to comment Share on other sites More sharing options...
heraldcoupe Posted June 5, 2008 Share Posted June 5, 2008 The GMC series are all modern number which have superceded the originals. It could be argued that any GMC cylinder is a replacement type, even though physically they may (or may not?) be the same.The cylinder bore is 5/8" (0.625"), which is the same as the clutch. The drum braked Herald used identical cylinders, with the small reservoir, for both brake and clutch. Disc brakes are hydraulically self adjusting, which requires a master cylinder with greater reservoir capacity to cover the full range of adjustment.To achieve the extra reservoir capacity, Standard Triumph used different approaches on different vehicles. On the disc braked Heralds, a taller cylinder was initially used, later vehicles reverting to the short cylinder body together with the extension you have. The Spitfire however has a lower bonnet line, so a cylinder with a wider reservoir was used instead. Later versions went from an integral cast reservoir to a plastic type. When selecting a replacement cylinder, be well aware of the issues of that low bonnet line. Two differently shaped mounting brackets were used on Spitfires, one with a shallower angle so the top of the reservoir sits lower. If your brake and clutch master cylinder mounting brackets share the same geometry, chances are they are the ones which sit the cylinder higher. This will be a problem with some aftermarket cylinders where the reservoir is fitted at a 90° angle to the body, the original being at approximately 45°.Sorry if that's not the simple answer you hoped for. Cheers,Bill. Link to comment Share on other sites More sharing options...
CharlieB Posted June 5, 2008 Share Posted June 5, 2008 The original (all alloy 90 deg large resevoir) master cylinder GMC224 is still available if you search eg: http://www.raceparts-direct.com/products/brakes_and_brake_components.asp?section=Girling+Master+Cylinders This may have a plastic lid but these guys do the one with the original alloy lid:http://www.powertrackbrakes.co.uk/wcylinder.html#cylinderThere's a guy who's always at the autojumbles selling them too, can't remember the name.Probably best to fit new seals if you buy an original type as its likely to have been sitting on the shelf for years. I didn't when I bought one from Powertrack and it started sticking which may have been old seals or maybe the silicone fluid (which I don't use anymore). Link to comment Share on other sites More sharing options...
heraldcoupe Posted June 5, 2008 Share Posted June 5, 2008 CharlieB wrote:The original (all alloy 90 deg large resevoir) master cylinder GMC224 is still available if you search eg: The 90° reservoir is not original to Spitfires,Cheers,Bill. Link to comment Share on other sites More sharing options...
CharlieB Posted June 5, 2008 Share Posted June 5, 2008 heraldcoupe wrote:The 90° reservoir is not original to SpitfiresReally? Every Spitfire I've ever seen has an angled small clutch cylinder & what I thought was a 90° large brake cylinder. Are you refering only to early Spitfires or all those with ally cylinders?What does the original one look like? Link to comment Share on other sites More sharing options...
heraldcoupe Posted June 5, 2008 Share Posted June 5, 2008 CharlieB wrote:Really? Every Spitfire I've ever seen has an angled small clutch cylinder & what I thought was a 90° large brake cylinder. I can find plenty of photographs to back up what you say.......Quote:Are you refering only to early Spitfires or all those with ally cylinders?What does the original one look like?The angled cylinders were fitted to the Mk1 & Mk2, including the tall type I attributed only to Heralds in my earlier post! Looks like there was a change to the 90° cylinder at some point before the end of Mk3 production, which would necessitate the shallow angled mounting bracket.I'll go and sit in the corner and eat some humble pie.... :BCheers,Bill. Link to comment Share on other sites More sharing options...
Ludwig Posted June 5, 2008 Author Share Posted June 5, 2008 Thanks chaps - that's answered every question I could have thought of - and explains why when my car came to me the master cylinder was fouling the bonnet!!Regards,AlexPS Bill, can we have Capt. Pugwash back :-/ Link to comment Share on other sites More sharing options...
heraldcoupe Posted June 5, 2008 Share Posted June 5, 2008 Ludwig wrote:PS Bill, can we have Capt. Pugwash back :-/Sorry - I'm going through a Barnes Wallis phase this week!Cheers,Bill. Link to comment Share on other sites More sharing options...
.thumb.jpeg.b15b81ef10abeea1c3039ae03c4a9f3a.jpeg)
Recommended Posts
Archived
This topic is now archived and is closed to further replies.