richardix Posted February 23, 2009 Report Share Posted February 23, 2009 Hello, I have a TR4A and I'm thinking of upgrading the single brake circuit for safety reasons. Searching the internet I found that Revington has an upgrade set, but with two single brake cylinders. Tilton sells dual circuit brakes also, but it is not clear to me if these are suitable for a TR4. Ofcoarse an option is exchanging the complete pedalbox with a TR6 model. I would like to ask if anyone has experience with upgrading the single circuit and how to carry this out. Thank you in advance, kind regards, Richard Quote Link to post Share on other sites
TR 2100 Posted February 23, 2009 Report Share Posted February 23, 2009 I have a TR4A and I'm thinking of upgrading the single brake circuit for safety reasons. SI would like to ask if anyone has experience with upgrading the single circuit and how to carry this out. TR Enterprises did my TR4 dual circuit brakes - two mini-bore cylinders that give the brakes a similar feel to original, without servo. Otherwise, as you say, you could go for the full TR6 setup + servo. PM me with your email address and I'll send you a couple of photos. AlanR Quote Link to post Share on other sites
MadMarx Posted March 15, 2009 Report Share Posted March 15, 2009 I also use a selfmade dual system. I have taken the smallest Girling cylinders with 15.5 mm bore (as far I remember). It has a little harder feel than the stock unit but under racing conditions it prevents you from locking up too easy. On normal road use they are fine. I used inox-steel for a nice shiny appearance. Cheers Chris Quote Link to post Share on other sites
wvukidsdoc Posted March 16, 2009 Report Share Posted March 16, 2009 I too have been thinking about this and have perused some of the dual single cylinder setups on the www. Although effective, I just don't like the whole balance bar setup idea. I've also looked quite extensively for a suitable dual circuit cylinder that would mount physically in the space of the stocker, or nearly so. I perused ebay looking at about 500 listed master cylinders for any car, old, new, etc, as well as looing at Wilwood and other racing suppliers to no avail. Anyone ever find anything short enough, space to the firewall is so damn limited. I'm not at all picky about fittings and making adapters on the lathe, if anyone has ever seen something suitably short with a non boosted pushrod configuration. I had given serious thought to the pile of VW late A1 and A2 masters I have around, rigging some pushrod system for use without the booster, as they are physically short enough, but haven't got around to giving that idea much serious thought. I've sort of settled on just replacing every single bit of the stock single circuit system and calling it at that if no-one has a great idea. John Quote Link to post Share on other sites
richardix Posted April 5, 2009 Author Report Share Posted April 5, 2009 In the mean time I had some contact with Tilton Engineering, who fabricates brake master cylinders. According to them the smallest bore is 0,625 inch (or 15,9 mm). I did some calculations by my own (and on advice of Tilton) and a 0,7 inch single brake master is equal to two brake master cylinders of 0,5 inch. This means that for the same pedal force and feeling in the original configuration, there is no brake master cylinder available. On the internet I read that a conversion to 0,625 inch is working fine. Another possibility (this pure theoretically I did not try this) is to change the ratio between pedal stroke and brake master cylinder stroke. For example by decreasing the distance between brake master cylinder connection and pedal bearing (originally 5 cm, change it to 3 or 4). Summarized: 0,625 inch bore is needed by twin circuit. No experiece yet if one (double) brake master cylinder will fit or not and if the only option is two brake master cylinders with balance bar. Next couple of months I am going to make some drawings of the possibilities and keep you informed. regards, Richard Quote Link to post Share on other sites
ianc Posted April 6, 2009 Report Share Posted April 6, 2009 As this is a safety (very!) critical area, you need to get it right. I suggest you have a good look at cars which have been fitted with conversions by Revington and TR Enterprises, as everything in the kit will fit and will work correctly. I have driven 3VC, which has the Revington twin-cylinder conversion, and it didn't seem very different to my own 4VC, which hasn't. Yes, you do have to push a little harder, but it wasn't a worry for me - and I am both small and old (and I don't want any rude follow-ups on that!). Ian Cornish Quote Link to post Share on other sites
badshead Posted April 6, 2009 Report Share Posted April 6, 2009 Hello, I have a TR4A and I'm thinking of upgrading the single brake circuit for safety reasons. I'm not sure dual circuit is such a big deal. If you lose the front brakes at anything over 20mph, you effectively haven't got any brakes as I found out last year in my TR6. Quote Link to post Share on other sites
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