mbayley77 0 Posted January 4, 2008 I am currently building a track car / tarmac rally car and have 307 brakes up the front with standard 309 calipers on the rear. I have put in a dual Wilwood servo system instead of the standard vacuum assisted servo. I currently have the incorrect servo size for the front but rather than change that one I am toying ith putting a standard vacuum assisted servo back in from a 307 or similar. Whats everyones oppinion on the two set ups? and the pro's / con's of each. Cheers Share this post Link to post Share on other sites
Tom Fenton 1,542 Posted January 4, 2008 In saying you have a Wilwood dual system I take it you mean master cylinders? If it is what I think it is there is no servo assistance, all you have is a master cylinder. If the wrong size master is fitted then it will either make the brake pedal very very hard, or soft and with long travel. Neither is nice to drive. My 205 track car has twin master cylinders, in the end swapped the front one with the back one to get a good balance, I can't remember what sizes we have off the top of my head, however once used to them I like them a lot, the harder you push the harder you stop. More than anything else with an MI16 engine it means there are no clearance issues with the master cylinders, I personally do not like some of the conversions I have seen with the master cylinder poised 10mm above the cambelt. Share this post Link to post Share on other sites
Rob Thomson 6 Posted January 4, 2008 If it really is a pure circuit/rally car then keep the bias box with the twin cylinders. I used to have one in my old 309 and it was great on closed roads but absolutely terrifying on the road due to the pedal forces required. Share this post Link to post Share on other sites
mbayley77 0 Posted January 4, 2008 Yes your right I have dual master cylinders without servo assist with adjustable balance bar. If you could let me know what sizes your using on yours that would be great as im hating mine at the moment and the balance bar doesnt balance anything at the moment! Share this post Link to post Share on other sites
Tom Fenton 1,542 Posted January 4, 2008 What is it like? Too hard or too soft? Car is not here at the moment so I cannot go and look. From memory one is 7/8" and the other 3/4". Can't remember which is which front to back though. Share this post Link to post Share on other sites
Rippthrough 98 Posted January 4, 2008 What is it like? Too hard or too soft? Car is not here at the moment so I cannot go and look. From memory one is 7/8" and the other 3/4". Can't remember which is which front to back though. I'd imagine 3/4" is for the fronts? Share this post Link to post Share on other sites
Rob Thomson 6 Posted January 4, 2008 I had 0.625" front and back and the balance was fine. Even with such small cylinders most of the pedal movement was bulkhead flex... Share this post Link to post Share on other sites
Tom Fenton 1,542 Posted January 4, 2008 I'd imagine 3/4" is for the fronts? Without looking at it I don't know, all I can remember is that we fitted them as we thought would be best, but the pedal was like standing on a brick, swapping the front and back made it a lot better. Share this post Link to post Share on other sites
mbayley77 0 Posted January 4, 2008 I have 0.625" front and back and its hard as nails with bulkhead flex - thats not so much of an issue for me but the rear is locking way before the front so need a larger cylinder for the back but which size? At £30 a pop i dont want to have to end up buying 3 different sizes before finding the right one. Have been kind of advised before of the 3/4" one for the rear. Hopefully should be able to adjust as well using the balance bar. Share this post Link to post Share on other sites
Rippthrough 98 Posted January 4, 2008 (edited) I had 0.625" front and back and the balance was fine. Even with such small cylinders most of the pedal movement was bulkhead flex... That's the main problem with running no servo - the slack in the rest of the system. Te best thing you can do is work to take as much flex out of the entire system as possible - including MC fluid ports, linkages, caliper knock back, etc. That way you can run smaller master cylinders with the same travel and get your braking power back. Edited January 4, 2008 by Rippthrough Share this post Link to post Share on other sites
mbayley77 0 Posted January 4, 2008 I am going to brace my bulkhead and try to reduce that, but the other things? How can they be improved....sorry if im missing something else here. Share this post Link to post Share on other sites
