turbogrill Posted March 23, 2017 Share Posted March 23, 2017 Hi, My 280zx race car doesn't brake very well. It stops quickly but not in a controllable manner. I have to baby the brakes a little otherwise it upsets the cars balance, I have to fight the car a little while braking. This costs time since I have to spend a little more time braking before each corner. I have stockish engine. Brake specs: - Stock 280zx brake system - Race pads (either Porterfield R4-E or Carbotech RP2. XP8 in the back) - Motul RB600 - Stock brake hoses - New stock rotors Suspension and chassi: - 6point welded in roll cage with door bars. - Front 4 point strutbar - Cut eibach springs and KYB excel-g - 200 treadwear tires - A little to much rust on the chassi I am not sure if it's a brake or chassis issue. Could it be to much grip in the pads in relation ship to the tires? Could it be that the chassi is flexing to much? It's pretty rusty (should have picked a different car). Could it be that my suspension sucks? Could it simply be that the 280zx brakes aren't up for the task? Thanks Quote Link to comment Share on other sites More sharing options...
Roberto260Z Posted March 23, 2017 Share Posted March 23, 2017 Is it possible the reaction disk has fallen off the piston rod in the booster? This will cause a low pedal and poor modulation. Quote Link to comment Share on other sites More sharing options...
tube80z Posted March 23, 2017 Share Posted March 23, 2017 If you want advice you're going to need to provide more detail on what it's doing. It could be all of the above. How does it upset the chassis? Pull to one side of the other? Does the back want to swap positions with the front? Does the front end wash out? More along those lines would help. Quote Link to comment Share on other sites More sharing options...
Neverdone Posted March 23, 2017 Share Posted March 23, 2017 What kinda racing are you doing? What speeds are you coming down from where you're "fighting the car"? Is it all the time, or only at the beginning/end of a series? Quote Link to comment Share on other sites More sharing options...
260DET Posted March 24, 2017 Share Posted March 24, 2017 If there is chassis flex due to rust damaged structural parts, slop in the rear suspension, weak dampers or any other similar age related deficiency then expect problems. With a semi trailing arm suspension everything has to be top notch, everything, for it to handle and brake well. Quote Link to comment Share on other sites More sharing options...
turbogrill Posted March 24, 2017 Author Share Posted March 24, 2017 If you want advice you're going to need to provide more detail on what it's doing. It could be all of the above. How does it upset the chassis? Pull to one side of the other? Does the back want to swap positions with the front? Does the front end wash out? More along those lines would help. It's hard to explain. It pulls a little to one side. Imagine how braking on uneven ice would be but it stops fast. Rear also have a tendency to lock up. What kinda racing are you doing? What speeds are you coming down from where you're "fighting the car"? Is it all the time, or only at the beginning/end of a series? It's most noticable when braking hard from fast. So maybe high revs 4th or 3th down to 2th. If there is chassis flex due to rust damaged structural parts, slop in the rear suspension, weak dampers or any other similar age related deficiency then expect problems. With a semi trailing arm suspension everything has to be top notch, everything, for it to handle and brake well. Top notch is not how I would describe the car The roll cage surely stiffens everything up. But there is still a lot of rust but it's mostly in the floor pan and those floor rails that goes front to back. Subframe is solid.All bushings are good. Dampers are crappy KYB. Quote Link to comment Share on other sites More sharing options...
kroegarn Posted April 13, 2017 Share Posted April 13, 2017 (edited) I´ve got some experience (7 years) from endurance racing and first of all make sure that pads, fluid and cooling ducts are up for the task of handling the heat. Since that does not seem to be a problem in your case, the biggest improvement by far, that the team experienced was when we did a proper corner weighting!! We had driven a few races after a major chassi overhaul and braking was all over the place, but after the CW braking efficiency was spot on. So I´d say, fix you dampers and get lower treadwear tires (if it is allowed?), then get coils and do a proper CW. Could perhaps still do a CW without coilovers by moving weights or stuff around in the car... but could get a bit tedious Edit: The car discussed above is a BMW M3, not the Datsun... just to clarify Edited April 13, 2017 by kroegarn Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 14, 2017 Share Posted April 14, 2017 This problem is likely looseness in the tension rod bushings causing big caster changes. Quote Link to comment Share on other sites More sharing options...
Miles Posted April 14, 2017 Share Posted April 14, 2017 (edited) My 240Z would wander and dart left - right under hard braking. Turned out to be rotted T/C and steering rack bushings. Replaced the T/C bushings with stock Nissan bushings and everything else with polyurethane bushings. Drives like it is on rails now You also stated: "Race pads (either Porterfield R4-E or Carbotech RP2. XP8 in the back)" What pads are on the front? Fronts should lock first. Could be that you or the PO tried to change the bias of the front vs rear brakes using different pad materials and now the back pads are a bit too aggressive. Based on your description it could be a number of other things. Edited April 14, 2017 by Miles Quote Link to comment Share on other sites More sharing options...
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