Thumper Posted August 3, 2005 Share Posted August 3, 2005 I have a 74 260z. It has tokico adjustable struts with suspension techniques springs. It has energy suspension bushings on everything except the t/c rods. The sway bars are I believe suspension techniques. The front is 1 1/8" and the rear is 7/8" The front swap bar has brand new endlinks and the sway bar mounts have been reinforced. The rear sway bar endlinks are in good shape and are tight. My problem is the car pushes way too much. It will only oversteer if persuaded to with lots of throttle. My guess is that the front sway bar is too stiff and this is causing the understeer. Any other thoughts what would cause understeer? If it is my front sway bar what are ways I can loosen it up? I have not had my car aligned yet so I am unsure of specs. This will be the first thing I do before I start adjusting other aspects. Also the struts are set at 2 in front and 1 in rear and are in good shape. Thanks Quote Link to comment Share on other sites More sharing options...
260DET Posted August 3, 2005 Share Posted August 3, 2005 1 1/8" = ~28mm The front suspension would hardly be independant at all with that great lump tieing both sides together. Around 22mm should be about it for the front, the rear bar is a bit heavy too. Although you Murricans do seem to use heavier bars I've noticed Quote Link to comment Share on other sites More sharing options...
auxilary Posted August 3, 2005 Share Posted August 3, 2005 too thick of a sway bar... are you also running staggerred wheels, ie. larger rear tires? change your rear struts to 3, and you'll also notice a difference. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 3, 2005 Share Posted August 3, 2005 We need more info to determine what's causing your understeer: 1. Is the understeer on corner entry, mid corner, or corner exit? 2. Does it understeer more under power? 3. How do you correct for the understeer? 4. How hard are you entering the corner under braking? 5. Are you trail braking? 6. How much racing experience do you have? 7. What size wheels and tires front and rear? 8. What air pressures are you running? 9. What are your alignment settings? 10. What kind of rear differential? Let's start with those questions. FYI... the problem is most likely NOT your front anti-roll bar. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 4, 2005 Author Share Posted August 4, 2005 Ok I will try to answer the questions to the best of my knowledge. Understeer is at all times. Under power it will understeer more When it understeers I slow down, because unless I powerslide the car will understeer I am not braking at all at corner entry No I am not trail braking I have a dozen or so solo II events in my miata never raced this z Front 225/50 yoko es100 Rear 225/60 bfgoodrich sports both on the stock turbo rim 15x6 Tire pressure is set at 32psi all around My alignment is unknown will check b4 I make any adjustments I have a 3.9 open diff will soon be upgrading to 3.36 open I have not driven this car at the track yet. The understeer problem is from some spirited driving so far. The rear sway bar endlinks were a just tad loose. I have tightened them so when the car is driving again I'll see if that helps. I see that arizona sway bar kits come with a 29mm front sway bar so i'm starting to agree with john that its not the sway bar. Although could it be that I have over-tightened my endlinks on the front sway bar? I have not had much chance to play with the settings. Only reason i'm concerned is how unbalanced the car feels. My 83' 280zx was a neutral handler. And this car feels like a sedan fwd. Thanks for your time. Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 4, 2005 Share Posted August 4, 2005 [*]Front 225/50 yoko es100 Rear 225/60 bfgoodrich sports both on the stock turbo rim 15x6 Why the mixed tires? es100's aren't too soft. Maybe the BFG's have a softer compound, I'd try swapping them F to R. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 4, 2005 Share Posted August 4, 2005 My suspension is setup very much like yours with the same ship-sized sway bars. Mine exhibits the same understeer, mainly when entering a turn. Off throttle, or light engine braking through a turn cures it to neutral through mid-turn. Accelerating mildly through the turn will cause it to push again. I can compensate a bit for the turn-in push with the Illumina's. The advantage of the large sway bars is that the suspension does not deflect much as the car leans; keeping the tires relatively flat to the road without having to run camber plates. The disadvantage is that no road is perfectly flat and bumps and waves can cause havok. I did have it on the track and the slight push made the car easier/safer to drive for me (beginner). Quote Link to comment Share on other sites More sharing options...
johnc Posted August 4, 2005 Share Posted August 4, 2005 With different brands of tires front and rear it will be hard to do any tuning. As suggested, try swapping tires front to rear and see what happens. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 4, 2005 Author Share Posted August 4, 2005 I did consider the tire compounds, but the bfgoodrich were bought for my old car when I wanted a taller final drive ratio. Since the rear tires are over an inch higher than the fronts it would look weird if I put them in front. Plus I will need all the traction I can get back there when my motor is up and running. I think i'm going to try to tune the understeer out through tire pressure, shock adjustment, and alignment. Quote Link to comment Share on other sites More sharing options...
auxilary Posted August 4, 2005 Share Posted August 4, 2005 well, the 225/50 and 225/60 tires are going to have the same footprint, 225mm across. What John is saying is that your rear tires are stickier than the front, and therefore induce understeer by not letting the rear pitch out as much as it would if you had es100s all around. Too bad you're not local, I would've loaned you 2 of my wheels with 225/50/15 es100s on them for testing Quote Link to comment Share on other sites More sharing options...
johnc Posted August 4, 2005 Share Posted August 4, 2005 Search this site for recommended alignment settings. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 4, 2005 Author Share Posted August 4, 2005 Thanks for the input johnc and auxilary. I have figured out what alignment settings I want to run. Only problem is my castor isn't adjustable. Oh well it is time for new t/c bushing anyways. Now I just need to save enough for adjustable t/c rods. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 22, 2005 Author Share Posted August 22, 2005 Ok I haven't had the money to do an alignment just yet but have gotten rid of the understeer almost completely. I loosened the front sway bar just a tad (I was smooshing the endlinks way too much), tightened the rear sway bar (they were alittle too loose), and then I upped the front psi to 32psi cold keeping the rears at 30 psi. This seem to help alot. I will get the alignment done in the next few weeks and I will fix the brake booster so I should be ready for my first track event soon:twisted: Only problem with the stock efi i'm having too much boost lag:x I need Megasquirt. Quote Link to comment Share on other sites More sharing options...
Guest Z Draci Posted August 23, 2005 Share Posted August 23, 2005 Your problem just sounds like the front wheels are toed out a bit too much. For your understeering problem, it's a good idea to toe in about 2 degrees up front. Don't go overboard with the toe in of the front wheels! It can cause snap oversteer in those early Z's. It's a good idea to have a mild understeer to let you know your front grip limits. I really don't think your sway bar can cause understeer in every single situation. It must be an alignment problem. I can't believe you didn't get an alignment after you got your suspension upgraded! Quote Link to comment Share on other sites More sharing options...
Drax240z Posted August 23, 2005 Share Posted August 23, 2005 Your problem just sounds like the front wheels are toed out a bit too much. For your understeering problem' date=' it's a good idea to toe in about 2 degrees up front. Don't go overboard with the toe in of the front wheels! It can cause snap oversteer in those early Z's. It's a good idea to have a mild understeer to let you know your front grip limits. I really don't think your sway bar can cause understeer in every single situation. It must be an alignment problem. I can't believe you didn't get an alignment after you got your suspension upgraded![/quote'] Uh, I think you need to check your information. 2 degrees toe-in up front is MASSIVE. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 23, 2005 Author Share Posted August 23, 2005 Actually I did get an alignment after I got the suspension upgraded. Or atleast the PO did. I just bought this car so I am unsure if the alignment is still good. I don't think I am going to run that much toe-in. From what I've read 0 toe-in is best. Maybe 0.2 degrees for help with understeer. I will see my specs soon enough. I just wanted to make sure everything was in good shape and nothing needed to be replaced. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 23, 2005 Share Posted August 23, 2005 For better handling, toe-out on the front of a Z is preferred. Typically its 1/8" to 1/4" total toe-out depending on how tight the important turns are on the track you're running. But, toe-out on a street car increases tire wear and causes the car to follow road imperfections. Toe is very easy to adjust and its something you can do when you get to and leave the track. Personally, I run about 1/16" toe-out on the street and about 3/16" toe-out on the track. On the rear, toe-in helps stabilize the rear and put the power down. Generally 1/16" to 1/8" total toe-in is a decent range. Some folks run more toe-in in back. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 24, 2005 Author Share Posted August 24, 2005 Thanks I think i'm going to try 1/16" toe-in on the rear, and no toe in front. One of my pet peeves is a skittish car at highway+ speeds. I will also be looking to replace my t/c rod bushings too and I probably will shim them while i'm at it. I looking at max 4 degrees but will probably do 2 since this car will mostly be driven on city streets and I have quick steer knuckles. I'll let you know what my alignment numbers are when I get a chance to take this thing in. Quote Link to comment Share on other sites More sharing options...
olie05 Posted August 24, 2005 Share Posted August 24, 2005 Ted, I don't know if I told you this but when they measured my caster, it was 2.9* with the g-machines bushing kit (solid aluminum cup and plastic ball). For reference, it was 2.1* with the stock rubber bushings. You would not be very far off from your ideal 4* if you got this kit... Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 24, 2005 Share Posted August 24, 2005 Thanks I think i'm going to try 1/16" toe-in on the rear, and no toe in front. One of my pet peeves is a skittish car at highway+ speeds. I would do atleast 1/16 toe in the front on a street car if you don't want it following every crack and paint stripe in the road. Quote Link to comment Share on other sites More sharing options...
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