Guest 240stu Posted February 10, 2007 Share Posted February 10, 2007 Hey all... I thought I would chime in on this thread even though it's quite old. I just searched for 'track increase' as it's something I want to do and was hoping it might be a common thing to do. Tony, if you can confirm the 18mm 300zx track increase that would help me out. I'm an Aussie too and I know that in NSW the authorities really don't like the idea of increased track... I'm not sure on Tassie laws (Tas rego is a B option for me). I'm not surprised that most of the autocross guys are for the track increase. I was pondering the wheelbase:track ratio a little while back and the Z is really on the long and skinny (relatively) end of the scale along with the likes of the first shape RX7. On the other end of the spectrum there are cars like the MX5 (miata) and 911. If anyone can offer some parts recipes for minor track increases - other than just using spacers - I would be interested. Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted February 12, 2007 Share Posted February 12, 2007 Using the Z31 hubs increases your front track by 18 or 19 mm. I have them on my 240. Getting a matching increase in track on the rear is a bit of a problem though, without using spacers. I am running about 30mm of spacer on the rear of my car. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 19, 2007 Author Share Posted June 19, 2007 I rego'd mine in the ACT and the engineer was a bit scractchy , I actually increase my track by approximately 25mm a side, which has differenately increased the scrub radius, Im running 17x8's on the front & rear of my zed with 235/45-17 tyres and under braking the car flyes all over the road (f#cking annoying actually), and does certainly wonder at high speeds, But there is certainly an increased feel in the wheel and it does handle alot better, with heavier steering at lower speeds, Whatever changes you do to increase or narrow track just do it before your engineer gets a chance to measure the track width, and then advise him what the original track was , Mine is now a shade over 700mm at the front, whereas it should be approx 654mm or something like that Now back to my original question about 18months ago - I have increased track massively JohnC - how do i lessen these scrub radius tendencies in my car??? , Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 19, 2007 Author Share Posted June 19, 2007 Actually, after doing some reading I have formed a theory that the experiences I am currently having with my car is probably not entirely related to the large track increases on my car, Maybe more to do with the thickness of my tyre sidewalls? having a 45 aspect ratio (as per Johnc), "A bigger issue is the handling problems caused by lower profile tires (45 aspect ratio and below). The Z chassis needs a certain amount of compliance to grip properly. If the suspension is not supple enough the tires tend to skate over bumps and the suspension isn't given enough lateral load to bite. Normally this compliance comes from the tire sidewall (50 aspect ratio and above) but when you go to a lower aspect ratio tire the sidewalls are stiffer. Now the compliance that once existed in the tire has to be moved somewhere else. It can be moved to the suspension bushings and/or the shocks. If you stick with spring rates around 200 lb. in. the Tokico Illuminas set at no higher then 3 will work with lower aspect ratio tires. With spring rates over 200 lb. in. the Illuminas set at 4 or 5 (to get proper rebound damping) have too much compresison damping which causes the tires to skate over bumps. The car feels like it wants to take a set but then unloads and moves a bit and then tries to take a set again." My front brakes are a touch large and i dont think i am able to stuff much less than 17" rims on them, Pretty much leaves me with alternativatives of 235/45-17 or 225/55-17 as common of the shelf tyre alternatives in Australia, However, I have stock suspension, well as far as I know, it is certainly stock ride hide, i would be extremely surprised if the spring rates exceeded 200lbs, but when i drive behind my zed there is almost no give in the springs going over reasonable bumps in the road at reasonable speeds (maybe not the best indicator of spring stiffnes, but not sure how eles to measure the spring rates except pulling them off), So someone before me could have increased the spring rate over stock but kept the stock ride height, With my current 235 tyres I do get the negative effects of the lower profile tyres and possibly the increases in the track, So - what should i do? change to a 225/55-17 (pretty f#cking big tyre though, like 680mm rolling diameter), or get rid of the 4-spots, change to a 2-piston floater and stuff on some 16x7's with a 10p offset and some 225/50-16 tyres? I dont really ever intend lowering the car, Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 19, 2007 Share Posted June 19, 2007 I widened my front 15mm per side by lengthening the control arms and am running 17x8's with 235/45-17's. I have run 225-45's and 245-40's also. Wheels have a 25mm offset. I couldn't be happier with how it drives. What's your toe and caster set at? Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 19, 2007 Share Posted June 19, 2007 I forgot, the AZC hubs are offset more than stock. Can't remember exactly but it was around 10-12mm. So I'm about 25mm wider per side. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 19, 2007 Share Posted June 19, 2007 I widened my front 15mm per side by lengthening the control arms and am running 17x8's with 235/45-17's. I have run 225-45's and 245-40's also. Wheels have a 25mm offset. I couldn't be happier with how it drives. What's your toe and caster set at? I know people do this, but it's technically not a good idea. I suspect you're running the AZC arms. If that is the case, the rod ends are 5/8" diameter. The rule of thumb for rod ends is that you should have 1.5x the thread diameter engaged. This means 15/16" of thread should be in the control arm. I think that leaves you with about 5/16" of adjustment max last time I checked. If you've got the rod ends turned out farther than 5/16" of thread showing, and it sounds like you do, then what you really should have is a longer control arm. As to tony's issues, before worrying about scrub radius, I'd look at some more conventional remedies for your ills. What kind of TC rod bushings are you using? This will drastically affect wandering under braking. What are your alignment settings? Toe in front and rear will reduce the tendency to wander. Less negative camber will also help. More caster will drastically reduce wandering at speed (at the expense of harder steering). Do you have an air dam? This too will affect wandering at speed. There are a TON of things you can do to affect your wander before you get into scrub radius. As to the ride quality, if the suspension is stock it's probably sagged out by now and also probably not stiff enough to be able to keep up with the increased unsprung weight of your big brakes and tires. Stiffer springs and better struts may seem like a backwards way to improve your driving comfort, but it may be something to look at. I can't tell you how uncomfortable I find it to ride in a car that needs struts. Not only is there that floaty bark-o-lounger feeling which makes me feel queasy, but then there is the hitting the bumpstops over small bumps or worse, in several of the Z's I've been in and owned, smacking the strut into the top hat because the bumpstop has rotted away decades ago. Nothing quite so uncomfortable as a metal-to-metal bottoming out of the suspension. Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 19, 2007 Share Posted June 19, 2007 Ya, I didn't want to turn them out that far but I had already welded in the camber plates when I had the factory lengthend arms on. I have the camber plates set for, all the way in for autoX and all the way out for street but that is with a longer arm. A stock length arm wouldn't work with it now and his arms only come in one length. Luckily I haven't had any problems yet. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 19, 2007 Author Share Posted June 19, 2007 The only thing I have negelected so far with my car is the suspension, It is as stock as it could probably get - I havent changed anything, having said that, I bought it from a bloke who about 7 years ago completely restored it, What kind of TC rod bushings are you using? They are just off the shelf rubber jobs i would think, but couldnt tell you for certain, What are your alignment settings? Toe in front and rear will reduce the tendency to wander. I have no means of adjusting the toe, without installing adjustable components right? Less negative camber will also help. More caster will drastically reduce wandering at speed (at the expense of harder steering). Do you have an air dam? Yes, I do have an air dam, But dont have adjustable radius rods, The ride quality in my zed is fine, It does not feel as if the shocks are bottoming out, It could do with a wheel alignment as my front left tyre is starting to wear unevenly, but other than that the suspension is as it was from the factory, So starting from scratch, Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 19, 2007 Share Posted June 19, 2007 If you have no adjustability added in then the only stock adjustments are front toe which should be 1/8" or about 3mm total toe in for street use. You can shim in some caster as well. Soft bushings in the TC rods will get you wander under braking, I don't think there is any real way to get around that. I know that there are some pretty severe limitations in some countries as to what you are allowed to change and remain street legal, so I'm not sure how far you can go with this stuff. Maybe slot the strut tops to even out camber if you aren't allowed to add adjustable bushings or camber plates or aftermarket control arms. Hard to say from over here... My point was that there are many other factors that you could get into before blaming the scrub radius, that seems to me to be one issue that very few even attempt to address, and it seems to me to be way down the priority list behind a whole bunch of other things. Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 19, 2007 Share Posted June 19, 2007 What are your alignment settings? Toe in front and rear will reduce the tendency to wander. I have no means of adjusting the toe, without installing adjustable components right? Based on this and your wander, I would guess you are toed out some. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 20, 2007 Author Share Posted June 20, 2007 Here are the measurements (sorry they couldnt tell me caster angle), Before, Camber = Left -0.3 & Right + 0.6 Toe = Left +7 & Right +2 After Camber = Left -0.3, & Right +0.6 Toe = Zero for both left and right, Car does feel better than it did, but its still tracking, Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 20, 2007 Share Posted June 20, 2007 How come you aren't running a little toe in on the front? It's a street car right? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 20, 2007 Share Posted June 20, 2007 Clifton is right, you definitely want some toe in on a street car. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 20, 2007 Author Share Posted June 20, 2007 Yes, daily driver, I Figured that one out after I left the place , it was like a tyre shop and their equipment was a touch dodge, I have a slotted crossmember, new tie-rod ends and balljoints that ive been trying to motivate myself to put in for awhiles now, so will do that this weekend and take the car to a proper steering and suspension place, that can measure the caster angle aswell , But it appears that I have 0 camber at this point, but from reading that is probably a good thing because of the largish increases in track I have, Also, the more folks I talk to it seems that my tyres may have something to do with what is happening with my car - they are middle of the road faulkens, This one bloke I spoke to said that his personal experience with faulkens was an extremely durable tyre that has an awfully sturdy and inflexible side-wall, two cars he got rid of faulkens for different tyres and they were different cars, Because of their design (stiff side-walls) the faulkens had a real tendency to follow the contours on the road, making the cars track like crazy, Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 20, 2007 Share Posted June 20, 2007 Stiff sidewalls aren't your problem. Lack of toe in will cause your tires to follow any imperfections in the road. Paint stripes, cracks, ruts, ect. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 20, 2007 Author Share Posted June 20, 2007 Oh ok, I will go back and get them to add some toe-in, Clifton, what are the size of your brakes on that silver zed mate? Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 20, 2007 Share Posted June 20, 2007 12.2"/ 308 mm. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted June 20, 2007 Author Share Posted June 20, 2007 I have 298mm with 4-spots on the front (same calipers as GTS-T R32) and the rears are 289 x 22 with single piston 44mm floaters, I am using a 1" master cylinder from a 1975-79 Nissan patrol, I have an adjustable bias value in place but literally had to cut all pressure to the rear brakes because i kept swapping ends!!! Looks like your rear brakes are a similar size, wondering if you had the same issue? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 20, 2007 Share Posted June 20, 2007 I have 298mm with 4-spots on the front (same calipers as GTS-T R32) and the rears are 289 x 22 with single piston 44mm floaters, I am using a 1" master cylinder from a 1975-79 Nissan patrol, I have an adjustable bias value in place but literally had to cut all pressure to the rear brakes because i kept swapping ends!!! Looks like your rear brakes are a similar size, wondering if you had the same issue? If you turn an adjustable prop valve all the way up it doesn't cut all the pressure to the rear. How much it actually reduces the pressure depends on the valve and also how much pressure you put on the pedal (because they aren't actually proportional), but I would expect it to be something like 50% max. If you can't get enough out of the adjsutable valve, the next step is dual master cylinders. Quote Link to comment Share on other sites More sharing options...
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