tube80z

Welcome to the big butt club How much of the inner fender did you cut out? On my car it's flat from the center of the inner fender to the outside. Cary

John, Take a look at http://www.jameshakewill.com/tech.htm. This site has a lot of good info on using free tools and low cost options to help you get the most from your data logger. You can see what he did with lapsim to see if it's worth the time to invest in learning it. Cary

First a couple of questions. How camber sensitive are these tires? And are you stuck with running radials? If the wider tire is more camber sensitive you'll probably have issues with a stock S30 chassis. While these may work for a BMW our chassis isn't as sophisticated. Have you considered running used bias ply slicks? These are a much better match in my opinion and a lot cheaper than the prices you mention for running the radials (perhaps a class issue). There are three primary factors for cornering speed. Weight, CG height, and track width. Your losing two of those for sure going to the bigger tire combo. If you have some basic data you may want to think about downloading bosch lapsim and trying it out. It may help you make the choice as to which is better. Cary

Don't you watch Mythbusters!?

And here, in case this is cheaper http://store.fedhillusa.com/cuniferbrakeandhydline.aspx Cary

It's inside front, if it says otherwise that's a mistake on my part. When you droop limit you will have the amount that the spring is pre-loaded. To get the tire off the ground you will need to transfer more than that, which is possible if the car will bicycle. My car won't lift the front tires on acceleration even when I have a true zero-droop setup. I think what you typically see are cars that are fairly soft that allow the chassis to move enough to get a tire off the ground. The weight transfer happens regardless of the roll angle. Movement of the geometric and/or forced based roll center standard in most any suspension. If it helps to think of it how do you calculate the RC in a suspension where one wheel is fixed and can't move. That's what we have here when the limiter tops out. And the change in ride height (net up/down) can be measured with a data logger. I don't know if I'm helping or hurting at this point. All I can tell you is this is a trick I use and it works well for me. It's not something everyone should do without understanding why. I have lots of pics of the people I run with and all the cars running stiffer spring packages keep their tires on the ground. All of the softer cars are running around with tires off the ground and many of them have loads of droop. Cary

The attached picture shows the outline of the t-bar. The pinion is actually hollow where the u-joint connects and inside this is a torsion spring that is hooked to the servo valve. The top of the pinion is hooked to the t-bar and the bottom to the servo valve. This is what controls the power steering and the feel. If you cut the top down and didn't keep the t-bar pinned you will not be able to have functioning power steering. And if you decide to weld the top of the pinion you need to be very careful because you can damage the t-bar, which happened in Dave's case. The first thing that happens when the t-bar breaks is the steering goes freaky light. If you get the servo valve cocked one way or the other then you have power steering in one direction and get to fight the pump to turn the other way. Cary

Cables between the strut tower and the lower control arm were used. Adjustments were done via turnbuckles. Very crude but it worked.

In your first pic is looks like I can see part of the t-bar. Did you pin that before this mod? It's hard to tell from the picture. You need to be very careful with that piece or you'll have steering that will not work correctly. Cary

Actually from what I can tell different types of race gas have different specific gravities and need to be tuned for when you have a motor on the edge. Probably not something you'd worry about in a normal auto engine. But something still to think about. Cary

Yokos are slower than the GY radials, even though the GYs are narrower. But if you have access to a bunch that are cheap why not use them. You probably already know this but you need to run stiff springs to really make those tires work. And the setup is going to be different between the GYs and the Yokos since the tire stiffness is different. And to make the rears work you will need to think about droop limiting or you will see high inside tire temps that look like too much camber. It's caused by inside tire roll when you put the power down. Cary

Yes, but only for that axle pair. Often before the tire is off the ground it may have almost no net load on it anyway. So even on the ground it wouldn't be contributing. See above. Well before the tire comes off the ground the most of the load has already transfered to the outer tire. If you pulled a loaded tire off the ground then I could see this happenning. I've really been waiting to get this issue because I wanted to see what Ortiz had to write. I've read the article about ten times and I still don't get it. He doesn't really answer the question, talks about dirt cars, and then says something with no real proof. Keep in mind I'm not an expert, I play in parking lots with traffic cones, and occasionally run up mountain roads but here's what I know about reduced droop. If we have a car with 500 pound springs, 500 pounds of corner load, and a motion ration of one, what happens when you set the car on the ground? I think the spring compresses one inch. What happens if I lift the car anything over an inch? I think the spring becomes unseated and there's no load on the tire (I'm not counting the unsprung weight in this case). So in the case of reducing droop to less than an inch I'm keeping a set amount of load on the tire. This is very similar to how the stock suspension works by having a soft rate and a spring the is longer than the available space and it's pre-loaded. I'm just using a lot less space. So here's what I think happens. Droop limiting either via pre-loading the spring on the strut, or using a mechanical stop allows the car to accept lateral loading and roll a specific amount before the inside spring tops out. At that point there is a certain amount of vertical load still left on the inside tire. For any further load transfer (and the necessary increase in lateral loading) the actual roll center moves to the center of the inside tire contact patch. For any further roll (from increased lateral loading) the car now pivots about that point, and lowers itself. That lowering in turn decreases the jacking effect. Roll stiffness from the springs and bars is not changed at all, so the net effect is a decrease in roll stiffness (or at a minimum, no further increase) When I started running stiffer springs (400 to 500 pound range) it was obvious when jacking the car up the springs would unseat with very little droop. I noted the fender gap when this happened. I then looked at pictures I've taken of the car under high lateral loads and saw that sometimes the gap appeared to be bigger than just having the spring unseated. I remembered back to playing with formula cars running droop limiters and figured why not try this on a tin top. My original idea was that it didn't do any good to allow the suspension to droop anymore than the spring becoming unseated, which was a little over an inch (lets say 30 mm). Running the car this way it worked better. I didn't see tires come of the ground and more importantly the rear tire temp were more even. Previously they looked to have too much camber. So then I played with this some more. I tried reducing droop at both ends to see what happened, then one or the other. I found a way to make a killer drift car (not what I wanted) and a way to get quicker turn-in and less roll, which was what I was after. Pictures of the car after it was droop limited have a lower roll angle. I think this is attributed to the car no longer being able to jack the inside up off the spring seat because it now has to overcome a specific load. It's sorta like running a larger swaybar and the car works better. Theory tells you that's wrong but sometimes it works anyway. In this case I think the tires are held flatter to the road. Cary

You're mistaking suspension droop with tire load. Just because you run reduced droop doesn't mean the tire is being pulled off the road. It's quite the opposite. At least if you're running spring rates to properly support the platform. What happens when a spring is unseated versus still having load on it? Reducing droop in this case keeps a set amount of load on the tire. What happens is you top out the shock and now the tire has to dampen all road irregularities, but it still has load on it.

I've seen a few cars setup this way. They work fine but generally have a problem of abusing the rear tires and the car goes away pretty quickly. Make sure you don't get too out of whack with frequencies front and rear. If you have access to a datalogger look at the roll angle of the chassis mid-corner. What you want to see if more or less an equal roll angle. This indicates the tires are used about the same. Cary

The crank was cleaned, checked for size, magnafluxed, and all the parts were checked for balance and found to be close after a few small drills. Race motor in this case is really just an autox car and you could have said hot street or something similar. It's not prepped to real race car levels. That said I've never had a problem with them coming apart like this ever and was sorta surprised. I should also mention this crank was put in to replace a crank that was killed then I had a balancer come apart and spun on the nose of the crank. I had a race the next week and needed to get the car together. So this was a rush job at best and what little was done was all my fault. Cary

I think the difference is something like 45 lbs of effort compared to 120 lbs of effort. Numbers could be off but it's a lot more.

That's easy, just don't screw up

From my experience running reduced droop you will notice much quicker turn-in and shouldn't really have any ill effects. If you try and run a true zero-droop setup you may get some bouncing that can be hard to tune out. It depends on how much anti-squat you have but that may cause problems when trying to put power down on corner exit. It works well in a straight line but not so well when you are turning.

You have subframe connectors, cage diagonals, etc. all welded in that help keep the floor from moving. Those are all going to help keep this from moving. Take a look at the top of the tunnel, I don't think you need a lot more than that to strengthen the bottom. From personal experience I can tell you that I've broke that crossmember (diff mount issue) and never noticed any handling issues. I even ran one race with just the caps and couldn't tell. I have broken cracked and broken the rear transverse mounts, which I can feel. So I'd say you're safe and I'd spend the effort at the back and leave this area alone. Cary

Or if you really think you need it weld a tab along the bottom of the RT mount for a bolt in crossmember. This would be more in line with the lower control arm mounts than a piece further up where the seat belt anchors are. I don't think you need much to strengthen this area given the rest of what you have done. Cary

Magnafluxed and all bearings are standard. Maybe a fluke but still impressive to see. Even more impressive when you think it was still revving to about 6K for a bit after this.

A friend has my old race motor and it started getting what sounded like a nasty rod knock. He took it apart expecting to find a broken crank. I've never seen one break like this and it was very close to coming all the way apart. This engine had one season under me 7500 RPM limit and a few events for him at a lower 7K limit. Just goes to show that these parts are getting older and racing is hard on things. Cary

If you have the large front damper it won't hack 7K very well. The first signs of a problem are bits of rubber that look like they came from the fan belt on the bottom of the hood and up the inner fenders. That's the sign of a damper dieing, and you better take notice. You also need to throw away the flywheel bolts and install new ones. When you lose one end of the crank the other takes all the beating. It may seem like overkill but you won't be very happy when the flywheel comes loose and wipes the end of the crank. Don't ask how I know this. Cary

You may want to take a look at http://www.jakelatham.com/radical/info/brake_calculators.shtml and see what your current system looks like before making changes. C

There's a group of us that are racing in XP, which has basically turned into our own little rivalry between a 89 vette and the rest of the Zs. If I look at the vette in pictures you can see the suspension on it does a much better job of keeping the tires flat to the ground. Currently the vette is quicker but if I look back at times against my old car they are closely matched. So like many things there are other variables at play that make a direct comparison difficult. I had the opportunity to race a 510 on struts and then run the same car converted to double a-arms. What I mostly noticed was the car had much better steering feel. The odd thing was that it didn't have a lot better front grip. It was very similar to the lexus setup discussed in a different thread. As Ron points out above the Z has a lot of SIA and this is what I think is more of an issue than the scrub. If you look at the tire contact patch you'll see the SIA has a tendency to roll it from edge to edge. There are a number of other effects too but I wonder if that is one that causes the front end to be harder on tires. My gut feel is that double a-arms will better for a car that's going to do much longer runs on the tires. I also think it's better under brakes especially if you are generating large longitudinal loads. I asked a similar question in the motec seminar because I knew they had experience with the V8 supercars and got a more thorough but similar reply. Cary