tube80z

We like to think we're fast but you live in the backyard of one of FP's big dogs. Drop me a PM if you're interested in the Oregon autox scene. Cary

No, just a general comment on a possibly easier way to do this. Unless there's a specific reason you need to mount a spherical. The rack ends offer an easy solution to making an adjustable TC rod and having a strong joint that you can boot. Cary

Why don't you use something like rack ends. Sentra ones work well. Cary

Yep, that's the one. Claude is really good at explaining complex subjects in a manner that is easy to understand. For instance, he gives an explanation of a tire as a series of springs. And when it coil binds in any direction it slides rather violently. And then tells you about how not to do this. The only issue with the seminar for me is that he's at a pro level and I'm just a lowly autoxer. So what I can use and afford is a lot different from what he uses and can afford. Aim PISTA (8 channels) versus Motec ADL2 (45 channels). Three really big things came from the class for me (among the hundreds of others). 1. Kinematic changes have a much larger influence than springs or shocks. Claude shared some stories about his days in F3 to back this up and we did some simulation that showed weight transfer etc. For me this means major changes to the front end of my tube car so this can be easily changed. 2. It is absolutely essential to have linear pots on your suspension if you want to be able to set the car up. Claude shared a number of nifty tricks that he'd used. My favorite was the use of pressure sensitive paper and trailer tie downs on one of the Aussie touring cars. They pulled the car down to match what the pots showed in a problem area. Camber and pressure were adjusted to maximize the contact patch and the car was instantly 1.2 seconds a lap faster and won the race. 3. Trying to measure tire temperature is a shot in the dark with a handheld pyrometer. Claude showed data from one of the flying lizard cars and asked us what to tune according to the data (looked like too much camber). On car tire temp measurement clearly showed it needed more. So that's 13 sensors at $250 a pop plus a system that can record all the data. What it really showed is that racing these days, even at an amatuer level, you really need data acquisistion. He uses the example of going to school and needing a report card to see how you're doing. In this case the driver has a report card and so does the car. And while expensive you can learn more with one of these systems in a weekend than most people can testing all year without (assuming you can understand what the data means). I figure this class put me about 3 to 5 years ahead of where I'd have been figuring this out on my own. I would add that for people operating at an amatuer level I learned more from the ICP seminar put on by Richard Pare and Steve Lathrop and it was a fair bit cheaper. Hope that helps, Cary

I'd have to look it up but I believe they are forced to run 52F/48R. We had a couple of the Speed WC guys in the motec seminar this year. It sounds like a number of new cars are supposed to be coming. I was chatting with one of the caddy crew in Portland and they were moaning about the reduced revs and additional restrictor they got for that race. I wouldn't buy a caddy but I have to admit they are probably one of my favorite cars at the moment to watch. Cary

Is it possible to install a linear bearing instead of a bushing? Cary

Is it possible to install a linear bearing instead of a bushing? Cary

I can't speak for road racing but for autox/hillclimb I'm pleased with the GC shocks. It did take a couple of revalves to get them in the range that I needed. And for the money I couldn't build a similar set of anything else but there are far better shocks out there. If I were truly serious I would use Penske or Ohlins, leaning towards the latter in 4-way configuration (T44). To answer your question about what real racers do (this will probably annoy many that race) is they look at their linear pots on the DA system and adjust so they the damper histogram is symmetrical. This will amost always make for a faster car. And in a non-aero car shocks will have one of the largest tuning effects outside of kinematic changes (suspension geometry). If you have linear pots on your car you'll find that each track will require changes to valving, etc. to get a symmetrical balance. Then you adjust your shocks so that you roll gradient is minimized, which puts less torsional stress on the chassis. Remeber that stresses on the shock shaft from the spring and how the strut works will cause the shaft to bend. It's best to run the piston either low in the strut housing or towards the top to reduce seal friction from this effect. Cary

I can't speak for road racing but for autox/hillclimb I'm pleased with the GC shocks. It did take a couple of revalves to get them in the range that I needed. And for the money I couldn't build a similar set of anything else but there are far better shocks out there. If I were truly serious I would use Penske or Ohlins, leaning towards the latter in 4-way configuration (T44). To answer your question about what real racers do (this will probably annoy many that race) is they look at their linear pots on the DA system and adjust so they the damper histogram is symmetrical. This will amost always make for a faster car. And in a non-aero car shocks will have one of the largest tuning effects outside of kinematic changes (suspension geometry). If you have linear pots on your car you'll find that each track will require changes to valving, etc. to get a symmetrical balance. Then you adjust your shocks so that you roll gradient is minimized, which puts less torsional stress on the chassis. Remeber that stresses on the shock shaft from the spring and how the strut works will cause the shaft to bend. It's best to run the piston either low in the strut housing or towards the top to reduce seal friction from this effect. Cary

No need to be sorry. I can relate to using what you have or can get at a good deal on as I've done that many times myself. The issue with the carbs has to do with the changes in cross sectional area. The change caused by the smaller chokes on the larger carbs is greater than on the 40s. On the flowbench this shows as a reduction in flow when you test them back to back. I'm not really sure why Weber made such small chokes for the 45s when the 40s would have worked better. take care, Cary

I know you don't like my advice. But if you're going to use small chokes you should really put 40s on the car. It will work much better. If you decide to put a larger cam in this engine similar to the old datsun comp rally or slalom cam then you may find the larger chokes to work a lot better. We ran 32 mm chokes on a autox car for quite a few years. It wasn't until we started testing some of these pieces did we find these just don't work as well as you'd think in 45s. In our case the larger chokes were better across the board. This engne had a little over 11:1 compression. Cary

The 15 inch Atlantic tires are a good choice and readily available. For what it's worth I run the 13 inch Atlantics and have similar pressures (looking for 18 to 18.5 HOT). Make sure you get fronts if you go for the smaller tires all round. In the 13s there is the same size that is a rear and when you get them on the front the car won't turn for crap. Just something to watch out for. If you go to a pro Atlantic race you may be able to haul off some of the yokohama radials. They are designed to run on a 12 inch rim in the rear and you'll be in the 24 to 26 HOT pressure range. I've found it much easier to use two sets of wheels/tires. I keep notes on use and match them that way and flip each on the wheel after three events. The bias ply tires will grow as they are used you can use this as a guage on what tires to match up if you buy used. Each year I introduce a new set to replace those that are in the worst shape. This has allowed me to drastically reduce my tire budget. I have the tires on nitrogen and they are bagged when not in use. Cary

That's a really bad thing to do. 32 mm chokes on a 45 are not going to flow was much air as a similar choke on a 40. I did this test years ago on a flowbench. You need to stay above 35 mm to break even with 45s. For an agressive cam I'd think you'd be looking at 38 and still have decent mid and bottom. Cary

A friend of mine runs the goodyear 16 inch radial in a 250 compound with 550 springs and koni insterts. It works very well although many claim the shocks can't deal with this. There's nothing wrong with picking a known quantity and the 16s certainly are. You might be faster on 15s or even 13s. But you'll have to figure out how to make them work. If you're up for the challenge it can be fun. It can also be very frustrating when you start going backwards. Cary

If you run with a pavement temp under 95 degrees the 25A may be faster. It also depends on how long you run and how hard the car is on tires. If the temps are higher or your car is hard on tires then I'd opt for the 35. Cary

Yes' date=' kinematic changes (suspension geometry) will have more influence to the handling than what you can get with spring/bar/shock changes. If you're looking to really increase performance this is an area to focus on. A good DIY book is Race and Rally car sourcebook by Staniforth. For more of an engineering approach, Milliken's Race Car Vehicle Dynamics. And an even better option would be to invest in Claude Rouelle's seminars in data acquisistion. He spends a couple of days talking about vehicle dynamics. It's like having a book you can ask questions of and get answers (http://www.optimumg.com). And if you're really fortunate the seminars by ICP (Richard Pare and Steve Lathrop), which are aimed at club racers and have a ton of good info on them. Cary

Active suspension doesn't defy the laws of physics at the end of the day weight will still transfer. It does offer extraordinary control of how that transfer is proportioned and that is the key. I seriously doubt anyone will offer a retrofit kit ever. The software would need to be fine tuned to each application (car, tire, use, etc.). A basic Motec data logger that has the minimum amount of channels to do this will set you back at least $5k. So it is interesting but probably not of much use to us. Cary

It was nothing more than being able to make a quick change in a repeatable manner. Often when we have sub-minute runs I only have 4 to 5 minutes at most before I run again. So taking temps, pressures, and deciding what needs to happen is really compressed. The tube car will have a number of adjustments done with shims so I can make changes very quickly. I'm hoping for the limited amount of time I have to practice it will help with testing. Most times if I get out of line than I have a huge wait. So the theory goes that I need to make as many adjustments as I can in line with very basic tools. Cary

I have the GC plates and originally got them for a 280Z. When I test fit them they seemed to have room for caster adjustment. So it may be that the older 240 has a much smaller strut tower and that's something I'll have to take a look at as I have friends with just about all versions. The instructions I got were a joke. You'd think GC could supply some instructions drawn on CAD with an acutal size template for drilling and cutting. What I got looks like a fax of something someone drew on a napkin. What I do like about the plates is how the transfer load from the spring to the plate rather than the spherical bearing. I ended up changing how these mount on my car. I put them on top of the tower and made a plate the goes under. My toughts at the time were to come up with a shim arrangement to allow quick camber adjustments while autoxing. Cary

I should point out that 13s do take some work to get good brakes and steering arm clearance. For tires you can check e-bay, local race tracks, http://jbracingtires.net/index.htm, and other sources. I get most of mine from John and he's always treated me very well. Tires are bagged when not in use, mounted with nitrogen, flipped every three events, and treated with Formula V as needed. I start with two sets and after a year I rotate in a new set. I keep a running log of their use and match them by diameter. It's important to do this with bias ply slicks as they grow as they are ran and you can end up with weird handling if you don't adjust for this growth. I try to keep tires matched by diameter on each end. Radials needn't worry about this. And I get the car off hot tires as soon after a run as possible. It all helps to make them last longer. Cary

Yes' date=' that the idea. If you mount the heim in the right spot you should be able to the keep the installed height about the same as a normal bushing. Even if it ends up being taller it won't be enough to cause a major issue. Keep in mind this was a Rocketsports TA car and they have deep pockets. They appear to have used a 3/8 MS spec rod end. I'd opt for lager cheaper ends. I'm guessing a half inch would be overkill but you can get a cheap grade. Or a decent grade 7/16. What's really cool about this mounting method is that it lowers the friction of the swaybar mounts. Poly mounts can have quite a lot and what most people don't realize is the solid U-shaped bars bow in the middle when worked, which leads to more friction. The heim allows this to happen with no worries. And reduced friction always equals more grip. And if you don't want to do this you can always wrap teflon tape over the bar where the bushing is. Or make plastic bushings that have better lubricating properties. The teflon tape will help against squeaks for street cars. I guess the pic helped Cary