Datsun Roadster Forum-311s.org

So for the 4th time in the past 5 weeks the roadster was back on the AutoX course. This time I had to drive the car to the race, no trailer.

So it was back to the Marina Ca airport for event #7 of 13 of the NORCAL UFO series for the year. The turn out was huge, about 150 cars. I was in the 2nd to last run group so I was able to roll out of here about 9am (sure beats my normal 5:45am departure time.) and I got down there with plenty of time to get a run in with someone else to see the course. I got the car setup, but for whatever reason, I didn't burn enough fuel off on the trip down (I only used about 5 gallons for the 155 mile trip. Most of that was spent at 5K RPM) Usually I arrive with about 2 gal in the tank and add 2 or 3 of race gas to allow me to retune the engine for best power. Well, not this time. I added about 2.5 gal and ended up with a 3/4 full tank. Not the best for racing but whatever. My first run was pretty quick, I did a 56.102 on cold tires, it was clean and I knew I left lots of time on the course. The second run out I managed to do a set of donuts after the 3rd gear straight that ended in a 300+ degree hairpin that I got a little over zealous with. I went around about twice and took off in the correct direction (I don't know how I managed to keep it running). That got me 4 seconds added onto my opening time. Not really what I was looking for. I guess it was a good show however. Run #3 I got things put together and ran a 54.901 knowing the class winning time was a 54.204. For run #4, everything went wrong. Suddenly the car didn't stop, and worst of all, it wouldn't turn. The tire pressure was the same as before (checked between each run.) Going into the first tight corner, it plowed, through the first slalom it was all over the place, at the end it wouldn't slow down, and when I went to turn it all I got was MASSIVE understeer. That threw me off for the next section. I got out onto the 3rd gear straight and had to get on the brakes early to slow the thing down to have any shot at getting through the hairpin. The hairpin was sloppy and very sideways, and the finishing slalom was the same. I ended up with a clean 56.4 but it was not pretty.
I don't know what happened with the tires, it was like someone flipped a switch between runs and now I was driving slightly stickier street tires. I might have been dealing with the marbles from the rest of the days runs drifting across the course as I was running, the wind was blowing pretty hard, and there was alot of rubber out on the course. It might have been that or something else, I really don't know. The engine held together, so it looks like I will be at Solvang with it.

The outcome? Someone in a Datsun 1200 with a 13b in it ran a 49.xxx for TTOD, but I managed to pull a second place in class out of a pretty mediocre performance. I guess I can't complain about that.

So the tally for the past 4 races, 2 class wins (PCA), a 2nd and 3rd in class (NORCAL UFO) those counted for season championship points, and a 3rd TTOD last week with the PCA. I think thats it for this month, I need a break (and so does the car.) Anyone else have 6 races in this year already?

Will

Falken's give up and die if you over heat them. Most radials have the same problem. It is like a light switch. Stick, stick, stick, crap. Once they are gone you might as well coast back to the grid spot cause they aren't coming back anytime soon. A liberal amount of water spray between runs may help some but ultimately you will have to conserve tires during the run. The trick on radials and a sticky surface is to not push them as hard as they will go at the beginning of the run. You have to hold back so that they don't overheat. You really have to choose which corners you need 100% and which ones you can give up and not lose too much time. You might also check the swaybar bushings which fall out on my car frequently. This will cause quite a push as the body rolls and the tire goes up on the corner.

I was running a set of Kumho V710s. They were on, then they went off. I have run them much hotter in the past (the either didn't get to temp, or just barely got there.) with little issue. As for the Falkens, they have one use and one use only on my car, daily driver tires. They are useless for anything else aside from a drift competition. We will have to see at the next event.

Will

How many runs have you got on the Kumho's? I've not heard anyone complain that they fall off quickly but you'll only get about 40 runs before they start to loose grip. By 60 runs most of the newer R-compounds are dead. Victoracers last longer but don't have as much stick.

Will are you tracking temps before and after each run? are you tracking how many runs (heat cycles) you have on the tires? are you rotating the tires in any particular sequence? Are you monitoring pressures that the beginning and at the end of each run. Are you tracking ambient temps of the track? Are you seeing any uneven wear on any of the tires? Did your alignment get thrown off when you spun the car?

Tracking all of this information will tell you when your tires are starting to go away. And or what changes you need to make. Since tires are such a big deal when it comes to autocrossing having the tires go off just right is a big key to TTOD. As I am sure you are well aware.

In road racing we see our tires get slick if they are underinflated even by a pound or so, as they will exceed temp quickly and get greasy. We run higher temps and have found that our tires will continue to improve as they come up to temp. The down side is that they are very slick when cold, and take a least a lap to warm up to temp.

It could be that the tires are going away. I think I have about 40 runs on them. I have been told that they are good for about 100. I have been keeping track of where the tires are on the car, and I rotate them every time. The next time out I will be back to where I had them last year (in other words where they are marked to be.) The tires were sitting at 97 on both the fronts, and 95 degrees in the rear. I'll have to see what happens next months event. I think I'm in the conserve tire and engine mode now. (Hmmm, the Alfa has Panasports with V700s on it right now.........)

Will

Put the Alfa tires or tires and wheels on the roadster.

The V700s are apparently heat cycled out and are only 185/60s. They came with the wheels they are on. I need a 205 series, but they won't fit without the use of a larger baseball bat to roll the rear fenders more (perhaps a bowling pin?). I think I would be far worse off with the V700s.

Will

I have some pics here.









And some of the competition. The blue 510 is class points leader, and the 240 Z is 2nd.







We need more roadsters to come out and play.

Will

Two more, the car that set TTOD.



Its powered by a 13B. It weighs next to nothing.

Will

Check those swaybar bushings. After seeing it drag the door handles in those photos I would say that there is something odd going on. See that your outside tire is rolling onto the sidewall. You have a problem with not enough negative camber possibly caused by too much body roll.

I'll be checking those later today. The car will be out on Sears Point this weekend for a NASA event. We won't be running the R-compounds however, I'd like to save those for points earning events. I'm using it as a testing event, so hopefully some useful info come out of it.

Ok, I'm off to do a pre-race once over on the car.

Will

Ok, I'm not quite out of here yet. Here are some pics of my spin on run 2.
















That little round about cost me 4 seconds off my opening time. Somehow I managed to keep the engine running and roasting off the tires in 2nd gear. The pictures are in order, shot rapid fire. Weeeeeeee! This wasn't what I had in mind when I said I'll take it out for a quick spin....

Will

I've also had problems with the upper A-Arm mounting bolts coming loose. When they loosen up they allow the camber adjustment shims to fall out. This allows the upper a-arm to flop around a lot. I've been using washers ever since. It is a PITA to set the alignment but allows you to just tighten the bolts after they come loose and not have to do a complete alignment trackside.

Everything is tight, swaybar bushings are right where they should be. Looks like my 23mm swaybar is too small. I have the Konis set full stiff, full comp springs. I'm not sure what else to do to limit body roll aside from having a blade style sway bar built and fabing up some custom mounts to install it.

Will