The Slow Lane

I really am trying to get you caught up with the developments of the car because I would like to blog about other things besides the Miata. But I don’t feel right about doing it when I’m three weeks behind with the updates. And so with this post we should be up to date. After the 9/23 SJR autocross where I found the front sway bar was hitting the upper control arm I got to work on a solution. The CSP driver I talked to suggested that I purchase some female rod ends from McMaster-Carr to make shortened end links. I wanted to salvage as much of the Mazdaspeed links as I could. They were not as expensive as some other end links I saw while looking around for solutions, but that is no reason to throw them away. I paid for them, I wanted to more than three events out of them.

So I came up with a plan to cut the middle part of the ends link. This is a piece of aluminum hex bar stock with a threaded hole down the middle. I took one end link apart to measure. It looked like shortening the middle part by 3/4 inch would do the trick. I found out that one of the rod ends was a left hand thread, opposite of normal. This meant I would have to cut the peace on both ends. And I also figured out that I would have to shorten the threaded shank of the rod ends themselves. I already had them threaded in about as far as they would go and much more and they would hit each other inside the middle piece. I took one of the left hand ones and test cut about 3/8 inch from it with my Dremel. It drained the Dremel battery down in the process but it worked.

I was skeptical about cutting the middle pieces on my own. A jam nut locks against the end of the middle piece, where I would be cutting. So if I cut badly (I probably would on a part this wide) There wouldn’t be a good seat to tighten the jam nut against. I talked to someone in work about using a band saw in our R&D lab to cut them. Apparently the band saw blade is quite dull and he suggested cutting them on our pipe cutting bench. I would have to wait almost two weeks till my next Friday off or borrow the key and go in on a Saturday. As I thought about it I got worried that the middle piece would not fit into the pipe cutting bench being smaller than most pipe and not very long. So I fell back to plan B and ordered the female rod ends from McMaster Carr. They were only a few dollars each.

In the mean time, the next weekend I had to fix the other issue with the sway bar which was binding in the bushings. I just used the washers under the bracket method. They were pretty easy to install. I worked one side at a time so I did not have to take the bar all the way down. Each bracket has to bolts holding it up. I loosened them both but only removed one at a time. I found that I needed not one, but TWO washers to space the brackets away from the frame enough to prevent binding. The bolts holding the bracket in are M8 but 5/16″ washers will work fine. The ones I bought from Autozone were marked for both. Once all the washers were in and everything tightened back down I could rotate the bar by hand. Sweet.

I also attacked the brakes. The car had developed an annoying squeak that sounded like brakes. If you recall when doing the suspension I discovered that one side of the rear pads were almost down to the backing plates. I suspected the noise was that side. I also had a vibration in the front from that snafu that happened with the rust under the rotor. The Miata, has a known issue in that they tend to lock up the front brakes. The balance is biased too much towards the front. The common remedy is to put an aggressive compound in the rear and a lower end pad in the front. Even though I don’t know what brake pads are on the front I don’t think they are anything special. So I left them alone.

For the rear the most aggressive street pad you can buy is the Hawk HP+. I had them on the front of my Prelude and hated them. They are very noisy. Now most of us “racers” are used to trading off noise for increased performance and bite. But the HP+ was just too much of a trade-off. They made noise all the time, especially when warm, like when you are in traffic! On the Prelude they were so aggressive I was constantly activating the ABS. The Miata doesn’t have ABS. And they dusted like crazy. So I chose the next step down, the Hawk HPS. They are a reasonable compromise. They have good bite, but good modulation. And not not squeal, grind or dust like the HP+.

I shopped around for the font rotors online. Autozone rotors are good enough for even the abuses of road racing so they are good enough for autocrossing. And they are normally pretty cheap. Not so for the Miata. They were somewhere around $50 each. The best price was $25 each for Brembo “blanks” through the Tire Rack. Brembo is a high end brand so that was a no-brainer. The brake stuff went without any problems (FOR ONCE!). I had to wait till Thursday for the female rod ends from McMaster. I put them in that night int he dark so I could take the car for a test drive Friday. The next autocross was on Saturday. I had to screw one of the rod end pairs together a lot. The other was at the minimum number of turns I felt comfortable with. Something seemed off but I had to just get them on and drive. Next post I’ll tell you how I did and I make some more adjustments to the car.

A little after the sloshing wet rain event I managed to find a diff for sale online. My plan was to just call up Planet Miata and buy a Viscous Limited Slip Differential from them. I did call them and they first told me the diffs did not come with a rear housing. That is the part I really need! They are an additional $150. Second they told me they didn’t have any viscous diffs. They are too hard to come by. So it would have cost me $350 for a complete open diff. Screw that. I decided to see what I could find for sale elsewhere. I had tried Miata.net’s classified section before and I did not get any email response from any of the diffs for sale. But I tried again and I saw 5 different 1.6L diffs for sale. Some open and some viscous. I actually got a response this time from someone selling a viscous. It cost me less than $200 shipped! Great deal. And it was from the south so it wasn’t all rusty!

The diff showed up within a week but right before an event on 9/2 at Boeing. Again not a lot to say about this event. The course was basically an oval loop with a slalom and some offsets in the middle. During the 180 turns I felt the car understeered a bit. But they were fairly tight as Boeing is a small lot. 4th out of 7 in class (.095 out of 3rd) and 26th out of 93 in PAX. I could have been distracted as this was the day I proposed to Irene! What a sweet day. I got to go autocrossing in the morning and proposed and had a great evening.

The next weekend I was up at Irene’s Dad’s to put the diff in. All went well except one of the bolts holding the cat to the exhaust didn’t want to come free and we broke the stud. So that had to be drilled out. We had some trouble drilling it out. It ate a few drill bits before we could put a 3/8″ slot in the cat flange. The drills were walking to the side. I went to Autozone and got some 5/16″ fasteners to stick in there. Well when trying to put the other bolt on that stud broke. The 5/16″ hardware on the other side wasn’t really working out anyway. So I ended up buying a cat from my Dad for $110. Sigh.

The new cat went in pretty easy. I had to grind two spots because the pipes stuck out past the flanges because of the angle the flanges were welded on. I used this opportunity to try and make the exhaust fit better. the center pipe hangs a little low and misses the hanger past the cat because of the snafu with the downpipe bracket when we first put the exhaust in.

I got to try out the diff the next weekend at South Jersey SCCA event. This event went very well on a couple of fronts. The lot SJR uses is at Camden County College in Blackwood, NJ. The lot is small. Not as small as Boeing, but small enough where you end up with a lot of tight elements. They usually set up the course so you run along the outside of the lot and get some higher speed elements and then the course kind of loops inside itself where you get the slow speed stuff. Unbeknown to me b/c I hadn’t run there all year they are doing construction right next to the lot and there was tons of sand that blew onto the course. And b/c the lot is old the asphalt binder has worn down allowing the sand to get caught in the valleys formed by the aggregate (those small rocks in the asphalt). If you got off line you just slid in the sand.

I didn’t really notice the diff working. The car felt pretty much like it did before. But the general consensus is that viscous diffs do not do much locking and when the get to high mileage they pretty much function like open diffs. But these are the same people who say it’s a must have item to be competitive. Who knows. Anyway I noticed that on a medium-to-slow increasing radius 180 turn the car would understeer on corner exit and I started noticing a clunk going into and out of the turn. I checked underneath the car between runs by turning the wheels to lock and saw that the sway bar was hitting the upper control arms! I thought there was enough clearance when I put it on but that was with the ar in the air. That would certainly cause understeer. I also suspected that the swaybar was binding in bushings as it is a common problem with the Racing Beat bar and I didn’t have a chance to remedy it when installing it a month or so ago.

Despite this the handling wasn’t bad and I got a win in STS2! Granted there was only one other competitor in class, Barry. We often talk and his car is less prepared than mine so I should beat him. But it is still nice to know that I didn’t allow him to out drive me. The bigger surprise was that I ended up 5th in PAX! I really wasn’t expecting that. The prevailing theory is that the lot is so sandy that street tires are a help and not a hindrance compared to R-comps. There were 2 very fast drivers on R-comps ahead of me so it wasn’t just the tires. I got a nice little “PAX” magnet and a boost of confidence. And now I knew I that little bit of understeer I felt sometimes was really something and shouldn’t be there. I had some more work to do on the car. But it is just the “working the bugs” out type stuff that I knew I would have to do some of no matter how much I tired to plan ahead. In my next installment we fix the swaybar issue and go autocrossing all weekend!

The first event I got to run on my pimpy new suspension was a Philly SCCA event at Boeing in Ridley Park, PA. The Boeing lot is small and the courses tight so not the best test for a new setup. It rained off-and-on the whole morning, including 30 min where it poured and an hour lightning break. Buy the time I ran in the fourth heat the ground was dry. The car handled well, but I thought on the tight turn the car understeered. With the short Boeing courses there isn’t a lot you can tell about the handling. I finished last in class (out of 6) and 36 out of 102 in PAX. Not the performance I was hoping for but this was the first outing. I still have to learn the limits of the car.

The next event was three weeks later at Warminster Community Park. Warminster is an old airstrip so the courses have a lot of transitional stuff and only one real sweeper, the turn around. But because of the length you always get some high speed elements. I figured it would be a good test. The weather had other ideas. It rained on and off the entire event.

Since I had no idea how the car would handle in the dry, much less the wet, my natural inclination is to take it easy if I feel unsafe. But I told myself I had to push it till I spin so I could learn the limits of the car. Thats part of what autocross is about right? Once on course though instinct took over and although I wasn’t babying it I didn’t push it hard enough to spin or loose control. The car was very good in the rain. Surprisingly good. Lots of grip. Well controlled. It didn’t oversteer. I ended up 5th out of 6 and 94th out of 176 in PAX. That’s all I can say about the first two events. I got wet. And I didn’t get to learn the limits of the car.