if you're doing the rear shackles, consider sliders instead if the class allows them. Consistent spring rate with no jacking/anti-jacking (if installed correctly), and better lateral location.

UPDATE

OK we inspected everything:

First it appears that the washer on top of the sway bar busing/end link is brushing the chassis rail, read the rail comes to rest on top of the washer. There is a few millimeters of the outer edge of the washer that is scuffed and that lines up with the chassis. On the chassis rail there is an abrasion on the radius that runs up the side a few millimeters. While this is not a smoking gun I have shortened the end link so it will no longer foul the rail.

Second I have a second pair of Koni shocks that are newer 80-2359 (old ones are 80-1977) which I will fit as they are in better shape. I plan to get a hold of a set of dampers that I can adjust both the compression and rebound. In the meantime I have marked the Konis in 1/4 turn increments and I will play with them.

There were some other things that could be better such as the rear spring shackles so I'll square those away as we'll.

With all that said we did NOT fit a panhard bar. My fabricator wanted to take care of the various things that need tidying first and then reevaluate. We also discussed that other 1200s were not experiencing this and that did factor into it, so thanks.

Tom

Could it be that the h190 leaf spring mounts are 15mm further apart than the h145? So the leaf pack isnt compressing or rebounding straight up and down as intended?.

B310gx, I've been using the Hoosiers since 2011 and run them at the same tire pressure I always have. When I installed the H190 I likely got something wrong. I am perfectly willing to play with tire pressures on the Hoosiers BUT when I bought the latest set of tires, the tire guy convinced me to try a set of Avon ACB9's as we think they may have some benefits.

As for fabbing up parts it is not a big deal, I have some links left form the sports racer that happen to be very close to the right length.

On the fancy parts versus driver talent, I have always felt that it's good to at least start with a basic car so that the driver has to dig for it.


Tom

and btw,l18_b110,

that coupe sure looks the goods mate

awesome!

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or could be your just a better driver..

many a cars ive seen where the driver is the difference!

so despite "fancy" parts the driver couldn't drive to full potenianal...
esp if the parts are track proven by provider over many many years of track experience.

Are you sure it's not just tyre wall deflection, as in the photo on page 2. If the rim is moving laterally inside the tyre, due to soft sidewalls, insufficient air pressure, etc, the car will seem to be slaloming from the back by itself. I had this happen with some 245/515x13 slicks on 7 inch rims, if the tyre prssure was too low. Looking at the 2 outside rear tyres on Harrys' cars, in both instances the rim is pretty much in line with the side wall of the tyre. As the tyre you use seem to be a Hoosier, I've found them to be weak in the sidewalls ( a mate uses them on his hillclimb openwheeler) & crossply's. It might just need a few more PSI to make a difference. It's also a bit cheaper to change than fabricating major suspension bits.

All,

I got my fabricator pal to look at the video and he also believes there is either something binding or something loose working like a hinge. The plan is to inspect everything including down checking the shell. With all that said we will be installing a lateral location device because it won't do any harm. When I get it on track we'll disconnect each component and notemthe effect.

My reason for think lateral movement is it does "feel" like something in the back is moving, having experienced the bottoming in the Miata it just doesn't feel the same.

Simon please explain uncoupling the springs, I think I know but not sure. Also you are correct making the car more predictable will let the driver get the last bit out of the car. It's not the car is way faster it's just that you can zero in on maximum grip immediately. I am pretty good at catching a car but doing that 12 times a lap for 15 laps is going to result in losing time even if it is only a couple of tenths.

Harry I am a big fan of low buck low tech ingenuity; case in point was my old Volvo 144 car that I used for rallycross. The suspension was a mix of other model stock parts, 164 front springs, wagon rear springs etc. I even ran used rally tires. I kicked butt with it, many a Subaru driver were left wonder how the old brick went so well.

Tom

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Thanks, yeah sold it to some guys in SA. Now has SR20DET and just about everything else changed too. Looks better than ever I reckon.

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Hi Tom(and everyone else),

I also don't think this is a lateral location issue.

I'd be checking for front spring eye bush wear, too much front toe out, Uncouple rear springs to prevent bind(I can help with this). Check rear toe(you want toe in) ensure enough bump and droop travel at each corner. Check all the Caster rod bushes, ball joints, tie rods and steering box for play. And lastly, it may need some more rebound in the shocks.

Putting the watts on my car made a significant difference to knowing what the rear was doing. It didn't initially give me more speed but gave me the confidence with predictability in the rear that enabled me to drive it faster. But as Retrorally has touched on, any lateral location device MUST be a lot more rigid(rod ends etc) than the spring location.

The other huge advantage is you can very quickly adjust the oversteer/understeer balance. Mine has a ball screw adjustment that takes less than 30 seconds to change.

My car used to do something similar. Mine was too soft in the rear and the second it lifted the front wheel, the outside rear would overload and would snap oversteer.