Does anyone know how to make a 67 Riv handle better? whereas I am considering putting 500 spring rate in front and leaving the rear stock along with heavy duty sway bars (from PST).I am also considering putting 295 40 20 wheels in front and 305 40 20 in the rear Any input would be a great help to me.

Add something similar to the factory GS sway bar package (front and rear sway bars), plus polyurethan sway bar link grommets (Moog has a replacement set with blue plastic which seems to be more durable than the clear ones other use). Putting a stiffer spring (ride rate at the same ride height) in the front without similarly stiffening-up the rear spring rate can make it understeer more.

"70" aspect ratio tires can provide a stiffer sidewall for a little more steering response. Plus running the front tires a few psi higher than the rears can help in that area too.

Sway bars and performance tires are the easiest things to do and should be "bolt-on" in nature. You can also check the condition of the many rubber bushings in the suspension--front AND rear. Replacing the suspension mounting-point bushings arbitrarily with polyurethane items can transfer stresses to places in the frame/body which weren not desired to handle that level of stress. Upper control arms are one place they can work, though, as are rear track bar bushings. It might be that only OEM-type rubber bushings are all that are available--in which case you might do an old shadetree trick of sinking some small finishing nails into the rubber to reinforce it and stiffen it up.

You can make it handle and steer with more precision, but it will take a significantly high level of modifications to make it a "canyon carver" rather than a vehicle which is safe and comfortable at higher speeds on the Interstate and more fun on some curvy roadways.

Just some thoughts,
NTX5467

Unfortunately, if you combine 500 lb. springs and 20 inch wheels, it will ride like a brick. I think 17s would be a good compromise between performance and appearance (I think huge wheels on older cars like this make them look like giant toy cars). Besides, going bigger than 17 inch wheels won't do anything except add weight. The car will get slower, braking and acceleration will suffer and the tires will be horrendously expensive (this big car will probably eat soft performance tires fairly rapidly). If you live anywhere there are potholes, you can probably expect to damage the rims hauling around that much heavy iron, too. The 17s with 45-series tires on my Mazda take a beating here in Cleveland. 40 series tires will be like O-rings on giant wheels like that. Depending on the diameter, your speedo might not read correctly anymore, either.

What kind of handling improvements are you expecting? This is a 4500 pound luxury car, so it's going to be hard to make it sharper around corners. NTX's suggestions are good ones, and are probably your best bet for getting some kind of improvement that will make the car more fun to drive without spending a fortune on serious modifications.

I'd also strongly recommend upgrading to some high-quality shock absorbers. Beyond tires, shock absorbers make the single biggest difference in handling, and good ones can dramatically improve cornering. Koni and Tokico might make some for a car like this, or you could cross-reference the sizes and find something compatible. Since the Riv is a kind of unusual car, you might have to do a little research.

Good luck and have fun with the car.

Thanks for your informative input

When you purchase tires, are you looking at the speed rating? This has to do with sidewall flex. The higher the speed rated tire, the stiffer the sidewall. You can change spring rates, add sway bars, go with different aspect ratios on your tires and all sorts of other things to try to help improve your car's performance. But, if you run too "soft" of a sidewall on your tires, all the other things you spent money on will be negated.

Speed ratings have several effects on how the tire is built. One is rubber compound (and softness thereof, or lack of). The sidewall in a radial tire is not specifically where the speed rating comes in, but in the tread plies AND "caps" on them.

When radials were real radials, the angle between the sidewall plies and the tread belt was right at 90 degrees. When the P-metric higher pressure radials came out, they had to soften them somewhat to compensate for the higher pressures and not have a lot of impact harshness at low speeds in the tires. In the earlier radials, if you put an unmounted radial on the floor (vertically) and leaned onto it, the sidewall would flex with the weight and the tread would just flatten against the floor (this is with an unmounted tire). One time, I got a steeple in a Pirelli P76 tire. I got the steeple pulled out and the tire returned to a round state, like it was re-inflating itself, rather than maintaining the flatten area.

If you do the same "lean on" test with a normal P-metric radial, it acts like a bias ply tire, the sidewall flexes and the tread buckles against the floor (just like a bias ply tire would do, when mounted, if it didn't have enough air in it). This has been my observation in this area.

Michelin has seemed to expand their "Banded-At-Zero" (BAZ) tire selection over the past year or so. This is the addition of the outside "cap" over the normal tread plies to further stiffen and stabilize the tread area of the tire. Same thing the "belted" tires did to bias ply tires, back when. The more stable the tread is as it contacts the road surface (stable = no flex or buckling or distortion), the better the tire will perform and have lower rolling resistance and generate less internal heat as it "works". It also provides a better platform for the manufacturer to use softer rubber compounds (for better handling or better ice/snow performance) without harming general wear characteristics. The Michelin BAZ technology also seems to be a key component to their "Green" labeled tires.

To me, where sidewall stiffness comes in is with steering response and ride harshness. Stiffer sidewalls can also make shocks and struts act differently, too, as it seems the less filtering of road shocks puts the valving into "high speed" mode rather than "cruise mode", so they feel firmer sooner.

Sidewall stiffness can also be affected (+ or -) by the relationship of the tire tread width to the wheel rim width. Each tire size has a "design" rim width it is optimized for. Going toward the more narrow sizing in that design spec will make the sidewalls flex more and ride softer (more "bow" between the tread and the rim). If you go the other direction, with a wider rim, the sidewall becomes more vertical to the rim (between the rim and the tread), which can increase steering response a little. Typically, the recommendation is to have the rim width approximately equal to the tire's tread width, or possibly up to 1" narrower.

If the sidewall becomes too short and/or too stiff, then it can be a hindrance in cornering as the car leans and the camber angle between the tire's tread and the road surface make for part of the wider tread not being in contact with the road surface. Plus, the lack of flex and impact absorption ability, relating to potholes or similar, can result in bent or broken wheels.

Personally, if I'm going to look for a tire with good higher speed endurance and performance, I'll look at the tread plies in the tire's construction first. Particularly, if the "radial cap" is there. This is one area of the design that is generally affected by air pressure only rather than the wheel the tire is mounted on. Then I'd look for a rim width that is toward the wider part of the design spec, to keep the sidewall more vertical intentionally, rather than rely only on inflation pressure to do that. All of this is BEFORE I look at speed ratings from the manuracturer.

Typically, when you get past the "H" rating, the sizing and wheel choices become more specific for the application. The lower aspect ratios are there more for handling and wider tread areas than high speed endurance, typically. And they'll generally have a softer rubber compound and less treadwear ratings, as a result. Sizings are also pretty specific in these higher speed rating tires as they are now generally purpose-specific designed for particular vehicles ONLY with no non-speed rated tires in those particular sizes.

Regards,
NTX5467