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| Joined: | 04-14-2005 |
| Location: | Columbia, South Carolina USA |
| Posts: | 156 |
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The biggest single cause of the J-H's oversteer: excessive rear roll stiffness. This comes mainly from the stock rubber bushings binding. What happens: as the body rolls in a turn, the bushing's rubber does not slide, it twists. The further it twists, the more resistance, just like any type of spring. The more resistance, the more likely the inside rear tire will come off the ground and voila: oversteer. A rear sway bar will make this worse, as will anything else that keeps the rear axle from 'articulating' under the car. Stickier tires can help with this but are not the true answer.
Urethane bushings are another partial answer, but to be effective the bushings for the top of the axle must be replaced as well. For a long time, they weren't available in urethane, I believe they now are. When installing the urethanes, grease the dickens out of them but do not use chassis grease; use either Energy Suspension's sticky urethane grease or dielectric silicone grease. Be sure to lube the flat faces as well as the steel tubes. This is very important; urethane is a 'sticky' plastic and will bind if not lubed, thus bringing back the oversteer issue.
Urethanes still have one problem: as the control arms move, the sleeve needs to move in two directions at the same time. Urethane is hard enough that it still adds a good bit of resistance to this two way motion. For 95% of street driving, this will not be an issue. The rear will be more predictable up to the very limit but will still come around when seriously provoked.
For the great majority of driving (99%) a combination of urethane bushings and stickier tires will be more than sufficient. That last 1% would mean spherical bearings or rod ends instead of the rubber and that is a difficult and pricey thing, I would put it at 4 cases on Greg's 'vino' scale.
EDIT: If you are looking for a reasonably priced truly sticky street tire, you could do a lot worse than the Falken Azenis RT615. They have a 200 treadwear rating, unfortunately the smallest size is a 195/60-14 and that one probably will be gone in a few years as sales drop. Currently that one sells for ~$70 each. If someone is planning to go to 15's anyway, they have a 205/50-15 that should fit under the fenders well (always assuming correct wheel backspacing, etc). That size usually goes for ~$95. It is not the worlds' greatest rain tire, though.
The supply of DOT approved race tires and other 'streetable' performance oriented 13" tires is rapidly drying up, unfortunately.
Last edited on 05-20-2009 07:33 pm by Jensenman