Rear Caster on Reynard

[bonessi]

Could any one tell me how to check the rear caster on an 84 Reynard. The book that I got with the car gave a starting point for the radius rod length and said to adjust to 0 degrees caster but does not tell you how to check it.

[Purple Frog]

There is a reason engineers have developed more modern cars since '84.

Let me see if I can explain this in less than 8 pages... The upright is wider at the top than the bottom. The rocker arm and the track rod attach at opposite ends of the top of the upright. The centerline of where those two fasteners attach to the upright needs to be level horizontally for that upright to have zero caster. Does that make sense?

Unfortunately, unless you build a special tool, it usually has to be measured with the wheel off. So... you set the car up on the scale pad. Then measure what angle the rear rocker is. Then remove the spring and wheel. Set the chassis back to the same position it was before on the pad. Then move the rocker up to the referenced angle. Then measure the angle of the caster. I used a long bolt that I screwed in place of one of the fasteners, then set my digital level on that bolt.

Once I went through this whole mess, I reassembled the whole mess, and put it on the scale pad. I 'zeroed' my digital level on a reference point i had marked on the chassis. Then I picked two points on the track rod and the rocker and measured that angle. Then I created a documented table. Let's say that if the rocker was set to 0 caster, but on the scale pad the assembled car measured negative 8 degrees between my selected reference points. Then anytime I needed to throw on a corner at the track, i parked the car somewhere, zeroed the level on my reference point on the chassis, then changed the drag link until my two reference points between the track rod and the rocker got to -8 degrees, and tightened it all up.

Totally confused now? OBTW, the ol' timers just eyeballed it.

[bonessi]

Thanks for the help. I was trying to get the car squared up and notice that that angle you were talking about was a lot different on one side. I just place my digital level on the top of the upright and adjusted the radius rod till the angle was the same on both sides. The wheel base on both sides matched once the angles were corrected. I assume it is probably more important that the caster is reasonably close to the same on both side and the car is square then to have precisely 0 degrees.

Thanks again
Dean

[kea]

Or,
you could just adjust the radius rod (trailing arm) until you get zero bump steer.
Keith

[RacerDave51]

Dean, good meeting you at the Atlanta SARRC--I've got the blue '89 Reynard. I didn't have as much time to chat as I'd like but we hope to see you at the Nashville event in Sept. Let me know if you need a hand & I'll do what I can to help.

Dave

[bonessi]

Dave, it was good to meet you as well. Unfortunately I will not be able to make the race in Nashville. My sons racing career comes first and we will be at the grand nationals in KY that weekend. I will probably make the Roebling race the following week and defiantly the ARRC. I might actually get these cars figured out but will need to get some track time as well, in the dry preferable.

Dean