Big Caster - New Front Suspension Xmember

[260DET]

From a discussion some time ago, some people for road/track were using up to 7 degrees caster. Now mine with 3 degrees results in the tyre running close to the front part of the guard (fender). So it looks like to increase caster more, the front edge of the guards will have to be cut out. Is this everyone's experience?

 

Anyway, I'm looking at fabricating a new Xmember mounted further forward, incorporating vertically adjustable steering rack brackets for bump steer adjustment purposes. Not sure that the stock rubber top strut mounts will allow the struts to be inclined forward that much. And the steering shaft from the rack to the flexible coupling may be too short, although the coupling itself could possibly be extended in length. Any other problems or comments?

[ZROSSA]

Do you have adjustable camber plates? You can get or make some that will adjust for camber and caster. The caster adjustment just moves the top of the strut back. This way you dont need to move your crossmember and you can change it around so you can find what works for you.

 

Douglas

[Guest Anonymous]

Any one have a design or blue print to make adjustable camber plates????

[blueovalz]

I moved the entire crossmember forward to increase my caster to roughly 7 degrees. The shaft that comes out of the steering column to the coupler is splined and will slide several inches with adaquate engagement. To use camber plates on top to account for all of the required movement would push the towers inside dimensions beyond their limits. Not knowing the static ride length of your struts, I am guessing that a minimum of about 1.25" movement will be required to achieve the 7 degree (4 degree change) caster. My first design consideration was to drill out the tower's spot welds, and then move the tower rearward, and re-weld, but then I realized the advantages of moving the crossmember forward (better use of polar moment & weigh distribution, increased clearance for the front of the V8 oil pan, and custom bodywork on wheel openings) instead, and chose that method.

[Mikelly]

MY Front suspension kit will place your caster settings further forward than you can use, due to tires rubbing fender/ spoiler front section. The guys I sponsor in California are running over 7 degrees of front caster and had to trim about and inch out of the spoiler/ fender to get the most out of it. However, You must use the control arm with the TC Rod, as rubber or urethane mounts don't allow enough forward movement without binding.

 

The more caster you can get, the less CAMBER you will need in most street/ autocross situations.

Mike Kelly

[johnc]

> The more caster you can get, the less CAMBER

> you will need in most street/ autocross

> situations.

 

Well... assuming you haven't done anything (like bumpsteer spacers) to screw up the standard camber gain curve then yes, you can reduce the amount of static negative camber. But you still want about 3.5 degrees of negative camber at full bump on the outside tire.

 

Running less static camber does help the car brake better and it can help it turn in better, assuming correct spring and anti-roll bar rates. Increasing caster will reduce steering sensitivity, increase the amount of road shock transmitted through the wheel, and (if taken to extremes) will cause the inside tire to be drug across the road surface increasing wear and inside half tire temps.

 

6 to 7 degrees of positive caster is about the limit on a 240Z for track events. I have seen (and run) up to 10 degrees for really tight autocrosses but that was very course dependent and my arms were like noodles at the end.

[260DET]

Thanks all, the idea is to improve turn in and to reduce loading (and wear) on the the outer edge of the outside tyre in a corner, without using more than around 1.5 degrees negative camber.

 

We have patented eccentric camber adjusters, which instal on the inner suspension arm pivot in the Xmember. No-one slots the strut towers around here that I know of.

 

Like your kit Mikelly but freight to here would be a killer. 1.25" forwards eh Terry to get around 7 degrees pos caster. Thanks for that info.

[260DET]

Looks like I'll go with Terry's idea and move the Xmember forward. Could fabricate a new one but there doesn't seem to be much point in that. Thinking of a modification to the steering rack mount, using heavy fixed threaded bolts, so the rack may be adjusted vertically for bump steer elimination purposes.