S30 and caster

[fusion]

I understand that a stock 280z has about 2-3 degrees of caster.  I have read that usually more caster is better.  For a 100% street car, would there be any advantage to having more caster?  Would I notice a difference at high speeds?  I am planning on electric power steering.

 

If so, has anyone ever slotted or made a new plate for the shock tower top to move the top of the strut or coilover back?

 

Thanks

[fusion]

Anyone have any input?

[jhm]

Not sure I understand what you mean "make a new plate for the shock tower top"; but there are a couple of camber plate options that allow you to move the top mounting point of the front strut assembly "rearward", in order to achieve a slight bit more caster.  DP Racing, K-Mac and Ground Control bolt-in camber plates are a couple examples.  EMI plates were a very popular option years ago, but they are NLA (new)....might be able to find some used.  If you use the camber plates to achieve increased caster, you are doing so at the expense of decreased static camber. 

 

A more effective technique to increase your caster is with adjustable TC rods.  To make any significant difference, you would need to use these in conjunction with a front LCA that incorporates a monoball mounting (i.e. not the stock rubber bushing).  You can fabricate your own monoball LCAs, or purchase them pre-fabbed from vendors like T3, Futofab and Apex Engineering.

 

The advantage of more caster in a track car is that it allows you to run less static camber (for better braking performance) and still achieve good dynamic camber characteristics on the loaded tire during turning.  For a street-driven car, I honestly don't know what the benefits of increased caster might be....perhaps better high-speed stability?  Keep in mind that increasing the caster will result in heavier steering at low speeds, because the wheels are having to actually "lift" the front end as you dial in steering input.  

 

Hope this helps.

Edited November 12, 2020 by jhm

[JMortensen]

If you go to coilovers you can run a much smaller 2.5 ID spring, and then you can move the strut top back within the existing tower. This is not something we can do with the S30, but the S130 has much bigger strut tops, so more room to play. They do it all the time on Mustangs, so it's a known solution. I haven't seen a double adjustable plate for a 280ZX, but anything that has the adjustments and is generic enough should work.

 

Might be able to just use the Mustang parts, just need adapter bushings to fit whatever struts you're running: https://www.maximummotorsports.com/Mustang-Caster-Camber-Plates-1990-1993-P254.aspx

Could probably use these 510 plates from DP and cut the hole to the rear to add caster if you prefer: https://www.dpracing.co/datsun-510-front-suspension-1

[fusion]

Thanks guys.  What I meant by a new top is that I could take a 1/8" plate with the shock holes drilled offset towards the rear and weld on the shock tower to give more caster.  I have BC coilovers now.  I think I could get 1/2" or so, maybe more.  I'm in the middle of a resto mod build so I don't mind doing it if it's a good benefit.

 

I don't plan on tracking the car, so I'm not concerned about the race benefits, I've just heard that the s30 has pretty poor camber from the factory.  I've read that any adjustments on the tension rod aren't as beneficial because it puts the LCA bushing in a bind, and you don't get much adjustment anyways.

 

Thanks

[JMortensen]

Why did I think we were talking 280ZX? Sorry about that.

Looks like a  280Z, there isn't enough room to move the strut back very far before the spring hits sheet metal, maybe an inch. You could cut the whole strut tower off of the upper frame rail and move it back, but that's a hell of a big job, and you better tie it all together well because it's a highly loaded part of the chassis.

It's a lot easier just to run an adjustable TC rod. You can completely solve the LCA binding problem by running monoballs or rod ends on the front LCA. The next issue is that the tire will hit the front fenders or the airdam if you have one. Can trim for clearance.

I haven't looked at it for a long time, but I seem to recall people getting into the 8 degrees range on race cars with adjustable TCs, and 5 degrees is easy. Caster made a huge difference on my Z, one of the best mods I did back when I was daily driving and autoxing every month.

[Cruzzar]

I don't know what EPS unit that you will be using but it appears that in many adapted EPS applications the owners complain that the after installation handling or specifically the 'return to center" is not as good as was previous to the change. In various domestic applications  some have even gone to 4 and 5 degrees of caster with some luck. I have a Saturn VUE EPS in my other car (53 Studebaker with aftermarket front suspension and R&P steering) and I dialed in 3 1/2 degrees of caster and I still have to manually return the wheel after going around a corner. You might want to ask if anyone has put an EPS unit on their Z and see what their opinion is. There are getting more and more specialized EPS units on the marker and maybe they have found a way to correct the return to center issue.

[fusion]

Thanks to everyone for your comments.  Another reason I am not excited to use the tension rod to increase caster is that I am not too keen on moving the wheels further forward in the wheel well.  It seems that even at factory settings the wheels sit slightly forward.