280Z 2+2 Sectioning with Tokico BZ3099 on all 4 corners and spring rate question

[matteblack]

Hey guys,

 

First post as I'm getting ready to build my 1978 280z 2+2.

 

1) I was wondering if there is any negative to running the BZ3099 on all 4 corners by making the appropriate spacer for the rears? Is there any real benefit to buying the BZ3015/BZ3012 etc? I assume it would be fine as people are running the Koni 8610-1437 in all 4 corners.

 

I can save $80 going this route but is it worth it?

 

2) Since I am working on a 2+2 is there a different recommendation on spring rates? The car will be Sundays and Autox only.

 

Thanks

Edited December 18, 2016 by matteblack

[JMortensen]

You can use the MR2 shocks, no problem. If you are still using rubber isolators, you can save yourself the hassle of sectioning the rear struts by grabbing some 240 isolators and running them in the rear. That will drop the car 1" without doing anything else, then you just make the spacer to fit the strut insert. When I did this about a decade ago, I found that a 1.5" x .095 tube fits the BZ3099 just right. You can buy that on www.onlinemetals.com by the foot.

http://www.onlinemetals.com/merchant.cfm?pid=7562&step=4&showunits=inches&id=283&top_cat=197

[matteblack]

Thanks for the reply.

 

I am planning on running camber plates on all 4 corners. Not sure if that is a requirement for a fast autox setup. I am planning on using ground control coilovers as well. It was my understanding you had to section and run coilovers to get to race height..

 

What spring rates would you recommend for a 2+2? It will be gutted, front and rear strut bars, fuel cell, 15x9 or 15x10, and most likely frame rails replaced to tie in front to back. I was thinking of 250f/275r

Edited December 19, 2016 by matteblack

[JMortensen]

I don't have a recommendation for 2+2 rates, but I would think the 250/275 would be fine for a weekend warrior.

If you run camber plates, you'll lose about 1.5" on the front height and 2.5" from the rear without doing anything else. Since most people want the car level or raked a bit, you might end up too short in the rear. I've only sectioned 240 struts, so I'm guessing on the 280 stuff, but I've seen numerous threads over the years from people who went too short in the back on the 280 struts. I'd keep searching or find someone who has 280 experience before you cut. I would think you'd want to cut the front and leave the rear. If you didn't have enough height in the rear you might have to add more in to the strut tube instead of removing it. Keep your pieces that you take out of the front struts, maybe you could weld them into the rear if necessary.

[matteblack]

I found an old thread from Johnc talking about ride heights and alignment settings. I will shoot to have something in those ranges I assume. I come from the land of front wheel drive hobbiest level racing, 1989 Jetta, 2003 Mazda Protege5, 2015 VW GTI, so all of this is rather new to me. It is surprising that for how old this chassis is, there isn't a ton of information to be found for setup and tuning. Most everything seems to end up back to yourself and or John.

 

What is the normal amount of lowering needed to end up at race heights? It must be more than just losing the rubber isolators?

 

Matt

[JMortensen]

John gave specific guidelines for ride heights, etc, that he got from ITS racers and his own experience. I don't really think that's the best idea; I would prefer that the guidelines should be more general. Correct spring rates should be figured out by what is necessary to manage body roll, heat up the tires, prevent the car from bottoming, etc. Stickier tires will necessitate more spring. This fact alone would be an obvious limitation of a specific spring rate suggestion. Even if you don't change the tire size, a Yokohama A008 in 225/50/15 from 1993 will be nowhere near as sticky as an A7 from 2016, but people are running all different sizes these days. Race ride height should be as low as possible before suspension geometry becomes an issue while also being sufficient to prevent the car from bottoming frequently.  The more you're willing to modify the car, the more extreme you can go with all of this stuff, eg if you want to run the car really low, you can do that by modifying the suspension pickup points to correct for roll center heights, bumpsteer, etc, and then you can run much stiffer springs to keep off of the bumpstops, etc. 

 

If you're just going to bolt parts on, using John's guidelines will get you in the ballpark and you can tune to your preference from there. For my part, there are a lot of guys here who know better than me. I just had a lot of time to post, and when I was building my car I modified just about everything and had long conversations about what should be changed and why. I had some new, original ideas, but a lot was just taken from other people.

[matteblack]

Im definitely willing to and will do all modifications necessary to have a good handling car within reason. I have been able to dig up some good threads from you guys with a ton of info.

 

One thing that I have a quation about is the Roll Center spacers. Looks like the FP builds all tun them. Would you still run them along with slotting the cross member?

[JMortensen]

I am running them with a slotted xmember.