#4G63510 Suspension

[jeffball610]

I'm planning on this being an updated thread of my setup and how I change it over time. I'm currently experiencing some issues I'll outline below.

Current setup:
TSW Kyalami wheels 16x7 +42 (I think) 10mm spacer
205/40/16 Firestone Firehawk Indy 500 340 treadwear
Tire pressure is usually 20-22psi at track
FRONT
S12 V6 strut housings
T3 Camber plates
T3 coilvers with 5k springs
Specialty Engineering supplied struts- 240Z KYB units 361002 C117 (I think)
Futofab lower control arms
Futofab T/C rods
Futofab 1" front sump sway bar
T3 bump steer spacers
Stock steering links with T3 steering box brace
REAR
Z31 R200 w/ Tomei CLSD
Z31 CV joints on Pathfinder axle shafts
Z31 5-lug hubs
Futofab adjustable control arm pickups
Specialty Engineering supplied rear springs
Specialty Engineering supplied rear shocks

Settings:
FRONT
-2.5deg camber
3.0deg caster
.01deg toe in
REAR
-2.0deg camber Left -1.6deg camber Right
+.38 toe in Left +15 toe in Right (that's the best they could get out of it)

The setup works fine on the street, but I've experienced pretty sever front understeer on hard cornering. The rear steers well with the throttle and the LSD with the current power and lack of rear tire grip. My current theory is loss of suspension travel in the front, but I'm open to thoughts. I'm not showing too much abnormal wear on the tires. I might have some wear on the outer edges, but it seems pretty even and temps are consistent across the tire.

I know I want more tire at some point and I'm trying to see if I can reasonably fit a 225 width tire and will run a 200 treadwear. That will help with grip, but it won't solve any underlying issues. I'm still very new to suspension tuning, driving, and modifying. I'm also in the process of adding chassis bracing. I'm open to suggestions on everything.

I've included a video below of my latest autocross along with one from the co-driver. I ran a best of 48.501 and he ran a 45.483, so I know I have more to learn and the car has more to give than what I'm getting out of it. For reference, the fastest car of the weekend, an Alfa 4c on sticky tires, ran a best of 41.4xx. I don't feel like the car is doing poorly, but I know there's a lot more I can do.

Mine
https://youtu.be/N8vES_FLiSE

His
https://youtu.be/ES68ImJDmYM

[RMS]

try 4 or 5 for caster 3 is a little steep.

[bertvorgon]

I agree with Robyn, I would shoot for 5 degrees for sure.

As a function, castor induces MORE negative camber in a turn, so on that course you show, it would really help as there were a lot of tight turns.

Make sure it is EVEN and that you or equivalent weight sits in the driver seat when setting suspension, 1/2 tank fuel.

The tires are ROCKS, that is a given, hard to make a good suspension work when there is no stick.

The front roll bar at 1" might be a bit light, but, I don't know what that spring rate is...5k? No doubt the Specialty springs at rear are good, too bad the rear toe is a bit of an issue...but...you say the car understeers so getting out of the throttle does not let the car want to come around? if not that is good at this point.

Biggest things at this point would be the castor and of course...better tires are just that.

Car looked good in terms of acceleration, the perspective was hard to really see in the video but, being able to get on the power earlier in the arc of those corners would help, but, you again would need to increase that front grip.

[jeffball610]

I agree with Robyn, I would shoot for 5 degrees for sure.

As a function, castor induces MORE negative camber in a turn, so on that course you show, it would really help as there were a lot of tight turns.

Make sure it is EVEN and that you or equivalent weight sits in the driver seat when setting suspension, 1/2 tank fuel.

The tires are ROCKS, that is a given, hard to make a good suspension work when there is no stick.

The front roll bar at 1" might be a bit light, but, I don't know what that spring rate is...5k? No doubt the Specialty springs at rear are good, too bad the rear toe is a bit of an issue...but...you say the car understeers so getting out of the throttle does not let the car want to come around? if not that is good at this point.

Biggest things at this point would be the castor and of course...better tires are just that.

Car looked good in terms of acceleration, the perspective was hard to really see in the video but, being able to get on the power earlier in the arc of those corners would help, but, you again would need to increase that front grip.

The way the car behaves is that it understeers going into a turn, and then swings around on throttle. Some of this is likely due to the shift in weight as I get on throttle, and some is due to the power and slipping of the rear tires under acceleration. It rotates well, and can be a handful if you're not ready for it. I did spin once earlier in the day due to some on throttle oversteer that was compounded by a dip in the surface mid turn. It bit me hard and spun me the other way 180 degrees.

I might have a bit more castor than what I listed. Those numbers are from my last alignment last summer. When I added the T3 Camber plates, there was a little bit of castor built into them. I'm getting another alignment soon, so I'll add more with the Futofab T/C rods.

Yes, the tires aren't great for "racing", but I do more street driving than racing. I'd love to have a second set of tires just for track days, but I'm on a Datsun 510 budget

I can't get a stiffer front sway bar unless I build my own. There is no adjustment in the Futofab unit, so that's out the window. The front springs are listed as 5kg springs. T3 does offer stiffer springs, but I was under the impression that with front understeer, I would want LIGHTER springs.

I was also told that adding a rear sway bar may help as well. I'm not a fan of the rear bar, but I'll do what is necessary to make this car handle as well as it can.

I have no issues with acceleration, other than growing a bigger set to get on the power sooner. I'd like to get the car dyno tuned to get it sorted a bit better and get an approximate power figure. I'm making at least 200hp/200lb/ft torque in a chassis that weighs somewhere near 2000lbs. Power is not my current concern. Getting it to the ground while turning is.

I'll add more castor, look at my camber curve, and hopefully add some stickier tires. I don't think I'll be doing another event until August, so I'll have plenty of time to get things straight and test it a bit. If there are any other suggestions, I'm all ears. I'll be posting a "braking" thread soon to get some help with that as well. Thanks for the input.

[bertvorgon]

You are correct that LIGHTER springs would decrease understeer. Sometimes though, the stiffer the front bar and springs, that decreases weight transfer to the front, or at least slows it down till, you transition from brakes to throttle.

I hear what you are saying, I too lived that for awhile back in my early days...then got the SOLO ONLY wheel and tire set.

Try the castor increase first at any rate, that won't hurt anything and it is the CHANGE ONE THING AT A TIME rule.

Yes, a rear bar could help, but, that would have to be determined by how much the car can tolerate the throttle application as an oversteering part of the equation. From what you describe though, a rear bar might take you too far in that direction. Too bad that you cannot get the rear toe sorted a bit better.

I make 250 to the rear wheels and almost the same torque, so I get the power thing. You have a good grasp of the situation, it is just a case of fine tuning.

[icehouse]

Dude I daily my 510 on R888r's! They only wear out when you are turning. A buddy that used to autox a little with me ran them on his Camaro, since he didn't race much he got 20k miles and 4 years out of them. I get about 9-10 months before I want to get new ones. I go to at least one autox a month and do about 20 laps on average. Get some RE71r's. I want to try them next.

[funwithmonkeys]

Your tire pressure seems a bit low for that tire. As everyone else said castor. I set mine to just over 5 degrees. How much actor you can put into it will also depend on your tire to fender clearance at the front of the tire. Anything over 4 on my car and the tire was hitting the fender. There are not many choices in 16" tires but I have heard good things about the re71. Don't be scared of going to a full R compound. If you are not over driving and sliding the car around a ton you can get 10 to 20k out of them.

[JordanTr]

If you could get the car set up for 205/45 then there are a bunch of options.

You didn’t mention if the strut tubes are shortened or not. If not, you may be sitting at a static ride height quite far down in the shocks travel meaning that the damping is poor. I’ve lived through this with my 280zx OEM length struts and it sucks!!

I run shortened s12 struts now and it’s very nice to ride in. And handles well.

Keep us posted. Very good lead in post!

[jeffball610]

If you could get the car set up for 205/45 then there are a bunch of options.

You didn’t mention if the strut tubes are shortened or not. If not, you may be sitting at a static ride height quite far down in the shocks travel meaning that the damping is poor. I’ve lived through this with my 280zx OEM length struts and it sucks!!

I run shortened s12 struts now and it’s very nice to ride in. And handles well.

I know I'm on the last bit of travel on the shock with full length S12 struts. I'm going to test this Friday how much I actually have. I'm just going to stick a zip tie on the tubes and do some figure 8s and see where the zip tie is after. I have a feeling I might be bottoming out.

As far as tire sizes, I used to run 205/45 but my current tire didn't have that section, so I'm running 205/40. I did have some very minor fender clearance issues up front, but I don't think it will be an issue with all the adjustment I have now.

[bertvorgon]

I have 2 3/4" of front travel, with 300 lbs/inch springs. Lack of suspension travel and/or hitting the bump rubber or stop is one of the worst evils for handling.

[duke]

Tires, tires, tires! I got a set of wheels a while back that had some generic tires on them and I was amazed by how much they affected the handling of my car. My car on the usual 200TW tires I run is very neutral and predictable. On the generic tires I experienced excessive understeer to snap oversteer and it was borderline scary. Get a set of one of the crop of 200TW tires and run them for a while to get a reliable baseline and then worry about the actual suspension setup. You might be amazed by the difference they will make.

[RMS]

I like the zap strap hack, faster than pulling a spring. but will it tell the hole story ?

[bertvorgon]

We use that trick on our mountain bike shocks. It is only good if you know or can see the zap and if it has hit the final bump rubber.

I'm with Duke, tires first.....then see what is going on.

[jeffball610]

After putting a zip tie on the strut and driving around a bit, it doesn't seem to be bottoming out. I still have about a half inch of travel on the strut. I didn't drive it like on track, but I figured the road bumps and speed bumps would cycle it enough. I'll follow everyone's advice and get some tires. RE-71Rs seem to be the ones to go with. I won't be putting them on this summer so I can use what I have a bit more for street driving and some road trips. I think my next autocross will be in August. I'll see if there is anything else to fix in the meantime. I'm not sold on this suspension setup, but I'd like to get what I can out of it before moving on to something more advanced.

[icehouse]

Dang we gotta wait that long!

After a few years of testing I’ve come to the conclusion that although suspension setting can help you are close enough. I went from 6 degrees of caster to 4. Couldn’t tell at the next autox.

Went from mega toe in to stock toe and couldn’t tell at the auto.

Went from R888r’s to the new Star Spec tires! Wow I only ran them for a short while. They sucked

Went from 300lb springs to 250. Maybe slightly faster. Maybe.

Went from steering box to rack and pinion. Noticed it more to and from the track then at the track. Really the steering speed was the most noticeable.

Went from manual steering to power. Way better!!!! I was very surprised. Our events sometimes have 360 barrels or 180’s. So nice to turn one handed and downshift with the other.


The biggest for sure improvement was tires. Then power steering.