Front Camber - Bushings, LCA relocate or longer LCA

[Meph]

Hey guys, I'm trying to get another 1 deg of front camber. 

 

Car is currently lowered with roll center spacers.  I've slotted the strut tower and currently have about 0.9-1 deg neg, looking for 1.5 to 2 total when autocrossing. 

 

My options are

 

-Relocating the LCA holes in the crossmember up and over. Hopefully help with bumpsteer geometrily and gain some camber. 

 

-LCA offset bushings. Giving me adjustability to move the LCA out or up or a combination of both without having to redrill the crossmember. 

 

-Physically making the LCA longer by cutting, lengthing and welding. 

 

Does anyone have any specific pros or cons. Looking for input on bumpsteer changes. I'm leaning towards option 1 or 2. 

 

For option 1 I think I'd move the hole up about 3/4" and out 1/4". Does anyone know if this would be excessive or a bad idea? 

 

 

 

 

[jhm]

Are you trying to avoid camber plates?  There are several bolt-in options, that will probably give more neg camber than anything else (except for longer/adjustable front LCAs).  Here is just one example of a bolt-in plate that's reasonably priced:  https://www.silverminemotors.com/datsun/datsun-260z/suspension/240z-260z-280z-camber-plates-bolt-in-lowering-kit

 

Redrilling the LCA holes in your front crossmember is not a small job, and I would hold off on that option until you have determined that you have roll center/bumpsteer issues that can not be solved any other way.

 

I used offset bushings in my front LCAs for several years without issue, although they do result in more road noise and ride harshness than the stock rubber bushings.  I have since switched to a monoball bushings in the LCAs and will eventually make them adjustable length.  Plenty of adjustable front LCAs out there off the shelf, but you can make your own quite affordably using the stock LCAs and good quality heim joints.

 

How much is your car currently lowered?  As you probably are aware, lowering the front suspension results in additional neg camber as well.  

[Meph]

The car is running a 4.8L lsx with custom mounts that don't attach to the sub frame. I also have a hoist setup so dropping the front cross is a pretty straight forward job. 

 

Im running poly bushings already with a home brew coilover setup with mr2 SW20 struts.

 

They have a slightly larger  nut size on top than the 240z struts so I'm worried strut tops won't accept them. 

 

As for tires I'm running 255/40/17 front with 17x9.5 and 275/40 rear with the same Rim.

 

You don't still have your old bushings by any chance? If so would you be interested in selling them? 

 

Thanks for the input 

 

 

 

 

 

[JMortensen]

There are problems with all of these solutions:

Bolt in camber plates won't move enough to get you the neg camber you need for autocrossing (I think you'll find 2 degrees isn't sufficient unless you're running all season tires and not real serious about it). Stickier tires will create more roll which requires more neg camber.  
 

Camber bushings with delrin/aluminum don't allow the control arm angle to change, which it HAS to do as the suspension compresses. TC moves in an arc, so the control arm should have some front to back movement available. Some of that might get taken up in TC bushing flex, some in crossmember flex, but it's not ideal. Camber adjustment with these also adjusts bumpsteer. 

Moving the xmember pivot requires removing the washers that are welded to the xmember, which is tough to do without screwing up the thin xmember metal. Moving them out will gain you some camber, but you can't go too far before you run out of threads on the tie rods. I slotted my xmember and found that moving the pivot up about 7/16" minimized bumpsteer. The old JTR recommendation was up 3/4, out 1/4, which is too high on the bumpsteer for my car, and still not enough neg camber.

Longer control arms will have the same problem with the tie rod threads.

My suggestion would be a better camber plate like Ground Control or TTT. This will allow enough movement to actually get the camber you want without worrying about the tie rods.

The tie rods used to be more of an issue, because one of them is LH thread 14x1.5, which is tough to find taps and dies for when making your own, but now there are several vendors selling aftermarket tie rods. If you get new tie rods with a turnbuckle, that basically doubles the amount you can adjust before you start getting too close to the end, and that frees you up a bit. If you go with replacement tie rods, then my second choice after the good camber plates would be custom LCAs with the heims joint inner, and you can decide to make them longer or move the pivot. Moving the pivot would have the added benefit of being able to adjust the bumpsteer.

EDIT TO ADD: if you're worried about the 14mm shaft on the top of the Tokicos in combination with monoball camber plates, Ground control makes bushings to fit them in a 5/8" monoball. I'm sure TTT does the same.

 

Edited June 17, 2019 by JMortensen

[jhm]

Don't forget the biscuit-style camber plates that EMI used to make, and DP Racing still produces.  They offer quite a bit of adjustability and are a bolt-on solution that requires no cutting of the strut tower.

 

The negative camber bump steer spacers offered by T3 are another potential solution; but like adjustable LCAs, may require the use of adjustable outer tie rod ends (depending on whatever other mods you decide to make).

[Meph]

Thanks for the great input here. 

 

(this reply got long sorry) 

 

Im not aiming for max performance at the track, just looking for a little more front grip. No race compound tires some Firestone indyhawk tires. 

 

 

When I checked my tire temps after runs at my last event the outside tire temp was about 4 deg C hotter than the inside. So I'm guessing (maybe wrongly) that I'm not all that far off camber.

 

I would hope by moving the lca up and out slightly I'd get some static camber and because the lca won't go beyond parallel in a turn I will gain/prevent losing camber like my current setup. 

 

Im running adjustable t/c rods for as much caster as I can fit in the wheel well. Though I Havn't checked the actual number (I will when I get some time and knowledge how) that should also help with camber

 

Here's my setup currently 

 

Spring rate 155F - 155R

Sway bar  1 1/8 F - 7/8 R

Camber    1.1 deg F - 1.75 R

T3 t/c rods

Toe 1/32 out F -  1/16 in R

Rear LSD

255/40r17 F 275/40r17 R

17x9.5 -12 F and R

Shocks are not adjustable and just basic mr2 F/toicko blue R

 

 

I know my springs are soft and my bars are stiff (came with the car but makes for a pretty smooth highway car). Looking to go down a size to 1 front 5/8 rear. And upping springs to 180 ish. 

 

 

 

Good to know about the strut tops having a larger hole, I have a lathe at home so turning a spacer is not a problem. What about ride quality VS the rubber? I daily drive my car most days to work in the spring to fall so racing is a small portion or its life. I would think that switching to plates on the front only could cause a little imbalance? 

 

Only in the last few months have in started looking suspension geometry beyond toe... Gets confusing sometimes! 

 

Thanks everyone 

 

[jhm]

Ah, didn't realize you were running adjustable TC rods.....you will want to stay away from the aluminum/delrin  camber bushings.  They offer no flex at all, as Jon pointed out.  Consider replacing the stock rubber bushings with monoball.

Edited June 17, 2019 by jhm

[JMortensen]

Re: ride quality. I took my dad for a ride in my Z with 200/250 springs, camber plates, heims jointed fronts and TC rods, and Illuminas on 1 back when he was about 75 or so. His comment: "Seats are comfy!"

With respect to camber change, what you're looking for is to keep the tread flat under load. With independent suspension, body roll = camber loss, so with soft springs you might be rolling over more than your static camber can compensate for, and then you roll onto the sidewall of the tire. You need more camber or less roll to keep that contact patch flat. If you have the camber right you should be a little hotter on the inside. Adding caster helps as that will give you more neg camber when the wheel is turned, but you'll have to trim your airdam/fender if you haven't already.

You seem like you are already past this stage, but for other people who might stumble in here, you can use a dab of shoe polish running over the edge of the tire onto the sidewall in 3 or 4 spots to see how far you're rolling over onto the sidewall. Inflating the tire more keeps it from flopping over as much but also hurts grip if you do it too much. Better to adjust the camber so that you can run the optimal pressure for your particular tire.

You're wrong about the camber going negative when the control arm goes past level. It's when the control arm goes perpendicular to the strut tube that you would actually start to lose camber. This was pointed out to me many years ago by blueovalz, who built a really awesome Z here, then sold it and moved on and no longer posts. You can confirm this with Dan McGrath's post here, in what is IMO the best thread on the whole forum: 

 

[Meph]

So I went ahead with plan A and relocated the LCA up and out in the cross member. 3/4" up and 6mm out. Drilled out washers, relocated and welded in. Then patched the existing  holes. My front camber is now about 1.75 deg which is right where I was aiming for for my daily driven car. 

 

Im going to look into strut tops for more camber and caster at events in the future. My front tires are as forward as I dare shove them with the t/c rods. (I still don't have a ton of caster right now) 

 

Moving the LCA creates a lot of small changes.

 

 - less theoretical bump steer, bringing it closer to parallel with the tie rod

- camber (6mm out creates about 0.75 deg change) 

-reduces the roll moment. roll center is improved and body roll theoretically reduced (I also raised the front end a little to help with this) 

-Wider front track. (only 12mm... Not much) 

 

While I was down there I did a few things to help with friction. 

 

-On the sway bar poly bushing I used a belt sander to eliminate any excess bushing material on the mounting surface that is normally pinched when you tighten the nuts, lots of moly lithium grease and thr bar move a lot easier

 

-on the LCA poly bushing I took the center steel tube and turned it down in diameter ever so slightly on my lathe and polished smooth, greased that bushing up good and it rotates with a lot less force than before. 

[Chickenman]

For a true test of ride comfort. drive your Z car from Blaine Washington to Seattle on the I5. Rough concrete with expansion joints for most of the way. Just came back from SOVREN Vintage races at Pacific Raceways. My 76 280Z has front DIY TT3 Coil overs, 250 lb/in Eibachs and Koni Sport Yellow shocks . Rear is " temporarily " Eibach Pro springs ( Don't know rate but they are pretty soft )  with KYB gas struts.

 

Edit: Forgot front Camber plates . Rear temporarily has the front Nissan top insulators installed to lower rear.  Will be getting Camber plates as well.  

 

Front was very comfortable on the street and on the I5 . I5 is brutal on cars with too stiff of springs and shocks.. Koni's are on setting 1 at the moment, but I will probably be turning them up to a 1.5 or 2.  Rear shocks and springs are comfortable, but too soft. I'll probably go to 225 or 250lb/in on the rear as well with Koni Yellow sports. TT3 Coil over kit.  Soft rear springs show up on track days when I get a bit too much rear squat exiting corners. 1.125" ST front Bar and 0.875" ST Rear Bar. 

 

Tires are Continental Extreme  Contact DW in a 225/50x16" .  The taller sidewall really soaks up bumps and expansion joints well. Very good Traction in Dry and Wet. Wet traction is important in the PNW. I may switch to a 225/45x16 in the Future. The Conti's are just a tad too Tall at 24.9". Considering amount that car is lowered. 

 

I'm using new stock rubber bushings all around for noise isolation and comfort. The stock rubber LCA bushings are far better than Poly. Monoballs transmit too much road noise for " my personal "  street car. Been down that Road before. This is just going to be a nice, quiet GT Touring Car. As you get older you appreciate comfort more and more. 

 

Picture of Camber Plates used for front and rear:

 

  

Edited July 9, 2019 by Chickenman

[JMortensen]

10 hours ago, Chickenman said:

For a true test of ride comfort. drive your Z car from Blaine Washington to Seattle on the I5. Rough concrete with expansion joints for most of the way. Just came back from SOVREN Vintage races at Pacific Raceways. My 76 280Z has front DIY TT3 Coil overs, 250 lb/in Eibachs and Koni Sport Yellow shocks . Rear is " temporarily " Eibach Pro springs ( Don't know rate but they are pretty soft )  with KYB gas struts.

LOL at I5 comment. I had a 99 Miata with factory Bilsteins. They overvalved the shocks, so that they packed down and you'd end up on the bumpstops, jackhammering your spine for a good 30 miles or so between Tacoma and Seattle, which is IMO worse than the part north of Seattle. Absolutely painful.