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Front Suspension Swap? Anybody done one


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5 hours ago, jpndave said:

Is this the LLT (and subsequent versions) direct inject you're referring to? Do you have the engine? I ask because I had one for a different project and sold it due to logistics and abandoned the project in favor of building my 240Z. I still have photos, dimensions somewhere along with an imported Australian 4L60E bellhousing and either a flexplate or the flywheel.

 

On paper sounds great, in reality not a good choice for a ton of reasons. I'd be happy to share but if you want suspension here maybe a different engine thread to not derail this further. 

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I started a thread in the engine swap section so we  can continue to discuss this 3.6l swap. I'd love to hear your thoughts and review your information

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The strut setup on these cars is ok, but there's a reason they aren't competitive anymore. No camber gain in roll and the nightmare front hubs (hello, scrub radius called...) are challenges that can't

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  • 7 months later...

Ok, back to the suspension. After taking a long hard look at this project. I have changed my direction abit. And this new direction raises more questions. I hope all that made comments earlier will come back with your thoughts.

I have decided to take the advice of others and try to tune the factory setup. I have made this decision due to cost and time to fruition. However, I too am interested in the SLA setup for a few different reasons.

 

First question to sorting the factory suspension. Scrub Radius, How do I deal with the large scrub radius when running wider wheels and tires on the stock setup. I would like to run as wide a tire as is reasonable. So if I go wider, I'll have to get a different offset wheel. This offset will most likely upset the scrub radius, and create other scrubbing problems while turning. It seems I may be able to overcome some of this by using a longer LCA and using camber plates with the strut pushed as far out as possible (adjusting the LCA to get optimum - camber) improving the scrub radius. Then I can use a wheel with less negative offset and still have the tire in about the same location reducing scrub radius. Has anyone used this approach.

Looking at the video of the SLA, it looks like it can help with the negative affect of the wider tires along with other positive affects.

Thanks

Roger

Edited by rabrooks
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On 6/19/2018 at 4:09 AM, caperix said:

The z can have camber change under compression as well with the factory struts. Use roll center spacers to keep the control arm at a downward angle. The arc of the arm will have camber gain until you are past the level point of the arm, then will start loosing negative camber.

This is incorrect. Many of us have held this erroneous opinion at one point, including myself.

BlueovalZ explained it to me maybe 15 years ago: the control arm doesn't need to be level to start losing camber, it needs to be perpendicular to the strut before it starts losing camber. This is basically impossible, unless you're running really tall tires and trying to scrape the frame on the ground. 24" wheels or something ridiculous would be required to get there.

There is a really good thread (IMO best thread on this site) started by Tom Holt and with lots of info from Dan McGrath, aka 74_5.0L_Z, where he takes on all the suspension kinematics. The Z has a very flat camber curve. It just doesn't have enough gain to offset the roll with soft springs.

Here is the post where he diagrams the camber curve: 

 

Edited by JMortensen
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The scrub radius issue is a problem. I've got ridiculously wide 15x14 wheels on the front of mine. Had to use spacers to clear the bumpsteer spacers on the tie rod. Car has about 6" scrub, which is a lot. I did this after talking to Tony Woodward of the custom steering rack company and he told me that it really wasn't that big a deal and he had seen plenty of fast cars with 6" scrub or more. I think his experience was more to do with circle track though.

 

You would want the camber plate as far in as you could manage to minimize scrub. The imaginary line from the top of the plate and the ball joint and through the tire contact patch is where the scrub radius is measured from. It's the distance from that intersection with the ground and the center of the tire.

Tube80z was looking at a dual LCA system to work with the strut to alleviate the scrub issue on this thread:

 
He kinda stalled out on that and I don't have software to figure it out, but that's an option if you have the software or know someone who can help you out with that. Otherwise, I think SLA is the best solution and you can solve other issues while you're in there, like adding more camber gain, fixing bumpsteer, using 5 lug hubs and bigger brakes, etc. 

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In essence, it sounds like there is no way to deal with a large scrub radius if you run a wide wheel and tire because it will have to run a high negative offset, driving the large scrub. I hoped to find a way to get a smaller scrub with the wide wheels. The only way I can envision this happening is doing what I mentioned earlier, running a longer LCA and then reducing the negative offset of the wheel. This will lower the scrub and leave the track as wide as it was with the high negative offset wheels. That was why I suggested pushing the top of the strut outward (because the lower ball joint moved out with the LCA). But I would set the camber to what it needed to be, not just shoving the top of the strut over until it hit the end of the camber plate.

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22 hours ago, rabrooks said:

In essence, it sounds like there is no way to deal with a large scrub radius if you run a wide wheel and tire because it will have to run a high negative offset, driving the large scrub. I hoped to find a way to get a smaller scrub with the wide wheels. The only way I can envision this happening is doing what I mentioned earlier, running a longer LCA and then reducing the negative offset of the wheel. This will lower the scrub and leave the track as wide as it was with the high negative offset wheels. That was why I suggested pushing the top of the strut outward (because the lower ball joint moved out with the LCA). But I would set the camber to what it needed to be, not just shoving the top of the strut over until it hit the end of the camber plate.

 

That just robs Peter to pay Paul.  Reduce scrub and you add steering axis inclination (SIA).  It depends a lot on what tires you want to run and how you plan to use the car.  With power steering you can increase caster to help cover some of this but you can't go too far.  And I suck and have only made it about half the way into trying to make a dual-balljoint front end layout in the suspension software I'm using (Susprog3D).  I can move points around but need to have a basic CAD model to make sure they'd actually be doable.  For my small 13-inch diameter wheels I think it won't work unless steering lock were severely limited. 

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21 hours ago, tube80z said:

 

That just robs Peter to pay Paul.  Reduce scrub and you add steering axis inclination (SIA).  It depends a lot on what tires you want to run and how you plan to use the car.  With power steering you can increase caster to help cover some of this but you can't go too far.  And I suck and have only made it about half the way into trying to make a dual-balljoint front end layout in the suspension software I'm using (Susprog3D).  I can move points around but need to have a basic CAD model to make sure they'd actually be doable.  For my small 13-inch diameter wheels I think it won't work unless steering lock were severely limited. 

At this point, this is all hypothetical. My plan is to keep the SIA as close to factory by moving the top of the strut out on the camber plate the same amount as I stretch the LCA. The LCA may get a little longer than what I can move out the top of the strut but not by much. I would set the negative camber after that setup is in place. and adjust whichever end makes the most sense given all the new geometry. So try to imagine taking the factory geometry and moving it outboard  while leaving the wide tires where they sit. I just get a wheel with a different offset, something more in the positive offset range. I haven't laid this out to see how wide a tire I can get mounted with this setup before the inner tire wall hits the strut. I could move the tire back out again with a different offset wheel to get the tire off the strut.
 

If none of this lays out correctly, I'll just have to deal with the scrub.

 

On the double ball joint setup, I ran across a BMW in the pick and pull with the complete front suspension. I may go back and pull it. I may be able to work out that setup or some version of it. I have a 335i. I've been looking at it trying to decide if I should do this. I'm willing to invest in the pick and pull parts for the sake of trying to figure it out. Just by coincidence, I have a complete set of lower control arms for my 335. I recently bought them to replace the old ones.

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2 hours ago, rabrooks said:

At this point, this is all hypothetical. My plan is to keep the SIA as close to factory by moving the top of the strut out on the camber plate the same amount as I stretch the LCA. The LCA may get a little longer than what I can move out the top of the strut but not by much. I would set the negative camber after that setup is in place. and adjust whichever end makes the most sense given all the new geometry. So try to imagine taking the factory geometry and moving it outboard  while leaving the wide tires where they sit. I just get a wheel with a different offset, something more in the positive offset range. I haven't laid this out to see how wide a tire I can get mounted with this setup before the inner tire wall hits the strut. I could move the tire back out again with a different offset wheel to get the tire off the strut.
 

If none of this lays out correctly, I'll just have to deal with the scrub.

 

On the double ball joint setup, I ran across a BMW in the pick and pull with the complete front suspension. I may go back and pull it. I may be able to work out that setup or some version of it. I have a 335i. I've been looking at it trying to decide if I should do this. I'm willing to invest in the pick and pull parts for the sake of trying to figure it out. Just by coincidence, I have a complete set of lower control arms for my 335. I recently bought them to replace the old ones.

Tube80z and JMortensen are correct, there's no free lunch on this. The only place you might "cheat" a little are coilovers with the smaller diameter spring allowing a little more width and larger diameter wheels the same. I think you either optimize what's there with coilovers, camber plates etc. the best you can and deal with it or go the SLA direction and clean sheet.

 

I am planning similar direction to tube80z but am even more pathetic on progress. I don't think I'll use the double joint lower but wouldn't rule it out. Minimizing the distance between the wheel mount surface and the pivot would help things out quite a bit. The SLA will require pretty much a complete new front subframe but since mine is a crusty mess and needs replaced anyway, why not? Sadly a new house/shop and Murphy living in my back pocket have prevented much of anything looking like progress.

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With S13 spindles (and others, i believe) and longer LCA:s is possible to achieve near zero scrub. At least not so wide wheels. I´v got 8" rim and scrub max. 10mm.

You should keep about 50% ratio between caster and KPI. My car has 13-14 degrees KPI and ~7 dergees caster. Shock upper mount is moved outwards aswell...

20160821_194259.jpg

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  • 2 months later...
On 3/1/2019 at 10:11 AM, TUME said:

With S13 spindles (and others, i believe) and longer LCA:s is possible to achieve near zero scrub. At least not so wide wheels. I´v got 8" rim and scrub max. 10mm.

You should keep about 50% ratio between caster and KPI. My car has 13-14 degrees KPI and ~7 dergees caster. Shock upper mount is moved outwards aswell...

20160821_194259.jpg

Would this work with control arms/ tie rods/TC Rods from Apex and/or T3? All attached to a stock Cross member? Trying to find a way to get rid of the front strut tube/spindle without breaking the bank with full T3/Apex Systems... and i like BC's. 

 

I've read through your build thread btw TUME, awesome work!

Edited by rbzed25
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https://youtu.be/N94E9jPvp84

 

This might be the ultimate truly engineered suspension swap kit made for the 240Z cars, check out the video it is amazing and Apex Engineering makes it for stock engine, RB, and V8's,

 

Bolt in upper and lower control arm conversion with 8.8 rear end that eliminates the rear mustache bar, and dog legs and converts it to a rear subframe that significantly strengthens the rear structure on the chassis.  This converts the McPherson strut to a modern double A arm dynamic.  This provides ability to adjust roll center, anti-squat, camber, caster, toe and many others.  Use the Viking dual adjustable coil overs with Hypercoil springs that was the winner of best engineered new product at SEMA 2014.  Also comes with axle shafts able to handle 1200 Ft/lbs of torque!

 

 

 

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On 5/24/2019 at 6:40 AM, rbzed25 said:

Would this work with control arms/ tie rods/TC Rods from Apex and/or T3? All attached to a stock Cross member? Trying to find a way to get rid of the front strut tube/spindle without breaking the bank with full T3/Apex Systems... and i like BC's. 

 

I've read through your build thread btw TUME, awesome work!

 

Thanks for comments.

Do you mean S13 control arms/TC rods.  I can't see why they won't work, of course it is possible they need some modifications but nothing major.

Of course left side arms goes to right, with S13 spindle and wise versa.

Also because longer arms, there will be enormous KPI angle which affects camber behaviour when turning wheel.

Thats why i modified shock upper mount in my car.

 

Btw, those ultimate bolt-on set doesn't ring my bells...

 

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Apex Engineered already has engineered not only a front crossmember and front and rear A-arms if you want to upgrade the stock design but they also have both a front and complete front and rear suspension swap that is bolt in.  No need to be experimental if you want to go extreme as they already worked out the design and executed in a high quality with a reasonable price given the design and components...

 

https://www.apexengineered.com/store/p25/Track_Attack-_Complete_Front_Suspension_Conversion.html

 

 

 

 

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