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280Z build w/ LS3 and 2015 Mustang spindles/8.8


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 And ideally use a toe-link rear arm design.  Just a thought.

The forward rod end on that arm uses a concentric double adjuster (RH male thread on outside, LH female thread on outside) so I can avoid using a separate toe link while still being able to adjust the toe on the car. This avoids creating a buckling load in a toe link and allows the lower control arm to react some of the torque of the engine/brakes instead of passing all that load up to the strut mount and putting additional bending load into the strut.

 

 

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First off would like to say I would never have had the knowledge nor courage to tackle this build without HybridZ and its awesome community so willing to offer advice and share ideas.  Purchased my ru

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I really like your design for the hub uprights.  While there is nothing inherently wrong with the TTT ones, they are needlessly heavy, and in fact I have noticed on their website that they now have a new design with a lot of metal removed to reduce weight.  Yours look even lighter.  Part of me hates seeing better designed parts, because it makes me want to bin mine and trade up.  But I have to stay the course or this damn car will never be "finished"....

 

Just a few notes about the TTT rear control arms/uprights....and I think would apply to your design as well....

 

I have been driving my car around quite a bit trying to iron out all the little details.  One thing I have noticed is a fairly loud clunking from the back of the car as the rear suspension loads and unloads going over bumps.

 

I "think" I have narrowed the source down to the long bolt on the outer end of the control arms....it goes through the two Heim joints and also through the tube at the bottom of the rear hub uprights.  I didn't initially have this bolt super tight, just snug, because I figured it only needed to function in shear and I also didn't want to put a bunch of side loading on the Heim joints.  But I think the clunking noise was caused by the uprights moving up and down on the bolt when driving over bumps.  The bolt is a fairly precise fit in the Heim joints but pretty loose where it passes through the tube at the bottom of the uprights.

 

So I carefully shimmed the long bolts to fully tighten them without putting a bending load on the Heim joints.  I'm hoping this sufficiently stabilizes the hub upright tube and gets rid of the clunking.

 

I was going to do a test drive today, but the potentiometer for my electric power steer decided to crap out, and the car is fairly undriveable without power steering....so I have to sort that to know if I succeeded in eliminating the "clunks" or not.

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7 hours ago, Ironhead said:

So I carefully shimmed the long bolts to fully tighten them without putting a bending load on the Heim joints.  I'm hoping this sufficiently stabilizes the hub upright tube and gets rid of the clunking.

 

 

While talking with Noah the other day I mentioned something about bolt sizing and strength in shear.  I think it was for the 10mm bolts I used for my trans mount.  He said there is a common misconception on how things are "held together" with fasteners.  It's the friction created between the surfaces the fasteners are connecting which provides the vast majority of the apposing force in the shear plane.  So I think the carefully shimmed play between the rod end and upright and having the through bolt torqued to spec for diameter will solve the chatter you are experiencing. 

 

"Finished" is a relative term right, lol.

I say get the car sorted, have some fun then tackle a few "quick and necessary" upgrades during winter months.

 

I thought while prioritizing the next build task it was to be the DIY headers.  While examining the driver's side area noticed that the OEM steering coupling bushing needs to go, it takes up too much space and need all the possible space for header tube routing.  Planned for a Saturn Vue EPS column to swap in case I needed assist after test driving with 275 front tires.  Well, looks like I should tackle the EPS first since your opinion is effort is high with that wide a front tire. 

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15 hours ago, Ironhead said:

The bolt is a fairly precise fit in the Heim joints but pretty loose where it passes through the tube at the bottom of the uprights.

I reamed the pivot tubes out to be a light sliding fit on the 5/8" pivot bolts with a hand reamer, they're ~0.627 right now and I'll do it again after welding to make sure they're still straight and cylindrical. The bolt shouldn't ever see the shear load unless the nut becomes loose, but it also helps make sure that your alignment doesn't change every time you take the rear end apart and put it back together.

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18 hours ago, 280Z-LS3 said:

 

While talking with Noah the other day I mentioned something about bolt sizing and strength in shear.  I think it was for the 10mm bolts I used for my trans mount.  He said there is a common misconception on how things are "held together" with fasteners.  It's the friction created between the surfaces the fasteners are connecting which provides the vast majority of the apposing force in the shear plane.  So I think the carefully shimmed play between the rod end and upright and having the through bolt torqued to spec for diameter will solve the chatter you are experiencing. 

 

"Finished" is a relative term right, lol.

I say get the car sorted, have some fun then tackle a few "quick and necessary" upgrades during winter months.

 

I thought while prioritizing the next build task it was to be the DIY headers.  While examining the driver's side area noticed that the OEM steering coupling bushing needs to go, it takes up too much space and need all the possible space for header tube routing.  Planned for a Saturn Vue EPS column to swap in case I needed assist after test driving with 275 front tires.  Well, looks like I should tackle the EPS first since your opinion is effort is high with that wide a front tire. 

 

Dude!  We're in Cali....I drive my project cars in the winter more than the summer.....LOL.

 

As far as the steering....keep in mind that in addition to the 275 tires....I also have a significantly quicker than stock rack (can't remember the ratio)....the shorter Apex steering knuckles.....and 6.5 degrees caster.  The steering is go-cart quick....maybe a bit too much, really.....but even once up to speed it takes a lot of effort to turn the wheel.  My initial plan was to have the power steering go off at 15 MPH....but after driving it.....nope....power is staying on.  I thought I wouldn't like the feel of the EPS....but it really isn't bad at all.

 

You are right that there is a lot of confusion about bolts used in tension vs shear.  In aircraft many bolt applications are pure shear, and AN bolts are designed to actually be used as such.  That's why you can get 1/2 height AN lock nuts...because the tensile strength is irrelevant.  But yes, on the TTT arms it is different, as the pivoting takes place in the Heim joints.  I should have realized that failure to fully tighten the bolts would lead to clunking.  

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4 hours ago, Ironhead said:

Dude!  We're in Cali....I drive my project cars in the winter more than the summer.....LOL.

 

Yes, absolutely right.  Summer is the down season for Cali, I stand corrected!  Here in SLO county it gets into the triple digits for weeks on end during summer.  Without A/C it's brutal. 

 

I had the opportunity to drive a friend's right hand drive 1966 Ford GT40 in July a few years ago.  Such a rare iconic Super Car couldn't pass the offer up.  After 20 mins with outside temp of 105F had to call it quits hoping for an ice bath while pulling into the garage.  As I pulled in literally soaked with sweat he asked me to take his nephew who couldn't drive a stick for a spin.  Kids these days, lol.  I almost declined it was that hot in the car.  The 2006 GT my wife got to play with is much more refined being fitted with the modern convenience of A/C.  Two years ago worked on his application (yes applications to buy GT cars are mandatory now because of speculators purchasing cars then flipping) for his newly delivered GT.  Covid has pushed back the promised piloting of that car which will surely be a blast! 

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If your "Z" turns out similar to mine, you will find it equally unrefined.  I'm actually a bit surprised how hot it gets inside.  I have Lizard Skin temp control on the inside, and reflective heat shield in the trans tunnel, and it still gets really warm inside.  Let's just say, a heater is unnecessary.  I guess just a function of too much engine/HP/exhaust in too small a space.

 

It's all good though.  I knew I wasn't building a luxury car.

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On 5/3/2021 at 5:55 AM, D1t said:

I reamed the pivot tubes out to be a light sliding fit on the 5/8" pivot bolts with a hand reamer, they're ~0.627 right now and I'll do it again after welding to make sure they're still straight and cylindrical. The bolt shouldn't ever see the shear load unless the nut becomes loose, but it also helps make sure that your alignment doesn't change every time you take the rear end apart and put it back together.

 

Sorry D1t...I don't completely follow.  Did you precisely ream the TTT control arms, or arms of your own construction?

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2 minutes ago, Ironhead said:

 

Sorry D1t...I don't completely follow.  Did you precisely ream the TTT control arms, or arms of your own construction?

I'm referring to the knuckles I'm building for 280z-LS3 and myself. I reamed out the pivot tube on the knuckle not the arm.

Edited by D1t
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