Suspension TECH Including Brakes, Wheels and tires

          
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Old 06-08-2020, 05:30 PM
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Originally Posted by Bob's GTO View Post
Yes, PPG version of Limelight Green. Paint formula indicates Chevrolet Frost Green.
Front and rear suspension is UMI Performance, at the time it was their Stage 4 kit. As I mentioned before, Viking D/A coilovers.
Right Stuff 2" dropped spindles, Speedtech shock relocation kit out back. This thing handles better than an F-body, and the ride is almost Caddy like.
Curious...what size rims/tires are those?

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Old 06-08-2020, 05:34 PM
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Originally Posted by 69gtocv View Post
If this helps, this is the stock specs on my 72, I would think 70 is pretty darned close.

Measuring 32" back from the centerline of the front wheels, measuring from the bottom of the rocker panel to the ground was 9.5" (10.5" with HD springs?) and at rear measured 19" forward from the rear wheel centerline, rocker to ground is 9.10" (also 10.5" with HD springs). So it proves that the front was higher than the rear as they came from the factory. Also check out some pictures I posted in my wheel thread of the old springs to new ones
Will do...thx.

Didn't think the suspension/stance could be so involved to get the right stance and performance (on a budget, that is).

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  #23  
Old 06-08-2020, 05:45 PM
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Will do...thx.

Didn't think the suspension/stance could be so involved to get the right stance and performance (on a budget, that is).

:
Exactly! I can't wait to hear how yours turns out and what suspension you go with. When are your wheels supposed to be shipped?

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Old 06-08-2020, 07:47 PM
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Wheels are due in at the end of the month, then mounted on the Nitto 555s and shipped.
Which is okay, since the car is apart for restoration.

Hoping it sits as good as yours, when all is done.

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Old 06-08-2020, 11:37 PM
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You'll love the Nitto 555's. I happen to have Nitto 555 G2's, Killer tire. The wheels and tires will make more difference to handling than any thing else you do.

With that being said...

There are two schools of thought:

Stiff springs, soft shocks
Soft springs, stiff shocks

They both handle well, the difference is when you come into a turn, if your springs are too stiff your car won't dip while braking to come into the turn. Not good. So, better to have springs on the soft side. This is according Herb Adams.

The thing about springs is no one really knows how much a spring is going to lower a car. Things like Engine, A/C, options are all a factor not to mention the wire the spring companies are using. Call any suspension company and nobody will guarantee anything. So, that's hit and miss. You may have to change a spring or cut it to dial it in, that's after they settle of course. If you have time, look up front coil springs in a MOOG catalog and you will see the amount spring part numbers available for your car is mind boggling.

With the exception of camber changes built into aftermarket control arms they offer no improvement in handling. So, if you go that way make sure they have that built in. Tall upper ball joints are always nice. They improve camber while in a turn. I would never use drop spindles because they cause bump steer, which you will hate. Hit a bump and your car is skipping all over the road. The geometry between the outer tie rod connection at the spindle and the contact patch gets all janky.

Lastly, I would invest in the adjustable rear upper control arms. Adjust-ability is always good. You may need to adjust for pinion angle.

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  #26  
Old 06-09-2020, 07:57 AM
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Originally Posted by vertigto View Post
Curious...what size rims/tires are those?
Front: 18X8 - 235/40
Rear: 18X9 - 275/40

  #27  
Old 06-09-2020, 12:43 PM
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Originally Posted by FrankieT/A View Post
You'll love the Nitto 555's. I happen to have Nitto 555 G2's, Killer tire. The wheels and tires will make more difference to handling than any thing else you do.

With that being said...

There are two schools of thought:

Stiff springs, soft shocks
Soft springs, stiff shocks

They both handle well, the difference is when you come into a turn, if your springs are too stiff your car won't dip while braking to come into the turn. Not good. So, better to have springs on the soft side. This is according Herb Adams.

The thing about springs is no one really knows how much a spring is going to lower a car. Things like Engine, A/C, options are all a factor not to mention the wire the spring companies are using. Call any suspension company and nobody will guarantee anything. So, that's hit and miss. You may have to change a spring or cut it to dial it in, that's after they settle of course. If you have time, look up front coil springs in a MOOG catalog and you will see the amount spring part numbers available for your car is mind boggling.

With the exception of camber changes built into aftermarket control arms they offer no improvement in handling. So, if you go that way make sure they have that built in. Tall upper ball joints are always nice. They improve camber while in a turn. I would never use drop spindles because they cause bump steer, which you will hate. Hit a bump and your car is skipping all over the road. The geometry between the outer tie rod connection at the spindle and the contact patch gets all janky.

Lastly, I would invest in the adjustable rear upper control arms. Adjust-ability is always good. You may need to adjust for pinion angle.
Great information...thank you.

I think the only front tubular control arm with camber changes built into the design are SPC, or am I mistaken? I like the BMR units (of course with tall ball joints), but I don't think they are designed that way...can anyone confirm?

Also, is the conventional wisdom that the front should be lowered more than the rear (e.g., 2" drop front with 1" drop rear or 1" drop front and stock height rear) to avoid the nose-up stock stance? Wondering if they latter is a better starting place to avoid sitting too low and front end scrap/bottoming out and springs could be cut if too high (although not ideal)?

I have come to realize after reading too many reviews about lowering springs, that a 2" drop doesn't necessarily mean that's where it will end up (even though most advertise @520 front and 125-200 rear). BMR does warranty (for life) that the springs won't sag...whatever that is worth.

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Last edited by vertigto; 06-09-2020 at 01:19 PM.
  #28  
Old 06-09-2020, 05:01 PM
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I think the only front tubular control arm with camber changes built into the design are SPC, or am I mistaken? I like the BMR units (of course with tall ball joints), but I don't think they are designed that way...can anyone confirm?
Correction: I misunderstood what you meant about the control arm design.

Per BMR: 'Upper A-arms are engineered to provide 2 additional degrees of positive caster for increased high-speed stability. Combine with BMR Lower A-arms, and you get 4 additional degrees of positive caster (2 degrees from the uppers and 2 degrees from the lowers). Added to the factory 2 degrees of caster, this allows you to achieve up to 6 degrees of total positive caster'.

Also, this is not including the tall ball joints.

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Old 06-09-2020, 05:02 PM
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Originally Posted by vertigto View Post
I think the only front tubular control arm with camber changes built into the design are SPC, or am I mistaken? I like the BMR units (of course with tall ball joints), but I don't think they are designed that way...can anyone confirm?
I'm fairly certainly most of the aftermarket tubular upper control arms use revised geometry that provides a significantly different camber gain compared to stock uppers. UMI uppers provide around 5-6 degrees of negative camber gain, which you won't get with stock upper control arms. That results in radically improved handling.

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  #30  
Old 06-09-2020, 05:04 PM
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I'm fairly certainly most of the aftermarket tubular upper control arms use revised geometry that provides a significantly different camber gain compared to stock uppers. UMI uppers provide around 5-6 degrees of negative camber gain, which you won't get with stock upper control arms. That results in radically improved handling.
Yep...I misunderstood the original comment at first (see above correction) ^^^

Thanks for clarifying.

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  #31  
Old 06-09-2020, 05:21 PM
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Yep...I misunderstood the original comment at first (see above correction) ^^^

Thanks for clarifying.
Yeah, honestly, I don't claim to be an expert here, either. I've just come to understand that they are different from stock, but I don't know the true specifics.

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  #32  
Old 06-09-2020, 05:27 PM
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Great information...thank you.



Also, is the conventional wisdom that the front should be lowered more than the rear (e.g., 2" drop front with 1" drop rear or 1" drop front and stock height rear) to avoid the nose-up stock stance? Wondering if they latter is a better starting place to avoid sitting too low and front end scrap/bottoming out and springs could be cut if too high (although not ideal)?
I personally like the rear about an inch higher than the front. I like a little rake.

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  #33  
Old 06-09-2020, 07:03 PM
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On my 69, I have 2'' drop spindles, ride tech upper and lower arms and viking coil overs, the Goat handles like it's on rails !

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Old 06-09-2020, 07:03 PM
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Just wanted to make a correction on altered geometry upper control arms.

Upper control arms themselves can not alter the camber curve. That is completely controlled by the height of the spindle in relationship to the pickup points of the control arm. The only way to alter the camber curve is to either change the location of the suspension mounting points or alter the height of the spindle. In almost all cases for the GM SLA suspension, and 100% of the time with the A and F body, you need more spindle height. This is achieved through tall ball joints, a taller spindle or in the case of 1st gen f-bodies, relocating the upper control arm mount (Guldstrand mod).

What upper control arms do is allow for more positive caster in the alignment and in some cases has that additional caster built in to the design. Positive caster helps to increase negative camber gain as steering angle increases. It's therefor highly important to handling grip in situations where you need a lot of wheel input, like an auto-x course. It's not helping you as much in the grip area on those fast shallow sweepers common to many road courses or the freeway on-ramp.

Positive caster also increases straight line stability, at the cost of steering effort. Except for people that run cars without power steering, it's almost always advantageous to run as much positive caster as you reasonably can without running into wheel centering issues, overly large stacks of shims or too much steering effort.

Setups like the SPC control arms reposition the lower ball joints so that at caster levels up to and exceeding about 5* positive, the wheel remains centered in the wheel well. Without this relocation of the lower ball joint, the wheel moves aft in it's wheel house and you may run in to rubbing issues as a result.

When you hear people rave about how much nicer their car drives after they swap to altered geometry control arms, it's typically because of a couple things.
1. They've replaced new items with old worn out items, specifically bushings and shocks
2. The additional positive caster has made the car more sure-footed and stable at speed
3. The shocks and springs added to the car are more suited to it's size and weight then the under-sprung and under-damped nature of these cars as they were delivered from the factory

With any control arm purchase for an A body or an F body, you absolutely should include at a minimum a .5" tall upper ball joint. While this does not completely correct the camber curve in the GM short long arm suspension, it drastically improves it. Combined with an altered geometry upper control arm that allows positive caster in the 3-5* degree range and coupled with a better spring and shock package, you start seeing suspensions that act like and provide similar feel to cars found in the mid to late 90's. For the vast majority of people here, that's going to really produce a car they want to get out and drive.

For those that need that little bit extra, ball-joint relocating lower control arms, large body modern valved shocks, taller effective spindle heights (tall spindle or .9" tall ball joint) and more aggressive alignments will produce suspension dynamics close to modern muscle cars.

SC&C claims that their street comp 2+ system produces negative camber gain curves that are over 90% of a 5th generation Camaro. I have no way to verify the validity of that claim, but I can tell you that my Firebird does things nearly at a level that my 2008 Z06 Corvette did and above that of the couple base model C6's I've owned. It has grip everywhere, is poised at the limit and rotates far better than it should considering it has a 650lb hunk of iron up front.

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  #35  
Old 06-12-2020, 01:31 PM
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On further thought, I may be taking a slightly different (and more expensive) direction, now that I think about how steep my driveway is (with a drainage ditch at the bottom).

For clearance, to be safe I would probably opt for the 1" lowering springs. However, I'm pretty sure I want the 2" drop stance and would always wonder if it would clear the driveway (and local speed bumps). Can't really justify ordering 2" and not be able to get in my own garage and don't want to bottom out a fresh resto.

So...now thinking about BMR front upper/lower control arms (tall ball joint), BMR rear upper adjustable control arms/poly differential bushings and Viking coilovers front and rear with UMI rear shock tower brace. That would allow me to adjust ride height with the spanner wrench/thrust bearings easily from below to accommodate my clearance challenges/maximize the drop. Not really sure the brace is necessary, but seems like good insurance (for $120) now that the body is off the frame.

The car is being restored, so can't easily try and swap out coil springs and I don't have much garage space to try swapping after the resto is done (if I went that route). Besides...I'll want to drive around for awhile when it's done, before tinkering more.

Although quite a bit more expensive than just lowering springs and some Bilsteins, I think this will be my best bet and a step up from the original plan. It's only money...right?

Thoughts??

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  #36  
Old 06-12-2020, 01:51 PM
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Thoughts??
What's the cost differential between a traditional shock & spring setup versus coilovers, including the added cost of the rear brace? If you installed 2" lowering springs and found that they were too low, my hunch is that it would still be cheaper to simply swap out the 2" lowering springs for 1" lowering springs compared to the cost of buying coilovers. Plus, you could sell the unused springs to recoup a decent amount of their value.

I'm not really a fan of coilovers in situations where the user does not require regular ride height and damping adjustment to suit varying road and driving conditions, which is 99.99% of us. I'm much more in favor of finding the perfect standard spring setup. I certainly don't take issue with the performance advantages of coilovers, it's just that most of us don't need that performance advantage and simply use them as a crutch to avoid having to figure out what springs to use.

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  #37  
Old 06-12-2020, 02:41 PM
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Much cheaper to swap out springs if they are an issue (@$800), but limited to 1" or 2" with BMR, unless I go with another manufacturer (which will lessen the cost difference).

Trying to factor in the ease of adjustability for my situation and assumed handling improvement using a quality coilover vs lowering springs/Bilsteins. Upgrade the shocks and the difference in cost is even less.

The bigger issue is the resto shop is 1.5+ hours from the house. So when the car is done, I would need the alignment set, drive 100 miles on the maiden voyage, see if 2" clears my driveway or else drive back out and have him swap/re-align. Obviously wouldn't be able to get into the garage to do it myself without some damage and even if I could, not sure I would want to after just getting back my car in December (hopefully) after a 10 month resto.

See what I'm getting at? So it essentially comes down to is an @$800 overexpenditure worth it to me for the ability to adjust and avoid the above? Again, I think the coilovers would be a handling improvement, so not necessarily an overexpenditure (per se), there should be an additonal benefit. If UMI runs their usual Spring Carlisle sale, would be more like a $650-700 difference.

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Last edited by vertigto; 06-12-2020 at 02:48 PM.
  #38  
Old 06-12-2020, 03:12 PM
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Coilovers don't inherently provide a handling improvement compared to a traditional spring & shock setup. They offer adjustability. If you select the correct springs and shocks for your car and conditions, they will offer the same performance as coilovers. So with coilovers, if you plan to set-em-and-forget-em, I'd urge you to rethink your plan.

Your concern about what would happen if you were unable to get into your drive upon taking delivery of the completed car is not much of a concern. If it happens that you can't get in at first, just stack up some wood as a temporary solution while you sort out the springs. No need to turn around and drive 1.5 hours back to the shop on the same day. You can also swap springs yourself in a few hours very easily.

Do as you will, but I think you're over-thinking this...

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  #39  
Old 06-12-2020, 04:41 PM
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Absolutely over-thinking it...that's why I haven't done anything yet.

I value everyone's input and their experience.

What I meant is that aside from the adjustability, I think the Vikings are a superior shock...rebuildable also. Maybe not $700-800 better, but...

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Old 06-12-2020, 05:13 PM
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Viking coilovers aren't going to have superior damping compared to a quality shock from Bilstein or Koni, though. I vote to keep it simple and dial it in using a traditional setup, and use the money saved elsewhere.

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