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#1052866 - 08/10/17 09:38 PM Suspension geometry effects of higher ride height?  
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Hunter79764 Offline
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Probably due to a lack of sleep coupled with too much coffee, I've had some ideas about a very mild lift and offroad style tires on my Monte. I know there a ton of people that will hate it, but I'm not destroying a clean SS, it's a low mile base car that has already been modified enough to lose any value from originality, and doesn't gain much value from my modifications. I built the car to have fun, and that's what it does for me.

Humor me here, this is more of a thought experiment rather than "I'm going to do this next week". I don't want to drop it on a K5 frame, I don't want to put 26" rims on it, just more like the old school Baja Oldsmobiles, or the charger from Fast and Furious 7. And I'd hate to dig in only to find out I'd take some poor geometry and make it worse. Obviously autocrossing wouldn't be in my future, but I'd like for it to not wallow and bumpsteer and understeer like crazy every time it hit a dip on the highway...

Anyway, I know that the front geometry is bad at stock settings and generally worse when lowered with drop springs. Does it actually improve when going higher to the tune of 2" or so? I'm thinking maybe installing taller but soft springs (maybe start in the catalog for Oldsmobile diesel springs or 2WD S10 lift springs), or using 2WD S10 2" lift spindles to maintain stock geometry, but not sure what either of those options does to bump-steer.

For the rear, I'd like to upgrade from the 7.5 and use an Explorer 8.8 and go with a truck-arm setup. From what I've seen so far, the biggest drawback of the Truck Arm arrangement on a Monte is the clearance underneath and the cost of any kits that are good enough at tucking up under the car. If I was to raise the rear a couple inches as well, it seems like that would give me the room to install a setup based on the older Chevy trucks, or possibly just a complete homemade kit.

Any thoughts? I've got my flame suit on...


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1052891 - 08/12/17 09:20 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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SSLance Offline
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For the front, raising the ride height with just springs will probably add negative camber. With a stock setup camber went positive under compression and negative under extension. As far as where this puts the centerlink in relation to the steering arm...good question. I would never suggest this as a fix or anything even past way temporary...but you might put coil spring extenders in the stock springs and give it a whirl. You'd have to check and reset your toe and camber for sure but it'll give you an idea anyway.

Not sure what the triangulated 4 link would do when raised...never even thought about that lol...


Lance
1985 Monte Carlo SS Street Car
#1052907 - 08/13/17 01:12 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Hunter79764 Offline
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I suppose the rear might not be too detrimental, I've run air shocks at full pressure and an empty trunk before which probably gets it close to the height I'm envisioning, but that would just be an intermediate step until I got a better axle under it...
On the front, that's a good point. "Shim" the springs a little higher and see if it becomes unstable. Even on the current wheels and tires I could see if it went too far south.

I know lifting these chassis can be done and is done all the time, but I don't know how much technical advice I want from the 26" chrome dub crowd...


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1052938 - 08/15/17 11:35 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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The front geometry actually gets slightly better when you lower it and align it. When you lift the car, the tires camber negative, so your camber behavior would be backwards. With the short upper arm, jacking could be a problem too. It certainly wouldn't be ideal, but how much do you care about handling with that setup?

#1052942 - 08/15/17 03:06 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Hunter79764 Offline
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Typical handling won't be much of an issue, but probably the biggest thing I want to avoid is making bumpsteer worse. I wouldn't be carving corners by a long shot, I hardly do that now, I just want to make sure it wouldn't go from bad to massively worse.
I think I know what you mean by "jacking", but can you clarify? And would the 8.5" circle track arms help? I'm running the 8" (right side/stock length) arms right now, not ideal but cheap and effective for the little use I put it through.


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1053052 - 08/23/17 05:11 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Jacking is when a lateral force creates a vertical force. So if the instant center is high, when you go around a turn, the car tries to "pole vault" over the wheel to a slight extent. It's the same effect as when you jack the car off the ground and set it back down and it sits higher than normal.

The longer upper arms will create more problems than they solve.

#1053337 - 09/11/17 12:54 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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markg Offline
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im working on a 84 non ss monte . I wanted to put the front up higher than my 86 cl .my "friend" specked out some springs that would put it up higher.
he came up with moog 5404s.they have the same ends but are 3 inches taller and 1840 lbs instead of 1640lbs monte had springs.
what a nitemare.it was very dangerous to compress these enough to fit in and it was nearly impossible to get the ball joint thread started.
once in the car sat about 3 inchecs higher in the front.i have no idea how it handles or works at all because im taking them back out this weekend and putting a set of moog 5608s in like my 86 monte.getting the compressor back out of the spring was also a problem and I think its way too dangerous to try to get them out with the compressor again .I plan on torching the spring to get it out and just choke the whole thing up to a lesson learned.
I think you could fit 31 inch truck tires on it now!


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#1053370 - 09/13/17 02:09 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Hunter79764 Offline
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Any chance you can snag a picture before you remove them? Call it morbid curiosity...
Good to know how those springs worked out (or didn't, as the case may be). Definitely won't go that route.


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1053376 - 09/13/17 10:23 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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markg Offline
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yes ill get a pic of it and post.


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#1053442 - 09/18/17 02:02 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#1053443 - 09/18/17 02:03 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#1053445 - 09/18/17 04:17 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#1053465 - 09/19/17 06:20 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Hunter79764 Offline
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Thanks, I'll add this to my notes.


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1053468 - 09/19/17 08:07 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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nj
extremely dangerous to get out also.
we torched them out but tried to get them hot enough so they would collapse before cutting thru them.
first side snapped and just about jumped completely out.
we had to cut them into 4 pcs each to remove them.


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#1053784 - 10/07/17 12:08 AM Re: Suspension geometry effects of higher ride height? [Re: markg]  
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MAP Offline
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So strange to come back here after such a long absence! Quickly, I completely agree with SSM's assessment. On the stock front end, going lower is better than going higher. With a stock front RCH that's already 2-ish inches below the ground, raising the front ride height will locate this virtual point even lower, increasing the jacking effect and increasing roll for a given transverse acceleration assuming constant vertical suspension stiffness. In my case, I lowered the front ride perhaps 1" to 1-1/2" (very roughly) below stock, and lengthened the LCA's by 9/16" to help get camber where I wanted it (close to -1 degree static,) and to reduce the scrub radius with a rim of increased backspacing. Doing so also helps to achieve the target camber with the stock UCA's without an enormous shim stack on the UCA cross-shaft. However, caster now needs some attention as well as bumpsteer - this should be a separate conversation.

Hunter, all of this just reinforces the notion that raising the car will do nothing good for its handling. Of course, I'm sure you've got a good personal justification for this, so no intention of launching any flames. As for the rear, I switched my thinking years ago from a live axle, to an IRS coupled with a 40/60% F/R weight ratio. A very long story that I won't belabor here...

Best,
MAP

Last edited by MAP; 10/07/17 12:11 AM.
#1053785 - 10/07/17 01:57 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Missed you MAP!

#1053797 - 10/07/17 11:08 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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MAP Offline
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Missed you folks too! I've been gone because with the syrocketing costs of doing effective hotrodding, the hobby has steadily receded out of economic grasp. That, and OE cars are light years ahead of the factory designs of a just few decades ago, BC ("Before Computers.")

Back to the previous post, I should have clarified that with a below-ground front roll center height, the jacking effect is negative instead of positive; that is, the front end tends to drop rather than rise in a turn. If there's anything good about that, it's that the effect is stable and self-limiting taken to an extreme: the more the front end drops, the lower the anti-jacking force for a given transverse acceleration.

Thanks,
MAP

Last edited by MAP; 10/07/17 11:14 PM.
#1053818 - 10/10/17 08:25 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Good to see you again MAP!

I'm thinking that raising the front would raise the RCH as the IC's climb up... am I confused?

The increased RCH would then increase the transient LLT, making the car push on turn-in and direction changes.

BTW, how did you increase the LCA effective length? I assume you started with tubular arms? I like that idea.

#1053825 - 10/10/17 11:41 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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MAP Offline
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Glad to see you're still here! Are you still working on suspensions for the government as I recall?

OK:

1. Negative RCH with stock front end: I wish I could draw a picture right now! Imagine an LCA that is horizontal, and a shorter UCA where the inboard side is higher than the outer BJ side (the stock kingpin BJ separation is smaller than the inboard pivot axes separation with the stock A/G-body design, like the first-gen Camaro.) In front view, the two central virtual lines extending through the pivot points will intersect several feet outboard of the wheel, and above the ground, at the same height as the LCA BJ. If a new virtual line is extended from this instant center to connect with the tire contact patch center, the normal to it will have negative camber, thus corresponding to a negative roll center height.

2. Yes, definitely a higher moment in turns with respect to the roll axis for a given transverse acceleration, so more LLT (Lateral Load Transfer,) more roll, more push-in (if I understand that term correctly: does that mean higher slip angle?) and more anti-jacking.

3. I took the stock arms, and cut them right where the two sections that house the inner suspension bushings, turn and join-up with the fore-aft interior wall of the LCA. Then, I took 1/2" x 1/8" mild steel bar, and made two U-shaped sections conforming to the sections created by the cuts. I welded the U-shaped sections into place, effectively lengthening the two inwardly-projecting suspension bushing housings by a net 9/16". After this, I ground the welds flat on the lower edges of the LCA, and cut two sections of mild steel that were about 2" x 2" x 1/8" each as I recall, and welded these to the LCA's centered on the bottoms of the two U-shaped sections I had previously welded. (I didn't want the first set of welds to create stress-risers anywhere.) Since the bottom spring perches were moved outboard by the same 9/16", the motion ratio was changed (about +6% motion ratio, so about +12% stiffness at the wheel. I made a canted bottom spring perch of lossy, compliant material, to improve load distribution on the now-canted spring. Some blows with a sledgehammer on the frame openings on the outboard side were also needed to increase clearance due to this tilt.) The LCA's performed flawlessly this way for roughly ten years before the car was sold.

Best,
MAP

Last edited by MAP; 10/11/17 12:02 AM.
#1053826 - 10/11/17 02:28 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Good to see you back in here, MAP!
So basically, it sounds like more push in the turns and more undesirable wheel positioning, but not exactly unstable or inherently dangerous (it would just handle like a shoebox on mud tires, for some strange reason...). For what I'd be using it for, that is probably good enough. And absolutely no offense taken at the understandable questions of "Why?", and the assumption that I'm not expecting handling to get any better by raising it up and running bigger tires is accurate as well smile
I just want to avoid involuntarily jumping off a cliff, figuratively or literally, with a raised setup.


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1053831 - 10/11/17 07:41 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Thanks, Hunter! I think you've got a thorough understanding of what kind of handling to expect, so short of some emergency situation that might require unanticipated and abrupt turning, you should be fine. HTH.

Best,
MAP

#1054098 - 10/27/17 09:30 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Obviously a different level of car than what I can pull off, but here's a nice picture of the type of look I have in mind...
Picture
http://hanabi.autoweek.com/sites/de.../public/mustang-ebay-6.jpg?itok=4ZTBn53r
Article
http://autoweek.com/article/sema-sh...Za6MCa_spot-im-frame-uid-468341_c_oKlTt8


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1054159 - 10/30/17 10:29 PM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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MAP Offline
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Hi Hunter,

That picture is illogical to me. If the point is functionality, and the point of this particular functionality is to gain lots of terrain clearance, then there's got to be a correlation between high general clearance, and lots of suspension travel. Or to say that differently, if we don't want large, upwardly-pointy objects to hit the car undercarriage, then there has to be a non-zero probability that one or more wheels will need to travel over said objects, hence, the simultaneous requirement for lots of suspension travel. That car passes the first criterion but misses the second badly. Unless - unless the wheels are expected to push fenders and quarter panels out of the way (!)

Best,
MAP

Last edited by MAP; 10/30/17 10:31 PM.
#1054164 - 10/31/17 02:56 AM Re: Suspension geometry effects of higher ride height? [Re: Hunter79764]  
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Yeah, there isn’t much room for compression there. I would much rather sacrifice a little tire width and gain a little more visible fender gap in order for it to actually work on rougher roads than a parking lot speed bump, but that particular car seemed to have more high dollar parts thrown at it, which doesn’t always equate with function...


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway

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