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 Post subject: Re: 308 suspension setup
PostPosted: Tue Apr 02, 2019 6:49 pm 
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Posts: 4250
TheDarkSideOfWill wrote:

The Swift is a tiny vehicle with low contact pressure to begin with. The fact that underinflating the tires (further reducing contact pressure) made it better in the rain says that was a problem with the specific make/model of tire you were using rather than a problem with the tire sizing. Of course you *should* have seen the opposite effect: increasing the tire pressure made it more resistant to hydroplaning. Tire carcass construction can have some really weird effects on handling. .


contact pressure= tire pressure. That is true for any tire, but the swift was light so very few in^2 actually on the ground at 35 psi....1800/35=51.4in^2 divided across all 4 tires. My bmw was double that at the same tire pressure. tire brand didn't much matter on the swift....they are all awful and it killed front tires about every 15k-20k miles so I got a lot of opportunity to test different options....clearly it also had a geometry issue.

This is where I was going though, most all the testing I've seen is for cars with normally sized tires that have a nearly square contact patch and the base model swift acted normal, the GT did not. My 328 has the factory sport wheel/tire package and is also quite prone to hydroplaning, I have a buddy with nearly the same car with base wheel package and he doesn't have the issue but mine get really unsafe when the tread gets anywhere near the tread markers. Its a wide tire giving an unhelpful shape contact patch in the rain thing I'm pretty sure that would go away with narrower tires.

Non of this really matters to the 308 I suppose since I have no real desire to drive it in the rain....the roof leaks.


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 Post subject: Re: 308 suspension setup
PostPosted: Thu May 30, 2019 9:20 am 
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The wider the contact patch, the harder it is to channel all the water out of the way, regardless of contact pressure pushing said water.


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 Post subject: Re: 308 suspension setup
PostPosted: Thu May 30, 2019 11:34 am 
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Sounds right.

I need to get the new wheels ordered but it's looking like 8.5" front and 10 rear to both fit the wheel wells and the available forgings


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 Post subject: Re: 308 suspension setup
PostPosted: Thu May 30, 2019 1:56 pm 
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Just cut out the 2x2 structural tubing and replace it with 1x3... instant 11" rear wheels. :lol:


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 Post subject: Re: 308 suspension setup
PostPosted: Thu May 30, 2019 2:30 pm 
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They still don't have a forging ;)

For me the issue is where I mounted the oil return pump....very little space left


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 Post subject: Re: 308 suspension setup
PostPosted: Thu May 30, 2019 3:10 pm 
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These guys have wide fenders at the stock wheelbase: https://www.berlinettamotorcars.com/fer ... ionkit.htm


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 Post subject: Re: 308 suspension setup
PostPosted: Thu May 30, 2019 4:04 pm 
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I've looked at those but am not sure I want to alter the body


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 Post subject: Re: 308 suspension setup
PostPosted: Thu Apr 01, 2021 10:02 pm 
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The new front springs came, 6" long to replace the 7s I had figuring these are nearly double the stiffness so they will want to be shorter...800lbs/in

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ride height visually looks right at about 4.5" but I still need to look at a few thing to be sure this is ok as far as the suspension is concerned.  I had to pull the rear wheel to get that sitting right for the photo op as there is no engine weight and 2" shorter 500lb/in springs I ordered are on back order.
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it is jut about as low as I can go even with the shorter springs, about 3/8" travel left on the collars which is about 5/8" left to drop.
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That said, I'm not so sure I get to decide that suspension rebuilding is a next winter project....it very honest looks like E36 M3.  The the steering rack is leaking, the bellows torn, the rubber bit falling apart and showing every bit of their 37 years.


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 Post subject: Re: 308 suspension setup
PostPosted: Sun Apr 04, 2021 10:07 am 
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Took a couple minutes and pasted the pic from the manual into onsahpe. I started by just throwing on a few lines that are the given track to establish scale.

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Then pasted in the pic eyeballing to my lines

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Then eyeballed points at the suspension pivots and put lines through them....instant center 295.36mm
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With a few dimensions added to fix the contact patch, a-arm lengths, upright and chassis a-arm mount distances and 1 to set the lower a-arm mount to ground (203.12 is where it came out in the manual drawing), I lowered the car 1" to 178mm

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the instant center changes from 295 to 80mm....that does not seem ideal. ut I still need to mirror it to see what the roll center is doing. The lower chassis a-arm mounts are bolt-on and not quite long enough to get the camber up to 3 degrees (I'm told) so since I probably need to make new mounts anyway I'll spend a little (as in many hours :) ) figuring out exactly where the car is set now and fiddling with finding a good location for the lower a-arm mount height....which will no doubt mess up the bump steer.....its always something.



Edit...roll center changed from 78.6 to 45mm not as bad I thought.

Edit 2 - I typo'd the 1 inch drop in CAD....roll center drops from 78.6 to 26.4 for a 1 inch ride height drop


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 Post subject: Re: 308 suspension setup
PostPosted: Wed Apr 07, 2021 6:53 pm 
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I have been giving this a good deal of thought while preforming semi-mindless spring tasks around the house.....I think Put the springs on and call the suspension done enough to drive. Yes, the suspension bushings are in pretty poor condition but they are still there and I NEED to get the engine running.   Next fall I'll likely build a new suspension.  The 18in wheels give me a lot of space inside and the F430 rotors sit out much further than the 308 setup so I have a lot of room to reduce both the kingpin angle,scrub radius, and roll centers if I make new spindles and a-arms and if I make new a-arms I can get rid of all the silly rubber.   I may still change my mind..... and cut the suspension apart now but I'll try to be strong.......



I've got some thoughts on the frame and the just plain wrong location of silly little the factory fender flares....be.strong....you need and engine......


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