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Old 02-12-2020, 12:25 PM   #1
jwernerny
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Default '88 760 v6 Suspension Questions

Hello!

I've decided to upgrade the worn out suspension on my 760 with b280. The plan is for Bilsteins all the way around, and 250 lbs springs in the rear mk 1 IRS. I like billies and have done 250lbs springs in mk 1 IRS before.

Here's what I need to know:

Do IPD's front swaybars for the 740/940/960 clear the oil pan on the V6?

Any suggestions for spring rates for the front? What is the stock front spring diameter?

Thanks!
-John
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Old 02-12-2020, 04:27 PM   #2
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Stock front spring diameter is 167mm. Wire diameter varies based on suspension code (check your build plate) but could be anywhere between 13.6 and 14.8 mm, which corresponds to (according to my math) 111-160 lb/in wheel rate (0.978 motion ratio). I don't know what the motion ratio is on the mk1 IRS but if it's anywhere near 1:1 those front rate options will not be nearly stiff enough. Unfortunately I can't help with the front sway bar question. You'll have to measure the motion ratio on the IRS to figure out what works, I would recommend calculating your front and rear ride frequencies to find a good front rate. Rallyboutique in Sweden also offers a 16.1mm wire front spring for the stock setup, which works out to 231 lb/in at the wheel.

P/Ns and wire diameters:
1329822 13.6mm (111 lb/in)
1329823 13.7mm (116 lb/in)
1329824 13.8mm (119 lb/in)
1329825 14.4mm (143 lb/in)
1329826 14.8mm (160 lb/in)

Unfortunately without knowing the wheel rate in the rear these numbers don't mean much but they're good for reference. It should be pretty simple to figure out what the motion ratio is in the rear if you get under the car with a tape measure. The wheel rate is equal to the spring rate times the motion ratio squared.

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Old 02-20-2020, 01:22 PM   #3
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Bump... Bump...

Any other thoughts on 940/750 vs. 760 swaybar fitment? Will the bars for 4 cylinders work on the V6?
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Old 02-20-2020, 11:06 PM   #4
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Quote:
Originally Posted by jwernerny View Post
Bump... Bump...

Any other thoughts on 940/750 vs. 760 swaybar fitment? Will the bars for 4 cylinders work on the V6?
Pretty sure the 4 cylinder one does not work on the v6, but the inverse does.
When I bought my first 780, it was a B280, so bought the ipd bar to fit. Then swapped the engine for a b230 and it drops quite far down relative to the engine and partially fouls the under engine pan.

Swapped the bar to successive B230 780s and still have it. Not sure if IPD sells them anymore and the used ones are snapped up pretty fast for v8 conversions as they fit nicely.
If you find a nice B230 IPD front bar I would consider swapping with you.

Not sure where you are in NY, but I am just north of Ogdensburg.

Patrick
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Old 02-21-2020, 12:41 AM   #5
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I have the IPD Nivomat rear conversion kit that I removed from a 1989 Bertone; like this one:

https://www.ipdusa.com/products/6326...cks-ipd-109635

Let me know if you're interested in it!
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Old 02-21-2020, 12:58 PM   #6
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Quote:
Originally Posted by HRPufNStuf View Post
Pretty sure the 4 cylinder one does not work on the v6, but the inverse does.
When I bought my first 780, it was a B280, so bought the ipd bar to fit. Then swapped the engine for a b230 and it drops quite far down relative to the engine and partially fouls the under engine pan.

Swapped the bar to successive B230 780s and still have it. Not sure if IPD sells them anymore and the used ones are snapped up pretty fast for v8 conversions as they fit nicely.
If you find a nice B230 IPD front bar I would consider swapping with you.

Not sure where you are in NY, but I am just north of Ogdensburg.

Patrick
Thanks for the info. I'm outside of Rochester, but I don't have a 740/940 bar (or any non-stock bars right now).
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Old 02-21-2020, 12:59 PM   #7
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Quote:
Originally Posted by swedishiron.com View Post
I have the IPD Nivomat rear conversion kit that I removed from a 1989 Bertone; like this one:

https://www.ipdusa.com/products/6326...cks-ipd-109635

Let me know if you're interested in it!
I'll pass. I do my own conversion with HD Bilstein's and Hyperco 13" long springs. I used 275 in the past, and it raises in rear end a little. I think on the 760, I'm going to try 250s. At $50/spring, I can afford to experiment.
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Old 02-21-2020, 10:58 PM   #8
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Quote:
Originally Posted by jwernerny View Post
I'll pass. I do my own conversion with HD Bilstein's and Hyperco 13" long springs. I used 275 in the past, and it raises in rear end a little. I think on the 760, I'm going to try 250s. At $50/spring, I can afford to experiment.
Do you have a link to the 250 hypercos? After 17 years, my ipd rear conversion springs have sagged unevenly.
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Old 02-22-2020, 12:31 PM   #9
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Quote:
Originally Posted by HRPufNStuf View Post
Do you have a link to the 250 hypercos? After 17 years, my ipd rear conversion springs have sagged unevenly.
Here's a link to all of the 5" dia, 13" long Hyperco springs that Amazon has. They have something like 150 lb to 375 lb in 25 lb increments:

https://www.amazon.com/s?k=hyperco+s...ref=nb_sb_noss

Sorry, the price is now $62/spring. :-)
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