Suspension: Springs - Page 9

BlpltGTV · #**121** (**permalink**) 02-17-2007, 09:28 PM

So I have found a set of progressive rear springs. They are bright red with O&K Muenchen/Germany HA 105/115 serie 35mm printed on them and a part # 75391. The rears are 15 inches tall, the bottom 6 coils are close together (4.12mm apart) however the 5 above are spaced 43.22mm apart. The wire dia is 12.74mm. The set for the front read the same, however they are 11.5 inches long, 8 coils (counting the end partial ones) the outter dia is 5.304in (134.73mm) and the wire is 16.5mm (.650in). The part # on those is 75390.

Has anyone heard of these? Is there enough info to calculate the spring rate? I tried using the formula posted earlier in the post but kept screwing it up (I am not the best when it comes to math.)
I figured for $200 for the full set it was worth the gamble. They are new never installed.

Thanks,
Will

vintage prep · #**122** (**permalink**) 02-18-2007, 10:37 AM

Dont know if you can accurately compute the spring rate. Best bet would be to consider it as two springs stacked on top of each other. Consider the first spring with 4mm spread as bottoming out (coil bind) first at approx 17mm travel, then add the second spring rate and travel to the first. Of course there is some progression between the phases. You might ask the vendor for more info. Keep in mind the spacing you quoted is not as installed. After installation, that 4mm might be more like 3mm.

Off hand, it sounds like the rears would be to stiff compaired to the fronts. Good price though.

BlpltGTV · #**123** (**permalink**) 02-18-2007, 06:23 PM

At this point, Im more worried about the front being too soft. I'd hate to lower it 1.5 inches, then find the springrate is about the same as the stock ones, and catch the oilpan on something. That would be all kinds of bad. It will also affect the roll center, I really need to know if the fronts will handle the change in geometry. As I said, I tired to use the previously posted formula but couldn't get a correct spring rate (I was coming up way soft.)

Thanks,
Will

CMSPer · #**124** (**permalink**) 02-19-2007, 11:31 AM

Interestingly enough, I got a set of 1100 lb/in 9.5" 5.5 speedway springs...they appear both taller and softer than the IAPs that I just got as well. And IAP is standing by their rate of 1300 lbs./in.

**msiert** · #**125** (**permalink**) 02-19-2007, 12:11 PM

Quote:

Originally Posted by CMSPer

Interestingly enough, I got a set of 1100 lb/in 9.5" 5.5 speedway springs...they appear both taller and softer than the IAPs that I just got as well. And IAP is standing by their rate of 1300 lbs./in.

clemensh83 · #**126** (**permalink**) 02-20-2007, 04:03 AM

Hi Will!

I have red OKP springs in my car (sorry, don't have the part number here...).

The car was at the front very very low, and to soft. Ofter a broken oilpan I changed the front springs to 125 kg/cm ( about 700 lbs/inch) and not so low, and now its much better.

Just have a look at the pics at the link in my signature.

The rear springs seems to be fine, with the close together coils you can vary your ride high by cutting the springs, without changing the spring rate, I cut about one winding, but the car could still be lower at the rear.

Clemens

bryan · #**127** (**permalink**) 02-20-2007, 08:10 AM

Quote:

Originally Posted by msiert

In the "The 105 Suspension Bible" Thread they said they had a confirmed rate of 985Lbs for the IAP's but I would like to know how they confirmed this? IMO I think that IAP front springs are close to 1,300 lbs.

BlpltGTV · #**128** (**permalink**) 02-20-2007, 08:45 PM

The front end is already too soft, and a broken oilpan is no good (makes a big mess, the engine doesn't like it either.). Did you run the spacers with your springs? Clemens, your front end was really low. I'm tempted to try these, but if the pan is obviously too low, I'll swap the stock springs back in, and just pull the spacers.

Will