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Front spring rates

 
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jjadczak  



Joined: 03 Jan 2003
Posts: 346
Location: Accokeek, MD

PostPosted: Fri Feb 07, 2003 12:53 am    Post subject: Front spring rates Reply with quote

Hello! This is the front spring rate from a Porsche 944 stock spring: 21.8 N/mm. It came from the technical section on this site. I also noticed that the stock spring rate for the 924 is 180 (I believe). the 944 front spring is heavier but I want to know what the stock 944 spring rate it is. Can anyone help translate the above number? Also I have a set of stock Koni front struts off of a 1988 Porsche 944. They should be able to fit my 924, right? I have upgraded to the 944 11 inch brakes so it should fit in the wheel well? I'm looking at having the struts revalved and rebuilt. With the 400 pound front springs and the capacity of the front struts to match would I have a problem with the top of the strut tower ie, is there a possibility that under extreame load the strut pierces through the top of the tower? Would I need to weld a plate in place to make sturdy?

Thanks

Jeremy
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924RACR  



Joined: 29 Jul 2001
Posts: 8794
Location: Royal Oak, MI, USA

PostPosted: Fri Feb 07, 2003 3:21 am    Post subject: Reply with quote

That converts to 127.5 pounds/inch, by my calculations. That should be very close to the front 924 spring rate, which I thought was more like 110#.

I would not expect those struts to fit the upright (steering knuckle). YMMV, though.

There is a concern that the top of the strut tower can be bowed by impacts, like curbs and jumps/offroading. I've had this happen. Ideal is, yes, to weld in reinforcement. Grey area of legality, though.
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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-nick  



Joined: 16 Nov 2002
Posts: 2699
Location: Cambridge, MA

PostPosted: Fri Feb 07, 2003 10:25 am    Post subject: Reply with quote

hey i've always wondered about the front spring rates listed in the 944 faq (presumably where you got the numbers in the tech section). i haven't seen the rates published anywhere else. where did they come from originally?

125 lb. springs seem pretty soft for the 944. those were even used on some 951's according to the faq. heck 914's used 110# or so and they're a whole bunch lighter than any 924/944. the rates go up to about 150 lbs as an option. still doesn't sound very heavy. i'm using 200# crapmeister springs and the difference didn't seem as dramatic as 75+ lbs.

ps- are there any other spring manufacturers out there? other than messing with coilovers which is a little overkill for what i need. i'd really like to find some progessive rate springs. they are stock for S2's and 968's but using those involves changing quite a few bits around.

-nick
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81turbo  



Joined: 03 Nov 2002
Posts: 1065
Location: Oakland, CA

PostPosted: Sat Feb 08, 2003 2:18 am    Post subject: Reply with quote

Well Weltmeister ("crapmeister" would roughly translate to crap champion, no comment) has a progressive rate #250 spring. I have been very happy with them. Easy enough for daily use but really dig in when you need it.
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dgz924s  



Joined: 03 Nov 2002
Posts: 592
Location: Kansas

PostPosted: Sat Feb 08, 2003 2:54 am    Post subject: Reply with quote

In my quest for spring knowledge I emailed a question to the PCA and was told that Porsche does not give out springs rates. However the stock spring rate on the 924S is believed to be circa 170lbs per Geo. B. of PCA Tech commitee. D
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John Brown  



Joined: 07 Nov 2002
Posts: 903
Location: Leesburg VA

PostPosted: Fri Feb 14, 2003 12:55 pm    Post subject: Reply with quote

I recall that when I compiled some of that info; a number that sticks in my mind is the sport spring for the 931 was about 160 lb/in. I thinks stock was about 140. The 944 was in newtons and uses, I think, a slightly different measuring method. So was difficult to convert. However, you can assume that the 944 stock standard spring is very very close to the 924. They are the same car so far as designing spring rates concerned. There is no reason to think they would be sprung very differently.
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-nick  



Joined: 16 Nov 2002
Posts: 2699
Location: Cambridge, MA

PostPosted: Sun Feb 16, 2003 5:29 am    Post subject: Reply with quote

the newton/mm to lbs is a straight forward conversion. it's not a progressive rate or anything. converting from the tech page numbers in N/mm gave me the 125 and 150 numbers.

81turbo- i thought all welt's springs were a linear rate? where did you get the 250's from? and the German translation would be "champion of crap"

-nick
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924 turbo  



Joined: 02 Nov 2002
Posts: 1566
Location: Simi Valley, CA, USA

PostPosted: Sun Feb 16, 2003 9:39 am    Post subject: Reply with quote

I have a set of progressive rate springs from Weltmeister. I bought them from Performance Products.
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