Thoughts on Coilover springs currently on EBay

[Black-Tooth]

WOW... I think you have found a solution, Mike...

BUT...

With the way they are NOW mounted... there is even more of a likelihood of the towers deforming as the pressure is solely on the three studs. The studs are also no longer just a "locating" device, but are now essentially supporting the weight of the car in each corner!

It would almost seem that if you were to hit a bump hard enough and bottom out the strut... it would rip the stud's nuts right out through the tower.

The use of some very LARGE HD washers underneath or better yet, the Plaia reinforcements would probably be a wise decision.

(Thinking about this some more though... the strength of the studs themselves, the threads and nuts also play a role in supporting the weight of the vehicle... I think I would also consider going to a larger BOLT and NUT combo in the Grade 8 category as well... Maybe I'm just being TOOOO cautious now... I dunno...)

Great work though... and continued success!

 

[Black-Tooth]

Rally, Ulix, Peter & Paul... I find this discussion...

... very interesting and you all bring some valid points to the table.

I also paused and stretched a bit and and reflected about what went into Steve Hoelscher's 5X Champ Car suspension...

Along with some other back-yard "improvements"... he took a pair springs off the back of a junker X1/9... cut them down and installed them up front... WHAAA-LA!

HA!... Just blind luck?

Anyway... Please continue...

 

[bpimm]

Unfortunately the Ksport is to fat under the plate to fit like that without cutting out the strut tower. I haven't tried but it doesn't look promising.

Bernice, I beg to differ about the spacers. I've been racing my X for 3-4 years like this with absolutely no problems and lets just say, I'm not gentle with it either. Thats not including the spirited thrashings/turbo testing on weekends.

My only suggestion is to take the camber plates off, revers the studs and mount them on top with the spacers. This way, you can adjust them without any difficulty.

 

[spiggs]

Bernice, I beg to differ about the spacers. I've been racing my X for 3-4 years like this with absolutely no problems and lets just say, I'm not gentle with it either. Thats not including the spirited thrashings/turbo testing on weekends.

The G-Force Engineering camber plates also mount the same way. You got to assume that some testing went into those as well but on my car I choose to use doublers under the strut tower since my towers had already started to deform with just the stock mounts, KYBs, and cut down rear springs. I could only imagine it would only get worse with triple the spring rate. This is on a 1975 X1/9, could there be any difference in the later cars that would explain why some people don't have any issues with strut top deformation?

 

[Rupunzell]

These camber plates are larger than the ones provided by K-sport and the camber plate mounting holes is near the edge of the strut tower. This area is more rigid than the center strut tower area where the stock mounting holes are located (think lever effect). Also, the spacers appear to be larger in diameter than the K-sport spacers. ... which could be why they have been OK so far..

When it comes to stuff like this, I'm rather paranoid and would rather error on stronger than just enough. It is not that difficult to plate up this area and distribute the load over a larger area. It's just not that difficult to do and provides a bit more peace of mind for the chassis.

To really get this done properly, the whole set up will need some structural analysis done with all known variables plugged in, then we can have a better idea of what is excessive and what will work.

Bernice

Bernice, I beg to differ about the spacers. I've been racing my X for 3-4 years like this with absolutely no problems and lets just say, I'm not gentle with it either. Thats not including the spirited thrashings/turbo testing on weekends.

My only suggestion is to take the camber plates off, revers the studs and mount them on top with the spacers. This way, you can adjust them without any difficulty.

 

[JimD]

Could there be a slight difference (update- I guess Bernice answered my question)

Bernice, I beg to differ about the spacers. I've been racing my X for 3-4 years like this with absolutely no problems and lets just say, I'm not gentle with it either. Thats not including the spirited thrashings/turbo testing on weekends.

My only suggestion is to take the camber plates off, revers the studs and mount them on top with the spacers. This way, you can adjust them without any difficulty.

Hi Mike,

I remember that your plates don't mount in the stock holes. Your mounting holes are much closer to the structural sides of the tower. The Ksports mount in the stock holes closer to the center of the top. So.... could it be that there is a difference in the stiffness/rigidity of the metal across the strut tower tops?

Here is your old thread from the archives?
http://www.network54.com/Forum/12159/message/1154218076/Oh+Nooooos

Just looking at the pictures of the Ksports, I don't think the tops are big enough to move the holes out to your locations anyway. I did buy a set of MarkP's Bigfoot plates, so maybe I will give this try someday.

 

[Rupunzell]

Some quick numbers:

3000 N = 674lb, coil bind * 130mm or 5.11 inch

1400N = 314lb * 200mm or 7.87 inch

650N = 146lb * 225mm or 8.85 in

about 168lb/in for this spring.

At 440lb/1957N compression is 175mm or 6.88 in.

Some one check this... and verify.

Bernice

Hi,

Recently, the stock springs were tested on a (very) professional spring tester. Here is the curve for the front spring:



The spring rate is the pink curve.
x-axis: overall spring length in mm
y-axis: spring rate in N/mm
(black curve is the compression force in N)
(the blue lines can be ignored)

The spring is fairly linear through much of its range.
What needs to be done is determine the range of force (or x) that the spring sees while in use on the car, and maybe convert the spring rate in that range to lbs/in. I haven't gotten around to that yet, anybody interested?

 

[rx1900]

Re: stock spring rates

Hi folks. There sure seems to be a wide range of opinions here regarding stock X1/9 spring rates. Let me add to the confusion!

My official factory service manual - from Fiat Motors on North America - for 79-82 U.S. models - states that a new spring should have a length of 6.69" under a load of 474 lbs for front, and 7.87" under load of 562 lbs for rear. Unfortunately thay do not state free lengths or rates.

However, Matt from Midwest claims good lightly used stock springs have a free length of 10.5" front and 11.5" rear. Thus we can calculate that the fronts have a rate of 474 / (10.5-6.69) = 124 lb/in and the rears have a rate of 562 / (11.5-7.87) = 155 lb/in.

Assuming the factory info is correct - Italian auto makers always tell the truth don't they? - and that Matt's lengths are correct - I know Matt wouldn't lie to us - ( if Matt's used springs have in fact sagged a little from new then the real spring rates would be a little lower), then I think this should be the definitive answer. Or maybe not...

Cheers, Doug

 

[Rupunzell]

Some notes on the spring curve Ulix posted:

Spring rate for free height of 260mm or 10.2 inches = 135 lb/in
Spring rate for a free height of 267mm or 10.5 inches =124.2 lb/in..
Close enough to agree with the numbers published in the FIAT factory manual.

Also worth nothing that there are two lines in this plot. One is for the spring being compressed (compression line) and one for Rebound (rebound line). There is a small gap between these two lines. It is due to the spring not returning all the energy put into the spring from compression. This loss is due to frictional losses at the atomic level which generates heat...

Bernice

My official factory service manual - from Fiat Motors on North America - for 79-82 U.S. models - states that a new spring should have a length of 6.69" under a load of 474 lbs for front, and 7.87" under load of 562 lbs for rear. Unfortunately thay do not state free lengths or rates.

However, Matt from Midwest claims good lightly used stock springs have a free length of 10.5" front and 11.5" rear. Thus we can calculate that the fronts have a rate of 474 / (10.5-6.69) = 124 lb/in and the rears have a rate of 562 / (11.5-7.87) = 155 lb/in.

Cheers, Doug