KONI 8610 with shorted strut tubes help

[Nismo_Gizmo]

I just finished shortening my strut tubes and put everything back together. After putting my wheels on, I realized that the rear fenders are touching the tire when the car is set onto the floor. The fronts have about an inch of room. Before setting the car down, I adjusted my ground control sleeves as high as they would go, resulting in the strut being extended the whole way. Keep in mind at this point, there is about 1.5 inches between the tire and the fender.

Is there supposed to be more clearance than this? Did I mess something up? I will say that all 4 struts have the entire threaded portion sticking through the strut cap and are torqued down.

I see two options here, I can unthread the struts a half inch or so and I have not yet cut my fenders for flares. This should give me more room. I really want to know what went wrong though. I followed the write up here http://www.betamotorsports.com/benchracing/StrutSectioning.html and everything seemed to check out.

 

Thanks in advance.

[74_5.0L_Z]

What rate and free length springs did you use?  What size tires? What year car?

Are you using camber plates?  If so, which ones?

 

Pictures?

Edited May 8, 2013 by 74_5.0L_Z

[Nismo_Gizmo]

Ground control kit, 10in springs, 225f 250r. 15x9 and 15x10 wheels, 275 50 15 and 225 50 15. No camber plates.

[74_5.0L_Z]

That is a really tall rear tire to try and use with sectioned rear struts.  You probably should not have sectioned the rear, instead put a spacer under the insert to fill the tube.

 

My struts are sectioned as per John's instructions, but I am running 23 inch tall tires (275/35/15), I have flares so that the tires car fit into the wheelwells, and I am running really stiff springs (8 inch 450 lb/in rear and 8 inch 500 lb/in front).  As it is, I only have 1.5" of droop travel at the rear.

 

Here is an old thread where I went through a simlar issue:

 

http://forums.hybridz.org/topic/62475-sectioning-struts-for-koni-8610-1437race-insert/

Edited May 8, 2013 by 74_5.0L_Z

[Nismo_Gizmo]

I unthreaded the rear struts a Half inch. I'm gonna preload the springs and add flares and it should be too. Where on earth did you find a 35 series 15" tire?

[74_5.0L_Z]

I run Hoosier A6 tires.  I only use the car for autocrossing and track days.   I found that my driving record stays a lot healthier when I don't drive the Z on the public highways. 

[Nismo_Gizmo]

Those are sweet. Maybe I'll get a set the next go round. How is the tread life on them? Do you think unthreading the rear struts is safe? The nuts that hold the strut shaft are flush with the top threads (I'm using 2 per strut.) My thought is that after preloading the springs, the force from them should hold the strut stable. I don't think that it should be able to bounce around. What do you think?

[johnc]

I've never seen anyone run a 26" tall tire on a S30.  Is this a 240Z or a 280Z?

[Nismo_Gizmo]

It's a 240z. I didn't have much choice going with 15" wheels. It was either the Hoosier A6's, or a 205 50 15. I also did not realize that the width of a tire attributed to it's height. That concept is a bit confusing to me.

 

I guess I may need to get smaller tires. I wish I could find a 245 50 15.

Edited May 8, 2013 by Nismo_Gizmo

[johnc]

The aspect ratio (the "50" in 275/50-15) indicated how tall the sidewall is in relationship to the tire width.  That means that tire sidewall height is 50% of its section width.  So a 275/50-15 will have an approximate sidewall height of 137.5mm (5.4") while a 275/35-15 will have an approximate sidewall height of 96mm  (3.75').  There's you're 1.5" difference (plus another 1/4")

[Nismo_Gizmo]

It all makes sense now.. Should I go with 205s and 225s or 225s all around?

Edited May 8, 2013 by Nismo_Gizmo

[Nismo_Gizmo]

I should mention, this is a sunday car but I want to take it to track days too. I'm planning a vq37 after I finish the paint.

[74_5.0L_Z]

 

I unthreaded the rear struts a Half inch. I'm gonna preload the springs and add flares and it should be too.

 

 

 

The gland nut that holds the insert in the tube must be fully installed and tight. 

 

You can and really should preload the rear springs of that rate and length.  As a rough estimate,  you can assume that you will have approximately 600 lbs of sprung weight at that corner.  Therefore when you let the car down off of the jack, the spring which has a rate of  250 lb/in will compress 600 lb / 250 lb/in = 2.4 inches.  If you don't preload the springs at all, then the car will drop 2.4 inches before the force in the springs equals the weight on the corner.  If you preload the spring by 1.2 inches then the car will droop 1.2 inches before the force in the spring equals the weight on the corner. 

 

Without knowing your exact corner weight, you will have to play with the preload.  Here is what I would do:

 

1.  Put a tie wrap or bump rubber on the shaft of the insert so that it is tight and will indicate the travel of the shaft in bump.

 

2.  Adjust the preload to 1 inch (250 lbs).  The loaded spring will be nine inches long.

3.  Install the struts, push the tie wrap or bump rubber down against the gland nut, and lower the car onto the ground.

4.  Verify that the tires don't rub and then roll it back and forth to settle the suspension.

5.  Jack the car back up and measure the distance that the tie-wrap or bump rubber moved when the weight of the car was carried by the springs.

-----The measured movement of the tie-wrap or bump rubber is the amount of droop travel that you have available with the springs preloaded by 1"

 

If that number is more than two inches and the car is still too low, increase the preload and repeat step 2 through 5 until you are happy with the ride height.

 

DON'T ADJUST THE SPRINGS TO GIVE LESS THAN 2 INCHES OF DROOP.

 

If you cant get the height you need with 2 inches or more droop, then you need to do one of two things:

 

Stiffer springs or redo the strut sectioning to make the tubes longer.

Edited May 8, 2013 by 74_5.0L_Z

[Nismo_Gizmo]

Thanks for the preloading advice. I didnt mean loosening the gland nut though, I meant the nut at the top of the strut. The one that threads through the strut top. Does this have to be torqued down to the end of the threads?

Also, I am sending the 275 50 15's back and am going to install 225 50 15s. That should give me another 2" of room.

[74_5.0L_Z]

Yes, that nut must be tight as well or else you will have slop in the strut during its motion.  What you can do though is to put a tubular spacer between the shoulder on the shaft and the isolator that attaches to the strut tower.  Just make sure that you have full engagement of the threads and that the nuts are tight. 

 

The 225/50-15 will fit much better 24.7 tall rather than 26 " tall.

Edited May 8, 2013 by 74_5.0L_Z

[Leon]

FWIW,

 

A 225/50-15 is 23.9" tall, not 24.7".

[74_5.0L_Z]

Thanks,

 

I was going by memory, and I am getting a little older....

[JMortensen]

I guess I may need to get smaller tires. I wish I could find a 245 50 15.

If you get some of the super racy street tires, Toyo R1R, Hankook RS3, BFG Rival, etc, their 225s are ridiculously wide. I was at an autox the other day and there was a guy with a common set of Miata wheels and the Toyos. I said: "Those must be the 8" wide rims, because they fit the 225s perfectly, he said they were 9" rims and that he compared the Toyos to a regular old 225 and it was about an inch and a half wider.

 

Did you section the strut housing to fit the insert? If so, that is your problem. Saw a 240 last season autox and the guy was spinning all over the place. He had sectioned the strut to fit the insert instead of using a spacer, and then jacked up the preload to try and fix. It still looked like it was dragging its ass, but it wouldn't remain pointed in the right direction for more than a turn or two.

[Nismo_Gizmo]

If you get some of the super racy street tires, Toyo R1R, Hankook RS3, BFG Rival, etc, their 225s are ridiculously wide. I was at an autox the other day and there was a guy with a common set of Miata wheels and the Toyos. I said: "Those must be the 8" wide rims, because they fit the 225s perfectly, he said they were 9" rims and that he compared the Toyos to a regular old 225 and it was about an inch and a half wider.

 

Did you section the strut housing to fit the insert? If so, that is your problem. Saw a 240 last season autox and the guy was spinning all over the place. He had sectioned the strut to fit the insert instead of using a spacer, and then jacked up the preload to try and fix. It still looked like it was dragging its ass, but it wouldn't remain pointed in the right direction for more than a turn or two.

I did section the rear strut  but I only took off about 1.5". I am also using a 1.25" spacer. The problem was those 26" tall tires. I'll look into some of those other tires eventually. Right now I am  going to use Kuhmo Ecsta's ASTs all around. They are about $65/ea and H rated. I think they'll do the job fine for now. My Z hasn't been on the road in 3 years, so i'm just looking forward to getting it back to that state. It goes in for paint on the 18th.

Edited May 10, 2013 by Nismo_Gizmo