240Z strut tube I.D. and fitament issues

[Guest Gr8White]

Hi guys,

Was wondering if anyone had some diameter dimensions for a stock 240Z strut tube. I am running into problems with my inserts and would like to verify that the strut tubes I have (junkyard sourced) are indeed 240Z. I have searched and I believe I can confirm that the OD is 2" for 240Z casings, but cannot find any listings for ID. The diameter dimensions on my strut tube is as follows:

 

OD= 2.00"

ID (measured at threaded portion of tube)= 1.660"

 

There were strut inserts (unknown brand) in the tubes that measure 1.625". I will be sectioning the struts approximately 1". The strut inserts I have (BZ-3125) measure 1.700", so you see the problem.

 

I have been told that the BZ-3125 inserts that I have do work with the 240Z tubes after calling and stating the problem was told that these will work with 240 tubes and the casings I have might not be 240Z casings. Other than the OD, the casings are identical to the 280Z casings I have, minus the difference in the brake bracketry.

 

I have read that the BZ3099 inserts are the ones that I see used most often, what are the OD dimensions on the BZ-3099's?

 

Any input here would be appreciated. I want to make sure I have all of my facts straight before I investigate further and cut my tubes for the sectioning process.

 

Thanks!

[timbo1jz]

I just went through a mess of the same problem, because my car is a mid year 74 260z. Finally got it figured out though. You need to go by Outside diameter. The 240z style use a 51mm O.D. and the insert is actually bigger than that of the 280z style. The 280z style uses a 56mm O.D. but the strut tube walls are thicker, so the insert itself is smaller than the 240z style. Hope this helps. when you stick a 280z insert into a 240z strut, their will be a lot of play and movement, and you will realize that it is not right.

[Guest Gr8White]

Thanks, appreciate the response and will check the numbers again.

[johnc]

The 280z style uses a 56mm O.D. but the strut tube walls are thicker, so the insert itself is smaller than the 240z style.

 

Not true. The ID of the 280Z strut tubes is larger then the ID of the 240Z strut tubes. I just pulled down a clean, media blasted front 240Z and front 280Z strut tube.

 

240Z - OD 2.005" ID 1.690"

280Z - OD 2.155" ID 1.728"

 

There are variances in these dimension due to seamed tubing manufacturing tolerances. The variance is typically .005 to .010".

[JMortensen]

Not true. The ID of the 280Z strut tubes is larger then the ID of the 240Z strut tubes. I just pulled down a clean, media blasted front 240Z and front 280Z strut tube.

 

240Z - OD 2.005" ID 1.690"

280Z - OD 2.155" ID 1.728"

 

There are variances in these dimension due to seamed tubing manufacturing tolerances. The variance is typically .005 to .010".

Are you measuring ID right at the top? I seem to remember the 240 strut tube opens up at the top and is thicker walled from about an inch down. Not sure if the 280 does the same. I suppose you'd need an inside mic to get the ID down in the main part of the tube...

[Guest Gr8White]

Not true. The ID of the 280Z strut tubes is larger then the ID of the 240Z strut tubes. I just pulled down a clean, media blasted front 240Z and front 280Z strut tube.

 

240Z - OD 2.005" ID 1.690"

280Z - OD 2.155" ID 1.728"

 

There are variances in these dimension due to seamed tubing manufacturing tolerances. The variance is typically .005 to .010".

 

I guess it would have been too difficult for Nissan to have left these alone on the first gen. cars..... This gives me an idea too- (One I should have already thought of, but couldn't see the forest for the trees)- I should try the 240Z gland nut on the strut tube and see if it starts. This will tell me what I do or don't have... I've got both 240z and 280Z gland nuts- what is obvious is that these gland nuts are not interchangable, confirmed by your numbers. You can see this just looking at them. I feel pretty ignorant for not trying the gland nut itself after I found that the strut insert was too wide... Thanks John!

[johnc]

Are you measuring ID right at the top? I seem to remember the 240 strut tube opens up at the top and is thicker walled from about an inch down.

 

C'mon Jon, give me some credit...

 

I measured about 3" down inside the tube.

[JMortensen]

Just making sure!

[timbo1jz]

thats weird, because I thought I had 280z style tubes so I ordered shocks for a 280z and when I stuck them into my 240z tubes they slid right in, but had a lot of play and didn't fit right. I then ordered 240z shocks and they slid in perfectly with no play.

[Guest Gr8White]

Yes, all of this is very strange and I believe that someone has definitely done some customization with the strut tube although I can't find any visual evidence to support this. Although the OD is correct for the strut tube, the 240Z gland nuts will not start! There is no threaded insert either (insert Twilight Zone music)....

 

Problem fixed, Gabriel at Techno Toy had some 240Z tubes already sectioned and powdercoated in his inventory, ready for coilovers and sent them my way- received them yesterday. My insert slid right in and Gabriel/Rick machined a shim so that the gland nut tightens up perfectly when torquing down the gland nut. Great products, excellent customer service.

 

Thanks all for the input.