Front Suspension shock tube modification

[Careless]

so it's a popular mod. everyone does it on toyotas and other cars and bla bla bla.

 

u know, the one where you mount the coilover sleeve over the shock tube after welding in a perch. so here's my question. Wouldn't it be better (structurally) and easier to have the shock tube tapped at the top where the threaded section that people usually cut/reweld is?

 

like instead of cutting off a huge 5inch section, why not clean up the sides like you would normally do after cutting off the stock spring perch, then cut the shock tube to proper height. THEN get someone to tap it with the same thread as the large nut that holds the strut in place?

 

Would this not be a bit more safe? I know strong penetrating welds are quite sturdy, but isn't the added peace of mind worth the extra work?

 

wait... im gonna take a guess... mounting them in a lathe to score out the inside of the tube, and taping it so that it accepts the holding nut is impossible because of the lower mounting section that is oddly shaped?

 

i would hate to be right at this point in time.

[JMortensen]

It is possible and has been done and discussed here before, but its a lot easier just to section the tube. If it's properly welded the strength isn't an issue, and it isn't hard to properly weld the tube. The tube gets really thin at the top to allow for the threads, so if you were to cut new threads I think they would have to turn the tube to a larger ID before cutting the threads. That's a lot of machining vs a relatively quick cut and weld. I think it was Dr Sideways that had his struts cut and had the threads cut in the end of the tube so if you want to search you might find that old post.

[Careless]

It is possible and has been done and discussed here before, but its a lot easier just to section the tube. If it's properly welded the strength isn't an issue, and it isn't hard to properly weld the tube. The tube gets really thin at the top to allow for the threads, so if you were to cut new threads I think they would have to turn the tube to a larger ID before cutting the threads. That's a lot of machining vs a relatively quick cut and weld. I think it was Dr Sideways that had his struts cut and had the threads cut in the end of the tube so if you want to search you might find that old post.

yah that's what i was thinking. they'd have to be set up on a lathe or a drill press to grind away at the interior of the tube to make it smaller before making new threads. =/

 

ok i'll look into it. =)

 

Thanks!

 

EDIT: here's a link to the post you mentioned, incase anyone ever searches for this topic rather than the other one

 

http://forums.hybridz.org/showthread.php?t=103860

[blueovalz]

My take on forces acting on the strute tube can be broken down into 2 forces. Shear and tension. The weight of the corner is on the lower spring perch. if the weld is above this then the only forces in-line with the new weld is a tension force from shock rebound. From the viewpoint of this single force, I'd feel more comfortable with the weight of the corner on the untouch tube (below the spring perch).

The second force is the shear or lateral forces. The top of the strut tube is constantly being pulled in all directions (braking, and cornering action) as the spindle attempts to pull the tube, along with the tube insert in what ever direction it can. The only thing keeping the top of the tube in place is the rod the extends out of the strut into the tower. So from this aspect, I would want the weld to be as high up the tube as is possible as well, which should reduce the shearing forces presented to the weld.

Tapping new threads would be an ideal solution to shortening the tube, but I do not know of a single instance where a welded tube failed at the new weld. I am going to the salvage yard tomorrow and see about getting a couple of SX front struts and see what is needed to shorten them, insert the 8610s and then install them under the SX.

[Jolane]

I agree with Terry about cutting the tube as high as possible to lower the load on the welded section. I will offer a different perspective as well though...

 

If you cut the tube really low, say maybe an inch from where it enters into the cast spindle, then you can actually put a doubler piece of metal around the welded joint and weld that up too. I have not seen anyone use that method (I am not sectioning mine as it won't be lowered enough to require it) though.

 

Just my 2 cents...

Joshua

[johnc]

The top of the strut tube is constantly being pulled in all directions (braking, and cornering action) as the spindle attempts to pull the tube, along with the tube insert in what ever direction it can. The only thing keeping the top of the tube in place is the rod the extends out of the strut into the tower. So from this aspect, I would want the weld to be as high up the tube as is possible as well, which should reduce the shearing forces presented to the weld.

 

Not really. The shock shaft is the main load bearing element and its supported at the top of the shock/strut tube and at whatever point the shock piston is within the shock tube. At the point of greatest lateral load (outside of the car in a turn or under braking) the shock is significantly compressed so that the load is spread along a wide base in the shock/strut tube (top and the shock piston near the bottom of its travel). So, the load is spread through the whole shock tube and then transferred to the strut tube, not just the top of the strut tube.

 

The shock/strut tubular combination structure is pretty dang strong. I've seen some very poorly welded strut tubes last for years of racing.

[Jolane]

Not really. The shock shaft is the main load bearing element and its supported at the top of the shock/strut tube and at whatever point the shock piston is within the shock tube. At the point of greatest lateral load (outside of the car in a turn or under braking) the shock is significantly compressed so that the load is spread along a wide base in the shock/strut tube (top and the shock piston near the bottom of its travel). So' date=' the load is spread through the whole shock tube and then transferred to the strut tube, not just the top of the strut tube.

 

The shock/strut tubular combination structure is pretty dang strong. I've seen some very poorly welded strut tubes last for years of racing.[/quote']

 

Maybe I misread Terry's reply, or misunderstand it, but I agree with him. Yes, the shaft is reacted by the shock tube throught the piston and the seal head, but in the end it doesn't matter where the piston is inside the shock (travel). The shock tube must be counteracted by the sectioned strut tube top and bottom. Maybe I am missing something, but the compression of the shock doesn't matter to the reaction forces on the sectioned tube. Does that make sense?

 

Joshua

[blueovalz]

Jon just added some detail I left off due to the very late (waaay past my bedtime) posting. The good thing about the 8610 inserts in the 240 tubes is that the tube and the insert are almost "one" in that gland nut is almost unnecessary in centering the insert in the tube (obviously it is needed none-the-less to afix the insert). With a tight fit like this, the entire tube length is used in spreading out the side loads and the weld becomes less of an issue. In a tube where the insert is a good bit narrower (smaller diameter), the gland nut is taking a lot of that force, and this force is then focused on the top of the tube,through any welds, to the rest of the tube.

[Careless]

Jon just added some detail I left off due to the very late (waaay past my bedtime) posting. The good thing about the 8610 inserts in the 240 tubes is that the tube and the insert are almost "one" in that gland nut is almost unnecessary in centering the insert in the tube (obviously it is needed none-the-less to afix the insert). With a tight fit like this, the entire tube length is used in spreading out the side loads and the weld becomes less of an issue. In a tube where the insert is a good bit narrower (smaller diameter), the gland nut is taking a lot of that force, and this force is then focused on the top of the tube,through any welds, to the rest of the tube.

hey blue,

 

are these the gland nut inserts that you're talking about?!

 

 

For ever and a day, people have been asking us to make a type of strut tube spacer that puts the shock insert at the BOTTOM of the strut casing on a full length strut casing.

Recently we began to have supply problems getting the stock AE86 Gland nuts for the strut casings, so we started CNC machining our own strut gland nuts from scratch.

Now we finally had a start on a design that could feasibly be made into an "upper strut tube spacer".

This Advanced strut tube spacer is machined from solid billet steel and is actually a gland nut with a spacer built in, specifically designed to cup the upper portion of the KYB AGX shock.

What this is used for:

1. Running the SW20 KYB AGX in a full length strut casing with NO modifications to the strut casings.
   
2. Perfect for putting the shock in the correct range of use when using coilovers. (No more "bouncy" shocks because they are over compressed)
   
3. Can be used with bolt on Coilovers OR lowering springs, with no adverse effects
   
4. Can be used with other short stroke shock options with small shims under the shock.

This is the EASY answer for those that want to run lowering springs and achieve the same handling as coilovers WITHOUT shortening the strut casing!

$60.00 for the pair

and is the AE86 gland-nut/ shock tube the same length or the same height?

[JMortensen]

If you put a spacer UNDER the shock then you can run a shorter insert in a longer tube and not lose any travel. For example, in the case of a Z, suppose you have 4 front struts, and you want to run them in front and back. You can run the spacer underneath the strut in the back and not lose any travel. This coincidentally is how Tokico ships their Z struts. Same strut front and back, rears have a steel spacer underneath.

 

If you put the spacer ON TOP OF the shock then you lose access to that much of the shock travel. Unless there is something about the KYB shocks that I am not aware of the valving in the shock should determine whether it feels bouncy or not, not where in the compression range it is (unless it is bottomed out). With this installed though, the top of the strut can never be pushed all the way in, so you end up losing about 2 or 3 inches of travel, however thick the spacer is. The bumpstop will hit the gland nut and the shock is still nowhere near all the way compressed.

 

So basically what this thing does is allow you to run a shorter strut than stock, and in the process it cuts out 2 or 3" of the travel that your new shorter shocks have.

 

IMHO this is not a good idea, and they'd be doing a service to their customers to offer a spacer that fits underneath the strut and telling their customers to use the stock gland nut.

[Careless]

So basically what this thing does is allow you to run a shorter strut than stock, and in the process it cuts out 2 or 3" of the travel that your new shorter shocks have.

 

hehe, i like when you answer suspension tech. That is exactly the part i had trouble getting my brain around. I though, how is it a perfect replacement (or so they say) when infact, you'd have a good 2 inches or more trapped in between that space at the top that will never come into play in terms of shock stroke.

 

which makes me wonder why they even sell that, and why not just include a spacer and a gland nut separately.

 

thanks for reassuring me =)

[blueovalz]

Can be used with other short stroke shock options with small shims under the shock.

This would seem to make a bad situation even worse

 

I am a bit puzzled as to why such a piece was created. In a lowered car, an OEM length insert in an OEM tube results in the car always riding in the lower 50% of strut travel. With this piece using a shorter insert in an OEM length tube, the car is always riding at the upper 50% of strut travel. What I want is access to 100% of strut travel.

 

I finally pulled an SX strut today, and found these struts are not very conducive to the type of modifications that I was looking to do. First, the case is only about 1/2" longer than the shortest 8610 insert. Second, if I were to raise the spindle mounting point (which would lower the body relative to the axle), then the lower spring perch would rub the top of the tires. A coil-over setup would not help in the second issue because the tire rides just under the 6" wide spring perch, and runs very close to the strut tube. The spring would need to be very short in order to work. The OEM spring has only 3 live coils (this small number helps prevent the coils from binding), but a coilover type of spring, with its many more coils, would most likely bind.

So...I looks like no solution at the present time is to be found. I'll continue looking.

[Jolane]

I am confused. Why does everyone think that the T3 spacer/gland nut will reduce travel. I don't see how it is any different than sectioning the tubes and using the the same shorter insert. The only difference I can see is less clearance from the top of the strut tube and the jounce stop. Otehrwise, it is exactly the same as sectioning the tube, right? A sectioned tube also reduces the travel...

 

Joshua

[JMortensen]

I have my struts sitting right next to my desk, so I'm in a good position to answer Jolane. In a stock Z strut you have about 6 3/4" of strut travel. In the MR2 strut that people use for the front end of a Z (Tokico Illumina BZ3099), you also have 6 3/4" of strut travel, just in a shorter shock housing. When you put the stock strut into the stock housing, you can compress the strut 6 3/4". If you were to put the BZ3099 into the taller rear housing and put a spacer underneath, you would have 6 3/4" of travel. If you put it in the rear and put a spacer on top, then part of the 6 3/4" travel is lost to the spacer, so you'd have 4 3/4" or so before the gland nut gets in the way. It would be possible to push the end of the strut INSIDE the strut tube, past the gland nut, but I don't think you're going to want to do that...

[johnc]

This is the EASY answer for those that want to run lowering springs and achieve the same handling as coilovers WITHOUT shortening the strut casing!

 

What a nutty statement! They will probably sell a million of 'em...

 

The only difference I can see is less clearance from the top of the strut tube and the jounce stop.

 

And that reduction of clearance is a reduction of bump travel. A typical 240Z shock has about 6" of total travel. When the car is at its stock OEM static ride height you typically have 3" of bump travel and 3" of rebound travel. By lowering the car you are reducing the clearance between the strut tube and shock bump stop. This reduces available bump travel because; even though the shock might have 3" of travel availabe, the bump stop hitting the top of the strut tube effectively limits bump travel. To get it back, you have to raise the ride height or shorten the strut tube.

[Jolane]

What a nutty statement! They will probably sell a million of 'em...

 

 

 

And that reduction of clearance is a reduction of bump travel. A typical 240Z shock has about 6" of total travel. When the car is at its stock OEM static ride height you typically have 3" of bump travel and 3" of rebound travel. By lowering the car you are reducing the clearance between the strut tube and shock bump stop. This reduces available bump travel because; even though the shock might have 3" of travel availabe' date=' the bump stop hitting the top of the strut tube effectively limits bump travel. To get it back, you have to raise the ride height or shorten the strut tube.[/quote']

 

I agree that the bump stop is now closer to the strut tube, but without a lot of experience here, I must ask, does it even matter. Would the spring bind before? In any event, lowering a car reduces the compression travel of the suspension. This means that you gain rebound if you use a stock length strut in a stock housing. If you section the housing and use a shorter strut, the rebound is limited as well.

 

The only issue with the T3 gland nuts is that the top of the strut tube might hit the jounce stop sooner. I don't see how this is different than a stock strut on a lowered car. When talking strut travel (top 50%, bottom 50%, etc), this is no different than using a shorter strut and sectioning the housing. A strut doesn't care where the travel is being used either, its damping (for these struts) is only velocity dependent, not position dependent.

 

Don't misunderstand me though...I am not so sure the T3 solution is the best, but it may be perfectly adequate for certain applications. IMO, the best solution would be to section the strut, but if you want to run a shorter strut WITHOUT cutting and welding (so the car can be lowered without bottoming the strut), this solution should work. Those bump stops are pretty long anyways, maybe shortening them results in a great setup...

 

Joshua

[JMortensen]

I agree that the bump stop is now closer to the strut tube, but without a lot of experience here, I must ask, does it even matter. Would the spring bind before? In any event, lowering a car reduces the compression travel of the suspension. This means that you gain rebound if you use a stock length strut in a stock housing. If you section the housing and use a shorter strut, the rebound is limited as well.

Yes it matters. No, the springs won't bind if you get the right springs. Lowering a car DOES NOT reduce the travel. Sectioning a housing does not reduce the rebound. It reduces the starting point. If you have a fender height of 25 inches and you section the struts to reduce that height to 23 inches, you still have the same amount of bump and rebound travel as you would at the 25 inch height. That's why sectioning is better than cutting springs. With cut or lowering springs you lose bump travel, but keep the rebound.

 

With the TTT piece you lose bump and rebound.

[johnc]

The only issue with the T3 gland nuts is that the top of the strut tube might hit the jounce stop sooner. I don't see how this is different than a stock strut on a lowered car.

 

You're right, its not. But lowering a car to the point that you have 1" of bump travel before its on the bump stops is bad for handling. Very bad at high speeds. This is true regardless if its a stock lowered car or a car with the fancy spacers.

 

When talking strut travel (top 50%, bottom 50%, etc), this is no different than using a shorter strut and sectioning the housing. A strut doesn't care where the travel is being used either, its damping (for these struts) is only velocity dependent, not position dependent.

 

Ok, we need to be clear on the terminology. Shock is the thing with the travel and Strut is the tube the shock is mounted in. Valving is not relevant for this discussion.

 

A shock has X amount of travel and in most street and racing setups where you are not limited by class rules you set up your shocks and the static ride height so the the shock is in the middle of its range of travel. There are exceptions to this but they are irrelevant for our discussion.

 

By placing a short shock inside a long strut and spacing that short shock down to the bottom of the housing you are losing bump travel by the exact amount of that spacer and you are NOT gaining any rebound travel (if the shock is setup in the middle of its range of travel with the static vehicle load on it). Bump travel is very important for racing. When a car hits the bump stops the spring rate increases at a very quick rate almost to an infinate number (body flex comes into play at this point).

 

By shortening the strut and spacing the short shock to the top of the shortened strut tube you retain as much bump travel as is practical. A 240Z with 5" of ride height (measured at the rockers) can have 3" of bump and 3" of rebound travel with shortened struts. Without shortening the struts or by using the fancy spacers we are discussing on the same car, you will end up with about 1" of bump travel and you'll use that up in roll on a fast corner.

 

I don't know how to explain it any better.

[RTz]

I agree that the bump stop is now closer to the strut tube, but without a lot of experience here, I must ask, does it even matter.

 

Jolane,

 

Yet another way to say all this... If you lower a stock car with springs only, you will use up some of the quoted 3" of travel. If you lower the car 2" then you would have only 1" leftover before the top of the strut tube hits the bumpstop. You can put any damper in the world inside that tube and it will never change that. The most direct way to add more bump travel is to install a shorter damper and shorten the tube accordingly. If you shorten it 1" then, practically speaking, you'll gain 1" of bump travel (setting aside motion ratios for the moment). So now, in this scenario, you have two inches. The T3 gland nut does not address this in ANY way. I don't even see the point of it. If you lower a Z and you expect good handling the strut needs to be shortened. There are a couple of other ways to increase bump travel but they are a bit of a tangent.

[Jolane]

Maybe what I said came across wrong. I agreed that you loose travel. I understand this as well. If you lower a car via the springs (regardless whether they are coilovers, cutting springs, etc), it brings the strut upper (pivot) closer to the strut lower (gland nut).

 

I wasn't sure about the amount of compression left though. It is common for someone to lower their car 1" and still use the stock SHOCK and strut tube (sorry John C, I was in a hurry and used them incorrectly, although I did know the difference. I should have proof read). The part that I was unsure of was the amount of bump travel available after lowering. Certainly running into the bump stop after only 1" of compression is a bad thing...BUT, the bump stops are rather long. Why not just shorten the bump stop to gain additional clearance? I thought the other reason people went to shorter struts was so that the stock strut did NOT bottom itself. I thought this was the main purpose of the shorter strut, to keep the shock piston from hitting the bottom of the shock body internally.

 

Anyways, I didn't mean to suggest that the T3 parts were the best solution, but rather was trying to understand whether it was really that bad. Consider a street car that has been lowered a little (not race car lowering mind you). I guess maybe just run a stock length shock then? BTW, is the stock travel really only 3" in compression, and 3" in rebound?

 

Joshua