12mm Rear Shock Upper Threaded Shaft

[jross20]

So I've been talking with dobinsons about paying them to custom valve a set of their 4th gen IMS shocks for a 3rd gen, and the question came up about the diameter of the upper mounting shaft. The rep I'm working with says the 4th gen IMS shock has a 12mm shaft while the 3rd gen one has a 10mm shaft.

I believe the land cruiser ones, like the older OEM shocks, use a 14mm shaft if I am not mistaken... I know they fit because I've ran them before... But I also know that apparently it's not really ideal with that size.

So my question is, do we think that a 12 mm shaft on rear shock will be that much of an issue? Or nay? And also, I'm curious what shims in should use in the stack.

Thoughts?

(Also, for those who might be wondering why, unfortunately their IMS shocks made for 3rd gens pretty much have a pathetic shock travel that's barely better than stock. I mean, it's basically the same as stock for our use. The 4th gen one would be excellent for builds like mine with 890 coils)

 

[brillo_76]

Worst case you could drill the the hole in the shock coil plate longer if you have too. I am not sure of its diameter though.

Sent from my SM-A505U using Tapatalk

 

[HiluxSurf SSR-G]

many members in here use the bilstien rear shocks for the 4th-5th gens without issues so the dobinsons shocks should fit without issues

 

[jross20]

many members in here use the bilstien rear shocks for the 4th-5th gens without issues so the dobinsons shocks should fit without issues

Any idea what the threaded shaft's diameter is for those?

And yeah I know like I've ran the Land cruiser shot before, but some people did say that it could damage the mounting point because it would limit its articulation. As in the shock wouldn't be able to pivot around as much and then this would put stress on the frame hole.

Although I'm thinking that since this is still smaller than the Land cruiser one that maybe it will be okay?

 

[HiluxSurf SSR-G]

the 33-313146 has a 14mm shaft


https://www.summitracing.com/parts/bsn-33-313146#overview

Any idea what the threaded shaft's diameter is for those?

And yeah I know like I've ran the Land cruiser shot before, but some people did say that it could damage the mounting point because it would limit its articulation. As in the shock wouldn't be able to pivot around as much and then this would put stress on the frame hole.

Although I'm thinking that since this is still smaller than the Land cruiser one that maybe it will be okay?

 

[GhostRing]

Absolutely lurking about this thread as I am in the exact situation as OP - 890 coils and don't want to drop Dobinsons coin on too-short a rear shock.
I'm happy to get involved/help in any way I can.

 

[gamefreakgc]

Just drill it out if it doesn't fit. Would only take 10 minutes of your time and would not affect the integrity of the mount.

 

[ZSW99]

Pretty sure the hole for the factory shock shaft is 19mm. I drilled mine out to 7/8”(22mm) to run the LC shocks. The size hole you need is dependent on the hardware for the mounting bushings. It just needs to be big enough for the top hat part of the washers to fit into the hole.

I’m not sure you would need to change the shim stacks in the shocks. Is a 4th gen significantly different in weight? If not then the valving is probably fine unless you’re trying to create some specific ride quality

 

[jross20]

the 33-313146 has a 14mm shaft


https://www.summitracing.com/parts/bsn-33-313146#overview

So 12mm is probably fine without modifications.

Absolutely lurking about this thread as I am in the exact situation as OP - 890 coils and don't want to drop Dobinsons coin on too-short a rear shock.
I'm happy to get involved/help in any way I can.

Welcome to the club, haha. I can let you know how it goes with these custom shocks.

Just drill it out if it doesn't fit. Would only take 10 minutes of your time and would not affect the integrity of the mount.

I know it's possible, but I've also read post from other guys where they were wary about doing that because once you've done it you can't go back. And yeah I'm sure that little bit of drilling won't affect the integrity, but I'm sure it would affect how regular shocks would fit right?

Pretty sure the hole for the factory shock shaft is 19mm. I drilled mine out to 7/8”(22mm) to run the LC shocks. The size hole you need is dependent on the hardware for the mounting bushings. It just needs to be big enough for the top hat part of the washers to fit into the hole.

I’m not sure you would need to change the shim stacks in the shocks. Is a 4th gen significantly different in weight? If not then the valving is probably fine unless you’re trying to create some specific ride quality

David with Dobinsons did that they could build the 4th gen shock to ride plush for 3rd gens. I imagine stock it might not be that great. I personally not been satisfied with any of the shops that I've tried, to me they're all about much too stiff and the truck ends up riding like a sports car. The only thing I can assume is that maybe they just assumed you're going to have a lot of extra armor and cargo which might offset the stiffness. Not sure...

By chance do you have the measurements of the stock top hat shim? The inner and outer measurements? If not, I might see if my local Toyota place has one that I can go by and take measurements of.

I'm starting to think that a 12mm shaft and the stock four wheeler top hat will probably be fine.

 

[gamefreakgc]

I know it's possible, but I've also read post from other guys where they were wary about doing that because once you've done it you can't go back. And yeah I'm sure that little bit of drilling won't affect the integrity, but I'm sure it would affect how regular shocks would fit right?

If you are concerned about how it will work again if returned to stock you might want to reconsider modifying your vehicle. Whenever you start adding aftermarket parts, or a step further with custom parts, you'll find that other things will have to be changed or altered to allow everything to work that you didn't necessarily plan on changing.

My 4Runner is so modified at this point it can never go back to stock but I'm totally fine with that since I never planned to anyway.

 

[jross20]

If you are concerned about how it will work again if returned to stock you might want to reconsider modifying your vehicle. Whenever you start adding aftermarket parts, or a step further with custom parts, you'll find that other things will have to be changed or altered to allow everything to work that you didn't necessarily plan on changing.

My 4Runner is so modified at this point it can never go back to stock but I'm totally fine with that since I never planned to anyway.

Oh yeah I totally get that. I mean I've read about some guys going to the Land cruiser shops and stuff like that and never going back. I mean it could be that I tried these modified chops out and love them so much that I do go ahead and modify the frame.

Basically I would only want to do some of the permanent things like that if I knew for sure that's what I wanted versus just wanting to experiment... Haha

You know I think I actually still do have the Land cruiser shocks with the stock top hat shim. And I also have my old original OEM shocks. I think if I can find a 12 mm rod I could do a rough comparison between the three to see how much angular freedom each one has. Again I have a theory that the 12 mm might not limit it enough that it even matters at all. I know for a fact that it did limit the Land cruiser shocks but that really only was a maximum flex I think...

If I can get this tested I'll see if I can post some pictures for anyone else who might be curious as well.

 

[jross20]

Alright boys I've ordered a 12mm steel rod. Once it arrives I'll do some rough, "good-e-nuff" testing and post the results.

 

[ZSW99]

Alright boys I've ordered a 12mm steel rod. Once it arrives I'll do some rough, "good-e-nuff" testing and post the results.

Cool keep us posted. Did dobinsons give you the length and travel specs for the shocks? I know the kyb land cruiser shocks I run are about 2.5” longer with 1.5” more travel than the ones they sell for 3rd gens

 

[jross20]

Cool keep us posted. Did dobinsons give you the length and travel specs for the shocks? I know the kyb land cruiser shocks I run are about 2.5” longer with 1.5” more travel than the ones they sell for 3rd gens

So the IMS shocks for 3rd gens is:

Extended -- 20.86"
Collapsed -- 13.543"
Travel -- 7.32"

For 4th gens the IMS shocks are:

Extended -- 23.23"
Compressed -- 13.98"
Travel -- 9.25"


It's also strange to me how the compressed length is barely longer on the 4th gen shock but the travel is so much better.

And also, their front IMS shock's for 3rd gens surprisingly have a lot travel based on others I've seen.

Collapsed -- 13.189"
Extended -- 18.622"
Travel -- 5.433"

 

[ZSW99]

Yeah interesting. Those are pretty impressive travel numbers for a mono tube shock. The gas volume must be pretty low which means it will have more ramp up deep into the travel. Maybe not the best for slow crawling and maxed flex but probably an advantage for general driving and faster off-roading

 

[jross20]

Yeah interesting. Those are pretty impressive travel numbers for a mono tube shock. The gas volume must be pretty low which means it will have more ramp up deep into the travel. Maybe not the best for slow crawling and maxed flex but probably an advantage for general driving and faster off-roading

Well the 4th gen shock is physically longer so that is where the travel comes from.

Also, for those who are interested, dobinsons has shipped me a pair of 4th gen shocks with custom valving they believe should ride plush for a 3rd gen. Wooooo!

As soon as they get here and I get them put on and tested, I will post my review about them.

 

[GhostRing]

Looking forward to the results!
Dob quoted me about $100 to re-valve a 4th Gen set, it that about right?
That does up the overall cost quite a bit...

 

[jross20]

Looking forward to the results!
Dob quoted me about $100 to re-valve a 4th Gen set, it that about right?
That does up the overall cost quite a bit...

I did not actually pay anything extra, however it might be that they wanted to do this because I told them that I would share and review on the forums because it seemed like a lot of people were interested.

I mean honestly though, I still think that's very fair if they actually do ride really well because then you have shocks that ride fantastic and the travel is great. Well again, hopefully they ride fantastic.

They will be here either tomorrow or Friday and I'll try to get them installed as soon as I can.

 

[jross20]

All right so some updates, I received the shocks and they look pretty awesome. I still need to get new top hat washers though...

I'll post some pictures here soon

 

[jross20]

In order

• Stock Rears
• 4th Gen IMS Rears
• OEM LC Shocks

Also, does anybody remember what the bolt hole size should be on the bottom of the shot? This is one thing that I forgot to confirm with Dobinsons and I'm hoping that they might have already swapped it out. It looks like it's around 19 mm internal diameter.