8s rigs 10mm shock alternative?

[aametzger]

I thought I would share an experiment that i'm working on with my arrma 8s rigs. When doing huge sends with the 8s rigs, bending or breaking shock shafts is possible. M2C came out with stronger shafts, but they still do break or bend in extreme cases. This got me thinking of alternatives. I found that the Rovan front shocks are about the same length as the outcast f/r and the kraton rears. They have 10mm shafts and aluminum caps and ends. I ordered a pair to test them out for fitment and functionality. I will keep everyone posted on the results. Here is a link to the ones I ordered.
https://www.rovanrc.com/product-rv853351s

I received them and they are slightly longer but installed no problem. I have not filled with oil yet, and need to rebuild the front of my outcast to replace the cracked gearbox before I can test them out. I am eager to see how they do. Does anyone have suggestions on oil weight? I was thinking 30ish like I run in the stock shocks. because of the larger shafts should I run a different weight? thoughts?

 

[KevinC]

Very very interesting bro. Great discovery. .......the fitment in the shock tower is good?

cheers,
kev

 

[aametzger]

Very very interesting bro. Great discovery. .......the fitment in the shock tower is good?

cheers,
kev

yes it is good. I think the top cap it slightly shorter so they don't rest inside and touch the top kinda like the stock ones do i think. I suspect bending and breaking the screws where they mount top and bottom might become the new weak point. Which could be a pain it is breaks off inside the shock tower. as mentioned i haven't ran it yet, but after a couple runs if i like them i will be ordering another set, and then eventually 2 more sets for my Kraton. - i am converting the front of my kraton to the taller outcast front tower and shock length.

 

[L3phturn]

A little longer is not a problem as travel will be limited by droop anyway so you could leave the droop as-is. Those are adjustable enough to set the same net spring length or preload. You could try running more droop and see how it affects handling, if at all.

If you disassemble those shocks or find documentation it should tell you the number and diameter of the holes in the piston, and if it is different than the stock pistons you shouldn’t use the same oil weight.

 

[KevinC]

My concern, particularly with the fronts is that the length of the shock may really force the suspension downward, creating a bend where the droop screws meet the chassis “ears”.
I guess if you have RPM arms it won’t matter too much.
Keep us posted.

cheers,
kev

 

[aametzger]

My concern, particularly with the fronts is that the length of the shock may really force the suspension downward, creating a bend where the droop screws meet the chassis “ears”.
I guess if you have RPM arms it won’t matter too much.
Keep us posted.

cheers,
kev

Yea I have rpm front arms. I am running droop screws in the rear with stock arms and granted I don't have oil in the shocks yet, but it didn't seem to be pushing too hard. I actually feel that in the front the longer shafts could be helpful because in the current setup the shocks get full extended to the stop when the wheels are off the ground. To be honest I would likely have put them on the front for test fitting but my front is mangled right now so I opted for test fitting the rear. I got some wrenching to do this weekend

 

[L3phturn]

My concern, particularly with the fronts is that the length of the shock may really force the suspension downward, creating a bend where the droop screws meet the chassis “ears”.
I guess if you have RPM arms it won’t matter too much.
Keep us posted.

cheers,
kev

That only applies if you are using different springs or and can’t adjust the collars enough to have the same effective spring length and preload. If the springs are different strength that will be a handling issue, but if they are similar strength springs you can simply adjust the shock collars so that there is very little preload. Even if you dialed in a lot of preload, it won’t be enough to bend an arm or the chassis ears.

 

[madf78]

Hmm, very interesting. Looking forward for the test results

 

[BashingBrian]

Holy look at the shaft thickness !!!

Surely they won't ever break..

 

[L3phturn]

Holy look at the shaft thickness !!!

https://media1.giphy.com/media/Zgo2...1a2cb74e7b0d75c614280faeb73270d&rid=giphy.gif

 

[aametzger]

Ok testing has begun, and I believe this may take some time to get it sorted. Taking a break for now cuz my feet are freezing . The space heaters in my garage are not keeping up!
I took 2 quick videos giving an update, but need to figure out the best way to post them. Peace for now.

 

[Megasty]

This is just the kind of beef I was looking for. 3 runs in with my O8S & both rear shafts are bananas. I was wrecked the stock arms & bent a front shaft on the 1st 2 runs so I went with RPM & the shafts can't handle how they flex.

 

[aametzger]

let me know if these links work

https://www.instagram.com/p/CKcyrNSHyU1/?utm_source=ig_web_button_share_sheet

https://www.instagram.com/p/CKc0euzHVZO/?utm_source=ig_web_button_share_sheet

 

[aametzger]

Well attempt #3 and i'm still not where we need to be.

In this attempt I switched to 50wt. It did seem less bouncy when I did a tail drop but still bottoms out the rear pretty good when doing a level drop from just a couple feet. During the refill with 50wt I looked at the piston an it has 4 holes. Can anyone talk to the number of holes and how more or less affects shock behavior? I'm also thinking I may try bleeding the shock differently. I'm not sure i am getting the right behavior. After bleeding, if i extend the shock it retracks back. i tried bleeding it less and then it wont let the shock compress all the way. I have rebuilt the stock shocks many times and understand that process, but these ones with bleeder screws is apparently challenging my skills. lol

Any suggestions or advice anyone can give that has a lot of shock knowledge, it would be appreciated. Whos the shock expert on this forum?
I am really trying to get this sorted, not just for me, but so others can adopt this method if desired, so i am very open to collaboration. I was just willing to spend the money initially and be the guinea pig.

I am really thinking i need to slow the rebound considerably. really i guess i need to slow the action in both directions.
My next instinct is to go up to 80wt and see what that gets. I have some 60wt but i don't think the 10wt is going to make enough of a difference over the 50wt.
Thanks everyone!

 

[KevinC]

Links work.

 

[L3phturn]

The size and number of holes in the piston affect the damping rate in rebound separately from compression. Larger and more holes = fluid moving faster which is less damping. Smaller and/or fewer holes means the fluid flows more slowly = more damping. With these simple pistons your compression and rebound rates are the same. You need some kind of valving to have rebound and compression rates be different.

That said, bottoming out is going to be as much about spring rate, and then you set your damping rate around the spring rate. Telling me it bottoms when you drop it doesn’t tell me how it behaves in rebound. When you drop it, does it bounce back up, stay down too long, or stick and come back up slowly enough not to bounce?

If you are bottoming too easily, are you heavier than stock? What is the spring rate of these springs compared to stock? You may need stiffer springs and more damping if your truck is heavier than stock. Trying to prevent bottoming with stiffer damping can break shocks and lead too poor handling and bouncing bad you end up with essential a counter progressive spring rate that is stiffer early (when you want it to move easily) and softer later in the travel, the opposite of what you want.

 

[aametzger]

The size and number of holes in the piston affect the damping rate in rebound separately from compression. Larger and more holes = fluid moving faster which is less damping. Smaller and/or fewer holes means the fluid flows more slowly = more damping. With these simple pistons your compression and rebound rates are the same. You need some kind of valving to have rebound and compression rates be different.

That said, bottoming out is going to be as much about spring rate, and then you set your damping rate around the spring rate. Telling me it bottoms when you drop it doesn’t tell me how it behaves in rebound. When you drop it, does it bounce back up, stay down too long, or stick and come back up slowly enough not to bounce?

If you are bottoming too easily, are you heavier than stock? What is the spring rate of these springs compared to stock? You may need stiffer springs and more damping if your truck is heavier than stock. Trying to prevent bottoming with stiffer damping can break shocks and lead too poor handling and bouncing bad you end up with essential a counter progressive spring rate that is stiffer early (when you want it to move easily) and softer later in the travel, the opposite of what you want.

thanks for the info. obviously we are in uncharted territory here since i'm experimenting with these rovan shocks. Additionally they are actually designed as front shocks for the rovan which explains the softer springs and lighter weight oil. Did you get a chance to review the 2 vid links i posted? that might help you understand whats happening. i don't show a drop in the vid but i can make another vid with the drop if that's helpful.
my outcast might be slightly heavier (m2c chassis and other m2c goodies) but not too much heavier(stock electronics etc)
thanks again for your response

 

[L3phturn]

thanks for the info. obviously we are in uncharted territory here since i'm experimenting with these rovan shocks. Additionally they are actually designed as front shocks for the rovan which explains the softer springs and lighter weight oil. Did you get a chance to review the 2 vid links i posted? that might help you understand whats happening. i don't show a drop in the vid but i can make another vid with the drop if that's helpful.
my outcast might be slightly heavier (m2c chassis and other m2c goodies) but not too much heavier(stock electronics etc)
thanks again for your response

Just watched them. Yep, stock springs definitely stiffer (and required) so you need much more damping. The bounce shows you aren’t damped enough for those springs. You can increase damping rate with thicker oil amd/or pistons with fewer holes and/or smaller holes.

 

[aametzger]

Just watched them. Yep, stock springs definitely stiffer (and required) so you need much more damping. The bounce shows you aren’t damped enough for those springs. You can increase damping rate with thicker oil amd/or pistons with fewer holes and/or smaller holes.

Thanks a bunch for your insight!! do you think starting with 80wt is a good place to try, or should i go even higher?

 

[L3phturn]

Thanks a bunch for your insight!! do you think starting with 80wt is a good place to try, or should i go even higher?

Most of my knowledge comes from racing 1:1 cars years ago so I don't have direct experience with anything similar in RC. I was not a great driver but I have some chassis engineering and setup chops. Look at and measure or estimate the hole size in the pistons on these shocks and the number of holes and compare to the stock shocks. That should give you some idea, but I wouldn't go too high too fast. You are looking to find a weight that moves similar to the stock setup in the front and it's going to take you some testing to find the right weight, but I suspect if you goo too heavy you won't know if you are just barely too heavy or miles beyond. Practically, I'd go with whatever weight heavier oil seems like a significant step that you can easily/cheaply get your hands on. If you have 80wt, go with it and see.