Sketer Shock set up.... Why

[Caleb90]

So i found that my front shock shafts were bent. While digging into it, i have found corally uses the same shocks front and rear on the sketer... To put the fronts on, you litterly compress them a good 3/8in . Why would they use this set up? Shock is half through its travel when the suspension is unloaded

 

[Horatio]

So i found that my front shock shafts were bent. While digging into it, i have found corally uses the same shocks front and rear on the sketer... To put the fronts on, you litterly compress them a good 3/8in . Why would they use this set up? Shock is half through its travel when the suspension is unloaded

Because they haven't tooled up to make a set of shocks 3/8" smaller. They just used the shocks they have available already.

Compressing the shocks to fit them shouldn't be an issue, provided that the ride height you require is achievable within the range available on the preload collar.

 

[Caleb90]

Because they haven't tooled up to make a set of shocks 3/8" smaller. They just used the shocks they have available already.

Compressing the shocks to fit them shouldn't be an issue, provided that the ride height you require is achievable within the range available on the preload collar.

The kronos front shocks are quite abit shorter than the rear. The rear shocks on the kronos are the same length as all four on the sketer. While the front would fit almost perfect on the sketer. Dosnt make sense

 

[razorrc]

So i found that my front shock shafts were bent. While digging into it, i have found corally uses the same shocks front and rear on the sketer... To put the fronts on, you litterly compress them a good 3/8in . Why would they use this set up? Shock is half through its travel when the suspension is unloaded

It doesn't matter if you have a long shock that is halfway through its travel at full extension, or a short shock that is fully extended at full extension. They'll act the same.

 

[Caleb90]

It doesn't matter if you have a long shock that is halfway through its travel at full extension, or a short shock that is fully extended at full extension. They'll act the same.

Yes they will performe the same as these don't have progressive valving. But the problem is, if you use a shock that is too long and is half way through its travel when the arms are unloaded. You will bottom the piston out before the arms reach full travel. Yes the sketer chassis will hit the ground to prevent that, but only if you land flat. If you land on one front wheel, the arms is going to try and move full travel but the shock compressed and the piston is hitting the cap. Take a set of long shocks and mount them on a rig that has short shocks and you will see what i mean

 

[Horatio]

Yes they will performe the same as these don't have progressive valving. But the problem is, if you use a shock that is too long and is half way through its travel when the arms are unloaded. You will bottom the piston out before the arms reach full travel. Yes the sketer chassis will hit the ground to prevent that, but only if you land flat. If you land on one front wheel, the arms is going to try and move full travel but the shock compressed and the piston is hitting the cap. Take a set of long shocks and mount them on a rig that has short shocks and you will see what i mean

You'd only hit the piston inside the shock if you a) forgot about your droop screws and/or b) couldn't be bothered to put silicon fuel tube under your piston to limit droop.

 

[Caleb90]

You'd only hit the piston inside the shock if you a) forgot about your droop screws and/or b) couldn't be bothered to put silicon fuel tube under your piston to limit droop.

Im talking about whe they are compressed not extended

 

[Horatio]

Im talking about whe they are compressed not extended

But the long shock is not 'half way' through it's travel - as you said, it's compressed about 3/8".

If you're worried about the piston hitting the cap before the suspension has reached full travel, you can measure the suspension travel vs the maximum shock travel, then put in a suitable length silicon fuel tube 'bump stop' on the outside of the shock shaft where the spring cup / shock end goes, to prevent the piston/valving from hitting first. Make sense?

I'd rather too long shocks than too short.

A bit like clothes in the military - when given the option of too small or too big - always go for too big!!

 

[KnowAir]

To test the theory, compress an arm fully with shock attached, then without being attached. Just detach at the top or bottom whicher is easier. Maybe leave one side of the truck connected, the other disconnected, see if there's any significant difference in travel.
I can see if the shock is too long being a problem if it is bottoming out on landings..
I haven't heard of anyone having this issue, but the Sketer isn't as popular as say a Kraton. Seems possible there is a design flaw, not sure.

 

[Horatio]

If a rig is bottoming out on landings, this isn't because there's too much suspension travel. It's because the spring rate/bound damping isn't sufficient for the conditions on the day.

If we ignore practical weight considerations, I don't think you can have shocks that are too long - provided you can adjust them to what your rig needs.

Pistons, bound, rebound, spring rate, ride height, droop.

The problem that off roaders face is what works well for bumpy tracks doesn't necessarily work well for tracks with jumps and vice versa. Increasing spring rate to prevent slap and increasing the damping can compromise the traction on bumpy parts.

That's the compromise you have to figure out when tuning the rig for a track.

Progressive springs where something I used to use for 1/8th Buggy when I struggled to find the right balance.

Where there's a will, there's a way.

 

[Caleb90]

If a rig is bottoming out on landings, this isn't because there's too much suspension travel. It's because the spring rate/bound damping isn't sufficient for the conditions on the day.

If we ignore practical weight considerations, I don't think you can have shocks that are too long - provided you can adjust them to what your rig needs.

Pistons, bound, rebound, spring rate, ride height, droop.

The problem that off roaders face is what works well for bumpy tracks doesn't necessarily work well for tracks with jumps and vice versa. Increasing spring rate to prevent slap and increasing the damping can compromise the traction on bumpy parts.

That's the compromise you have to figure out when tuning the rig for a track.

Progressive springs where something I used to use for 1/8th Buggy when I struggled to find the right balance.

Where there's a will, there's a way.

Ok, lets say the a arms have 3 in of travel from fully unloaded to fully compressed. You put a shock on that has 3.5 in of travel. You have to compress said shock .60 in to mount it. 3.5 - .60 = 2.90. so you end up with 2.90in of shock travel but you need 3in of travel. This will make the piston contact the cap, then in turn bending the shaft. Yes you can put fuel line on the shaft to act as a bump stop. Now im not saying this is whats happening, as i have not measured a arm travel and shock travel. There might be enough shock travel left after being mounted, to handle the arm travel.

This same thing applies to, car, trucks, atvs, snowmobiles ect.

 

[razorrc]

Yes they will performe the same as these don't have progressive valving. But the problem is, if you use a shock that is too long and is half way through its travel when the arms are unloaded. You will bottom the piston out before the arms reach full travel. Yes the sketer chassis will hit the ground to prevent that, but only if you land flat. If you land on one front wheel, the arms is going to try and move full travel but the shock compressed and the piston is hitting the cap. Take a set of long shocks and mount them on a rig that has short shocks and you will see what i mean

I agree 100% with you which is why I don’t suggest people use super big tires on the Sketer, but you should be OK with stock sized tires IIRC.

BTW, the piston shouldn’t hit the cap because the shaft should be short enough, but yeah you would have other issues (rod end bottoms out and puts stress on the rod end or mounting screws).

 

[Caleb90]

I agree 100% with you which is why I don’t suggest people use super big tires on the Sketer, but you should be OK with stock sized tires IIRC.

BTW, the piston shouldn’t hit the cap because the shaft should be short enough, but yeah you would have other issues (rod end bottoms out and puts stress on the rod end or mounting screws).

Im just going off my experiance with powersport suspensions. You can bottom the pistons out on that type of stuff. Will bend shock shafts, blow pistons apart, crack shock bodies

Im just going off my experiance with powersport suspensions. You can bottom the pistons out on that type of stuff. Will bend shock shafts, blow pistons apart, crack shock bodies

I do want to put bigger tires on my sketer. The stock ones are a bit of a joke

 

[KnowAir]

If a rig is bottoming out on landings, this isn't because there's too much suspension travel. It's because the spring rate/bound damping isn't sufficient for the conditions on the day.

If we ignore practical weight considerations, I don't think you can have shocks that are too long - provided you can adjust them to what your rig needs.

Pistons, bound, rebound, spring rate, ride height, droop.

The problem that off roaders face is what works well for bumpy tracks doesn't necessarily work well for tracks with jumps and vice versa. Increasing spring rate to prevent slap and increasing the damping can compromise the traction on bumpy parts.

That's the compromise you have to figure out when tuning the rig for a track.

Progressive springs where something I used to use for 1/8th Buggy when I struggled to find the right balance.

Where there's a will, there's a way.

I totally agree with you. Ideally, the chassis should rarely touch the ground, and in racing, it's feasible. In "bashing" however, not even possible to launch an rc 15 foot or more without severely bottoming the suspension and subsequently the chassis. Okay, maybe "possible" but, such stiff suspension wouldn't even move when hitting scale bumps and such. It would drive like a dump truck. LOL
If we look at even the most accomplished "big air" youtubers, they're all slapping chassis on every big jump regardless of aftermarket suspension and extensive tuning. Just not possible to have suspension that can land 20x 100 foot jumps AND drive like we want it to.. gotta take the good with the bad in the bashing scene.

 

[Horatio]

I totally agree with you. Ideally, the chassis should rarely touch the ground, and in racing, it's feasible. In "bashing" however, not even possible to launch an rc 15 foot or more without severely bottoming the suspension and subsequently the chassis. Okay, maybe "possible" but, such stiff suspension wouldn't even move when hitting scale bumps and such. It would drive like a dump truck. LOL
If we look at even the most accomplished "big air" youtubers, they're all slapping chassis on every big jump regardless of aftermarket suspension and extensive tuning. Just not possible to have suspension that can land 20x 100 foot jumps AND drive like we want it to.. gotta take the good with the bad in the bashing scene.

Yes - there comes a point where given sufficient height of a jump, even with big ground clearance and plush suspension with good travel - the chassis will still slap.

Mitigating how hard it slaps will undoubtedly compromise some other aspect of the handling.

Like a dump truck!!

There will always be a trade off of some kind.

It's always sad when the beautiful new chassis gets scraped.

 

[Horatio]

Ok, lets say the a arms have 3 in of travel from fully unloaded to fully compressed. You put a shock on that has 3.5 in of travel. You have to compress said shock .60 in to mount it. 3.5 - .60 = 2.90. so you end up with 2.90in of shock travel but you need 3in of travel. This will make the piston contact the cap, then in turn bending the shaft. Yes you can put fuel line on the shaft to act as a bump stop. Now im not saying this is whats happening, as i have not measured a arm travel and shock travel. There might be enough shock travel left after being mounted, to handle the arm travel.

This same thing applies to, car, trucks, atvs, snowmobiles ect.

"If" your suspension had 3" of travel at the hub and the shock had 2.9" of piston stroke before hitting the top of the shock - we only have a problem "If" there is 1" of suspension travel for each 1" of piston stroke. "If".

I'm not sure this explains your shafts being bent but it's been interesting talking about what may cause it to happen.

Please measure the travel of the suspension at the hub vs the available suspension travel with the shock attached.

Note that because of the geometry of the shock absorber angle to the arm, the travel the shock shaft has in inches within the shock body does not equate to the amount of suspension travel at the hub.

What is it that limits the suspension up travel? It shouldn't be the piston in the shock body. "If" it is, the suspension system is poorly designed and will result in bent shock shafts.

 

[Horatio]

I think the fuller picture of how shock shafts bend include this explanation from brice_arnold, over on the Large Scale Forum in relation to Baja 5B shocks bending all the time:

"1. the shafts are extended too far from the piston body such that [they] then can get cocked and bend

2. All of the suspension components are made from very flexible plastic which moves. This include motion perpendicular to the motion of the shock shaft. Thus causing bent shock shaft.

You are proposing that the shock shaft is buckling due to dirrect axial loading. If you crunched the numbers to calculate the forces for this type of failure you would find that to be an unlikely scenario.In which case changing the dampening or spirngs will have no effect."

This is why it can be so tricky getting to the root cause of these kind of problems.

Could you mount an action cam and actually watch what could be causing the issue?

Edit to add: in the end, tethers were found to help on the Baja (there aren't any droop screws) so people generally preferred this option over down limiters under the piston. Also, upgraded, much thicker shock shafts. This started with the SS and the revised shocks from HPI, followed by really burly shocks with umbrella seals - such as those made by Innovative RC. If they made shocks for Corally rigs - all the issues would magically go away.

 

[razorrc]

Yeah it really just isn't an issue. More likely to bend a shock shaft from ramming into something than from jumping and landing.

 

[Horatio]

Yeah it really just isn't an issue. More likely to bend a shock shaft from ramming into something than from jumping and landing.

I think plenty of people bend their shock shafts on Corally rigs, so it is definitely a thing - but it's not because the shocks are too long.

 

[KnowAir]

I think plenty of people bend their shock shafts on Corally rigs, so it is definitely a thing - but it's not because the shocks are too long.

Thanks for the Baja reference, I think this is a very possible cause.. too much flex of the arms. Redcat Kaiju suffers similarly I feel. Often resulting in split diff output cups, bent shock shafts and cvds.