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Suspension tuning.....not impressed

wrightcs77

RCC Addict
Joined
Feb 25, 2005
Messages
1,496
Location
Minneapolis
Looking for some advice on what people are running for oil, piston and springs.

I have a XL kit, built it up. Stock springs, 37.5 oil front, 30 wt oil in back. Did not feel good on the "bench" test, so I moved the rear shocks to the "back" locations top and bottom.

The front just feels "dead." No ride height, no rebound, nothing.....lol.

I built the shocks with Associated green slime on the seals, pistons and shafts seem to move "ok" with no oil in them. Not as smooth as what I am used to (1/10th scale 2wd electric buggy shocks) but, this is larger and heavier, so I assume there will be more stiction in the shocks.

Anyway, what to do about the front end? I drove it for literally 45 seconds and it pissed me off so bad I stopped.
 
LOL! Don't let it get to ya. This is a MONSTER rig built for handling desert and rock terrain so the suspension is going to be soft. I'm not happy with it either but I bet it works great where it was tested.

Considering your 1/10 buggy is about 4 lbs and the Yeti is over 14 lbs, you can absolutely expect it to handle like a slug. I'm sure you are just a meticuluous with your buggy as I am with my SCT/ST race trucks so I am certain you will get to tuning soon enough and come up with a very viable solution to the existing issue.

For me, currently I have the ride height pumped up a little bit (manual suggests 14mm - LOL) and that gives a fairly nice ride. I'm 100% convienced that the 30 wt front and the 10 wt rear (especially with a 6 hole piston) is simply not enough dampening for where I drive and the springs are going to be upgraded as many have already talked about.

When you find something that works, do share. I'm going to replace the rear piston with a 4 hole and probably try 45 wt oil to start before I fart around with the springs...those are going to be harder to come by.
 
I just purchased these shock springs for the front of my kit. They are 23mm diameter which is the same as stock. They are slightly longer than stock and rated at medium spring rate for an Hpi Baja 5b. The 5b weighs over 20lb so these should add ride height to the front of the yeti XL. Best part is they are dual rate and black in color just like stock. I will let you know how they work when installed.

HPI 86762 Rear Shock Spring Set | eBay
 
I never understood the dual-rate spring in a single reservoir setup. The piston travelling through the shock fluid dictates how fast or slow the shock reacts to compression and rebound. What is the stacked spring trying to accomplish other than maintain ride height?
 
In the RC world, a dual rate spring is mainly for looks. A real dual rate spring will have a stop collar on the shock body where the compression for the secondary(upper) spring stops and the main(lower) spring takes over sole duties. This gives you a softer spring rate(both springs working together) and then a much higher rate later in compression(main spring acting solely). Hence the name. My full size crawler has 2 inches of compression before it changes to a higher spring rate, and then 4 more inches of compression before it hits the bump stop, which compresses another inch or so.
 
My biggest complaint about the Yeti XL has to be the front end. Specifically the suspension and shock tower. I have the RTR and the front shocks were not working for me. I agree with the "dead" feeling. I tried different set ups (oil weights, positioning, HPi Baja rear lower springs, etc.) and I couldn't come up with the "ride" I was looking for as a basher. I ended up installing a set of LST2 shocks with 30wt oil and firm and medium springs. Absolutely love the way it handles with the medium springs! Problem solved, right!? Nope, I think Axial wasn't intending to have this heavy of a shock/spring set up because the front shock tower can't seem to hold the suspension. Now I do run on 6s and fairly rough terrain (mainly dried up lake bed) but, in any event, the shock tower bends backwards and eventually breaks at the shock mounts. I'm on my third tower so far. There isn't any lateral support for the shock tower. Something I've been racking my brains to fabricate. If you look at all of the larger 1/5 scale vehicles out there, there is plenty of additional support for the shock towers. It makes sense, bigger vehicle, more support. I'm hoping to upgrade to an aluminum shock tower soon but have been thus far hesitant due to the lack of options...
 
Trouble is an aluminium shock tower will just transfer all the energy down into an already weak bulkhead.
 
i have to agree with you the lst2 shocks are the shocks that should of came with this thing man they are great. i dont run mine too much due to having other commitments but i do run it once in a while and its a great RC, and even better with the lst2 shocks.
 
Ok, I received my shock spring set for HPI Baja 5b today and here is what I found. The long spring is long enough and stiff enough to be used alone. This definatly added ride height and rebound but was a little stiffer than I wanted.
What I ended up using was the short spring from the HPI Baja and the Axial Yeti XL kit long front spring. With this dual rate combo I was able to get the ride height and rebound just the way I want it.

HPI 86762 Rear Shock Spring Set | eBay

 
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I would say no. The front is stupid soft even with 30W. BobTeagle found a potential cure with the front in mind. The back is better than the front w/ 30W but still too soft to me. I cranked down the adjuster collar at 14mm Front and 20mm in the rear.

The biggest problem is that though it worked for BobTeagle, his terrain and driving style might be the total opposite of yours. It is up to you to decide if the mod seems worthy. For now my current setup is fine to me and the terrain i run in. Could it be better. Oh you bet. Suspension and tires will make a crappy handling truck become go kart on the dirt. I won't spend the tuning $$ and time until there are more spring tuning options but i thank Bob and everyone for sharing their input to help me when the time comes.
 
I spent an hour the other night fiddling with different setups.

I am doing the same for front and rear:

HPI Baja black/medium helper springs
Yeti XL kit yellow lower springs (front springs used on rear now as well)
30wt oil
6 piston rear / 4 piston front

Ride height is good, but the HPI is still too hard.. If you fully compress the front or rear of the truck, the main spring will fully compress as the top HPI spring compresses maybe 15%. It is working throughout the entire stroke of the shock, but it's not doing enough on the bench test.

I am going to try it as is for now, see if the truck handles any better.

I attempted 60wt oil up front, it's too slow to rebound. Tried 45wt, also too slow (almost couldn't tell the difference). Went back to 30wt... The rear is still nice and plush, but feels much faster at recovery.


** If I were to spend $35 on springs again, I would get the SOFT HPI spring set **
 
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Tried the new suspension setup yesterday... It drives like what the RTR looks like out of the box. One front wheel is always high-fiving making it very hard to steer. It goes over bumps and drops really well, but, drivability has taken a dive. Thinking about moving both front springs to the back and eliminating the HPI piece on that axle. Will see what happens.... Seems like I could really use a front sway bar now!
 
Tried the new suspension setup yesterday... It drives like what the RTR looks like out of the box. One front wheel is always high-fiving making it very hard to steer. It goes over bumps and drops really well, but, drivability has taken a dive. Thinking about moving both front springs to the back and eliminating the HPI piece on that axle. Will see what happens.... Seems like I could really use a front sway bar now!

Are you using 4 or 6s?

Using 4s my front wheel only raises slightly when on pavement.
I have stock long springs with hpi medium helper spring with 30wt up front.
Shocks upper and lower outer mounting positions.

I have stock springs in rear with 30wt.
Shocks upper and lower mounted as far back as possible.

I also have my slipper adjusted so there is slight slippage with hard acceleration.
 
I am running 5S.

Front:

30wt oil
Kit main front spring lower, HPI medium upper
Aluminum shock tower, so I am 2nd highest mount position (highest touches body when lid is down), and outer position on suspension arms.

Rear:

30wt oil
Kit main front spring lower, HPI medium upper
Using front mount on rear upper and regular position at the bottom

I have the slipper tightened a bit, so maybe that's another contributing factor. I had a thread about my non powered rear which I thought was a loose slipper, but also found a completely stripped wheel hex.

I'm going to try the stock lower rear spring again and see if that helps a bit. Still looking into front sway bar.. I might take one off of my MT4 and see if it will bolt up.
 
I am running 5S.

Front:

30wt oil
Kit main front spring lower, HPI medium upper
Aluminum shock tower, so I am 2nd highest mount position (highest touches body when lid is down), and outer position on suspension arms.

Rear:

30wt oil
Kit main front spring lower, HPI medium upper
Using front mount on rear upper and regular position at the bottom

I have the slipper tightened a bit, so maybe that's another contributing factor. I had a thread about my non powered rear which I thought was a loose slipper, but also found a completely stripped wheel hex.

I'm going to try the stock lower rear spring again and see if that helps a bit. Still looking into front sway bar.. I might take one off of my MT4 and see if it will bolt up.

I think u would benefit from moving the rear shocks to rear position. This helped mine with stability and torque twist.
 
When you guys are moving shocks to the rear, are you specifically just moving the top mounting position? Or are you using two further back locations at top and bottom?
 
When you guys are moving shocks to the rear, are you specifically just moving the top mounting position? Or are you using two further back locations at top and bottom?

I use the back bottom and the top back position. I use the Dhawk aluminum plate at the top. It adds a few more positions.
 
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