Thread: Rear Sus - SLS, Springs, or Polyairs?

Depends what your doing with the vehicle - there's no best setup for all situations. I love the SLS. Great handling and great load carrying abilities. But it's not everyone favourite.

Regarding your poly bag idea I think you need to do a lot more reading on how SLS works as it's a lot more complicated than you seem to think. The system is continually monitoring and making adjustments.

The floor that I can see in your thinking - is poly airs will not lift.. Unlike an air spring, sitting inside the coil, they simply make the existing spring harder to compress - so if the springs are compressed - you can blow up the polys as hard as you like - it wont lift the vehicle back up.

Personally I'd lift the SLS and put longer travel shocks into it..... others will tell you to scrap the SLS and go springs only....each to their own..

PM Joel0407.

He recently went the other way over the past 12 months and reinstalled his sls
And ditched the coils.

He ould be the best person I can think of to talk to about your options.

Cheers, Chris

IMO the air suspension is what makes a real difference between a D2 and a D1... beside the SLS and ORM it has the extended mode too(which many people dont know about or forget about it) ...the extended mode is a brilliant enhancement if you go off road, helped me not once(i dont have any lift)....and the ORM is not neglectable as well

Extended mode
The extended mode is automatically operated by the ECU and requires no input from the driver. Extended mode
operates when the chassis is grounded causing the rear wheels to spin. This information is generated by the ABS
function of the SLABS ECU.
When the ECU senses that the chassis is grounded and the vehicle speed is less than 6 mph (10 km/h), the ECU will
operate the compressor and energise the air control valves for 25 seconds to raise the rear of the vehicle. This
operates irrespective of the mode that the SLS system is in at that time. To inform the driver, the ORM warning lamp
will flash continuously at all times that the system is in extended mode.
The driver can exit the extended mode by depressing the ORM switch for not less than 0.5 seconds or by exceeding
8 mph (13 km/h).

Have a search but I went through the whole idea of using the SLS system to control the poly-air.

I have a pretty strong opinion on Poly air. They are fine for those who drive around town every other day then occasionally apply a fair load to the vehicle and still stick the black stuff.

As someone said above. Poly Air can't be used to lift a vehicle. It will only stiffen it where it's at. If you putting a load on, you need to apply the pressure before you put the load on. They press out against the coils and actually prevent it extending because of the friction of the bags on the inside of the coil spring.

This also effects them when they are not in use. I have read it a few times now that they are fine without any pressure but all the manufactures recommend that you keep 5psi is the bag to prevent it being pinched by the coil. The problem with this is there is always that friction of the bag restricting the movement of the coil and effecting ride.

My vehicle came with the SLS removed and Poly-air with coils fitted so I had the opportunity to test the above. I could actually jack up the vehicle then drop the pressure in the bag which would allow the axle to drop slightly as the bag let the coil go.

The standard LR SLS system also works on far higher pressure than Poly air. My vehicle is at normal height (2" lift by spacers) with about 70psi when empty and I haven't tested it when loaded. Poly air manufactures recommend less than 30psi max.

My initial idea was to fit some very light weight 2 inch lift height coils. Basically coils that would have no chance of holding the vehicle at the full 2 inch lift but just enough to keep it off the bump stops and then use the LR SLS system controlling the poly airs to keep the vehicle at height. I thought I'd have the comfort and ride of the SLS but reliability of coils. After I found out all the above I realised, that's just not possible.

I think people worry far too much about the reliability of the SLS. New bags are only 50 pound from the UK so I bought 3 and carry one as a spare. They have push in 4mm pneumatic air tube fitting so I also carry 2 x short lengths of 4mm tube with schrader (normal tyre) valves so if the compressor fails, I can pump them up with a bike pump. Carrying those couple of things, I think I'm more reliable than coils.

The Off Road Mode also gives you an extra 2 inches over normal ride height so with my 2 inch lift I can go to 4 inches if I need.

One thing I haven't sorted yet and I should really get into is I have read that with the SLS bag spacers, the bag internals can bottom out before the axle hits the bump stop. I have extended my bump stops just incase but none of the spacer manufactures mention this so I think it's a fallacy. I just need someone to cut open a buggered bag, put the top and bottom together and measure the height.

The spacer blocks are all only 1 1/2" not 2" but the sensor extensions are usually 2 inches so the bags over extend 1/2 inches to get the full lift. You can also use nanocom or the like to adjust it where you want it. I didn't end up with a full 2" from my from coils so I needed to adjust mine a little.

My thought are that the spacer blocks are only 1 1/2" to prevent the problem that the internals could come into contact before the bump stops.

I don't know how much travel you want but I have Bilstein 7100 short body 10" shocks and when we put it on the hoist last the Mech was a bit concerned as he knew of RRC that could tear the bottom of the bags if over extended. Mine went half way up the hoist before the wheels left the ground and the bags were still rolled over the base.

One of the reasons I haven't been to motivated with the bags bottoming out thing is I haven't had any problems bottoming out in the rear but I top out easily if I go over a mound too quickly. I'm more inclined to fit white tiger bottom shock mount riser and leaving my bump stop spacers in place. This will allow me further drop but my upward travel will still be limited which hasn't been a problem yet.

If you want to know any more measurements and stuff. Flick me a PM and I'll send you my PH number.

Happy Days.

Wow. Thanks Joel! Mega post! Seems ur line of thinking is the same as mine!

I'm not against the SLS at all, it's a cool system, I just dislike the idea of limiting my up-travel (and essentially down travel) just to gain height. I cant believe someone doesn't do an extended replacement bag.

I might pursue a longer bag option, be it custom built or otherwise.

I would like to pair it up with a set of billies also.

What coils do u have in the front?

i've fitted these on mine [ame=http://www.ebay.ie/itm/Extended-Bump-Stops-Discovery-2-/111279021154]Extended Bump Stops Discovery 2 | eBay[/ame]

Up front I have the Dobinsons +40mm heavies and they are not heavy enough with my bar and winch to give me the full 40mm.

I guess no one does an extended bag as they are long enough as standard. remember they made long enough to run in extended mode/Off road mode, what ever you want to call it, plus 2" as standard.

Why do you think the blocks limit your upward travel? Have you measured some closed bags or is it just internet rumor like I'm going of?

Happy Days