VB Air Suspension

[wildslammer22]

Hi @wildslammer22 ,

We have our VB suspension since 2013, and have taken it in the off road mode through some pretty challenging circumstances over the years. Think criss cross the Icelandic highlands, Spanish Pyrenees sea to ocean on mountain tracks, West Alps, many Scandinavian dirt and mountain roads, etc. We have always been very happy with its performance.

I have no idea what you expect of the air suspension, when I see you write about the ‘harshness’ of your current rides. The air suspension does not turn your van into a Citroen DS… It makes for a very stable ride, however your van is loaded, it will always be ‘straight’, and rock solid on the road. No wobbling after a traffic bump, etc. The perceived ‘harsness’ is probably due to your tyres sooner, than your suspension. E.g we have driven with load index 107, and found that ‘harsh’. Nowadays we drive 103, which we think is a lot more comfortable. With the higher flanks (225/70) we can still deflate enough when the terrain asks for it.

Thanks, that’s very helpful. In describing the ride as harsh is probably a bit misleading on my part, I guess ‘scuttle’ over pot holes and bumps is probably more accurate. I assume a lower setting for road driving will help alleviate that and make the ride more ‘settled’?


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[bvddobb]

I assume a lower setting for road driving will help alleviate that and make the ride more ‘settled’?

We feel the air suspension as such makes the ride already a lot more ‘settled’. We feel it makes the van steady as a rock on most roads, however bad.
We only use the lowered ’sports’ mode on highways, we don't feel we need it for a steady ride as such. The -2 cm give an about 8% lower fuel consumption on highways, according to our board computer…
The - 7 cm parking garage mode we use only every now and then. But the automatic levelling: all the time!

 

[kurienp]

appreciate you sharing how much better the ride is

@wildslammer22 , ride is very subjective and as Bart mentions in his post - multiple things that can impact it. The state of your tyres, the load rating of your tyres, the suspension bushes, the anti-roll bars (ARBs) - lots of factors that can play on this. To see how much difference it makes, it is best for you to experience this.

Again, as Bart mentions in his post - air suspension does not make it ride like a DS. It is a van in the end and it will drive like a van, but it is much more stable and handles much better with an air suspension and most importantly, the thicker ARBs (especially if the problem is with sloppy handling).

I have a Cali with 17in wheels with VB Air and am in Newbury - if you want to try it anytime, you are most welcome.

BTW, what spec BFGs do you have?

 

[B J G]

We feel the air suspension as such makes the ride already a lot more ‘settled’. We feel it makes the van steady as a rock on most roads, however bad.
We only use the lowered ’sports’ mode on highways, we don't feel we need it for a steady ride as such. The -2 cm give an about 8% lower fuel consumption on highways, according to our board computer…
The - 7 cm parking garage mode we use only every now and then. But the automatic levelling: all the time!

Is that 2% done on a test with normal height & then lowered height on the same road/distance?

 

[bvddobb]

Is that 2% done on a test with normal height & then lowered height on the same road/distance?

Yes, on a 120 km flat stretch (we have those in NL…) of motorway, at a steady pace on cruise control, 60 km normal, 60 km lowered.
Scientifically not perfect, but gives a rough idea!

 

[andyinluton]

I can’t see why the ride hight would make any difference to fuel consumption. The frontal area of the van remains the same, just the size of the gap under it that changes.

 

[wildslammer22]

@wildslammer22 , ride is very subjective and as Bart mentions in his post - multiple things that can impact it. The state of your tyres, the load rating of your tyres, the suspension bushes, the anti-roll bars (ARBs) - lots of factors that can play on this. To see how much difference it makes, it is best for you to experience this.

Again, as Bart mentions in his post - air suspension does not make it ride like a DS. It is a van in the end and it will drive like a van, but it is much more stable and handles much better with an air suspension and most importantly, the thicker ARBs (especially if the problem is with sloppy handling).

I have a Cali with 17in wheels with VB Air and am in Newbury - if you want to try it anytime, you are most welcome.

BTW, what spec BFGs do you have?

Thanks and I may take you up on your kind offer next time I’m heading up the A34


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[bvddobb]

just the size of the gap under it that changes.

And that improves the aerodynamics.

 

[andyinluton]

And that improves the aerodynamics.

You are having a laugh.
If VW could improve a transporters fuel consumption by 8% by dropping it 20mm don’t you think they would all come lowered as standard.

 

[sidepod]

You are having a laugh.
If VW could improve a transporters fuel consumption by 8% by dropping it 20mm don’t you think they would all come lowered as standard.

Theoretically slightly smaller frontal area at low ride height due to reduced tyre frontal area.
Possibly better due to lower pressure under the van (smaller area/increased air speed) affecting the rear end drag condition.
Without a smooth flat underside, probably invisible/un measurable. In other words, vendor talking bollox.

 

[andyinluton]

Theoretically slightly smaller frontal area at low ride height due to reduced tyre frontal area.
Possibly better due to lower pressure under the van (smaller area/increased air speed) affecting the rear end drag condition.
Without a smooth flat underside, probably invisible/un measurable. In other words, vendor talking bollox.

Don't forget this van is running 20mm higher due to oversized tyres in the first place, so dropping it 20mm brings it down to the same level as a standard van.

 

[babble]

I don't know the exact statistics, but I do have a friend who was working in this field and the space under a car can have a surprisingly large impact on fuel economy. (Although there are lots if other variables involved, like how smooth the underbelly is and other things related to drag and turbulence) Of course if you lower a vehicle too much you have terrible ground clearance.

You are having a laugh.
If VW could improve a transporters fuel consumption by 8% by dropping it 20mm don’t you think they would all come lowered as standard.

Found this quote online:

p. 219: The effect of ground clearance (e) on lift and drag is less clear-cut... In "normal" vehicles, ie., vehicles with structural roughness on the underbody, the drag decreases as a car is set closer to the ground.

However, vehicles with a smooth underbody, in this case the Citroen DS 19, have the opposite tendency. For these vehicles the drag increases with reduced ground clearance, in the same way as for a streamlined body [example given is the Schlor car - on right, in image below - which has an entirely smooth underbelly with cutouts for the wheels.]

This rise in drag can be traced to the increasing effective thickness of the body with reduced ground clearance... This thickness effect is more than offset on vehicles with rough underbody, as the (high) underbody drag decreases when the flow between vehicle and road is impeded.

 

[sidepod]

You could potentially get a better result from jacking up the front relative to the rear. This should create a slightly downwards departure angle at the rear of the roof and , theoretically, have a positive effect on overall drag reduction.

Without extensive testing, all a bit pointless.

 

[WelshGas]

I can’t see why the ride hight would make any difference to fuel consumption. The frontal area of the van remains the same, just the size of the gap under it that changes.

But that change in height can make a difference to the air resistance drag, as shown in the F1 cars of today.

 

[B J G]

I can’t see why the ride hight would make any difference to fuel consumption. The frontal area of the van remains the same, just the size of the gap under it that changes.

I've never seen any appreciable difference with previous VB system and Bilstein, which can be set lower than VB, but then I'd need more than 5% difference to count as a difference.

I do recall, from the dim and distant past, car drag tests showing that the lower the ride height the lower the drag figure. All to do with the air flow over the vehicle compared to what goes under it.

Anyone got a wind tunnel to test that out?

 

[sidepod]

The lower the ride height the more of the tyre is hidden up behind the lower lip of the spoiler when viewed from the front , therefore the exposed frontal area of the tyre is reduced. Consequently the overall frontal area is reduced.

On an open wheel car such as F1, ride height has little effect on frontal area is simple terms.

 

[bvddobb]

Ha ha, talk about thread-napping!

Well, I’m a very empirical person. To measure is to know, and all that. Love all the theory on here, but don’t know how to manipulate all those drag factors on my van but one: ride height. Did that while keeping all other factors (road type, speed on cruise control, weather/wind etc. during a ride on the highway through our polders) as constant as I could. And then monitored our fuel consumption cf our board computer. It said 8% less when lowered, averaged over 60 km high and 60 km low. Can’t help it…

Let’s allow for some measurement error and be a bit conservative, then it still looks like a 4% reduction is in the ball park, somewhere, I’d say.

 

[wildslammer22]

@wildslammer22 , ride is very subjective and as Bart mentions in his post - multiple things that can impact it. The state of your tyres, the load rating of your tyres, the suspension bushes, the anti-roll bars (ARBs) - lots of factors that can play on this. To see how much difference it makes, it is best for you to experience this.

Again, as Bart mentions in his post - air suspension does not make it ride like a DS. It is a van in the end and it will drive like a van, but it is much more stable and handles much better with an air suspension and most importantly, the thicker ARBs (especially if the problem is with sloppy handling).

I have a Cali with 17in wheels with VB Air and am in Newbury - if you want to try it anytime, you are most welcome.

BTW, what spec BFGs do you have?

Sorry I missed your question on tyres, I’m running ALL TERRAIN KO2 LT255/55R18 109/105R


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[soulstyledevon]

You could potentially get a better result from jacking up the front relative to the rear. This should create a slightly downwards departure angle at the rear of the roof and , theoretically, have a positive effect on overall drag reduction.

Without extensive testing, all a bit pointless.

So we’re moving into the saggy rear bottom territory.
You don’t wanna go there. There’s a bloke in Cannock already fixing that issue…

 

[andyinluton]

The lower the ride height the more of the tyre is hidden up behind the lower lip of the spoiler when viewed from the front , therefore the exposed frontal area of the tyre is reduced. Consequently the overall frontal area is reduced.

It's running bigger tyres which give a 20mm increase in height & then by using the low setting its dropped 20mm ie back to normal hight. So will be showing exactly the same amount of tyre as a normal van.


I think what the numbers show is that jacking the van up 20mm using bigger wheels has an adverse effect on fuel consumption & that penalty disappears when the van is dropped back down to its normal height.

 

[bvddobb]

It's running bigger tyres which give a 20mm increase in height & then by using the low setting its dropped 20mm ie back to normal hight. So will be showing exactly the same amount of tyre as a normal van.

We ran the test with standard tyres, so the 2 cm drop was below standard height.

 

[bvddobb]

Sorry I missed your question on tyres, I’m running ALL TERRAIN KO2 LT255/55R18 109/105R

The load index of 109 is pretty high... Could well explain your experience of a somewhat harsher ride, with such stiff tyre walls. We had that same feeling with 107, and the main reason we moved down to 103.

 

[wildslammer22]

The load index of 109 is pretty high... Could well explain your experience of a somewhat harsher ride, with such stiff tyre walls. We had that same feeling with 107, and the main reason we moved down to 103.

I'll look at that when the time comes to replace the horrendously expensive BFG's!



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[Californication69]

I'll look at that when the time comes to replace the horrendously expensive BFG's!



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I’m running Michelin WinterContact TS870P 255/45/18” XL(very quiet, very grippy, love them)
4Motion.
At 72 mph on Waze, I’m getting 27mpg on 80%motorway, 20% A roads.
At 65mph on Waze I’m getting 32mpg.
So speed is a 5mpg factor.

My old BFG’s were very noisy.

 

[wildslammer22]

I’m running Michelin WinterContact TS870P 255/45/18” XL(very quiet, very grippy, love them)
4Motion.
At 72 mph on Waze, I’m getting 27mpg on 80%motorway, 20% A roads.
At 65mph on Waze I’m getting 32mpg.
So speed is a 5mpg factor.

My old BFG’s were very noisy.

Thanks for the tip, I’ll make a note to look at those. I’m also running a 4motion 204 and I’ve been pleasantly surprised at how frugal it is on the motorway. I comfortably exceed 30 mpg sat at 68mph (also Waze!) despite the BFG's and Bilstein lift kit. The tyres are noisy though.


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