Semi-Air suspension - explain to me about impact on TORSION Bar suspension?

[Jev88]

Hello Funsters.

I understand the principles of air suspension modification. I also understand thre Al-Ko torsion bar suspension isn't covered by many manufacturers of kits.

Semi-air - how does this impact the torsion bar and why is it that having it fitted increases the available loading for that axle? Does the air bag take some of the strain off the torsion bar system?
If it does relieve the torsion bars of some of their load I see this as a good thing as it must surely extend their life, but I want someone to explain this in simpler terms if this is the case?

Thanks all.

 

[Lenny HB]

I'm not a 100% sure but I think the torsion bars are replaced with ones with lighter torsion bars, that's what they do with full air. They have to retain the torsion bars to locate the axle. Then the suspension load is taken by the airbags.

 

[SandraL]

On our alko axle there are 3 torsion bars in each side of the axle.
These are designed to take the load of the rear axle, say 2500 kg.
The air bags are a supplementary aid. They do not replacethe torsion bars.
A bracket is added to the rear of the wheel hub which supports the bottom of the air bag.
The top is bolted to a bracket that is in turn bolted to the chassis.
The pressure in the air bag resists the upward movement of the wheel thus aiding the torsion bars.
Most engineers will give an axle increase of 200kg, so 2500 to 2700, for the addition of airbags.
Some conpanies change the torsionbars for lighter? bars when adding airbags but i think this is for ride quality purposes only, not if to raise rear axle weight.
Sorry its a bit wordy, but well done if you made it this far!

Edit, only company that changed torsion bars when i researched 4 years ago was travelworld, the hymer people who used goldschmitt kit.

 

[Lenny HB]

Edit, only company that changed torsion bars when i researched 4 years ago was travelworld, the hymer people who used goldschmitt kit.

With Full air both VB & Goldsmittch systems replace the Torsion bars.

 

[Steve and Denise]

On our Iveco the front has torsion bar that run along the chassis when air bags are fitted or factory supplied the tension is reduced on the torsion bars as there is an adjustment at the end.

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[Minxy]

For semi-air virtually all companies add the system alongside the existing suspension rather than replace it, they are supplementary and thus give additional support to allow the weight capacity for the axle to be increased (assuming it's not at the absolute max already).

 

[Hettie's Crew]

Our Alko torsion bar rear end/axle was rated as 2000kg but our weight on the rear was around 1970kg when loaded for the off, though only half a tank of fresh water. Our B544 always sat level but we would get the occasional noise from the rear over bumps and it felt at it’s limit. Air assistance fitted by AS Suspension in Warrington transformed it to working suspension but did raise the rear end a little, because it takes some of the strain off the bars, giving us a slight nose down stance.
Ours was a real success because the torsion bars needed help. I think if the torsion bars are stiff to start with adding air assistance won’t improve the comfort but can aid the control.
It may be possible to remove one of the three bars or fit lighter ones to balance up with the air assistance.
We are now rated as 2240kg on the rear.

 

[Minxy]

SAP did ours and we didn't have any of the torsion bars removed as we work on the principle that if something ever goes wrong with one suspension system the other will compensate until we can get the fault rectified, ie we have built-in 'redundancy'.

 

[jezport]

The air springs fitted on full air are massive compared to the additional ones you see people DIY installing.

 

[teamem]

Best not to remove any of the 3 torsion bars as they retain the trailing arm. Or you could remove one of them plus a couple of the wheel bolts too I suppose..
Semi-air supplements the existing torsion bars,
Full air sees the original torsion bars replaced with 3 lighter duty ones, but the torsion bar count remains the same.

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[Jev88]

Thanks for the info people. No way am I having the torsion bars changed. The original axle failed for the previous owner and he had them professionally replaced (roughly £3,000). I have them greased every year. I will only be going semi air if I do it but was just trying to better understand how the air system actually takes load away from the existing system and hence increases the axle load capacity. Seems it is akin to adding an extra suspension component that works alongside the existing and spreading the load?

 

[Mr B]

SAP did ours and we didn't have any of the torsion bars removed as we work on the principle that if something ever goes wrong with one suspension system the other will compensate until we can get the fault rectified, ie we have built-in 'redundancy'.

I’m with Minxy Girl on this one..
If they replace/remove the torsion bars and the air bag/s fail (unlikely, but we live in a strange world), the suspension would be on its arse... as we say ooop north. Semi air on an Alko does two jobs, increase rear weight limit (if it’s possible), or in our case, to make it a far better ride.
We had ours fitted by GlideRite at Liverpool a few days ago and I am more than happy with the quality of their kit and the professional way in which they fitted it. All done in a day, and in MO, makes the ride miles better.

A few pics of the kit before fitting.
As we already had the heat exchanger control in the way, the fitter made an excellent job in positioning the suspension controls in the final place.

 

[Jev88]

I’m with Minxy Girl on this one..
If they replace/remove the torsion bars and the air bag/s fail (unlikely, but we live in a strange world), the suspension would be on its arse... as we say ooop north. Semi air on an Alko does two jobs, increase rear weight limit (if it’s possible), or in our case, to make it a far better ride.
We had ours fitted by GlideRite at Liverpool a few days ago and I am more than happy with the quality of their kit and the professional way in which they fitted it. All done in a day, and in MO, makes the ride miles better.

A few pics of the kit before fitting.
As we already had the heat exchanger control in the way, the fitter made an excellent job in positioning the suspension controls in the final position.
View attachment 486687

Thanks for this. GlideRite is my first choice if I do go air.

 

[Ninjabob]

Gliderite Semi Air can lift the suspension by inches whereas VB Semi Air (owned by ALKO) only assists the existing suspension on the torsion bar chassis and gives little change in ride height. What is the difference between these kits and is there a negative effect on the torsion bars lifting the rear so high using the Gliderite?

 

[SandraL]

Gliderite Semi Air can lift the suspension by inches whereas VB Semi Air (owned by ALKO) only assists the existing suspension on the torsion bar chassis and gives little change in ride height. What is the difference between these kits and is there a negative effect on the torsion bars lifting the rear so high using the Gliderite?

We have gliderite semi air on an alko axle. It only assists the torsion bars. The torsion bars are still taking the majority of the load.
The Firestone 9000 air bags used have a max load of 1200 lbs each, 545kg, this is at max pressure of, i think, 100psi. We run at about 45psi but only need 200kg max assistance on the axle to raise axle limit from 2500 to 2700 kg.
In practice we probably relieve the torsion bars of more than 200 kg.
Do not run the air bags empty! They will deflect and rub on mounting brackets until you have a hole, just replaced mine..... Min pressure 1 bar, 14psi at all times.
Ours were fitted by Gliderite at Liphook about 4 years ago. Very satisfied with their work, took a full day. On older vans they sometimes struggle to dismantle the rear hub from the swinging arm due to corrosion.

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[Jev88]

We have gliderite semi air on an alko axle. It only assists the torsion bars. The torsion bars are still taking the majority of the load.
The Firestone 9000 air bags used have a max load of 1200 lbs each, 545kg, this is at max pressure of, i think, 100psi. We run at about 45psi but only need 200kg max assistance on the axle to raise axle limit from 2500 to 2700 kg.
In practice we probably relieve the torsion bars of more than 200 kg.
Do not run the air bags empty! They will deflect and rub on mounting brackets until you have a hole, just replaced mine..... Min pressure 1 bar, 14psi at all times.
Ours were fitted by Gliderite at Liphook about 4 years ago. Very satisfied with their work, took a full day. On older vans they sometimes struggle to dismantle the rear hub from the swinging arm due to corrosion.

What did you do about getting to Liphook? Camp over night? And is there anything to do local whilst they work? Thanks.

 

[Jev88]

I’m with Minxy Girl on this one..
If they replace/remove the torsion bars and the air bag/s fail (unlikely, but we live in a strange world), the suspension would be on its arse... as we say ooop north. Semi air on an Alko does two jobs, increase rear weight limit (if it’s possible), or in our case, to make it a far better ride.
We had ours fitted by GlideRite at Liverpool a few days ago and I am more than happy with the quality of their kit and the professional way in which they fitted it. All done in a day, and in MO, makes the ride miles better.

A few pics of the kit before fitting.
As we already had the heat exchanger control in the way, the fitter made an excellent job in positioning the suspension controls in the final place.
View attachment 486687

What did you do about getting to their site? Camp over night? And is there anything to do local whilst they work? Thanks.

 

[SandraL]

What did you do about getting to Liphook? Camp over night? And is there anything to do local whilst they work? Thanks.

No I turned up at 0830 with sandwiches, deckchair and a book.
It was a sunny day, local walks over woodland and fields.
All finished by 4ish and drove home.
Their industrial estate is rural.
I was able to discuss job with their enginneer, agree position of compressor while van was on jacks, very tall jacks! And inspect all when finished. Very happy with their work.

 

[Jev88]

For anyone reading this thread - Glide-Rite have said they can not do my 1999 Alko Torsion bar suspension at all.

Described it as "an over die chassis" ........ Need to carry on searching then.......

 

[Hettie's Crew]

For anyone reading this thread - Glide-Rite have said they can not do my 1999 Alko Torsion bar suspension at all.

Described it as "an over die chassis" ........ Need to carry on searching then.......

Have you spoke with AS? I remember when they did ours Phil said until they actually see it they can’t be 100% exactly sure which kit is needed due to the large number of variations. I sent loads of photos and luckily the kit ordered fitted. Highly recommend AS, very helpful knowledgeable good people.

AS Air Suspension

AS Air Suspension UK Ltd. The No1 Air Suspension for all vehicles, ALKO & Non ALKO chasis. If you're not happy with the ride of your motorhome or you keep grounding at the rear then air suspension is what you need, Just read our testimonials. It will make your motorhome feel like a new vehicle!

www.as-airsuspension.co.uk

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[Jev88]

Have you spoke with AS? I remember when they did ours Phil said until they actually see it they can’t be 100% exactly sure which kit is needed due to the large number of variations. I sent loads of photos and luckily the kit ordered fitted. Highly recommend AS, very helpful knowledgeable good people.

AS Air Suspension

AS Air Suspension UK Ltd. The No1 Air Suspension for all vehicles, ALKO & Non ALKO chasis. If you're not happy with the ride of your motorhome or you keep grounding at the rear then air suspension is what you need, Just read our testimonials. It will make your motorhome feel like a new vehicle!

www.as-airsuspension.co.uk

Hi, Yes I am mailing AS and a couple of others as I have forgotten who said they can and can't do it. I knew there were a couple of Alko chassis designs but mine must make it 5 variations now? I also have pictures I have sent as that was when Glide-Rite spotted the issue for their system.

Update - AS can NOT do vehicles pre-rear disk brakes. So they are out of the picture too.

LNB or LN Towbars say they can £2,000 but cant remember if with or without VAT.

Glide-Rite had a good price too at £1750 fitted.

 

[Hettie's Crew]

Hi, Yes I am mailing AS and a couple of others as I have forgotten who said they can and can't do it. I knew there were a couple of Alko chassis designs but mine must make it 5 variations now? I also have pictures I have sent as that was when Glide-Rite spotted the issue for their system.

Update - AS can NOT do vehicles pre-rear disk brakes. So they are out of the picture too.

LNB or LN Towbars say they can £2,000 but cant remember if with or without VAT.

Glide-Rite had a good price too at £1750 fitted.

I think you’re better off ringing up and speaking to Cath, they’ll appreciate the photos to help identify the type/fittings etc. Ours was £1750 but that was about three or four years ago now.

 

[Jev88]

I think you’re better off ringing up and speaking to Cath, they’ll appreciate the photos to help identify the type/fittings etc. Ours was £1750 but that was about three or four years ago now.

It's Cath that has said no.