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Progressive Rated Shock Absorbers

H

HOVIS1

We have just retned to Caravaning afte 5 years,from Motorhoming due to health problems.

Back then,I fitted Progressive Rated Shock Absorbers to my Tow Vehicles - the type with a Spring around the outside.

Can anyone advise as to where I can now obtain these- I can't find anywhere.

Thanks

Hovis
 
Provided you keep the trailer loads/weights within the vehicle specifications, spring assistors should not be necessary on modern vehicles
 
If some form of spring assistance is required when towing then it would also be required when solo and the boot full. There is a limit to the rear axle load of the car which must not be exceeded whether noseweight is applied or not. In other words, if the car is loaded to the limit, then it would be overloaded if noseweight is applied on top of what's already there.
 
John L,

Most vehicles are designed with suspension to suit their primary taks. For example a saloon car has relaticvely soft suspension to allow comfort for rear seat passengers while an estate has harder suspension as it is more likely to carry heavy goods.

So if you have a saloon for towing then it will display a nose down attitude probably when you sling 75-100 kg on the very back, even though the suspension will handle it. So adding assisters, or in my preferred opinon, the correct suspension set up, will allow you to use a vehicle for towing better.

I have a saloon and fitted the self levelling suspension normally fitted as standard to the estate. This allows me to keep the outfit on a level keel more easily.
 
John L,

Most vehicles are designed with suspension to suit their primary taks. For example a saloon car has relaticvely soft suspension to allow comfort for rear seat passengers while an estate has harder suspension as it is more likely to carry heavy goods.

So if you have a saloon for towing then it will display a nose down attitude probably when you sling 75-100 kg on the very back, even though the suspension will handle it. So adding assisters, or in my preferred opinon, the correct suspension set up, will allow you to use a vehicle for towing better.

I have a saloon and fitted the self levelling suspension normally fitted as standard to the estate. This allows me to keep the outfit on a level keel more easily.
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Slight typo errors. The van will have the nose down attitude and the tow vehicle will have its a...e on the ground. But I am sure you unertsand what I meant
 
As I se it the main market for any vehicle is not the caravanner and so the suspension is set up for a softer ride than is best suited to towing and so its not a bad thing if after market suspension aids can improve on the original by firming it up a little
 
As the rear axle load is no higher towing a caravan than if the car is solo with the boot full, the ride will not be softer just because the manufacturer appears not to have taken towing a caravan into account.
 
John W. and Scotch lad

If things are not specification, reject them! You can be sure the car manufacture is very strict with their suppliers even invoking penalty clauses if non-conforming products holds up a production line. I find hard to accept the Lad's implication that cars are supplied with incorrect suspension set ups.

If a car is sitting too low at the rear, then it is either designed poorly, or something is faulty, or it is over loaded. Considering the level of investment of time money and expertise that the car manufactures put into vehicles it is not likely to be a fundamental design problem, so that leaves either a fault or over loading.

Adding spring assistors will not correct a fault, or reduce an overload. They offer no performance improvement. They are technically unnecessary.

If you believe that your car needs spring assistors to enable it to do its job, then the job you are asking it to do is beyond is designed specification.
 
Our Mazda MX-5 has Bilstein height adjustable shockers. My old Suzuki GSX 750 had adjustable shockers.

Depending on the terrain you could adjust the suspension to suit.

So I think your statement John L is technically correct but should allow for OME variations, where it is accepted the standard issue will not suit every situation.

Scotch Lad's mod seems a very reasonable improvement to me .

Cheers

Dustydog
 
John W. and Scotch lad

If things are not specification, reject them! You can be sure the car manufacture is very strict with their suppliers even invoking penalty clauses if non-conforming products holds up a production line. I find hard to accept the Lad's implication that cars are supplied with incorrect suspension set ups.

If a car is sitting too low at the rear, then it is either designed poorly, or something is faulty, or it is over loaded. Considering the level of investment of time money and expertise that the car manufactures put into vehicles it is not likely to be a fundamental design problem, so that leaves either a fault or over loading.

Adding spring assistors will not correct a fault, or reduce an overload. They offer no performance improvement. They are technically unnecessary.

If you believe that your car needs spring assistors to enable it to do its job, then the job you are asking it to do is beyond is designed specification.
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Thank you for your input
 
Hello Dusty

If the manufacturers are fitting adjustable shock absorbers, then that is part of their design brief.

Shock absorbers do not affect ride height or load capacity, all they do is to limit a springs ability to freely oscillate after being being stimulated. They still allow the full travel of the spring, but they restrict the speed at which system can respond to stimuli.
 
hi all

while john L is undoubtedly correct "technically" there is no doubt however that some cars do benefit from some sort of spring assistance or ride height control, the old mondeo springs to mind the suspension was so soft on a poor road surface with the van on the back one could get mildly sea sick. uprated srings and progressive shocks cured the problem instantly although technically not a standard fitment.

sometimes it is nessesary to "think outside the box" to cure a apparent fault where one technically does no exist. I for one do not believe that manufacturers build anything that encompasses all situations in thier designs, just the most likely to occure during use.

if this was the case all cars and vans would be kitted out so no modifications would ever be required ever? cars would have towbars and double electrics as standared as with roofbars ect; and vans would come with shock absorbers, disabled handrails and a pullout step.

if you think about it why has a car that is designed to carry 5 people "signified by having 5 seats and belts" and is also is capable of towing 1500kg worth of trailer with a max of 75kg nose weight, have a maximum train weight well below what would be required to carry 5 adults and tow a 1500kg trailer at the same time. its a either or senario that is left to the owner.

I am no engineer but experience has taught me the difference between a load applied to the tow bar "at the far extremities of the vehicle" and one applied inside the wheel base, I assume SL has a similar background of experience and the reason he did the vehicle mods mentioned.

colin
 
The "either/or scenario" that Colin refers to has nothing to do with ride height as the the caravan does not apply a higher load to the rear axle than if the car were fully laden and solo. The only "either/or scenario" is whether the the boot is full or a noseweight is applied, but in both cases the maximum rear axle load is the same.
 
Morning John

Don't forget there are shock absorbers that do affect ride height irrespective of the load applied. I have the Sachs shockers on the rear, preset at the factory to maintain a set height.

A number of vehicles are so fitted as OME. It's a cheaper SLS than the sophisticated Landie pump system but works very well.

I think Colin makes a number of valid points.I too am no engineer but it does appear a caravan hitched onto the towbar must surely add both static and dynamic loads.

Cheers

Dustydog
 
The dynamic loads will undoubtedly be higher when towing because they are applied differently to when the boot is full, but static loads are not. If you hitch up the caravan you can put less stuff in the boot, but the net maximum static load on the rear axle is the same.
 
I had rear dampers on the Peugeot 404 estate that included an internal progressive rubber bump stop and they did a very good job of improving the ride height and the stability including roll

My Citroen dealer recommended MAD helper springs between the bump stops and the suspension arms and again it reduced roll and sag

I had uprated MAD springs fitted on the last X Trail and on the present one have prgressive rate MAD coil springs inside the existing ones and again feel the benefit of reduced sag and roll

Maybe I should have sold all the vehicles and spent thousands of pounds on a car with self levelling suspension but I chose the cheaper route of improving on the original spec and still enjoyed the cars I liked at the time

In practice I have been very pleased with the improvement for my purposes and if necessary will continue in the future if the next car does not come with self levelling suspension or load assist as standard

What concerns me is the result not the feeling that it could be better but that it is as manufactured so its beyond improvement
 
I had rear dampers on the Peugeot 404 estate that included an internal progressive rubber bump stop and they did a very good job of improving the ride height and the stability including roll

My Citroen dealer recommended MAD helper springs between the bump stops and the suspension arms and again it reduced roll and sag

I had uprated MAD springs fitted on the last X Trail and on the present one have prgressive rate MAD coil springs inside the existing ones and again feel the benefit of reduced sag and roll

Maybe I should have sold all the vehicles and spent thousands of pounds on a car with self levelling suspension but I chose the cheaper route of improving on the original spec and still enjoyed the cars I liked at the time

In practice I have been very pleased with the improvement for my purposes and if necessary will continue in the future if the next car does not come with self levelling suspension or load assist as standard

What concerns me is the result not the feeling that it could be better but that it is as manufactured so its beyond improvement
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Citroen Picasso
 
I take issue with people who infer that car manufactures supply inadequate suspension systems for the loads stated in the car's specification.

Anyone who believes that the car manufacturers supply sub-standard suspension systems should take it up with the manufactures.

On the basis the car manufactures do supply adequate systems, there is no imperative need to alter what they supply. If there IS an imperative need to change suspension parts, then it means a part is defective, the car is over loaded or your expectations are unreasonable.

No change to any part of the suspension can legally increase the maximum loading capacity of a type approved vehicle.

If a manufacture includes SLS, spring assister, or variable rate shocks as an OEM option, then it will be taken into account in the type approval process when assessing loading. If any of those items is added after manufacture they cannot increase the loading capacity, as it was not part of the type approval process for the vehicle as supplied.

The use of such devices will change the characteristics of the vehicle and its handling. Whilst some additions may 'improve' a characteristic, that does not devalue the manufacture standard specifications.
 
Hi John

I can't see anyone has made any adverse inferences , moreso they have found it desirable to improve upon that given by the manufacturer in the first place.

Any specification has to be a compromise across a broad range of loads. At the extremities of range I do not believe I can expect the same performance at say mid range. Any spring has to give under load and those at full load will clearly compress more than light load.

Hence we have a number of good manufacturers who know their vehicles will be load luggers , hence SLS , sachs shockers etc. Alternatively heavier duty springs are also fitted to some estate models.

I think a balance has to be found and in a lot of cases suspension mods do solve a problem even where the suspension is to spec. If they were all so good , then it is hard to explain why there are so many suspension aids currently available to caravanners including the large array sold at most dealers.

I emphasise these mods are not a licence to exceed the manufacturers load ratings .

Cheers

Dustydog
 
I really can't see why towing a caravan enters as such an issue concerning the softness or otherwise of suspension systems. If one is of the opinion that the suspension is too soft then this applies equally to the car in its solo condition and has nothing to do with towing. The only 'softness' that really makes any difference to the way the car handles when towing compared to its solo handling performance is lateral compliance of the suspension system as this is an important factor in the stability of the outfit, but no suspension assistance or harder springs are going to make any improvement to this characteristic.

Depending on the type of market the car manufacturer is aiming for, he may offer products with soft suspension systems and lots of spring travel or harder springs with less deflection, but so long as neither bottom out unnecessarily under maximum design load, both can be equally suitable for towing. If they aren't suitable for towing, they are not suitable solo under maximum load either.
 
Hello Dusty

Quote from SL " So adding assisters, or in my preferred opinon, the correct suspension set up, will allow you to use a vehicle for towing better." The conclusion is that SL believes the system as supplied is not correct.

If the system was not "correct" the car manufacture would be very worried and making recalls.

The standard kit will be suitable for all loads within the manufacture specification. That does not preclude improvements (not corrections) from being made. However where a manufacture offers different specifications on a particular model they will have been checked for compatibility with all other aspects of the vehicle, where as after market devices will not.
 
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