Spring assistors

[Brent_374427565]

Hi,

has anyone any experience of using spring assistors on your tow car?

Are they any good?

Brent

 

[otherclive]

Brent, I used MAD assistors ona Saab 9000 CSE and they made a significant improvement to its towing whilst not affecting the solo drive. I had them fitted at a local garage and it took them about an hour to fit.

 

[ProfJohnL]

I am obliged to point out that the car manufacturer does all the necessary calculations and testing to ensure the car is fitted with springs that will carry the maximum weight the axle is specified for.

If you need spring assistors to prevent the suspension from bottoming, then you have either overloaded your car, or something is not to specification.

Spring assistors may restore the ride height under heavily load conditions, but they do not increase the permitted load.

 

[otherclive]

That is as it may be but some cars will adopt a nose up attitude under loading which will lead to some possible lack of traction on take off under load. In the case of the SAAB 9000 the manufacturer assumed that the boot would be fully loaded when the car was, but in the absence of two rear passengers anda towbar that takes the load center beyond the cars perimeter the MAD assistors worked well. If manufacturers get it right then why do some estates come with self leveling fitted as standard. Even PC have commented on the unfavourable aspect of the Legacy estate under review. I do agree though that spring assisters are not meant to allow the car to be over-loaded.

 

[Lutz]

Levelling a car that has a nose up attitude will not affect traction. More load in the boot (and/or the towbar) reduces the front axle load, that is true, and this will have a negative effect on traction, but levelling the car without redistributing the load will not improve traction. (The small effect due to the attitude change can be neglected because the centre of gravity is relatively low)

 

[ProfJohnL]

Hi Clive (the other)

It is a fact of life that ALL front engined cars will adopt a nose up attitude when the boot is heavily loaded. Most suffer from front wheel slip whether loaded or not. Though I do agree that heavy rear loading does detract from front wheel traction.

as you hint the reason is that the Centre of Gravity moves rearwards with greater rear loading, but at no time can the CoG move outside the extremities of the car, to do so would cause it to tip up!

As Lutz states, changing the attitude of a car with spring assistors will have a negligible effect on front wheel traction.

I know from experience with two Saab 9000's that they also exhibit this fact, But that is why most cars these days have dashboard headlight aim adjusters.

I have also had Vauxhall Carlton Estate that had pneumatic spring adjustor's factory fitted, but this was delux model and the basic models did not have them. As I recall the hand book made the point that the adjusters did not increase the load capacity, but did allow the car to ride at a more aesthetically pleasing attitude.

The only technical advantage that spring assistors offer is make the driving position better for short drivers. all other aspects are cosmetic.

 

[xtrailman]

Apparently the rac replace the rear springs on there new vans.

The replacements are heavy duty, due to the amount of heavy equipment they carry.

A common reason for fitting spring assistors is to restore the ride high, lost with aging springs.

A cheaper solution than replacing the rear springs.

I have in the past used the rubber doenuts, these hold the rear end up, allowing a more level ride, with the van on the back.

I left them on permanently, as i found the stiffer rear gave a sportier ride.

 

[shropshirefuzzyed]

there is a more serious element here.If the car is relatively new it will probably have some sort of traction control or ESP as it is on my passat.This would be useless with assistors as it would redefine all the cambers and settings.the first comment is right why is the car sitting down? Overweight,bad loading wrong combi,address the disease not the symptom.

I tow a virtually 100% comination but it sits level and old boy told me if you cant physically lift the front end of loaded single axle caravan you havent loaded it right

regards

andy

 

[ProfJohnL]

Hello Andy,

You won't be surprised that I agree with the bulk of your comment, however I do take issue with your method of assessing nose weight.

Whilst I appreciate that you may have been suggesting a quick and simply means to asses the nose load, I cannot support your method.

Nose weight is one of the aspect of a combination that is measurable and subject to legal requirements. What you and I can lift are likely to be very different, so as means of assessing the actual nose weight your simple approach will not be consistent or accurate.

 

[Lutz]

ESP senses lateral acceleration and traction control relative speed of the 4 wheels to one another. They do not require any input of camber angles.