When our passat estate is loaded with all the camping gear and 4 bikes on the rack in rides very very low.

I thought about heavy duty springs but then i found these spring assisters for a tenner and the obvious advantage of fitting and removing when needed.

http://www.towsure.com/product/Towing_Spring_Assisters_prod

Anyone use either, any comments?

thanks

anyone?

How old is the car? springs tend to get softer and sit lower over the years. First step would be to make sure what you have is in good condition.

Old car? Springs wear out and get softer over time.

Spring assisters are to stop the back end squatting when towing not for increased loads in the vehicle itself,
Might be tired springs as said above, if not you might be overloading which is bad (and illegal) and unsafe in an emergency
If you have a towbar it might be worth looking for a small trailer instead
Edit, heavy duty springs will work but when it’s not loaded it’ll ride like a bag of spanners

We have a passat estate SE that sits very low at the back with little weight in it. Think they were pretty bad when new for it but as time takes its toll (150,000 miles and 10 years) on the springs it gets worse. I am pretty sure you can fit the rear springs from a the sport model which are stiffer and will stop it sitting so low. I just live with it, but don’t do any towing.

does it matter? I’ve driven thousands of miles in cars on the bumpstops before. bit less comfy for those in the back but doesn’t realy matter. just put a bit more air in the rear tyres so you’re not sitting on the rims

If its that low, you might well be over the max laden weight for the vehicle anyway

by the way – does anyone have any evidence of springs getting softer over time? i’ve heard it spouted on here many times but i’m not sure its true. my old mondeo (180+ thousand miles) sits at the same ride height it did when it came out of the factory

My old old Passat rode low laden – I changed the springs, and it wasn’t much better. But that could’ve been poorly specced cheapo generic aftermarket springs.

You can get inflatable spring assisters for towing, which I like the idea of. It’s a retro-fit version of the self levelling suspension you get on trucks and volvos, and is an option on Passats.

I have Airide air-bag helper suspension on my truck. It has the advantage of being able to air it up when you need to carry a heavy load then air it down when you don’t.

My 06 Plate Skoda Octavia did the same, but my kn@b head ex girlfriend now has that issue. Spring assistors were the way I was going to go, for the money they were worth a go.

http://www.springassisters.co.uk/

have a look at this site or all the options for your car, cheap rubber assisters do work but the car seems to bottom out very easily with a clunk when driving off the pavement etc.

Unfortunatly this is a bit of a myth, springs do not actually get softer, if you can change the spring constant of steel over time then you need to go to Cambridge or Imperial and get your PHD now.

They might sag through a bit of creep, or even get get deformed, but the spring rate will not change significantly, even with a geom change due to creep/plastic deformation.

Its possible they were soft in the first place.

Towbar mounted bike racks put a large moment on the towbar, possibly more than a trailer/caravan which has its own wheels.

I’m pretty sure they do get softer?

Take metal bar, bend one end, fairly easy.

Take the same metal bar and compress it (without letting it buckle) pretty much impossible.

Push it ar any angle between the 0 and 90deg mentioned above and the modulous is proportional to the angle.

Coil it into a spring, and the flatter the coils (i.e. the more its saged through plastic deformation/creep) over time the softer it gets. It’s also shorter. So the spring is both a bit softer and a bit shorter, so the result it it bottoms out easier.

If you don’t believe me, come and have a look at my car, after 45 years on the same springs the drivers side is about 1″ lower than the passenger side!

Towbar mounted bike racks put a large moment on the towbar, possibly more than a trailer/caravan which has its own wheels.

Towbars have a maximum nose weight, usualy 50-75kg, whether thats from bikes or from a trailer makes no difference, apply a given acceleration (say 2G ~20m/s2 vertiacely) and the towbar feels the same form 75kg of trailer or bike rack, about 100-150kg.

Towbar mounted bike racks put a large moment on the towbar, possibly more than a trailer/caravan which has its own wheels.

Not really an issue – towbar weight on most cars will be 75-85kg, that’s a lot of bikes. I can verify that a towbar mounted rack with two MTBs on does affect the ride ever so slightly (normal people would not notice) but a caravan loaded to near the max of the towbar (as recommended) is very noticeable.

75-85kg,

My 4 bike mottez with 4 dh bikes on weighs about 85 kg. Assuming distributed load over 1.2m length of rack sticking out the back of the car, thats a moment of 6120 Nm,(fag packet calc) that is not the same as a point load of 75 kg on the tow ball in any way. Both my ex 406 estate and my current accord both squish severely with the tow bar mounted rack.

It’s also shorter. So the spring is both a bit softer and a bit shorter, so the result it it bottoms out easier.

If you don’t believe me, come and have a look at my car, after 45 years on the same springs the drivers side is about 1″ lower than the passenger side!

I don’t doubt it, and 45 years is a long time, for sag/plastic deformation, but the spring rate does not reduce as spring sags, I’m just looking for the maths as to why. If anything it would increase as it will go to end coil effects sooner. That’s the whole point of a coil spring- linear rate.

Both my ex 406 estate and my current accord both squish severely with the tow bar mounted rack

As they would with a caravan.

Bear in mind that 4 dh bikes is a bit extreme.

But what’s your point? The OP’s springs are too soft, we all agree?

a caravan has a different sort of load to a bike rack though. A caravan will push straight down on the towbar, with a force. A bike rack has more of a twisting force on the rack, as the bikes are being supported 2-3′ from the back of the car (depending on the rack). Whilst the force is the same, the moment of the force could cause damage

i’ve never seen a bike rack actually screw a car, just supposing that it could, even if the weight was within the load limits of the car

But what’s your point? The OP’s springs are too soft, we all agree?

Too soft for that application, but they haven’t got softer, so replacing them with new stock springs with new stock springs will have no effect is a waste of money.

My point is to offer knowledge to save the OP cash. It is a myth that springs get softer. He could buy higher rate springs as lots of caravanner’s do, but then his car would be harsh when unloaded…

5lab, I think you’ll find that’s exactly what I’ve been saying…

toys is right I think – reduction in spring rate will me small if any – the reduction is in ride height as they sag / take a set / creep however you want to describe it

New stock springs will give a higher ride height

A caravan has a twisting force on the tow bar once you start moving though 5lab.

Air spring assisters are ideal, but £200 for my Passat. You can also get slightly shorter progressively wound springs that sit inside the original coils – these stiffen up quickly when you load them. You won’t keep the original ride height but you will improve performance once loaded and it’ll ride somewhat higher. They are significantly cheaper tho, about £100 for the same car.

The car is a 55 and its always been the same so if there is any ‘softening’ then I’d say it was negligible.

I’ve spoken to VW today and while they don’t offer heavy duty springs themselves the chap advised that was the way to go and I’ve found some aftermarket ones for £40 each so I’m going down that route.