Golf R Springs on a GTI?

[EB2019]

Hi

I've had a detachable tow bar fitted, only for a mountain bike rack, as modern full suspension bikes are getting just too heavy for me to put on the roof these days comfortably without the fear of something going wrong. 

Therefore with full fuel, 2 bikes 13+kg each, the tow bar (installed behind the bumper and probably weighs 15kg+), and the bike rack 17kg, I think its sitting very near the bump stops, as the weight is a long way past the rear axle.  Thinking that going to Wales or Germany won't be pleasant fully loaded as well.

This kind of rules out any suspension upgrades that go lower as the tow bar bike rack sits low and extends out a reasonable distance.  Parking off road sometimes looks perilously close to grounding out.

But was wondering if Golf R rear springs would be an option? 5mm lower but with a higher spring rate they might be more supportive? (likely won't lower due to the lighter GTI which is fine) The Golf R non DCC does run a different spring, bump stop and shock so I could purchase all 3 parts? The TCR non DCC runs the same springs, bump and shocks as the GTI so thats not an option for increasing support over the rear axle.

Other option may be to go for Bilstein B6 dampers, as a more supporting alternative but keep the rest the same, but can't really find anyone saying anything other than they feel harsh.

Any other random thoughts or suggestions welcome.

[fredgroves]

The amount of weight you've got on your hitch is nothing like as much as the nose weight a caravan would put on it. Caravan would be somewhere between 80kg and 150kg.

Shouldn't be bogging down your rear suspension at all...

[EB2019]

What do you think? sagged springs? Car has less than 40,000 though.

Its definately sitting like 3 people are in the back when it has the bikes, rack and full tank, which seems to be, or at least feels like it doesn't have much travel, may be i'm just a bit sensitive to the change.

Perhaps I will take a photo next time its loaded up and have a measure.

[Adam T7]

Not sure if this helps?

https://www.golfgtiforum.co.uk/index.php?PHPSESSID=3659p40gk5bibn28p696pc7vg2&topic=289011.msg2653782#msg2653782

[fredgroves]

Maximum towing weight is to do with largely braking but what I'm on about is nose weight... Which is the amount of force down on the hitch. You try to balance your trailer but there is always a weight on the nose. If you've ever seen a badly hitched caravan with the car all bogged down at the rear then you'll know what I mean...

[Exonian]

Sorry, bit late here, been busy, small child, large dog, too much food, misbehaving prostate in any random order.

Interesting subject.
A few things to consider: the weight of the extra dangly bits (propshaft and rear diff etc) sits under the springs of an R not above it, plus the rear suspension of an R is different to a GTI so the rear spring lower mounts might be a different size.

The slight lowering of R springs will still be in effect as the R hardware sits under them not above. Any extra weight piled on the rear axle from above will lower the car further. This is assuming the rear lower spring mounts are set at the same height, in the same position, bearing in mind the R has a full drive system dangling under its belly not just a set of wheels attached to springs and dampers.
The R’s springs will be rated to carry a little more weight at the back but when matched to GTI springs at the front you might get an imbalance of spring ratings when the car is not heavily rear loaded (ie. Most of the time). This may or may not cause the car to understeer or oversteer in extreme circumstances as the chassis won’t have been developed to run that particular spring set up.

[EB2019]

haven't been out to take and measurements yet due to weather.

I was surprised to find that the top mount and rear arms (support for the springs anti roll bar links and other gubbins) are the same part number GTI, CS, R. The shock is different on the R, and the bump stop, possibly to coincide with the change in spring rate and small drop. Because the platform the spring sits in and the shock top mount are both the same, I think I would be on safe ground to assume all would fit, but like you say, should you do just because you can?

The FWD TCR springs are not a fortune front and rear, stiffer and only a few mm drop like the R. You can buy them for the price of Eibach springs I think, keeping OE+ and the spring rate designed around a specific motion ratio front to rear would be maintained. The TCR has a DSG and not sure how much the DSG weighs over the front axle compared to the manual GTI as everything else is the same??

Doesn't really solve the issue though, that a change of springs would be placed on old pretty cheap Sachs dampers.

Perhaps the next step is just put some Bilstein B6 dampers which would provide a better/supportive platform while also sorting out the old dampers? And go from there if I still want to change springs later on.

Thanks for everyone's help.

Will get some B6 next month, chuck them on front and rear and leave you all in peace.   

[EB2019]

just an update for those looking in the future on the forum.

loaded the car with bike rack, bikes and a full tank, marked the damper body with a marker pen where the dust cover compressed to, then removed the shocks and pushed down on the top mount and checked how much free travel I had before the bump stops.

Turned out the difference between the marked line and pushing further down on the shock till I got resistance from the bumpstop was 5mm.

This means that although its not sitting on the bump stop when stationary it will have a massive spring rate change over the slightest bump in the road, and this is what I was feeling.  Therefore I fitted new top mounts, B6 dampers and cut the bump stops a little (2cm) to help with free travel, however not so much that when it does hit the bump stop, its becomes edgy.

I decided to cut a little off the top and the bottom. Couldn't find a definitive answer online but both ends are specifically designed. The top is made to sit tight in the mount and I didn't want it lose on the piston shaft, and the bottom is more deformable so I wanted to retain some of that feeling.  I guess the plastic ring is so it doesn't spread and split easily during prolonged use and I didn't want to cut that much off one end.



 

 



B6 body length compared to standard damper, note the thickness of the bottom bush and surrounding metal. Damper body is actually slimmer, due to mono tube design I guess.








I'll be doing the fronts next month, and will report back in another thread (I started one about what suspension to fit). 

[Spooky212]

Keep us posted and if you can get picks of the car sagged please fire them up. I’m about to push the button on a detachable tow bar for the exact same reason. My heaviest bike is about 16kg so reading about the sag is pretty concerning.

[Exonian]

Good to read your update Emmett and workaround with the bump stops. Will be interested to see the further updates and results.