Golf R Springs on a GTI?

[EB2019]

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.

Sorry didn't take any pics before I installed the rear B6 dampers, should have done so. I would say that 4 adults and boot full luggage is likely the same if not more lowered. Bumpstops are engineered as part of the spring rate by manufacturers these days I read, so its not the end of the world if it sits on them, but I'm just fussy about how it feels 

The brief feedback on the B6 fitted to the rear is that its not noticeable stiffer, its raised the height by 3mm

If you intend to drive to a local trail centre with your bikes I probably wouldn't bother doing anything, but I like taking the bikes to Wales and will be taking them to Germany this year and didn't want that feeling for long journeys, and like you say bikes are getting heavy!

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

Thanks will let you know when its all done. 

[Paul70]

Great read EB2019! Looking forward to the next update and your overall review of the B6 shock upgrade.

Assume you kept the standard springs and did not change to the TCR or other?

[fredgroves]

I still can't believe that a bicycle rack can upset the rear as much as a caravan can and will...

I've driven cars fully loaded with a caravan on the back and it doesn't do what you are describing - honestly!

[EB2019]

Great read EB2019! Looking forward to the next update and your overall review of the B6 shock upgrade.

Assume you kept the standard springs and did not change to the TCR or other?

Correct about the TCR springs, after looking into it, the TCR springs for non DCC are the same on the front as the GTI Performance, so if the front isn't a lower uprated spring I'm assuming the rear springs although different to the rear of the GTI performance, aren't lower or massively uprated.  With that in mind I decided to leave the originals for now. DCC and the performance option pack with lower ride height and limiter removed are different, but I think all DCC springs are different to non DCC that i have looked into.

[EB2019]

I still can't believe that a bicycle rack can upset the rear as much as a caravan can and will...

I've driven cars fully loaded with a caravan on the back and it doesn't do what you are describing - honestly!

I understand your reasoning, And i'm not sure why either, but the marker pen marks on the dampers don't lie. For reference my car height is 365 to 370mm at the rear, centre of hub to arch without any load.

The only thing I can think is that a fully loaded car would be on the bump stops too, or close to it at the rear, at least in my car, and yet all the mass would be inside the wheel base and at least more evenly distributed front to rear, what I am using is sitting maybe 4 feet behind the rear axle.  Like holding a snooker cue a little at the thin end, it doesn't weigh a great deal but once extended out at one end it is heavy.  This would be like your caravan scenario in theory, but a caravan is sitting on its own wheelbase half way along and pivoting around that?  Therefore it can slow the vertical movement due to its weight, and working against the rebound force?

Perhaps my theory isn't sound. 

but I still wasn't happy with the 5mm of travel before the bump stops so chopped a little off them.

[fredgroves]

Well yes its all about weight acting at a distance.... but as I said earlier, a caravan puts 80-150kg directly onto the towing hitch.

You said you had:

2 bikes 13+kg each - 26kg
the bike rack - 17kg

(I'm ignoring the weight of the tow hitch as its the same with the caravan scenario, as is full tank of fuel and stuff/passengers in the back seats and boot full of stuff)

So you've got 43kg but if that is acting even half a metre away from the tow hitch vertical (and its not a simple calculation to work it out short of trying to balance the whole thing on scales like you do with a caravan nose weight check) that force increases quite a bit.

I'm sure some clever physics type could work it out or rather a rough calculation, but still would be surprised if it got to 80kg.

[MinchCS]

Well yes its all about weight acting at a distance.... but as I said earlier, a caravan puts 80-150kg directly onto the towing hitch.

You said you had:

2 bikes 13+kg each - 26kg
the bike rack - 17kg

(I'm ignoring the weight of the tow hitch as its the same with the caravan scenario, as is full tank of fuel and stuff/passengers in the back seats and boot full of stuff)

So you've got 43kg but if that is acting even half a metre away from the tow hitch vertical (and its not a simple calculation to work it out short of trying to balance the whole thing on scales like you do with a caravan nose weight check) that force increases quite a bit.

I'm sure some clever physics type could work it out or rather a rough calculation, but still would be surprised if it got to 80kg.

The mass is the same, but the moment (think force used by a lever) increases around the pivot point (the attachment of the bike carrier) the further the weight is away from the car. The resulting force will try and turn the car around the pivot point (so front lifting).Higher rated rear springs will help resist the car moving around the pivot. So, as you point out, the further away the bikes are from the back of the car, the stiffer rear springs you need.

[fredgroves]

Well yes its all about weight acting at a distance.... but as I said earlier, a caravan puts 80-150kg directly onto the towing hitch.

You said you had:

2 bikes 13+kg each - 26kg
the bike rack - 17kg

(I'm ignoring the weight of the tow hitch as its the same with the caravan scenario, as is full tank of fuel and stuff/passengers in the back seats and boot full of stuff)

So you've got 43kg but if that is acting even half a metre away from the tow hitch vertical (and its not a simple calculation to work it out short of trying to balance the whole thing on scales like you do with a caravan nose weight check) that force increases quite a bit.

I'm sure some clever physics type could work it out or rather a rough calculation, but still would be surprised if it got to 80kg.

The mass is the same, but the moment (think force used by a lever) increases around the pivot point (the attachment of the bike carrier) the further the weight is away from the car. The resulting force will try and turn the car around the pivot point (so front lifting).Higher rated rear springs will help resist the car moving around the pivot. So, as you point out, the further away the bikes are from the back of the car, the stiffer rear springs you need.

So springs and not dampers...

But of course this would be optimising it for the loaded scenario and the rest of the time you'd be oversprung and have the rear end bouncing around?

[MinchCS]

Well yes its all about weight acting at a distance.... but as I said earlier, a caravan puts 80-150kg directly onto the towing hitch.

You said you had:

2 bikes 13+kg each - 26kg
the bike rack - 17kg

(I'm ignoring the weight of the tow hitch as its the same with the caravan scenario, as is full tank of fuel and stuff/passengers in the back seats and boot full of stuff)

So you've got 43kg but if that is acting even half a metre away from the tow hitch vertical (and its not a simple calculation to work it out short of trying to balance the whole thing on scales like you do with a caravan nose weight check) that force increases quite a bit.

I'm sure some clever physics type could work it out or rather a rough calculation, but still would be surprised if it got to 80kg.

The mass is the same, but the moment (think force used by a lever) increases around the pivot point (the attachment of the bike carrier) the further the weight is away from the car. The resulting force will try and turn the car around the pivot point (so front lifting).Higher rated rear springs will help resist the car moving around the pivot. So, as you point out, the further away the bikes are from the back of the car, the stiffer rear springs you need.

So springs and not dampers...

But of course this would be optimising it for the loaded scenario and the rest of the time you'd be oversprung and have the rear end bouncing around?

I am a medic rather than a physicist / engineer, but stiffer rear dampers will also resist the tendency to pitch over bumps when driving.

[japes1275]

Have you looked at spring helpers? Used to be a fairly common and they still do them - Google 'Spring helpers for towing'. They just fit in between the coils - though how easy they are to fit/remove I'm not sure!!

My Mk7 GT hatch used to be OK with two bikes on a Thule hitch carrier but you could tell it was on the car when driving. I also used to tow a 1000kg trailer with it and you could hardly notice it, strangely you can on the GT estate I now have, must be to do with the distance the tow bar is from the rear axle.