Just to recap here's the camper details:
-Chassis is a 2002 model 814DA with approximately 230K Kms
-Overall height 3.5m
-Overall length 7.2m
-Wheelbase 3.7m and rear overhang of 2.2m
-Weight: Front axle 2600Kg, Rear Axel 3400Kg
-Original wheels were standard 17.5Inch rims with Michelin 9.5 R17.5 XZT tyres and with duel wheels on the back.
-New wheels are 8.25 x 19.5 wheels (+ 98mm offset) with 285/70 R 19.5 Continental HDR tyres and with just singles on the back
-New Koni adjustable dampers have been fitted and with the damping adjusted by 1.5 turns
-The rubbers in the anti-roll bars have been replaced
-The rest of the suspension is original
The problems
1) On a good smooth road steering inputs feel like they are delayed and then when the steering change is felt, the rear feels like it’s swinging around. This can lead to me over steering and then over compensating. Not a nice feeling. However on long fast curves, the steering is slow to react and the tail feels like it’s swinging a bit, but then the van settles into the corner and can carry good speed.
2) On bumpy or poor road surfaces (we have a lot of this in Ireland
) the van does not want to track straight. It will tend to change direction without warning even on small things like centre white lines. This is very disconcerting.
Steps taken to try and resolve or at least diagnose the situation
1) I replaced the suspension rubbers on the anti-roll bars. There was no noticeable change
2) I got in touch with Continental and they advised me to change the tyre pressures down to 4.5bar front and rear. They also pointed out that the HDR tyres are “Drive Only” tyres and not designed for steering, but they felt they should be “Ok”. The lowering of the pressure (from about 5.5bar) improved the ride comfort but didn’t help on the two problems
3) Fitted the new Koni dampers. This did help somewhat. But the problems still exist as described.
4) I refitted the original 17.5Inch wheels. This made some difference to the first problem. The steering felt a little quicker to react and the rear didn’t swing quite as much – although there was still tail swing. The big change was that the van was far less troubled by poor or bumpy roads and tracked straight.
5) I then put the 17.5" wheels on the front and the 19.5" singles on the back. Tail swing was somewhere between having all 17.5" wheels fitted (including duals on the back) and all 19.5" wheels fitted (closer to this). Steering felt like all 17.5" setup and it tended to track pretty straight.
These are my thoughts on why changing back to the original wheels helped:
1) The dual rear wheels – This probably would have helped reduce the feeling of the rear tail swing, but I can see how it helped with the feeling of steering or the changes of direction on poor roads
2) The new (custom made) 19.5inch wheels may have a different offset – This may explain the changes of direction on poor roads?
3) The HDR tyres have a much wider contact patch which might be more susceptible to following the poor road surfaces and causing changes of direction?
4) The HDR tyres are designed to be drive only tyres and are not at all suited to steering?
Options
1) Going back to just 17.5" wheels seems to be the safest option. Problem is that I'd have to buy 5 good tyres (£280 a pop) plus a rim and plus I'd have to do a fair bit of rework as I used the space left free by going to the singles to route the black water 3" pipe.
2) Buy 2 steering/all location tyres for the 19.5" front. Trouble is - I don't know if this will behave the same way as the 17.5".
Any thoughts/suggestions or even criticisms welcomed!
