Wednesday, Jul 05, 2017 at 10:28
Stefan
Think very carefully about why you would want a GVM upgrade.
I purchased a 60th anniversary model in 2011 TTD with the KDSS and drove it in standard form for about 120k before fitting and ARB upgrade
suspension (all the components that come with their GVM upgrade but without the certification), and the vehicle just was not so nice to drive as before the upgrade.
The ride was firmer which was a good thing on dirt and corrugations as the rear of the car did not 'bounce out' to the same extent as when standard, but the vehicle just did not steer as nicely on the highway and tended to not follow a straight line as nicely as when standard. Handling, as in cornering, did not appear to be significantly affected.
This straight line ability is in large part to do with the reduction that occurs in the Castor angles that happens as a result of raising the front ride height. This reduction, whilst not always sufficient to cause the vehicle to 'wander', does have an effect on the driving comfort when driving in a straight line. There can also be problems reducing the Camber to acceptable limits, in my case the camber adjustment was at its limits when camber adjusted to 0.30' (or 1/2 of a degree) which is the maximum camber recommended by Toyota, and the maximum castor angle that could be attained was just 50% of that recommended by Toyota.
As the front ride height is increased then, due to the geometry of the front
suspension, the camber increases and the castor reduces.
It is Camber that gives you the self centre effect, Castor gives straight line stability particularly under heavy braking. Excessive camber will cause outside edge tyre wear.
There are replacement upper control arms available that claim to address these issues, some may be good but some do not have any dirt/dust sealing for the ball joint, it could be argued as to the legality of using some of these replacement arms and the life of these arms and joints could also be of concern.
Also of some concern is the change in the angle of the Panhard Rod fitted to the rear
suspension. AS the rear ride height is increased so to is the angle of the panhard rod relative to the rear axle centreline. The greater this angle then the greater the sideways movement of the rear axle as the
suspension raises and falls. This also becomes obvious when looking at the location of the rear wheels in relation to the vehicle's body work. Some will say that is easily corrected by fitting an adjustable panhard rod, this can be used to place the wheels back into a symmetrical position at ride height, but does nothing for the axle moving sideways with
suspension rise and fall. This sideways movement causes the rear of the vehicle body/chassis to move sideways in relation to the road which effectively gives some rear end steering, further upsetting the overall balance of the vehicle.
Hope this helps.
Athol.
AnswerID:
612354
Follow Up By: Stefandsal - Wednesday, Jul 05, 2017 at 19:46
Wednesday, Jul 05, 2017 at 19:46
Thanks heaps Athol, very informative.
FollowupID:
882600
Follow Up By: Rob K (VIC) - Thursday, Jul 06, 2017 at 09:08
Thursday, Jul 06, 2017 at 09:08
Athol, agree with what you have discussed above.
Regarding the upper control arm (UCA), there are DOT approved replacement UCA's available from Superior Engineering and these have the ball joint encased in a grease capsule (and a grease nipple) which allows for adjustment to the camber and castor. About $1500 fitted to a LC200. A mate of mine had it fitted earlier this year in
Melbourne. It certainly improve the handling for his vehicle which was fitted with a Ironman 2" lift kit.
Cheers
Rob K
FollowupID:
882610
Follow Up By: mountainman - Monday, Jul 10, 2017 at 01:02
Monday, Jul 10, 2017 at 01:02
Athol
you happen to live in Cardiff by chance?
Newcastle
FollowupID:
882664
Follow Up By: Athol W1 - Monday, Jul 10, 2017 at 16:10
Monday, Jul 10, 2017 at 16:10
Mountainman
Negative,
Gold Coast for me.
Rob K.
The issue I have with all of these
suspension kits is that the suppliers do not inform the purchaser in any way that there could be an issue. Also those buying the GVM upgrades done PRIOR to first registration never get to know what the effect is, or how good the vehicle was to drive in standard form.
As this modification to the UCA's is required to attain the original steering/front end geometry then they should be included in the modification package, but that would put the kit in the too expensive bracket.
A GVM upgrade that retained the standard (or near to standard) ride height would be a good thing, but this would most likely result in a very harsh or pronounced ride, and that would be enough for most people to decide against such a modification.
There are also some kits that claim to only 'bring the front up so as to make the vehicle sit level'. These would obviously avoid the issues with the rear
suspension moving sideways under the vehicle as the axle rises and falls, but would still introduce the front
suspension geometry issues, but may be not to such a great extent as the general stance of the vehicle would help with the lack of castor.
Also there is the matter of DOT approved. Which DOT did approve such item and for what purpose/vehicle. Often DOT approval refers to the USA DOT and has nothing to do with any Australian DOT. At one stage in Qld you required approval on an individual vehicle basis for such a modification (UCA's), however the current situation in Qld is that it is up to the component manufacturer to ensure that his REPLACEMENT part meets all recognised engineering standards, and if so then no further approvals/certifications are required. This only applies to normal replacement parts and not to major alterations to the vehicle's design which still require certification either by written approval from DOT QLD or an Authorised Person under the Code of Practice fo Modifying Vehicles.
Regards
Athol
FollowupID:
882670