Corner weight weirdness
Discussion
I think I'm losing it!
o car is tuscan mk1 2002
o never liked the handling, but improved over the years with various tweaks
o have just replaced all bushes for poly (rg)
o stripped and re-assembled each corner at a time, no big dramas
o went to set up corners/ride heights and found massive imbalance across one diagonal
Here's where I am:
o ARBs off (have tested with them on and still can't win)
o Shocks (GGPs) set to finger tight pre-load at each corner
o Set car onto wheels on level ground with 80Kg in drivers seat
o FR is *very*compressed (wheel top almost invisible behind arch), BR quite compressed too, FL is up in the air (3" gap to arch), BL also up
o Try to adjust, ended up with FR under nearly 3" of pre-load (on 400lb spring), FL at around -1" pre-load i.e. 1" slack in full droop...and I still can't get it right
o I have a corner weight set so measured that now and it confirms that in finger-tight case there is +125Kg on FR and RL !!!! :O
o Basic measurements from top spring mounts to level ground when chassis also level at front (by spirit level) -> all 4 corners show no more than 5-10mm diff side-side
So 2 main questions
1. Has anyone ever corner weighted with ARBs *off* i.e. how good is the balance without the ARBs to shunt the weight around ?
2. Assuming the chassis isn't seriously twisted (measurements imply its not) then what else could cause such a large offset ???
o car is tuscan mk1 2002
o never liked the handling, but improved over the years with various tweaks
o have just replaced all bushes for poly (rg)
o stripped and re-assembled each corner at a time, no big dramas
o went to set up corners/ride heights and found massive imbalance across one diagonal
Here's where I am:
o ARBs off (have tested with them on and still can't win)
o Shocks (GGPs) set to finger tight pre-load at each corner
o Set car onto wheels on level ground with 80Kg in drivers seat
o FR is *very*compressed (wheel top almost invisible behind arch), BR quite compressed too, FL is up in the air (3" gap to arch), BL also up
o Try to adjust, ended up with FR under nearly 3" of pre-load (on 400lb spring), FL at around -1" pre-load i.e. 1" slack in full droop...and I still can't get it right
o I have a corner weight set so measured that now and it confirms that in finger-tight case there is +125Kg on FR and RL !!!! :O
o Basic measurements from top spring mounts to level ground when chassis also level at front (by spirit level) -> all 4 corners show no more than 5-10mm diff side-side
So 2 main questions
1. Has anyone ever corner weighted with ARBs *off* i.e. how good is the balance without the ARBs to shunt the weight around ?
2. Assuming the chassis isn't seriously twisted (measurements imply its not) then what else could cause such a large offset ???
Figured it out
I was using 4 individual scissor platforms to raise the car. I made sure they were all level to each other but there must be enough twist in the them to mean the weight they each take depends on whether the road wheels are perfectly central to the platforms. Once I put the car on the floor it all made much more sense.
Have now got it all set up and must say, anybody wondering whether to fit polybushes or not...do it ! Amazing difference, nice and compliant, almost feels like a production car! Only the worst B roads cause any bumps or clonks (previously it was sooo crashy). I also used RGs improved drop links.
I was using 4 individual scissor platforms to raise the car. I made sure they were all level to each other but there must be enough twist in the them to mean the weight they each take depends on whether the road wheels are perfectly central to the platforms. Once I put the car on the floor it all made much more sense.
Have now got it all set up and must say, anybody wondering whether to fit polybushes or not...do it ! Amazing difference, nice and compliant, almost feels like a production car! Only the worst B roads cause any bumps or clonks (previously it was sooo crashy). I also used RGs improved drop links.
PetrolHeadPete said:
Figured it out
I was using 4 individual scissor platforms to raise the car. I made sure they were all level to each other but there must be enough twist in the them to mean the weight they each take depends on whether the road wheels are perfectly central to the platforms. Once I put the car on the floor it all made much more sense.
Have now got it all set up and must say, anybody wondering whether to fit polybushes or not...do it ! Amazing difference, nice and compliant, almost feels like a production car! Only the worst B roads cause any bumps or clonks (previously it was sooo crashy). I also used RGs improved drop links.
Its great when people explain how they sorted their problem and very pleased for you with how the car is now!I was using 4 individual scissor platforms to raise the car. I made sure they were all level to each other but there must be enough twist in the them to mean the weight they each take depends on whether the road wheels are perfectly central to the platforms. Once I put the car on the floor it all made much more sense.
Have now got it all set up and must say, anybody wondering whether to fit polybushes or not...do it ! Amazing difference, nice and compliant, almost feels like a production car! Only the worst B roads cause any bumps or clonks (previously it was sooo crashy). I also used RGs improved drop links.
Well done Pete.
I bet you were not sleeping right for a day or two there!
Know what you mean about poly bushing. The Tuscan drives better than the Sag, and it isn't just tyres as it did feel good on the last set of tyres. Replacing the under trays made a difference, lot stiffer. Be interesting to try a car on the scales and lift the rear on one side to record the front end weight shift results with the stainless tray Vs the tube one, a before and after.
J
I bet you were not sleeping right for a day or two there!
Know what you mean about poly bushing. The Tuscan drives better than the Sag, and it isn't just tyres as it did feel good on the last set of tyres. Replacing the under trays made a difference, lot stiffer. Be interesting to try a car on the scales and lift the rear on one side to record the front end weight shift results with the stainless tray Vs the tube one, a before and after.
J
Im running 225 at front 255 at rear
Front is
-0.75o camber each side
Full caster (spacers both to front-> measures as 5.5o)
Toe in around 4' each side
4mm wheel spacers (I'll now try removing them as a comparative)
Measured KPI is 5.3o just for interest
Rear is
-1.5o camber each side
Toe in around 6' each side
GGPs all round and 400lb springs all round
Need to fiddle with dampers because its still too bouncy!
@SagiBadger: Someone's been a busy boy
Love it. Bet its way lighter too. I can't imagine its any weaker than the original and more likely to be stiffer in reality. As you say lifting would be interesting but from what I saw from corner weights, its so mega sensitive to wheel position that you may get odd results. Think you'd need to make a twist measurement somehow: long Ali reference tube or something front-to-back perhaps
Front is
-0.75o camber each side
Full caster (spacers both to front-> measures as 5.5o)
Toe in around 4' each side
4mm wheel spacers (I'll now try removing them as a comparative)
Measured KPI is 5.3o just for interest
Rear is
-1.5o camber each side
Toe in around 6' each side
GGPs all round and 400lb springs all round
Need to fiddle with dampers because its still too bouncy!
@SagiBadger: Someone's been a busy boy
Love it. Bet its way lighter too. I can't imagine its any weaker than the original and more likely to be stiffer in reality. As you say lifting would be interesting but from what I saw from corner weights, its so mega sensitive to wheel position that you may get odd results. Think you'd need to make a twist measurement somehow: long Ali reference tube or something front-to-back perhapsEdited by PetrolHeadPete on Saturday 14th October 17:09
(top of wheel tipped in)TVRMs said:
Are you really running +ve camber with full castor?
Edited above to correct my errorBTW: I looked at the rack and its already pretty much maxed out...I reckon around 7-8mm spacers. I had a good play with the front movement while it was all easy to access...my conclusion, like other folk's, is that a slight lift to ride height gets you to a point where the amount of toe change with modest +/- movement is pretty negligible, then changing to moderate toe-out under hard bump (which is OK as I read it). So I raised the ride height so that the lower control arms have lower edges that are just beyond horizontal i.e they slope very slightly downward from inboard to outboard. Then raised rear to give a little bit of front to back rake. So far so good.
PetrolHeadPete said:
You mean 6mm at front and 2mm at back?
Always felt the front of my first Sag was numb and didn’t turn in well. Pushed both spacers up front, turn in was much quicker but too quick really. 6 and 2 as you describe was excellent. Never played around after that - content...Gassing Station | Tuscan | Top of Page | What's New | My Stuff