Desperate of Somerset !
Discussion
My car has been running well and with specialy no problems in the steering department.
I then decided to replace the manual steering rack with a newly reconditioned power rack.
Nothing was changed or altered in any way except for a new longer lower column, new u/js, new pump, hoses and of course the rack itself.
The problem now (and my local indie says it,s too dangerous to drive), is that when exiting a bend and relieving pressure on the wheel the car continues to turn at the same rate. The steering only returns if you actually move the wheel...very,very scary!
Steering wheel return, as far as I know, is created by the castor angle and this in turn is created by the 8mm spacer in front of the top ball joint. This has not been touched since it was in manual rack mode.
Any advice will be most appreciated.
I then decided to replace the manual steering rack with a newly reconditioned power rack.
Nothing was changed or altered in any way except for a new longer lower column, new u/js, new pump, hoses and of course the rack itself.
The problem now (and my local indie says it,s too dangerous to drive), is that when exiting a bend and relieving pressure on the wheel the car continues to turn at the same rate. The steering only returns if you actually move the wheel...very,very scary!
Steering wheel return, as far as I know, is created by the castor angle and this in turn is created by the 8mm spacer in front of the top ball joint. This has not been touched since it was in manual rack mode.
Any advice will be most appreciated.
most Pas runs more caster than manual i'd look there to see if you can add caster
new UJ can be a bit stiff, perhaps you have one that is but that would tend to feel notchy in operation too
there is normally a spring loaded tensioner in the pinion, which keeps the rack and pinion pressed together. if that isn't properly lubricated, or is too tight, then it will hold the steering rack in position, and need additional effort to return to centre as you have described.
new UJ can be a bit stiff, perhaps you have one that is but that would tend to feel notchy in operation too
there is normally a spring loaded tensioner in the pinion, which keeps the rack and pinion pressed together. if that isn't properly lubricated, or is too tight, then it will hold the steering rack in position, and need additional effort to return to centre as you have described.
Yes, the toe settings have now been checked twice and are as TVR spec.
Top and bottom balljoints are good as are the inner and outer track rod joints.
Don't see how I can increase the castor angle as the 8mm spacer is the maximum that space allows for...shouldn't have to anyway as all other Griffs and Chims have the same setting.
Thanks for the input.
Top and bottom balljoints are good as are the inner and outer track rod joints.
Don't see how I can increase the castor angle as the 8mm spacer is the maximum that space allows for...shouldn't have to anyway as all other Griffs and Chims have the same setting.
Thanks for the input.
I read this with interest as I had a similar problem on a trip years ago. The racing green mech with us had a look and couldn't spot an obvious problem but greased all areas and it didn't reoccur. On return I replaced the ball joints with new and ensured they don't get to dry especially in the heat and haven't had a problem since. It may not be related but jus a thought and worth a check.
Hedgehopper said:
Thanks MCOSH, pretty sure ball-joints are all OK and that rack is greased.
Can anyone tell me what the torsion bar that is inside the pinion does?
the torsion bar is the bit that twists within the pinion, and in twisting opens the fluid pathway so that the fluid can push on either side of the plate in the rack housing. It is the "valve" mechanism for the steering fluidCan anyone tell me what the torsion bar that is inside the pinion does?
Thanks Steve, however I can't get my head around this. How does the pinion turn two turns lock to lock but the torsion bar inside it only turn a few degrees to open the ports left or right? Obviously the torsion bar isn't going around wih the pinion or it would continuously be opening and closing the ports.
the torsion bar is inside the pinion. the top part of the pinion and the lower part of the pinion are connected by the torsion bar which twists, opening pathways. it only twists under force from the steering wheel. so under light turning loads it wont twist and you get no pas, under heavier loads it twists and you have pas
so the bar is an integral part of the pinion, you cant see it, and it turns with the pinion flexing just a couple of degrees to open fluid flow.
the spool valves are also part of the pinion mechanism, and rotate with the pinion. basically a bunch of fluid paths enclosed within o ring grooves , these provide equal pressure to either side of the ram, but when the torsion bar is twisted, the flow is biased to one side or the other, creating assistance.
hope that helps
Edited by SteveSPG on Tuesday 30th July 11:44
Edited by SteveSPG on Tuesday 30th July 11:45
Steve, thanks.
So, if you jacked up the car and turned the steering wheel there wouldn't be any load, so the top half of the pinion would drive the torsion bar which would then drive the lower half of the pinion as if it were one assembly? Wheels on the ground and therefore under load the torsion bar would slightly twist and open the fluid ports? Does that sound like I've got it at last?
Hamish, Yes, the steering is smooth wheels on or off the road, with or without the engine running. Have Googled the problem which seems to be not uncommon but no answers unfortunately.
Could any of this cause the rack not to re-centre coming out of a turn?..feels like power assistance is still being applied.
So, if you jacked up the car and turned the steering wheel there wouldn't be any load, so the top half of the pinion would drive the torsion bar which would then drive the lower half of the pinion as if it were one assembly? Wheels on the ground and therefore under load the torsion bar would slightly twist and open the fluid ports? Does that sound like I've got it at last?
Hamish, Yes, the steering is smooth wheels on or off the road, with or without the engine running. Have Googled the problem which seems to be not uncommon but no answers unfortunately.
Could any of this cause the rack not to re-centre coming out of a turn?..feels like power assistance is still being applied.
Edited by Hedgehopper on Tuesday 30th July 17:30
Edited by Hedgehopper on Tuesday 30th July 22:35
Hedgehopper said:
Steve, thanks.
So, if you jacked up the car and turned the steering wheel there wouldn't be any load, so the top half of the pinion would drive the torsion bar which would then drive the lower half of the pinion as if it were one assembly? Wheels on the ground and therefore under load the torsion bar would slightly twist and open the fluid ports? Does that sound like I've got it at last?
Hamish, Yes, the steering is smooth wheels on or off the road, with or without the engine running. Have Googled the problem which seems to be not uncommon but no answers unfortunately.
Could any of this cause the rack not to re-centre coming out of a turn?..feels like power assistance is still being applied.
yes, that is about correct. the amount of assistance is controlled by how much twist is on the torsion bar, and how biased therefore the fluid flow is.So, if you jacked up the car and turned the steering wheel there wouldn't be any load, so the top half of the pinion would drive the torsion bar which would then drive the lower half of the pinion as if it were one assembly? Wheels on the ground and therefore under load the torsion bar would slightly twist and open the fluid ports? Does that sound like I've got it at last?
Hamish, Yes, the steering is smooth wheels on or off the road, with or without the engine running. Have Googled the problem which seems to be not uncommon but no answers unfortunately.
Could any of this cause the rack not to re-centre coming out of a turn?..feels like power assistance is still being applied.
Edited by Hedgehopper on Tuesday 30th July 17:30
Edited by Hedgehopper on Tuesday 30th July 22:35
Someone on the Technical Forum has pointed this out to me....
http://www.racetechdirect.co.uk/tvr-car-part-h0749...
Where does it go? The only spacer I know of is the one in front of the top ball joint. Is this one the very same or are there spacers under the rack mounts?
http://www.racetechdirect.co.uk/tvr-car-part-h0749...
Where does it go? The only spacer I know of is the one in front of the top ball joint. Is this one the very same or are there spacers under the rack mounts?
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