Power Steering - I think it can be done
Discussion
Well I have just bought a Chimeara power steering rack (and it was cheap - even better), and guess what - I'm pretty sure it will fit on my V8S (well it fits on the mountings).
There are a few minor considerations to overcome but I reckon it will work.
I've done a rough comparison and the rack geometry looks identical (I know the input shaft is longer) which I have thought for a while that it would be - I just reckoned noone had tried comparing it with an S rack.
I really hope this will work as if I'm no longer allowed to drive I'll keep the car and Mrs Barkychoc can drive it. She likes the car but hates the heavy steering.
Here's a pic, non assisted rack at top, chimeara PAS rack at bottom (I didn't get the shafts lined up very well).
Close up of input shafts
There are a few minor considerations to overcome but I reckon it will work.
I've done a rough comparison and the rack geometry looks identical (I know the input shaft is longer) which I have thought for a while that it would be - I just reckoned noone had tried comparing it with an S rack.
I really hope this will work as if I'm no longer allowed to drive I'll keep the car and Mrs Barkychoc can drive it. She likes the car but hates the heavy steering.
Here's a pic, non assisted rack at top, chimeara PAS rack at bottom (I didn't get the shafts lined up very well).
Close up of input shafts
Edited by Barkychoc on Thursday 8th May 17:37
I've looked into the pump and it is looking very much like I can mount an engine driven pump on the engine on the passenger side - I think there's room - I've already spoken to a local Range Rover breakers and they will do me one with all brackets and reservoir for £45.
Then I just need to get the hoses made up (and fair play to the range rover breakers although I doubt they would fit they recommended I used new hoses anyway), and I then need to change the lower steering UJ for a griffith Power steering one to allow for the longer input shaft on the power steering rack, and I don't think its then far off.
Similarly on the V6 I think all you'd need to do is get a granada PAS pump & mountings and get hoses made up.
Getting hold of the rack is the hard bit
It all sounds too easy.
Chris
Then I just need to get the hoses made up (and fair play to the range rover breakers although I doubt they would fit they recommended I used new hoses anyway), and I then need to change the lower steering UJ for a griffith Power steering one to allow for the longer input shaft on the power steering rack, and I don't think its then far off.
Similarly on the V6 I think all you'd need to do is get a granada PAS pump & mountings and get hoses made up.
Getting hold of the rack is the hard bit
It all sounds too easy.
Chris
Edited by Barkychoc on Friday 9th May 11:30
OK been having another look at this.
The chim rack doesn't sit flat on the mountings as the rack body is fatter than the manual rack.
I thought that there would be some bushes or something that I needed to mount the rack on, but it seems I need to modify my rack mountings slightly (with a grinder!!).
Here's my mounting - its the 2 bolts above the skateboard.
and here's pics I found of a griff chassis, thanks to http://thegriffithpages.com
Can you see the mount is cut away & curves inwards between the bolt holes - I need to make my mountings the same.
I reckon the S mounts are well over engineered - that metal is very thick so even if I grind it away like the griff I am convinced it will still be strong enough (and thats how it is on the Griff anyway).
Interestingly the Griff / Chim rack bolts straight onto the chassis - it isn't mounted in rubber mountings like the S.
This does mean its holding up my chassis refurb as I want to make sure its all done before it goes to be blasted & coated, but I reckon to determine if this is feasible it will be well worth it.
The chim rack doesn't sit flat on the mountings as the rack body is fatter than the manual rack.
I thought that there would be some bushes or something that I needed to mount the rack on, but it seems I need to modify my rack mountings slightly (with a grinder!!).
Here's my mounting - its the 2 bolts above the skateboard.
and here's pics I found of a griff chassis, thanks to http://thegriffithpages.com
Can you see the mount is cut away & curves inwards between the bolt holes - I need to make my mountings the same.
I reckon the S mounts are well over engineered - that metal is very thick so even if I grind it away like the griff I am convinced it will still be strong enough (and thats how it is on the Griff anyway).
Interestingly the Griff / Chim rack bolts straight onto the chassis - it isn't mounted in rubber mountings like the S.
This does mean its holding up my chassis refurb as I want to make sure its all done before it goes to be blasted & coated, but I reckon to determine if this is feasible it will be well worth it.
Edited by Barkychoc on Friday 9th May 13:42
on the subject of PAS, as the S uses a vauxhall chevette derived rack it may be of interest that the Isuzu Piazza uses the front suspension and steering also derived from the GM cars (chuv-it and manta) and has a PAS rack on some if not all models. may be a straight swap? it turned up during trawling the web for scimitar SS1 stuff which uses chevette derived front susp/steering also. im guessing isuzu bought the rights to the discontinued designs and tweeked them?
Barkychoc said:
The chim rack doesn't sit flat on the mountings as the rack body is fatter than the manual rack.
I thought that there would be some bushes or something that I needed to mount the rack on, but it seems I need to modify my rack mountings slightly (with a grinder!!).
Can you see the mount is cut away & curves inwards between the bolt holes - I need to make my mountings the same.
I reckon the S mounts are well over engineered - that metal is very thick so even if I grind it away like the griff I am convinced it will still be strong enough (and thats how it is on the Griff anyway).
Interestingly the Griff / Chim rack bolts straight onto the chassis - it isn't mounted in rubber mountings like the S.
The important part is to keep the steering rack in the same place as the existing rack: moving it forward/backward or upward/downward in relation to the chassis will change front wheel geometry when steering. It won't make a huge difference, but you'll find it hard to improve on the original design. Maybe it is better to make some spacers to put between the bracket and the rack.I thought that there would be some bushes or something that I needed to mount the rack on, but it seems I need to modify my rack mountings slightly (with a grinder!!).
Can you see the mount is cut away & curves inwards between the bolt holes - I need to make my mountings the same.
I reckon the S mounts are well over engineered - that metal is very thick so even if I grind it away like the griff I am convinced it will still be strong enough (and thats how it is on the Griff anyway).
Interestingly the Griff / Chim rack bolts straight onto the chassis - it isn't mounted in rubber mountings like the S.
I think the lack of rubber mountings is a good thing, as it will make steering more precise: with the rubber mountings, the first degrees of steering wheel angle just result in the rack housing moving in its rubber. The rubber does reduce kickback from the front wheels however.
By altering the mountings the centre line of the rack shaft will be exactly the same as the original non PAS rack.
If I use spacers it will be slightly forward / up in respect of the original position.
The non PAS rack mounts flush onto the chassis - but the PAS rack is fatter and bulges behind the profile of the brackets - which is why the Griff chassis has different rack mounts on the chassis to allow for the bigger rack.
Interesting comment above regarding Isuzu racks - I'll keep an eye out if one turns up cheap enough on fleabay I may just be tempted to see if it fits!
Chris
If I use spacers it will be slightly forward / up in respect of the original position.
The non PAS rack mounts flush onto the chassis - but the PAS rack is fatter and bulges behind the profile of the brackets - which is why the Griff chassis has different rack mounts on the chassis to allow for the bigger rack.
Interesting comment above regarding Isuzu racks - I'll keep an eye out if one turns up cheap enough on fleabay I may just be tempted to see if it fits!
Chris
Edited by Barkychoc on Friday 9th May 19:46
Barkychoc said:
By altering the mountings the centre line of the rack shaft will be exactly the same as the original non PAS rack.
If I use spacers it will be slightly forward / up in respect of the original position.
The non PAS rack mounts flush onto the chassis - but the PAS rack is fatter and bulges behind the profile of the brackets - which is why the Griff chassis has different rack mounts on the chassis to allow for the bigger rack.
I stand corrected If I use spacers it will be slightly forward / up in respect of the original position.
The non PAS rack mounts flush onto the chassis - but the PAS rack is fatter and bulges behind the profile of the brackets - which is why the Griff chassis has different rack mounts on the chassis to allow for the bigger rack.
. The brackets certainly seem beefy enough. It will be interesting to see how you get on with this project!Edited by Sweet Thunder on Friday 9th May 22:18
Sweet Thunder said:
The important part is to keep the steering rack in the same place as the existing rack: moving it forward/backward or upward/downward in relation to the chassis will change front wheel geometry when steering.
Are you sure? I would have thought it would have only changed the steering ratio slightly between Road Wheel and Steering Wheel.Edited by clarenceboddiger on Saturday 10th May 06:54
Chris
just had a quick dig out in the garage and I have the following item from an SD1,(I used the engine years ago for my MG and will hopefully get it into an S2 one day)If its of use Its a freebie for your project. As you can see it has all the brackets but I'm sure the front cover is different on the 4.0, however the mountngs may be adaptable.
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just had a quick dig out in the garage and I have the following item from an SD1,(I used the engine years ago for my MG and will hopefully get it into an S2 one day)If its of use Its a freebie for your project. As you can see it has all the brackets but I'm sure the front cover is different on the 4.0, however the mountngs may be adaptable.
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[/pic]Look this Chimeara chassis is on ebay (and I think Griff / Chim chassis is identical anyway) - it must have had manual steering - same brackets as the S.
So I reckon Griff / Chim have different style brackets depending on whether they have PAS or not.
and just found this pic - with PAS
So I reckon Griff / Chim have different style brackets depending on whether they have PAS or not.
and just found this pic - with PAS
Edited by Barkychoc on Saturday 10th May 12:52
clarenceboddiger said:
Sweet Thunder said:
The important part is to keep the steering rack in the same place as the existing rack: moving it forward/backward or upward/downward in relation to the chassis will change front wheel geometry when steering.
Are you sure? I would have thought it would have only changed the steering ratio slightly between Road Wheel and Steering Wheel.Edited by clarenceboddiger on Saturday 10th May 06:54
Sweet Thunder said:
For what I've been told, the offset of the steering rack influences the amount of ackermann.
OK I admit I didn't know what the hell this meant - so here's a linkhttp://en.wikipedia.org/wiki/Ackermann_steering_ge...
The only way I'm prepared to do this is with identical steering geometry to the manual rack - I will not compromise on that - if the chim rack won't do this the car will stay as manual steering.
I am not getting bogged down with steering theory - its either the same or it isn't!
Chris
Edited by Barkychoc on Wednesday 14th May 21:37
OK here's a comparison of the V8S and Chim racks with the gaiters off.
The geometry is not identical.
The rack portion is shorter in the chim rack housing than the V8S rack, by about 20mm each end (maybe a bit less).
Here's a pic - the black line is lined up with the inner track rod ball joint of the V8S rack at the top of the picture - you can see it does not line up with the chim rack inner ball joint.
Here's a shot further out - but because of the camera angle it is not all that clear.
So what do I do?
Sell the Chim rack or fit it anyway and see how it pans out?
Are there any suspension experts out there that can tell me how severe the bump steer wil be?
Also note that the V8S rack lock to lock is 135mm, Chim is approx 126 mm so no issues there.
Chim rack is approx 2.1 turns lock to lock - V8S is 3 turns.
HOWEVER when on the car the V8S rack was only 2.4 turns - so it must rely on the hubs to limit the steering travel.
Not sure if this will give issues with PAS rack and may mean it is less than 2.1 turns lock to lock as it is off the car which will make the steering pretty quick.
Chris
The geometry is not identical.
The rack portion is shorter in the chim rack housing than the V8S rack, by about 20mm each end (maybe a bit less).
Here's a pic - the black line is lined up with the inner track rod ball joint of the V8S rack at the top of the picture - you can see it does not line up with the chim rack inner ball joint.
Here's a shot further out - but because of the camera angle it is not all that clear.
So what do I do?
Sell the Chim rack or fit it anyway and see how it pans out?
Are there any suspension experts out there that can tell me how severe the bump steer wil be?
Also note that the V8S rack lock to lock is 135mm, Chim is approx 126 mm so no issues there.
Chim rack is approx 2.1 turns lock to lock - V8S is 3 turns.
HOWEVER when on the car the V8S rack was only 2.4 turns - so it must rely on the hubs to limit the steering travel.
Not sure if this will give issues with PAS rack and may mean it is less than 2.1 turns lock to lock as it is off the car which will make the steering pretty quick.
Chris
Edited by Barkychoc on Tuesday 20th May 18:02
Sorry Chris, I can work out that it makes a difference in theory, but I'can't tell you what difference this modification will make in practice. Maybe it won't even be noticeable, but you'll only know by trial and error. Maybe someone on the major mods forum has a bit more experience with this?
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