Ultima Geometry
Discussion
Some of you may know I am building a replica of a Ferrari 330/P4 (F355 powered) from a kit originally desigmed by Lee Noble along with the Ultima right up to the Ultima Mk3 (which is essentially the same as an Ultima Sport)
One chap who owns a similar P4 rep has firm views on the suspension design of the Ultima, especially at the rear. if you own a GTR, the rear suspension is different, so you may not suffer these problems.
The problem with the setup is that under varying degrees of bump and droop, the rear toe and camber change. In an ideal world these would remain the same.
Given the unequal length non parallel wishbones and mounting points out of line with the centreline of the car, shared by the P4 and all Ultimas, this chap has gone to some length to address the issue by scrapping the Noble (identical to Ultima Sport and GTR) uprights and fitting rear uprights from a Lola T70 no less to suspension he has engineered himself.
Thats a big of a bold and costly step for me, so I am wondering if there is an easier route to take, as I do intend to use this car on track.
Does anyone have any pictures or drawings of modified rear suspension which may have been tried on a Mk3 or Ultima Sports?
Ultima made many revisions to the chassis between the Sports and the GTR, not just new body attach points as some suggest.
My other option is to graft on the mounting points of the GTR and use GTR rear wishbones (assuminmg this leaves the rear wheels in the same relative position to the bodywork). Does anyone have some measurements for camber and toe at the rear under droop and rebound for a standard GTR chassis?
Any help in this regard much appreciated. I have attached a pic of the std P4 rear suspension as the car was some months ago so you can see the uncanny likeness for yourselves!
One chap who owns a similar P4 rep has firm views on the suspension design of the Ultima, especially at the rear. if you own a GTR, the rear suspension is different, so you may not suffer these problems.
The problem with the setup is that under varying degrees of bump and droop, the rear toe and camber change. In an ideal world these would remain the same.
Given the unequal length non parallel wishbones and mounting points out of line with the centreline of the car, shared by the P4 and all Ultimas, this chap has gone to some length to address the issue by scrapping the Noble (identical to Ultima Sport and GTR) uprights and fitting rear uprights from a Lola T70 no less to suspension he has engineered himself.
Thats a big of a bold and costly step for me, so I am wondering if there is an easier route to take, as I do intend to use this car on track.
Does anyone have any pictures or drawings of modified rear suspension which may have been tried on a Mk3 or Ultima Sports?
Ultima made many revisions to the chassis between the Sports and the GTR, not just new body attach points as some suggest.
My other option is to graft on the mounting points of the GTR and use GTR rear wishbones (assuminmg this leaves the rear wheels in the same relative position to the bodywork). Does anyone have some measurements for camber and toe at the rear under droop and rebound for a standard GTR chassis?
Any help in this regard much appreciated. I have attached a pic of the std P4 rear suspension as the car was some months ago so you can see the uncanny likeness for yourselves!
Edited by Fat Arnie on Sunday 8th November 10:33
There are very few on here that have changed the rear suspension to any degree that you refer to, the Ultima controls the rear camber change by not having a large amount of bump or droop and on the road its not an issue... Im also pretty sure the current cars have parallel wishbones so toe remains constant.
So what has your mate done to the front?
So what has your mate done to the front?
Fat Arnie said:
Ultima made many revisions to the chassis between the Sports and the GTR, not just new body attach points as some suggest.
What revisions are they? My GTR has a Sports chassis. The only modifications the factory made to the chassis before fitting the GTR body were a larger radiator "cage" (this came with front clip mounting points), brackets for the door gas rams and, as you say, mountings for the rear clip. Also the GTR comes with larger side pod "luggage holes". The suspension mountings are exactly the same in Sport and GTR models. Edited by Fat Arnie on Sunday 8th November 10:33
Camber change is ok, as long as it's the right amount. But Toe change on the rear I find hard to beleive as the toe adjuster is parrallel to the lower pickup point on the Upright. The only way you would get any toe change was if the upright was not perfectly vertical and so the toe eye was at a slightly different hieght to the Bottom joint. But even if the upright had a say 3 deg angle in the vertical centre line, the toe change would still only be small.....
Have you measured yours ??
Have you measured yours ??
Richard, I explain the differences in teh setups below.
Andy, some P4 owners have moved the upper wishbone mounts on to the top of the top rail and constructed longer wishbones accordingly. The wishbones may be parallel, but the upright means they are vastly different in length - 185mm top vs 330mm lower overall arc.
As Clive says toe change on the rear seems odd, but will occur unless the axis of the wishbone bushes is parallel to the centreline of the car. I did a rudimentary measurement of mine and it appears the bush pairs on each wishbone are indeed parallel to teh centreline. So I too am not convinced how the toe change on the rear can occur. This chap making the comments however also owns an Benetton B197 which he drives in Historic F1. Seeing as he does a lot of engineerting on his cars, I'm inclined to believe he knows his stuff, but taht would also be like saying Lee Noble didn't have a clue. A tricky one.
His P4 replica is in a different league to any other - its now powered by a 1990's ex F1 engine - detuned to 600bhp and with mechanical valve gear. In order top spolve this problem personally, he has more recently ripped the whole rear end off his car and built a setup using Lola T70 uprights all round.
Moving back on topic, if there is camber change occuring, eliminating travel certainly reduces the issue, and having examined the geometry, it will only crank on the -ve camber as the sideways load increases compression in teh suspension. I might suggest this isn't a particularly bad thing, especially as these cars run on wide (295), high profile (50 series)tyres on 15" rims in order to keep 'the look'.
Mikie, I'd be interested in seeing a pic of your rear suspension. I am led to believe and looking at the photos on the Ultima web site that the Mk3 and the Sport use the same wishbone setup. This is what makes me belive the GTR has vastly different suspension although maybe late Sports had some engineering changes which were carried through to the GTR.
I'll try to calc the camber change on the rear and see what I can come up with.
Andy, some P4 owners have moved the upper wishbone mounts on to the top of the top rail and constructed longer wishbones accordingly. The wishbones may be parallel, but the upright means they are vastly different in length - 185mm top vs 330mm lower overall arc.
As Clive says toe change on the rear seems odd, but will occur unless the axis of the wishbone bushes is parallel to the centreline of the car. I did a rudimentary measurement of mine and it appears the bush pairs on each wishbone are indeed parallel to teh centreline. So I too am not convinced how the toe change on the rear can occur. This chap making the comments however also owns an Benetton B197 which he drives in Historic F1. Seeing as he does a lot of engineerting on his cars, I'm inclined to believe he knows his stuff, but taht would also be like saying Lee Noble didn't have a clue. A tricky one.
His P4 replica is in a different league to any other - its now powered by a 1990's ex F1 engine - detuned to 600bhp and with mechanical valve gear. In order top spolve this problem personally, he has more recently ripped the whole rear end off his car and built a setup using Lola T70 uprights all round.
Moving back on topic, if there is camber change occuring, eliminating travel certainly reduces the issue, and having examined the geometry, it will only crank on the -ve camber as the sideways load increases compression in teh suspension. I might suggest this isn't a particularly bad thing, especially as these cars run on wide (295), high profile (50 series)tyres on 15" rims in order to keep 'the look'.
Mikie, I'd be interested in seeing a pic of your rear suspension. I am led to believe and looking at the photos on the Ultima web site that the Mk3 and the Sport use the same wishbone setup. This is what makes me belive the GTR has vastly different suspension although maybe late Sports had some engineering changes which were carried through to the GTR.
I'll try to calc the camber change on the rear and see what I can come up with.
Hi Arnie,
I might have missed something, I don't think you covered the chassis changes, did you mean suspension changes? I'm interested because my understanding is the same as GTRMikies, as it happens I too have had a GTR Bodied Sport in my workshop and the only difference in the chassis is the radiator cage and the body mounts. I've studied it pretty closely and taken some expert advice on the subject too.
Suspension wise I can only speak reliably of the later Mk4 Sport and GTR and these would appear to be the same, I've seen earlier Ultima front wishbones with different lower ball joints but have no experience of Mk3 or earlier.
Looking at the suspension on your car it seems if you change the wishbones for GTR ones you'll have to move your mounts at least, possibly engine/tranny (you'll probably be doing this already of course to fit the fezza lump), but if you change the mounts will the wheels still centre in the body? Seems like a lot of work for perhaps a minor improvement I wonder if it's really worth it.
Have you spoken to the current manufacturers of the P4 rep? Have they got any modifications in the pipeline or is it early days still?
Cheers, Richard
I might have missed something, I don't think you covered the chassis changes, did you mean suspension changes? I'm interested because my understanding is the same as GTRMikies, as it happens I too have had a GTR Bodied Sport in my workshop and the only difference in the chassis is the radiator cage and the body mounts. I've studied it pretty closely and taken some expert advice on the subject too.
Suspension wise I can only speak reliably of the later Mk4 Sport and GTR and these would appear to be the same, I've seen earlier Ultima front wishbones with different lower ball joints but have no experience of Mk3 or earlier.
Looking at the suspension on your car it seems if you change the wishbones for GTR ones you'll have to move your mounts at least, possibly engine/tranny (you'll probably be doing this already of course to fit the fezza lump), but if you change the mounts will the wheels still centre in the body? Seems like a lot of work for perhaps a minor improvement I wonder if it's really worth it.
Have you spoken to the current manufacturers of the P4 rep? Have they got any modifications in the pipeline or is it early days still?
Cheers, Richard
Hi Richard,
You mentioned the Mk4 Sport. Was the Mk3 an earlier generation Sport? This is what I had been led to believe.
As for chassis mods. the Mk3 has the pickup points for the wishbones as per the P4 chassis. This is confirmed. If I move to GTR suspension then you are correct, the mounts for the wishbones on the chassis would also need to be moved.
Dunlop Systems - the new owners of the Noble/Foreman P4 IP and tooling are slowly piecing together tehir first car, but they do not seem to be making any changes at this point to the final Foreman design so far as I am aware. The P4 project is also not a primary business for Dunlop Systems, more a bit of fun on the side to demonstrate their engineering skills. I don't think they are in it to make a significant profit, they are just enthusiasts like the rest of us.
I have made some rudimentary checks in Autocad and it seems there is a camber change of about 1deg to negative for every 35mm of bump. I'm geting someone more expert to model it in Solidworks to check my figures as I do not think that is excessive.
You mentioned the Mk4 Sport. Was the Mk3 an earlier generation Sport? This is what I had been led to believe.
As for chassis mods. the Mk3 has the pickup points for the wishbones as per the P4 chassis. This is confirmed. If I move to GTR suspension then you are correct, the mounts for the wishbones on the chassis would also need to be moved.
Dunlop Systems - the new owners of the Noble/Foreman P4 IP and tooling are slowly piecing together tehir first car, but they do not seem to be making any changes at this point to the final Foreman design so far as I am aware. The P4 project is also not a primary business for Dunlop Systems, more a bit of fun on the side to demonstrate their engineering skills. I don't think they are in it to make a significant profit, they are just enthusiasts like the rest of us.
I have made some rudimentary checks in Autocad and it seems there is a camber change of about 1deg to negative for every 35mm of bump. I'm geting someone more expert to model it in Solidworks to check my figures as I do not think that is excessive.
Hi Arnie
IMO if you are getting toe change on the rear there is something wrong, as Clive says if the upright is machined to the centre line and the wishbones are all parallel to the centre line of the chasis then there wont be toe change in your type of suspension... also you do need an amount of camber change on the rear.. the large difference between the top and bottom is to accomodate for the short length of them and to give the correct amount of camber through the range.
By adjusting the length of the wishbones you will also be changing the roll centres and thus you would need to look at the front to ensure compatability.... it sounds like your friend has done a lot of engineering in his car... if you copy one element alone it MAY ruin your car.
If I was you I would do some measurements for yourself and actually see were you are, should take half a day, if its the same basic design as the Ultima then set the wheel to ride height bead upright and measure it over 30mm bump and 30mm rebound and see what changes in camber are... It will also show if you have any toe change at all.
IMO if you are getting toe change on the rear there is something wrong, as Clive says if the upright is machined to the centre line and the wishbones are all parallel to the centre line of the chasis then there wont be toe change in your type of suspension... also you do need an amount of camber change on the rear.. the large difference between the top and bottom is to accomodate for the short length of them and to give the correct amount of camber through the range.
By adjusting the length of the wishbones you will also be changing the roll centres and thus you would need to look at the front to ensure compatability.... it sounds like your friend has done a lot of engineering in his car... if you copy one element alone it MAY ruin your car.
If I was you I would do some measurements for yourself and actually see were you are, should take half a day, if its the same basic design as the Ultima then set the wheel to ride height bead upright and measure it over 30mm bump and 30mm rebound and see what changes in camber are... It will also show if you have any toe change at all.
Fat Arnie said:
Hi Richard,
You mentioned the Mk4 Sport. Was the Mk3 an earlier generation Sport? This is what I had been led to believe.
As for chassis mods. the Mk3 has the pickup points for the wishbones as per the P4 chassis. This is confirmed. If I move to GTR suspension then you are correct, the mounts for the wishbones on the chassis would also need to be moved.
Hi Arnie, Yes, I believe the Mk3 is an earlier Sport, The Mk2 was a significantly different body shape. Sorry but I don't know about the differences between the mk3 and 4 chassis. You mentioned the Mk4 Sport. Was the Mk3 an earlier generation Sport? This is what I had been led to believe.
As for chassis mods. the Mk3 has the pickup points for the wishbones as per the P4 chassis. This is confirmed. If I move to GTR suspension then you are correct, the mounts for the wishbones on the chassis would also need to be moved.
Andy's idea about measuring the Geometry sounds like a good idea, I think it's possible to increase toe on bump if the top and bottom mounts aren't on the centreline.
Edited by qwick on Monday 9th November 21:34
s
thotfast said:
thotfast said:GTRMikie said:
Fat Arnie said:
Mikie, I'd be interested in seeing a pic of your rear suspension.
Sorry can't post any pictures of my original suspension because my car now has a new, complete GTR rear end, after this:
Arnie,
I don't know what sort of power you have in mind but wouldn't it feel safer to have a triangulated upper wishbone/A-arm?
Look at the pictures on this thread: http://www.pistonheads.com/gassing/topic.asp?h=0&a... sump tanks
That may show the changes you're wondering about too.
B.
I don't know what sort of power you have in mind but wouldn't it feel safer to have a triangulated upper wishbone/A-arm?
Look at the pictures on this thread: http://www.pistonheads.com/gassing/topic.asp?h=0&a... sump tanks
That may show the changes you're wondering about too.
B.
What is the arrnagement of the shock, lower upright wishbone attatchemnt point, and toe control link?
is it solidly spaced or is there a couple of rod ends in their. one on the shock and one on the tie rod. If there is compliance in the shock bushing will that allow the upright to move?
you also have the Tie rod and the upright in single shear on the bolt
Can you mount the lot on one long bolt that goes through to the rear most connection point on the wishbone.
having the shock where it is will give you a good wheel rate to shock motion ratio. which will allow the damper to move more fluid for less wheel travel and allow for better small bump performance. its just the flex and compliance issues with the way you have it bolted together ATM.
What size is the diameter of the shaft as well ?
Kind regards Ryan
V8Dom said:
did you try to avoid the coke can on the n/s/f wing?????
see it hit you and stayed there
or were you just trying to balance it on the wing while driving and just wasnt watching the road...................... just the can????
Dom
I phoned the wife up to tell her I had probably written off the GTR, and would she come and pick me up, and her first thought was to bring me a can of Coke!see it hit you and stayed there
or were you just trying to balance it on the wing while driving and just wasnt watching the road...................... just the can????
Dom
For those who have not seen previous posts, the factory made a superb job of fixing the car (in fact the panel fit is probably better than it was before the "incident") and it has been back on the road for nearly 18 months.
SLowM, I think there is definateley some mileage in triangulating the top wishbone. It is completely different to the GTR setup. (the lower wishbone looks the same as a GTR item but inverted - horizontal location from the rear of the chassis)
I do only intend to run about 400-450bhp in the car.
Ezakimak, the shock is bushed, only the tie rod is rose jointed (as you would expect. The shock being bushed would not have significnat effect upon the geo. The rest of the suspension is going to get nylatrons in final assy as its a road car also.
Its a good point about putting the tie rod and shock into double shear. Inexpensive and good engineering practice.
The damper shaft is 11mm dia. Shocks are a bit of an unmknown - Protechs - get good reviews in the Elise community, I think these are the factory issue item with the GTR also? Shocks are easy to change once the car is up and running.
Thats good info/ideas from both of you guys, many thanks.
In teh meantime I have calculated that by moving the top wishbone mounts above the chassis (as opposed to outboard of) the camber change can be significnatly reduced. I am tempted to do this and fit longer top wishbones which I could then triangulate. At the moment teh geo is as shown below - scales are mm's (travel - minus values are rebound)and degrees (camber).
Also below is a better pic of the rear sus. Bear in mind the car is upside down in this photo, so the top wishbone is furthest from the camera. (Front of car is on right side of photo) #
I do only intend to run about 400-450bhp in the car.
Ezakimak, the shock is bushed, only the tie rod is rose jointed (as you would expect. The shock being bushed would not have significnat effect upon the geo. The rest of the suspension is going to get nylatrons in final assy as its a road car also.
Its a good point about putting the tie rod and shock into double shear. Inexpensive and good engineering practice.
The damper shaft is 11mm dia. Shocks are a bit of an unmknown - Protechs - get good reviews in the Elise community, I think these are the factory issue item with the GTR also? Shocks are easy to change once the car is up and running.
Thats good info/ideas from both of you guys, many thanks.
In teh meantime I have calculated that by moving the top wishbone mounts above the chassis (as opposed to outboard of) the camber change can be significnatly reduced. I am tempted to do this and fit longer top wishbones which I could then triangulate. At the moment teh geo is as shown below - scales are mm's (travel - minus values are rebound)and degrees (camber).
Also below is a better pic of the rear sus. Bear in mind the car is upside down in this photo, so the top wishbone is furthest from the camera. (Front of car is on right side of photo) #
Hi Arnie,
I don;t think Protech's are standard factory now, I can't remember what is but they used to be in early GTR and in later Sport days for sure. I have a set and the service & quality is pretty good. Make sure you spec the thicker diameter rods than the standard shocks, Rod at Protech will understand, in fact, if he knows what it's for he'll insist!
Regards, Richard
I don;t think Protech's are standard factory now, I can't remember what is but they used to be in early GTR and in later Sport days for sure. I have a set and the service & quality is pretty good. Make sure you spec the thicker diameter rods than the standard shocks, Rod at Protech will understand, in fact, if he knows what it's for he'll insist!
Regards, Richard
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