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Its macpherson strut suspension, so to me if you draw an imaginary line from the TCA inner pivot centre to the centre of the top mount spherical, then the steering rack inner ball joints centres should intersect it at the rack neutral position (i.e. straight ahead) to minimise bump steer.
You then need to ensure Track rod ends are the correct height above the lower pivot on the upright to prevent that end causing excessive bumpsteer.
If you adjust camber via inserts on the upright you may need to reshim the heigh of the track rod end, and if you adjust the camber via the top mount you may need to shim the rack to reset the bump steer.
When I was working out rack position on my hotrod I made a jig to mount the rack so I could adjust up and down easily and a bump gauge (using a DTI) to measure the toe changes.
The episode of project binky on youtube where they do the front suspension is worth a watch to see the buggerance they went through to get it sorted.
Brilliant, Thank you. I will re-watch the binky episode….that is a good call and I will do as you say above.
my camber adjustment is small at the top mount but I have a big range via inserts / shims on the upright on the base of the coilover. I will try to do a jig too. Would you have the car wheels off the ground when doing the dti?
You need to be able to move the suspension over its full range unencumbured, so I raised my chassis off the ground so on full droop the wheels were still clear.
You need to be able to move the suspension over its full range unencumbured, so I raised my chassis off the ground so on full droop the wheels were still clear.
If you draw the lines as in the picture you get the virtual reaction point, also know as the instant center. The line through the track rod should also end up in the same instant center to have no bumpsteer.
If you draw the lines as in the picture you get the virtual reaction point, also know as the instant center. The line through the track rod should also end up in the same instant center to have no bumpsteer.
Last edited by Marc sierra; 01-07-2022 at 10:12 AM.
Thank you, I will use that pic and what you have written and get out the suspension books, watch binky and then thoroughly confuse myself!
in that pic, what determines the virtual reaction point as that looks way past the centre line of the car and almost at the other wheel? Is it just extending the top mount angle and the track control arm until they meet?
Last edited by Caddyshack; 01-07-2022 at 04:06 PM.
Thank you, I will use that pic and what you have written and get out the suspension books, watch binky and then thoroughly confuse myself!
in that pic, what determines the virtual reaction point as that looks way past the centre line of the car and almost at the other wheel? Is it just extending the top mount angle and the track control arm until they meet?
The virtual reaction point is the intersection point of the line through the track control arm pivot point (the bolt) and the center of the track control arm ball joint. The visual angle of the control arm can be different depending on the shape of the arm. The other line, from the top mount, is at a 90 degree angle of the line from the top mount pivot point (can also be a ball joint) to the TCA ball joint. The virtual reaction point can be meters away from the car, as it is just a virtual point. It can also be below ground level, which is very bad for the roll center and thus for the handling.
The roll center is the point where the line from the center of the tyre on the ground to the virtual reaction point intersects with the same line from the other side of the car. When the car is stationary that will be on the center line of the car. But when the car is cornering the angles all change and the roll center moves both vertically and horizontally. Keeping the roll center point as closest to its stationary position while the car is cornering gives the most predictable handling. In practice this means the line from the TCA should be pointed slightly upwards to the center of the vehicle, just like in the picture.
The virtual reaction point is the intersection point of the line through the track control arm pivot point (the bolt) and the center of the track control arm ball joint. The visual angle of the control arm can be different depending on the shape of the arm. The other line, from the top mount, is at a 90 degree angle of the line from the top mount pivot point (can also be a ball joint) to the TCA ball joint. The virtual reaction point can be meters away from the car, as it is just a virtual point. It can also be below ground level, which is very bad for the roll center and thus for the handling.
The roll center is the point where the line from the center of the tyre on the ground to the virtual reaction point intersects with the same line from the other side of the car. When the car is stationary that will be on the center line of the car. But when the car is cornering the angles all change and the roll center moves both vertically and horizontally. Keeping the roll center point as closest to its stationary position while the car is cornering gives the most predictable handling. In practice this means the line from the TCA should be pointed slightly upwards to the center of the vehicle, just like in the picture.
Thank you again for taking the time to explain, I am trying to build some adjustability in to the Mount design if I can do it robustly and safely so that a chassis set up company have some choices,
Today I cut out the two passenger side cage base mounts that were comically large and stopped the seat moving and the front one was a danger to the passengers ankles. The original boxes had also not been primed on the inside which is not great.
I made up the L plate and welded that to the cage base, then welded that to the floor. I primed the insides first.
Cleaned up this part of the floor after stitch welding. Then I used a rust killer and sealant from bilt hamber I will sort out the red bit of the shell soon. After the rust treatment cured I sanded it lightly to give a key and take off the high spots. Ready for seam sealer and then another coat of epoxy primer
It's look great! And hats off to your welding skills that you just learned to build this car!
I know it is not perfect but I am getting there and I have had some useful hints and tips from people...even one coded welder has offered to come and do some lessons. By the time it is finished I think my 944 track car will benefit from all the practice as I have got to put a cage in that and finish the transmission tunnel for the 1.8t 20v engine (although my confidence is growing so might change course and do a V8)
Coming on well, must be a good feeling correcting the small mistakes to make it 100%
It is. I found it a little overwhelming at first which is probably why I didnt take it back from MK far earlier as I wasn't sure how to finish it myself and having spent all of that money I then didn't want to do the same with a new company and potentially not see it for another year with another company who could also dick me around....BUT, just like eating an Elephant you just need to do one bite at a time.....
In a lot of cases I find that if you want to have something done correctly, you should actually do it yourself. At least you can then blame yourself if you mess up.
In a lot of cases I find that if you want to have something done correctly, you should actually do it yourself. At least you can then blame yourself if you mess up.
Very true. I also know when I am lying and when I am being honest with myself....you cannot always tell that with other people.
Agree,
Our house build is coming to an end and there’s a few bits I’m not happy with.
I’ve to the conclusion I will sort the issues myself as it’s the only way it will be 100% perfect!
Its just annoying when you pay an ‘expert’ and the end result leaves you thinking you could have done better yourself after a few YouTube vids!
Agree,
Our house build is coming to an end and there’s a few bits I’m not happy with.
I’ve to the conclusion I will sort the issues myself as it’s the only way it will be 100% perfect!
Its just annoying when you pay an ‘expert’ and the end result leaves you thinking you could have done better yourself after a few YouTube vids!
Yes, you have to ask yourself if it is worth the aggro when the trades have been paid and are defending their work etc...I said to a client today that they need to trust their gut when they pick their builder as it is so easy to fall out with them. You almost need to build a contingency to either finish some bits yourself or pay another trade to finish off.
We had some flooring done in a house recently and I had to get a decorator to go round and make good the half arsed attempt the flooring guy had done to finish off. Just things like poor silicone work where the flooring went under the new skirting etc....
A lot of it comes down to the person caring enough...."How long of you worked for your company?" Answer: "since they threatened to fire me"
Good ol’ Stuart Day has sorted me out with the handbrake setup off the WRC fiesta which has never actually turned a wheel. Electronic handbrake …mot friendly on a switch with ecu and brackets to go straight on my hubs.
i am going to take over my hubs and wheels and try the big brakes too.
Good ol’ Stuart Day has sorted me out with the handbrake setup off the WRC fiesta which has never actually turned a wheel. Electronic handbrake …mot friendly on a switch with ecu and brackets to go straight on my hubs.
i am going to take over my hubs and wheels and try the big brakes too.
Another problem ticked off the list.
He has an Aladdins cave lol sorted me out more times than I can remember over the 20 years I’ve had mine.
I think the Grey Fiesta might be trying to escape piece by piece as I have also bought the hydraulic hand brake. Stuart is going to media blast it and then powder coat it for me. Another job jobbed.
edited to clarify….the pic above is The Fiesta, not my car.
Last edited by Caddyshack; 06-07-2022 at 09:05 PM.
Great job mate. That handbrake was made for my car. That’s the tilton cylinder he stole from me.
What’s the gearbox?
Really? It’s a funny old world with what we find out eh? Like the T45 Cradle and my steering rack etc… The pic is of the WRC grey fiesta, I think it had a quaife gearbox that he bought second hand Iirc.
The engine in these pics is too low, this is because I have the engine mounts the wrong way up. When I raise the engine it hits the scuttle panel / rain tray so I needed to make some room. You can see where the cam position sensor and the breather will make contact.
Today I have cut the scuttle right back (these photos were before the plasma cutter came out). I put the windscreen wiper mech in and rotated it so I knew how far back I could cut. I have then folded a 1mm steel box and welded it under the top rail of the rain tray…so, when the bonnet is on and the rain tray is in place you won’t see anything different to a standard 205 but there is now a big box under there to allow the engine stuff to tuck right up under and not hit.
Underside of the car. I always though this bit of the shell (below) is as a poor solution. The “cave” in the tunnel would just trap dirt and rust. Mark added a new floor where the rear foot well would have been but left an empty drum where the old floor was. Of course, he did not fill it with weld though primer so I worried that it would rust from the inside. My plan was to plate over the cave but as I got cutting I realised there was a better solution. The pics show me part way through.
The cave The tunnel cave. Old foot well meets new floor and tunnel. So why not just cut the whole lot out?
30-06-2022, 08:49 PM
