CR Rear suspension mods

[Rebel1]

Mike, do you have a phone contact for Ozwheels, Oz-wheels, whoever?

I can't seem to find the number.

Cheers

[Aussie Mike]

Hi Les,

The guy that owns Ozwheel now is a fellow named Peter. He seems to be producing a good product without the long delays I experienced with Tom.

Here's a link to his web page: Ozwheel Australia: citysearch

Cheers

[Aussie Mike]

Well I got back into the shed today. I decided I'd work on dialing in the rear bump steer and try a few experiments and see what resulted.

I made a new spread sheet that graphs the bump steer in relation to ride height. With the wheel bolted on I was able to work out what the aproximate ride height would be and where that would fit in to the total suspension travel.

I made a few educated guesses when I welded my new shock mounts in as I didn't have a wheel I could use to check the ride height. I wanted ride height to be about in the middle of the shock travel. I have 170mm of wheel travel and ride height came in at 90mm of travel. That's close enough for me. That gives me 80mm of compression before I hit the bump stops.

I figured that when the wheel alignment is done they set your toe adjustment at ride height. So all measurements need be referenced to ride height. In the graph below I've set toe to zero at ride height (90mm) and worked the bump figures back from there.



With the tweeks I've made to the setup there is virtually no bump steer from about 20mm below ride height and up. With the wheel at full droop there is only 5mm of toe out but with a couple of mm of rear toe added at the wheel alignement so I don't think this will be a problem. I don't reckon I'll be able to tune it any better without changing the points where the arms attach to the chassis.

For comparison I've included the graph for the stock Ford arms. I'm very happy with the improvement.

Cheers

[boxhead]

I reckon you should be happy too.

It will be great to see how the car feels now that you have all but eliminated the bump steer issues.

[LoBelly]

that's a pretty startling improvement

have you done both sides? - there's an open practice at winton on good friday...

LoBelly

[Aussie Mike]

Nearly finished the passengers side but I won't be doing the track day. I'm just going to concentrate on getting everything sorted prior to the nationals. I've got a heap of other things I want to do. Front brakes, rear brakes, new fuel tank, roll bar etc.

Cheers

[Aussie Mike]

There was a bit of a discussion on one of the other threads about fitting aftermarket calipers. Part of my mods is upgrading the rear brakes so I thought I'd post a few pics of how to build an adaptor bracket for a radial mount caliper.

Radial mount calipers are much easier to adapt to a custom setup than a lug mount caliper. Start with a block of alloy about the right size (I used a 32mm square section). Mark out a center line on the block as all your measurments will be taken from here.

With the caliper sitting in place on the disc resting on its pads measure the distance from the mounting face on the caliper the center of the bolt holes in the the hub. Mark a line on the block at this distance. Now you can drill the holes in the block for the bolts that attach it to the hub. The spacing needs to be equal either side of the center line. You can measure the distance between the lugs off the old caliper as it's easier to measure on a hole that's not threaded.

Once you have the block bolted to the hub you can double check the pads are centered on the disc face. If they are out to far you can machine the face of the block down to get the pads in the right position.

Next you can get the caliper centered either side of the disc. Measure the width of the slot int the caliper. Mine are 31mm wide and my discs are 26mm thick. This gives me 2.5mm clearance either side of the disc. work out the distance from the inside edge of the caliper to the center of the mounting hole. Add your 2.5mm clearance and to this number and mark that hight on the block relative to the face of the disc. Now you can drill and tap the holes in the block where the caliper will bolt to. Work out the distance between the mounting holes (mine were 154mm) and mark that on your block in relation to the centerline. If the caliper mounting holes and holes to bolt to the backing plate are both referenced to the center line then the caliper should be concentric to the disc.

Here's a pic of my roughed out bracket. The caliper is mounted in the right position and everything is square. I've just got to machine off the excess material and make the bracket look pretty.





Cheers

[LoBelly]

Had to look up what a radial mount was..

..mmmmm.....brake porn

LasciviousBelly

[Aussie Mike]

Here's the finished bracket looking a bit sexier. Some time on the mill has cleaned it up and removed a lot of excess material that didn't really add any extra strength.







Here's the disc and caliper in place. I'll probably slot these discs to match the front. DBA didn't bring out the slotted versions till after I'd bought these







One of the things that can be a problem with fitting aftermarket discs to these rear ends is there isn't much clearance between the disk and the wheel hub. The calipers I ordered are the low profile version so I gained about 1/4" over the regular version. I also spent a fair bit of time working out how deep the boss needed to be on the back of the wheel and where clearance could be gained. Peter at Ozwheel did a great job finding clearance with the numbers I gave him. He couldn't make the wheel boss any deeper because of the pin drive hubs. He machined the backs of the spokes to gain the extra I needed. There's about 3 or 4mm clearance between the caliper and the spoke which is plenty.







Cheers

[Cameron Parsons]

Mike... you're scaring me....

Amazing quality of work you are putting out there.

Cameron

[400TT]

When Mike turns up to club events he will have to bring his own hoist so we can all admire the engineering that has gone on underneath.

Looks fantastic. It's a real inspiration.

[Aussie Mike]

Thanks guys. I have a heap of fun working on this stuff. This is a problem in itself because I should be enjoying driving rather than working on it.

Cheers

[400TT]

Don't worry your certainly not the only one, there are quite a few of us here that enjoy working on the Cobras as much or sometimes more than driving them. I know it's sad in some respects.

[Mando]

Hi Mike,
I know everyones said it before, but the suspension work is stunning. I think we all love seeing all the pictures as you go along, keep it up.

Regards.

[Aussie Mike]

Thanks Mando, Seeing the pics of your narrowed CR rear end were part of the reason I had a go at this.



Your car is going to be stunning when it's all done.

Cheers

[Aussie Mike]

I've been pretty busy with work so haven't had much Cobra time. I finally got back into it over the last couple of weeks and my rear suspension is pretty much done. I've still got to build a rear sway bar setup but thats another project.

Here's the view from the rear



I ran into some trouble with my rear axles and had to have a bit of a rethink. I didn't have enough plunge in my drivers side axle to give me a decent range of camber adjustment. After a trip to the wreckers I found some shorter axles with plunging CVs at both ends. I machined up some new drive flanges to suit and its good as gold now. The new setup also has the same axle left and right so I bought an extra one as a spare in case I break one.



The rear end also went on a bit of a diet. I deleted the cross brace with all the sway bar holes and put in a 1" tube. The sway bar pickup will clamp to this tube. I changed the mount for the track control rod and machined up a simple spacer rather than the clevis i had. I found there was enough clearance in the rod end to mount it this way and the spacers were tidier and easier to make. I also reworked my camber adjusters and machined a heap of material out of them. These were fun to make.



Routing the brake lines in was a bit of a challenge. I already had braided line made for my old calipers and didn't want to have to change them. I had to work out a routing that would keep the line out of harms way and also let it flex up and down with the suspension. After a lot of twristing things round in different positions I found a run that works well.



The only job left to do (apart from refitting the springs) is to finish machining the passengers side caliper bracket. It just starts as a lump of 30mm square by 200mm long aluminium. Now that I've built one side duplicating it isn't hard as I can take all the dimensions off the first one.



Cheers

[boxhead]

Great stuff Mike, It is a pity when work gets in the way of Cobra stuff.

It will be good to see your car with all the mods you have done and still are doing, Hope to see you at the Nationals.

[stephen low]

Mike

I think you need a second car so you can just drive one and keep on re-working the second!!

I know I'm hanging out to get mine back on the road but there's a lot of work between now and that point of time, much of it out of my hands too.

Cheers

Steve

[LoBelly]

Noice

Great post - my favorite kind
You're going to have to bring some mirrors to put under your car at future events.

LoBelly

[Beejay]

Awesome work Mike!!!

It will be great to hear your thoughts on the handling after these mods.

Ben