Sierra Cosworth 4 pot callipers

[brightside]

I know this has been posted before but has anyone actually achieved the conversion to put 4 pot cosworth callipers on a Chim/Griff (1992). I have mounted the cosworth 2 wheel drive hub carriers needed to do the conversion / 283mm discs and 4 pot callipers but now have the problem of the lower ball joint hitting the 15" wheel rim. It catches by about 4mm so I may be able to modify the lower arm but thought I would ask if anyone has done this first. I don't really wont to put bigger wheels as I am trying to keep it original. Many thanks in advance.

[antonyj]

Ian , what you doing in the Chimp zoo????

Get back in the griff section quick before they see you.


Why does the ball joint catch the rim?
I cant see why changing the calipers would cause this....

I run 283 discs on the standard sierra uprights.

>> Edited by antonyj on Sunday 28th May 17:29

[brightside]

Hi Anthony, I have posted on the Chim forum as there are more conversion's done here as more chims made and the running gear is the same. I searched the Griff forum but very few results compared to here. To fit 4 pot Cosworth callipers you need to use a 2wd Cosworth hub carrier which are actually longer so this puts the bottom ball joint lower hence the reason for posting. I hope it works out as the idea came from these forum's, Someone has done it? and I have now committed to doing the job, if it doesn't work out I will need two new std sierra hub carriers. The old one's were so badly seized to the bottom ball joints that they had to be cut off. Nightmare.

[antonyj]

So the 2wd calipers dont fit on the standard sierra uprights?
I didnt realise that !

[brightside]

Yeah,the 4 pot callipers need the rwd cosworth front hubs to fit. As you can see it's not straight forward. It's the bolts at the bottom of the lower ball joint that catch the wheel as the hub is longer.

[GreenV8S]

If you're changing the position of the lower balljoint, what effect does this have on the suspension geometry and handling?

[brightside]

I was hopeing that the ride height would be addressed by the shock absorber, then all other suspension geometry would be able to be set up by topcat racing when the car goes there to have a full geometry set up, camber etc on the top ball joint. Any advice is appreciated. If anyone knows that this shouldn't be done please speak out now.

[GreenV8S]

You can correct the ride height and the static geometry settings, but moving the outer ends of the wishbones is going to affect how the geometry changes when the car pitches and rolls.

[brightside]

Peter, the hubs are about 1.5" different in overall height, hence it will change the distance between the top and bottom arm, will this create a big problem as you say. I still have time to stop and get an original pair of sierra hubs and put back to original.

[GreenV8S]

brightside said:

Peter, the hubs are about 1.5" different in overall height, hence it will change the distance between the top and bottom arm, will this create a big problem

I don't know, gut feeling is probably not enough to matter, but it's something I'd want to check out before I changed it.

[trackcar]

It would be nice if most of that extra length was from the bottom ball joint to the hub centreline, will neatly raise the front roll centre (if you were planning on lowering the car) and correct some of the bump steer in the front of the chim/griff in one go

[brightside]

I'm trying to keep up with you and think I understand, the additional length is from the centre of the hub to the bottom ball joint fixing, it all fits together no problem and bolts up ok inc arb rose joints (Steve Heath), but as the ball joint is now lower and the bottom arm bolt fixings for the ball joint catch the inner wheel (just). I am thinking maybe to put the bolts in from the bottom with nyloc nuts on top, may also need to take about 3mm off the bottom of the bottom wishbone, where fixed. Do you see any problem doing this.

[pupp]

Is it just as simple as machining the wheel where it interferes?

[brightside]

Hi Pupp, not sure I want to do that, but may consider. As I said at the top of the forum I am still trying to find anyone who has actually done this conversion and the downfall of doing it. I would prefer to keep the wishbones at there original angle but still don't know if I complete the conversion if this is going to create me further problems.
Many thanks for posting.

[shpub]

pupp said:

Is it just as simple as machining the wheel where it interferes?

And weakening its strength at the same time. Not a good idea. I know it's been done but it is a very risky solution.

To be honest this conversion usually involves the manufacture of different mounting brackets so that the original upright is used. If the upright is changed then all the geometry goes out of the window and you may not be able to get it set up correctly.

There is also the insurance issue: What mods have you done? machine 3 mm off the wishbones and wheels is not likley to go down too well.

>> Edited by shpub on Monday 29th May 10:55

[antonyj]

shpub said:

pupp said: Is it just as simple as machining the wheel where it interferes? And weakening its strength at the same time. Not a good idea. I know it's been done but it is a very risky solution. To be honest this conversion usually involves the manufacture of different mounting brackets so that the original upright is used. If the upright is changed then all the geometry goes out of the window and you may not be able to get it set up correctly.

I would definately go with SHPUB, I run 283's as stated , but I have used Granada Cosworth calipers.(essentially the same as the TVR 500's caliper) this fitted without any bracket.
If you have the uprights and discs and calipers on the bench it shouldnt be to difficult to see what bracket is required.

[brightside]

Ok fair point, as you can see the whole idea of asking these question's is to see if anyone has done this conversion. Nothing has been machined or fabricated as yet. I will however need to get a pair of std sierra hub carriers to put it all back together which I need urgently, which sierra are they off or has anyone got any.

[that daddy]

i do know the 4 pot calliper off the original 2wd cosworth with the whale tale,dont fit with the disc from same car 283mm the mounting lugs are out by about 7mm you can not machine this off the lugs as there is not enough meat there to do this,i know because i found out the hard way,brackets are no answer either.kept disc 283mm but settled on big single piston callipers much better power,if it makes you feel better those 4 pots are HEAVY......AND WERE NOT THAT GOOD ANYWAYS.hope this helps out some way.

>> Edited by that daddy on Monday 29th May 11:28

[jwoffshore]

Mr "Brightside",

I looked into a similar conversion a while ago and concluded it was a non-starter. The hubs I was looking at were late model 2WD Sapphire Cos ones with 4 pots. They were incompatible with the TVR setup in the following ways:
1. Bottom balljoint fixing was a parallel pin with a split boss/pinch bolt fixing whereas TVR was a tapered pin into a solid boss.
2. Top arm of the hub, (where the McPherson strut would fix on the Sierra, or the top balljoint adapter on the TVR) was higher up and further inboard relative to the wheel centre. I guess this was done on the Cossie to create more clearance for wider wheels. However, this will mean that fitted to the TVR you would have a lot of positive camber, unless you modified/replaced the top wishbone to suit.

As regards the bottom ball joint location, this seems much the same on the Cos Sapphire hub as the TVR one, just the pin fixing was incompatible. What Cossie did your hubs come off - was it an old 3 door Sierra hatch? Sorry, I don't know if these are the same as the later Sapphire ones or not.

To get replacement hubs same as your original TVR ones, you need ones off a 2WD NONE Cossie Sierra. You need to check that the bottom ball joint fixing is a tapered pin. If you get a hub from an ABS equipped car, I don't think that matters too much. You would have to blank off the ABS sensor hole. The ABS sensor lug is left unmachined on the TVR hubs - it is the bit of a lump at the front of the hub, above the steering arm.

I hope this is some help to you. If you are determined to fit the Cos 4 Pots, I think one of the guys at Steve Gugliemi's place managed it by machining back the lugs on the caliper (seemed a bit dodgy to me, but apparently it works). Myself, I bought a Wilwood BK5K 4 pot kit which bolts straight on to the TVR hubs with a 283mm Cossie disc.

Feel free to PM me if you want more info.

Regards, Jonathan W

>> Edited by jwoffshore on Monday 29th May 16:35

[that daddy]

machining back those lugs to fit standard chim hubs is a no go,there just isnt enough left,that would be highly dangerous,to much stress for whats left no no no....no.as JWoffsure said it can be done but dont i agree.