Cosworth brakes

[s3 bob]

I've been offered a set of disks & 4 pot calipers from a 2wd sierra cosworth which 'should' be a straight swap for the standard sierra front brakes currently fitted (so I'm told). Has anyone been down this route or know any reason why it shouldn't work? Is it possible that they might be too powerful and upset the balance of the car? ( at least it might provide an excuse for ending up facing the wrong way on track days )

[GreenV8S]

The term 'straight swap' normally just means the mounting holes are the same - there's a lot more to it than that. Measure up the piston area of the standard brakes, and compare to the total area of the pistons on one side of the new calipers. The new area will probably be the same or greater. Also check whether the disc is a different diameter. If it is, compare the distance from the axle centerline to the center of the old pads, with the distance to the center of the new pads. The new distance will also probably be the same, or greater. Work out the factor by which these two things have increased, multiply the two factors together and this gives you an indication of how much you are changing the overall mechanical leverage of the brakes. If this is increased by more than about 25% you will need to modify the brake balance valve to restore the front-rear brake balance. The simplest way to do this is to remove the original valve (which I believe is an inertial cut-off on that car) with a adjustable balance valve. I used a Tilton valve although there are other types around. BTW you have rear drums don't you? Not much point upgrading the fronts on their own, the rears are hopeless and will cook way before the fronts do. The S4 and all the following models used discs on the backw tih those same front brakes you have, and with those the front brakes are the limiting factor. Hope this helps, Peter Humphries (and a green V8S)

quote:I've been offered a set of disks & 4 pot calipers from a 2wd sierra cosworth which 'should' be a straight swap for the standard sierra front brakes currently fitted (so I'm told). Has anyone been down this route or know any reason why it shouldn't work? Is it possible that they might be too powerful and upset the balance of the car? ( at least it might provide an excuse for ending up facing the wrong way on track days )

Edited by GreenV8S on Friday 30th March 14:31

[s3 bob]

Thanks for the tips Peter. Do you know what the front to rear balance should be? I know it'll change during use as the brakes get hot, but as a starting point I thought I'd ask my local MOT centre to test the brakes and use their figures as an indication. I've seen the previous postings about upgrading the rear to disks, will standard sierra do or is it worth going bigger at the back as well?

[LeeBee]

I am looking at fitting the rear disc set-up in the next few weeks so I will keep you posted.I plan to use a standard rear set-up from a scrap Sierra (only found one out of about 20 with rear discs though!) so I am hoping that it shouldn't upset the balance too much though?? Cheers Lee (S2)

[s3 bob]

Thanks Lee, I'll be interested to hear of any problems you encounter. The cosworth front brake conversion has hit a major setback. Apparently, you need to change the front hub carrier as well. Simple enough on a sierra upgrade, but as the S3 uses a TVR hub carrier its a bit of a no go. The only solution being to have a bracket specially made to enable the new calipers to fit the existing hub carrier. From their website, I think thats how Tower View do their big disk upgrade. I suppose I could just try to source cross drilled or grooved standard sierra disks and fit better pads. Anybody recommend a particular brand? I've heard people speaking highly of the 'EBC greenstuff' range but I don't know if thats just because they're trendy.

quote:I am looking at fitting the rear disc set-up in the next few weeks so I will keep you posted.I plan to use a standard rear set-up from a scrap Sierra (only found one out of about 20 with rear discs though!) so I am hoping that it shouldn't upset the balance too much though?? Cheers Lee (S2)

[LeeBee]

The Tower view set-up use a plate that basically moves the caliper out to clear the disc.I have these and they are pretty good (283mm x drilled discs) but I am looking at replacing the standard calipers for something a bit better in the future.As it stands now if I nail the brakes on, the car easily locks up and slides down the road if you are not careful! (as I found the first few times!!!) Cheers Lee P.S I used to be involved in a race team (MGRV8) that switched to the greenstuff pads and the general opinion was that they were very good, I also know people who use them on their TVR's and the opinion is the same Edited by LeeBee on Monday 2nd April 10:09

[GreenV8S]

TVR hub carrier? You sure? I thought it was a standard Sierra upright, with a TVR-special adapter at the top taking a Saab top balljoint. Never had to change the upright myself so I can't be sure, but I thought it was a standard Ford. The bearings, calipers and so on certainly are. The adapters Tower View use for their big brake upgrade are to space the caliper out to suit bigger discs not to match the centers. BTW I know I already mentioned this but as long as you're running discs at the rear, it is a waste of time modding the fronts. Stick in some hard pads and DOT 5.1 fluid and they will last far longer than the rear drums ever will. I use EBC Greenstuff pads on the front of the V8S and they are very impressive. From cold they feel like ordinary road pads. When they get good and hot the friction level increases by about 50% and it feels like the harder you use them the more positive they are. Quite the opposite from normal 'fast road' pads which start to feel quite spongey when you really push them hard. Down side is disc wear, which is significantly higher with these pads. In order to get the brake balance right, you need to sort out the static balance (i.e. brake balance under gentle braking), the dynamic balance right (as you increase braking, the bias moves to the front to match the weight transfer) and the thermal balance (the dynamic balance mustn't change a lot as the pads heat up and change cooefficient of friction). The static balance is determined by the geometry of the brakes and can only be changed by a balance bar or attenuator. The dynamic balance can be changed by a proportioning valve like the Tilton valve I use. I can tell you the pressure curve I use but it won't mean anything to you since your brakes will run at different line pressure. You can correct the thermal balance by changing pad compounds and/or adding cooling, but the important thing is to make sure the balance doesn't move to the rear as the front brakes start to overheat. Fitting EBC in the front seems to do this nicely on the V8S. Peter Humphries (and a green V8S)

quote:Thanks Lee, I'll be interested to hear of any problems you encounter. The cosworth front brake conversion has hit a major setback. Apparently, you need to change the front hub carrier as well. Simple enough on a sierra upgrade, but as the S3 uses a TVR hub carrier its a bit of a no go. The only solution being to have a bracket specially made to enable the new calipers to fit the existing hub carrier. From their website, I think thats how Tower View do their big disk upgrade. I suppose I could just try to source cross drilled or grooved standard sierra disks and fit better pads. Anybody recommend a particular brand? I've heard people speaking highly of the 'EBC greenstuff' range but I don't know if thats just because they're trendy. [quote]I am looking at fitting the rear disc set-up in the next few weeks so I will keep you posted.I plan to use a standard rear set-up from a scrap Sierra (only found one out of about 20 with rear discs though!) so I am hoping that it shouldn't upset the balance too much though?? Cheers Lee (S2)

Edited by GreenV8S on Monday 2nd April 14:29

[s3 bob]

Don't know for certain, just using info from Steve Heath's book. Haven't had a look yet to see if they've got any identifying stamps or marks on them. Seems like I need to read up on this braking lark, anyone recommend a good book or website?

quote:TVR hub carrier? You sure? I thought it was a standard Sierra upright, with a TVR-special adapter at the top taking a Saab top balljoint. Never had to change the upright myself so I can't be sure, but I thought it was a standard Ford. The bearings, calipers and so on certainly are.