300mm brake upgrade for SR3

[radicalracer]

While visting the factory several months ago I noticed that most of the SR3s I saw had upgraded front and rear brakes. Most of the cars ordered in the US only have the 280mm upgraded fronts, with the Focus brakes (or whatever they are) on the rear.

I figured you guys know what you are doing in Europe, so I was thinking of upgrading my front brakes to 300mm (same as the SR8) and move the 280mm brakes I have on the front to the rear. Thus I would have 300mm fronts and 280mm rears.

Any thoughts on this configuration? Pro/Cons? Would the braking be substantially better than having 280mm in the front and the small brakes in the rear?

Thanks,

G

[panas]

You can't move the front to the rear as the pistons are two different sizes in each caliper so if you move the front to the rear your leading and trailing piston will be the wrong way round that said if you remove the blead nipples and the connecting pipe then turn them upside down fit the bleed nipples where the pipe was and vise versa then this will work but the pipes are locktighted in so you may wreck them trying

[radicalracer]

panas said:

You can't move the front to the rear as the pistons are two different sizes in each caliper so if you move the front to the rear your leading and trailing piston will be the wrong way round that said if you remove the blead nipples and the connecting pipe then turn them upside down fit the bleed nipples where the pipe was and vise versa then this will work but the pipes are locktighted in so you may wreck them trying

So for almost 9 months I am wondering why my rear brakes had no stopping power. I kept complaining to the local mechanics until finally someone checked the brakes. Low and behold - the pistons were the wrong way round. Ugh... painful. I thought they would have sorted this out when they swapped the front to the backs. I owe you one for this info!

G

[BertBert]

panas said:

if you move the front to the rear your leading and trailing piston will be the wrong way round

Being a bit of a thickie, I can't imagine how this is. Have I got the understanding of leading and trailing wrong? I thought it was by reference to the rotation of the wheel.
Bert

[radicalracer]

BertBert said:

Being a bit of a thickie, I can't imagine how this is. Have I got the understanding of leading and trailing wrong? I thought it was by reference to the rotation of the wheel.
Bert

I am no expert in this area, but the pistons have to be in the right positions because I believe the top part of the pad wears faster than the bottom. So they put a smaller piston on top to equal out the pressure. If you don't swap the fittings, you will by default put the calipers in with the pision in the wrong position. Again, this is my layman explanation. My foot knew there was a problem, I just didn't know what it was.

[BertBert]

radicalracer said:

I am no expert in this area, but the pistons have to be in the right positions because I believe the top part of the pad wears faster than the bottom. So they put a smaller piston on top to equal out the pressure. If you don't swap the fittings, you will by default put the calipers in with the pision in the wrong position. Again, this is my layman explanation. My foot knew there was a problem, I just didn't know what it was.

Can you define "top" and how it changes by moving the calipers from front to rear? I still don't get it! Cheers.

[radicalracer]

BertBert said:

Can you define "top" and how it changes by moving the calipers from front to rear? I still don't get it! Cheers.

When you move the calipers from front to back, if you don't change the fittings the only way they will go on the car is upside down. Meaning the small piston will be at the bottom rather than the top. With the calipers fitted, the small piston should be upper most on the rear, basically so the small piston acts first.

If the small piston is on the bottom you will effectively only get half the braking power. Again, I am giving you the drivers version, not necessarily the mechanics version of how this works.

Hope that helps.

G

[BertBert]

but rotating the calipers in the plane of the brake disk won't change which piston comes first. To do that you have to turn the calipers 180 degrees around the vertical axis of the upright (if that makes sense?).

[radicalracer]

BertBert said:

but rotating the calipers in the plane of the brake disk won't change which piston comes first. To do that you have to turn the calipers 180 degrees around the vertical axis of the upright (if that makes sense?).

I am stretched beyond my area of expertise at this point. Maybe someone else can jump in. As I said, if they are not right you get half the braking power which was suboptimal to say the least.

G

[BertBert]

radicalracer said:

you get half the braking power which was suboptimal to say the least.
G

now that I do understand

[dunc_sx]

Yeah pretty sure they go by rotation and not which is physically on the top, my calipers have a rotational arrow on them for example much like on a road tyre

If you were swapping left to right then they'd be wrong but not directly front to back (keeping on the same side). I could be wrong

Dunc.

Edit: that's not to say they are on the correct way on your car!

[BertBert]

right, got it. They are on the opposite sides of the hub from front to back. So to move from front to back, you turn them through 180 degrees. No problem there except that they are now upside down and cannot be bled as they have the chamber connecting pipe at the top.

So the answer is to swap corners to get the connecting pipe at the bottom. So RF goes to LR, and LF to RR. Now they have been rotated through 180 degrees about the vertical axis of the upright and are on the wrong way around. How slow am I?

Bert

[radicalracer]

BertBert said:

How slow am I?

Bert

Hopefully not slow on the track! However, keep in mind that you have to move the nipples around to make sure you get the small piston in the right location.

Edited by radicalracer on Wednesday 4th April 00:03

[splitpin]

Picture paints a 1000 words?

Hi-Spec Non Floater R/H Front



Hi-Spec Non Floater R/H Rear



Note difference in lugs.

Edited by splitpin on Wednesday 4th April 00:34

[radicalracer]

splitpin said:

Picture paints a 1000 words?



Only problem I can see is swapping link pipe and bleed nipples if somebody has 'permanent loctited' them in - if they have, I doubt it was Hi-Spec that did it - both are taper-type brass threads from memory and a bit of ptfe tape should be more than sufficient.

Edited by splitpin on Wednesday 4th April 00:28

You nailed it! My guys swapped everything around and it seems fine.

[splitpin]

radicalracer said:

You nailed it! My guys swapped everything around and it seems fine.

No issues with those lugs?

[splitpin]

Got me thinking about how much easier to swop about those (admitedly less effective) Wilwoods used to be, like on the Prosport; banjo connection onto side, internal fluid connections, two same size pistons, bleed nipples top and bottom!

[radicalracer]

splitpin said:

No issues with those lugs?

I have not tried the car yet, but the guys who did it said it worked. I can give you a better update when I get into the car. I hope that was the problem and we are finished, but I am not sure yet.

G

Edited by radicalracer on Wednesday 4th April 06:03

[dunc_sx]

My Wilwoods do have unequal size pistons but yes they have bleed nipples top and bottom so you can do what you like with them, better for spares

Dunc.

[splitpin]

You got me thinking so I checked - so much for the memory! - yep, the fronts did have unequal size pistons (smaller one leading) and a rotation arrow on the outer scripted face, so they are 'one side use only'.

Incidentally if anyone wants the unused outer half caliper (front right hand side) let me know: for 'safekeeping', it's bolted to an old inner half which I replaced as the bleed nipples of that had sheared due to a previous owner being over-zealous. Why did I just replace the inner half? Well the outer half has to be milled slightly (as Radical did) to clear the C/L hubs and I was pushed to do that at the time, I 'cheated'. Wilwood Part No is CU-120-5321. 'Dynalite Billet Pro' from memory?