pdapaul's YellowSpeed Time Attack EKK24 on ITBS


Thanks John. I think need to strip it down to the basics and start again. It was the movement on the rear m/c that was concerning me. If that was incorrect then setting the rest of the system would be virtually impossible.

Can you confirm that when bleeding the rears that the in car bias should be set at fully open so it isn't exerting any pressure on the system?

The full system is as follows
Front .625 wildwood m/c
Rear .75 wildwood m/c

Front brakes Yellowspeed 4 pot BBK
Front pads standard y/speed

Rears standard EK9 calipers
Rear pads ferodo ds2500

Tilton in car bias on rear line

Braided line throughout
 
Not sure if it has to do with anything, but the obp leaflet you put up that's showing "typical asphalt application" says larger MC should be at the front and smaller at the back?
 
Ok so the missing thing is the number and precise diameter of the pistons in your front calipers. With that I can tell you the bias with the valve in the car open, and the pedal central on the bar.
 
I understand the concept of MC diameter and pressure, but using larger MC on a significantly smaller brake caliper would mean the rear MC would have to move a lot less than the front to get even braking performance from both, maybe try swapping the MCs as per the leaflet?
 
oifovo said:
Not sure if it has to do with anything, but the obp leaflet you put up that's showing "typical asphalt application" says larger MC should be at the front and smaller at the back?
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I think it means larger calipers as it talks about piston size. I think :)
 
Oifovo - this is precisely why the bar needs to pivot. The small master piston and large slave area on the front compared to the converse on the rear means the M/C will move notably more. This is not an issue.
 
Paul. You set the angle so that under pressure its HORIZONTAL. As a result it WILL be at an angle in the rest position. This is not desired as such, its just a consequence of the different throw. IT would be nowhere near 45 degrees.
 
JohnTurbo said:
Ok so the missing thing is the number and precise diameter of the pistons in your front calipers. With that I can tell you the bias with the valve in the car open, and the pedal central on the bar.
Click to expand...

Piston size 28mm/28mm
Disk 286 x 22mm
 
JohnTurbo said:
Paul. You set the angle so that under pressure its HORIZONTAL. As a result it WILL be at an angle in the rest position. This is not desired as such, its just a consequence of the different throw. IT would be nowhere near 45 degrees.
Click to expand...
Is this why the components feel like they are under tension. The balance bar thread is difficult to move at rest
 
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pdapaul said:
I think it means larger calipers as it talks about piston size. I think :)
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Sorry I think you're right I didn't read it properly. Still could it be that the difference between front and rear caliper piston size is too large for the balance bar to compensate?
 
I'm struggling to find the diamter of the stock rear piston.

28 is very small. They are 4 pots? If so thats half (51.8%) of the brake force compared to standard fronts.

Paul - its this angle business that is cocking you up, I'm sure of it. Its stopping you bleeding and its running out of movement and locking.
The diagrams are trying to show you that the angle changes through the sweep but they are very much exaggerated.
 
JohnTurbo said:
I'm struggling to find the diamter of the stock rear piston.

28 is very small. They are 4 pots? If so thats half (51.8%) of the brake force compared to standard fronts.

Paul - its this angle business that is cocking you up, I'm sure of it. Its stopping you bleeding and its running out of movement and locking.
The diagrams are trying to show you that the angle changes through the sweep but they are very much exaggerated.
Click to expand...

Ha ha..I'm such a knob..I was reading the rear calipers!!! God I'm so stressed!!!!

They are 36mm/36mm :)
 
JohnTurbo said:
Happy to chat on the phone if that helps you!
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Cheers John, that's really good of you! What I'll do is strip it all out and set everything back central and then rework using your suggestions. If I'm lost from there then a quick chat (or a shoulder to cry on ) would be most appreciated!
 
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86% then. - Definately resolvable with your setup.

The rear slave cylinder is giving 33% more effort to the rear than the front from that portion of the system. On the whole I expect you would have the pedal nearer to the front cyclinder taking these two into account. Just annoying I cant find the rear piston diameter!

....ahh nice work Oifovo then I will be 2 ticks....
 
Ok, so you're 65% front biased with the thing central.

So you will want to be more front biased than that.
 
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