Bias Bar again!

[3Dee]

Might seem obvious to some...unfortunately.. not for me!

I have left this for the last-ish job - does someone have a diag or picture of the correct adjustment (21mm - yesh right! )BUT where-to-where the measurements are taken. I can't find anything with clarity on here!

there used to be a picture with adjustments show, but that site is no longer there!

cheers

[Steve_D]

On your build manual disc (root folder)there should be a pdf 'brake bias adjustment'.
If you can't find it ping me a mail and I will attach it for you.

Steve

[UltimaCH]

This topic arrives at the perfect moment as I was doing this operation today. I have cleared all the powder coating inside the pedal bushing using 600 grit paper and the bias bar slides in and out smoothly.
I have printed the instruction sheet and it seems perfectly clear how to adjust the front bias (21mm) from the end of the bar. However where do you place the bias for the rear brakes? In the middle, towards the end closer to the pedal or farthest away? Seems like some instruction is missing...

[3Dee]

There is no such pdf it appears!

[UltimaCH]

I'll send a copy to you via PM...

[Steve_D]

I've sent the pdf.

If anyone in the UK is doing this then before you install the rod you need to drill a small hole throgh the end of the rod so you can wire lock it for IVA.
I've had to do this retrospectively on a few kitcars now and it is not easy to drill a 1mm hole in steel upside down in a footwell.

Steve

[3Dee]

Shh!

I have heard that the Factory gets them through locknutted but no wire?

[pilbeam_mp62]

Have the rules been watered down recently ? I thought there should be no means of adjustment and the nuts had to be welded to the threads....

[Steve_D]

3Dee said:

Shh!

I have heard that the Factory gets them through locknutted but no wire?

Yes I've tried that but our local station apply the Section9B Note 5 to the letter.

Note 5: Bias bars and other mechanical adjusting devices fitted to twin master cylinders must be rendered inoperable by mechanical means
e.g. lockwiring of components.

Even though a locknut is a 'mechanical means' they won't play.

Steve

[pilbeam_mp62]

Steve_D said:

3Dee said:

Shh!

I have heard that the Factory gets them through locknutted but no wire?

Yes I've tried that but our local station apply the Section9B Note 5 to the letter.

Note 5: Bias bars and other mechanical adjusting devices fitted to twin master cylinders must be rendered inoperable by mechanical means
e.g. lockwiring of components.

Even though a locknut is a 'mechanical means' they won't play.

Steve

Ok - so it appears to have been watered down - because I thought that Note 5 used to say " must have no means of adjustment"......... " will be deemed acceptable if the nuts are fully welded to their threads" ........" Permanently rendering them unadjustable"....

[Steve_D]

pilbeam_mp62 said:

Steve_D said:

3Dee said:

Shh!

I have heard that the Factory gets them through locknutted but no wire?

Yes I've tried that but our local station apply the Section9B Note 5 to the letter.

Note 5: Bias bars and other mechanical adjusting devices fitted to twin master cylinders must be rendered inoperable by mechanical means
e.g. lockwiring of components.

Even though a locknut is a 'mechanical means' they won't play.

Steve

Ok - so it appears to have been watered down - because I thought that Note 5 used to say " must have no means of adjustment"......... " will be deemed acceptable if the nuts are fully welded to their threads" ........" Permanently rendering them unadjustable"....

Yes, a while back it did require welding but this proved to be completly impractical as most builders had no way to get the balance right before the IVA test. At least now you can make adjustments during the test then climb in and wire lock whilst the tester goes away to fill in your pass certificate.

Steve

[UltimaCH]

Steve_D said:

At least now you can make adjustments during the test then climb in and wire lock whilst the tester goes away to fill in your pass certificate.

Steve

.....and remove the wire lock when you get bach home again

[UltimaCH]

UltimaCH said:

This topic arrives at the perfect moment as I was doing this operation today. I have cleared all the powder coating inside the pedal bushing using 600 grit paper and the bias bar slides in and out smoothly.
I have printed the instruction sheet and it seems perfectly clear how to adjust the front bias (21mm) from the end of the bar. However where do you place the bias for the rear brakes? In the middle, towards the end closer to the pedal or farthest away? Seems like that instruction is missing...

Back to my question please.
Any instructions on how to adjust the rear brake rod (distance from the end) or does it not matter??

[Steve_D]

UltimaCH said:

UltimaCH said:

This topic arrives at the perfect moment as I was doing this operation today. I have cleared all the powder coating inside the pedal bushing using 600 grit paper and the bias bar slides in and out smoothly.
I have printed the instruction sheet and it seems perfectly clear how to adjust the front bias (21mm) from the end of the bar. However where do you place the bias for the rear brakes? In the middle, towards the end closer to the pedal or farthest away? Seems like that instruction is missing...

Back to my question please.
Any instructions on how to adjust the rear brake rod (distance from the end) or does it not matter??

You have assembled the pedal, bias bar and clevises for each piston push rod. As per assembly instructions there is 1-2mm end float. (this means you can only slide the bias and clevises side to side by 1-2mm).
As you wind the bar in and out it will move the same amount through each clevis so the 1-2mm will always remain the same.
The ball is the fulcrum point in the tube. Moving it from one side to the other (by turning the bar) will change the leverage the pedal applies to each cylinder. Having set it to 21mm has set the correct bias between front and rear.

Steve

[UltimaCH]

Steve, thanks for the explaination

[JohnMcL]

Don’t worry 3DEE, I’m about to ask an even dumber question on this topic. Why have a bias bar at all?

As I understand it, the purpose of the bar is to reduce braking effort to the rear when conditions (e.g. rain) of reduced grip increase the likelihood of rear lockup during weight transfer to the front. But would this not be more easily achieved by a pressure limiting valve in the line to the rear and a single master cylinder? The valve could be the manually adjustable type or work automatically by sensing weight shift.

What say all you guys with more knowledge?

John McL

[Steve_D]

JohnMcL said:

Don’t worry 3DEE, I’m about to ask an even dumber question on this topic. Why have a bias bar at all?

As I understand it, the purpose of the bar is to reduce braking effort to the rear when conditions (e.g. rain) of reduced grip increase the likelihood of rear lockup during weight transfer to the front. But would this not be more easily achieved by a pressure limiting valve in the line to the rear and a single master cylinder? The valve could be the manually adjustable type or work automatically by sensing weight shift.

What say all you guys with more knowledge?

John McL

In a race car yes you would adjust for driving conditions. On a road car this adjustment is not allowed so in this situation the bias bar is used to set a balance suitable for passing IVA and is then locked in place. When Ultima sell a kit they have no idea what brakes will be fitted so having this adjustment is the best solution.

Weight shift or pressure systems are possible but the research and trials/testing would be cost prohibitive.

Steve

[spatz]

I must add that 21 mm did not do it for me, there was too much overbreaking of the rears, I have moved the bias bar a lot more to the front. I have not measured it but it is definetely more biased to the front, since it is not so nice when the rear wheels lock up !

[JohnMcL]

[quote=Steve_D]

In a race car yes you would adjust for driving conditions. On a road car this adjustment is not allowed so in this situation the bias bar is used to set a balance suitable for passing IVA and is then locked in place. When Ultima sell a kit they have no idea what brakes will be fitted so having this adjustment is the best solution.

Weight shift or pressure systems are possible but the research and trials/testing would be cost prohibitive.

Steve

Hi Steve,
I was thinking more of using something having manual adjustment, like a Wilwood Proportioning Valve, with a single master cylinder. Saves a master cylinder, makes the pedal box more simple, cuts out all this hassle over locking the bar but still allows all the adjustability you might want.
John McL.

[Steve_D]

JohnMcL said:

Steve_D said:

In a race car yes you would adjust for driving conditions. On a road car this adjustment is not allowed so in this situation the bias bar is used to set a balance suitable for passing IVA and is then locked in place. When Ultima sell a kit they have no idea what brakes will be fitted so having this adjustment is the best solution.

Weight shift or pressure systems are possible but the research and trials/testing would be cost prohibitive.

Steve

Hi Steve,
I was thinking more of using something having manual adjustment, like a Wilwood Proportioning Valve, with a single master cylinder. Saves a master cylinder, makes the pedal box more simple, cuts out all this hassle over locking the bar but still allows all the adjustability you might want.
John McL.

Agreed it is simpler but is not allowed under IVA. Ok for racing though.

Steve