Brake bias valves and the IVA

[TonyHetherington]

Hi all

We're building a kit car at the moemnt, and we live very near the VOSA testing station in Gillingham. Having read the IVA test we believed that our installed brake bias valve would not be acceptable. My dad went to have a chat with them and the guys agreed that you're not allowed a brake bias valve. He said the brakes should be balanced by design.

Yikes.

Surely this is dam difficult?! We're running sierra rear axle with discs front and rear.

Not exactly sure what I'm asking, but our balance valve is nicely tucked away and worked in (has been for about a year of building as we did it long ago!), but this seems to have brought us to a bit of a stop.

Any thoughts?!

[singlecoil]

If they suspect that there is anything out of sight in the car that shouldn't be there, they are entitled to have the panels opened so they can look. It's a good idea before closing an area to take clearly identifiable pictures of the internals. Good example would be the transmission tunnel in cars where the tunnel isn't open underneath.

I know cars with Sierra discs and drums are normally able to get through without a valve, so maybe the same is true for your set up. There's also the possibility of doing something with the pad selection. Tricky.

Probably your best bet is to get on the forum of locostbuilders.co.uk and ask for anecdotal information on whether similar set-ups have passed without the valve.

Alternatively, take the test and see what happens, at least it will give you a yardstick, and the chances of a first time pass aren't terribly high anyway.

[TonyHetherington]

Thanks

Yup we're almost going to treat the first test as a "what needs doing". Don't get us wrong, we're building this (Robin Hood) to the highest quality we can (see www.johnskitcar.com) and taking a long time doing it.

Also, have taken millions of photos so that should be failry ok.

Interesting you say it's do-able with the setup though, thanks.

[singlecoil]

TonyHetherington said:

Interesting you say it's do-able with the setup though, thanks.

It's doable with drum brakes, but I'm not sure whether it is so with rear discs. Locostbuilders is your best bet.

[Jonleeper]

My understanding, from reading the regulation and talking to a few people, was that it is not the bias valve itself that is banned but it must be suitably locked, lockwire was suggested, and the driver must not be able to adjust it from within the car. Hence a bias system located the other side of the bulkhead and lockwired in place would pass but one with the knob style adjuster on the dash would not.

It's best to go to the test centre and ask the question directly, the answer often depends on the interpretation of the tester anyway, especially as they are not too far away from you.

[Toltec]

singlecoil said:

TonyHetherington said:

Interesting you say it's do-able with the setup though, thanks.

It's doable with drum brakes, but I'm not sure whether it is so with rear discs. Locostbuilders is your best bet.

AshG on there has just done an IVA at Gillingham, his car used Sierra disc/drums and passed the brake test OK.

[TonyHetherington]

Jonleeper said:

My understanding, from reading the regulation and talking to a few people, was that it is not the bias valve itself that is banned but it must be suitably locked, lockwire was suggested, and the driver must not be able to adjust it from within the car. Hence a bias system located the other side of the bulkhead and lockwired in place would pass but one with the knob style adjuster on the dash would not.

It's best to go to the test centre and ask the question directly, the answer often depends on the interpretation of the tester anyway, especially as they are not too far away from you.

That's how we understood it too - and as such the valve is unreachable from "inside" the car, and we could have locked it also. However, apparently that's not acceptable any longer unfortunately.

[singlecoil]

TonyHetherington said:

Jonleeper said:

My understanding, from reading the regulation and talking to a few people, was that it is not the bias valve itself that is banned but it must be suitably locked, lockwire was suggested, and the driver must not be able to adjust it from within the car. Hence a bias system located the other side of the bulkhead and lockwired in place would pass but one with the knob style adjuster on the dash would not.

It's best to go to the test centre and ask the question directly, the answer often depends on the interpretation of the tester anyway, especially as they are not too far away from you.

That's how we understood it too - and as such the valve is unreachable from "inside" the car, and we could have locked it also. However, apparently that's not acceptable any longer unfortunately.

That's my understanding too. Brake bias bars were acceptable when locked, but not now, the bar and nuts have to be welded all along to prevent future adjustment.

Looking at it from VOSA point of view, a car could pass the test and then be sold to someone who might wonder what would happen if he tweaked the bias a bit, cutting lockwire or removing a split pin wouldn't stop that person doing so. Then he touches the brake in a corner and........

[FlatPack]

My car (disks front and rear) passed SVA using the standard (unadjustable) Sierra brake compensator... Strange thing you mount at an angle pointing front / rear and it provides a bias effect as the nose of the car dips under braking.

It makes the bias far too far forwards on a light car, but that doesn't seem to matter for SVA.

[TonyHetherington]

That's what we wondered about - using the sierra one, but couldn't understand how they'd test it at the IVA (because it's all done using momentum, surely)?

[Steve_D]

TonyHetherington said:

That's what we wondered about - using the sierra one, but couldn't understand how they'd test it at the IVA (because it's all done using momentum, surely)?

If you tell them the valve works on momentum they will test in the road rather than on the rollers.

Steve

[Comadis]

IVA regulations don´t say that you arent allowed to fit a bias brake...but the bias, once adjusted, must be permanently secured against further adjustment.

[bassett]

When i went for one of the last SVA tests i was talking to the inspector and we got onto the situation of bias bars. He said that if using a bias bar these must be welded so they cannot be adjusted. Once the test is over do what you like with it but it must be permanent from what the chap told me.
Adam

[anonymous-user]

Found this stuff about brake biasing here

http://www.completekitcar.co.uk/Resources/M1%20Ins...


Note 4: Hydraulic valves that only operate automatically and react to vehicle loading or braking forces are permitted (Load Sensing and Gravity valves) Manually adjusted valves (other than to permit presetting the automatic function of a valve) are not permitted to be fitted even if they are rendered un-adjustable.

Note 5: Bias bars and other mechanical adjusting devices fitted to twin master cylinders must have no means of adjustment. However they will be deemed acceptable if the all nuts etc are fully welded to their relative threads and all the threads originally intended to provide adjustment are welded along their length i.e. permanently rendering them un-adjustable.

[TonyHetherington]

Yup that pretty much defines it!

Thanks so much for everyone's help