Reading the IVA manual I think it's covered under Brake Performance 09E - Note 6: Decelerometer test – This method must only be used where the vehicle cannot be tested in the roller brake tester due to a design characteristic.
...
Drive the vehicle on a level road at a steady speed of approximately 20mph and apply the service brake sufficient only to obtain wheel lock. Observe whether all the wheels of the rear axle(s) lock prior to both wheels of the front axle.

Having a deceleration sensitive valve would mean that was the only way the brakes could be tested, and it's definitely a design characteristic.

Still I haven't been through the IVA so this is all theory

Matt

Decel is used for 4wd etc and has no bearing on the Sierra valve if used for the Roadster.

Every MOT station in the land has a decelerometer for 4wd.

Better to use a pressure reducer as per previous post's and alter after IVA.

Someone on here posted on this. They fitted 4x4 sierra front calipers which are a slightly bigger piston diameter which got round the imbalance thing and it passed sva. No gadgets needed so try and keep it simple.:)

Bob

Hi all
I am going to agree with Flyerncle on this thread, these devices were fitted to the donner car which were much heavier and carried 4 passangers, so big differnce in weight to the roadster and therfore not suitable!!!!

However I am not sure what is avaliable from any of the specialist to fit either and to be IVA compliant ?

It seems there's no good way out of this - either I have to pick a random pressure reducer and hope that the balance is good enough, or rely on a valve from the donor which was designed for a completely different weight of car.

I've got an MOT station within 1/2 mile of my house so once I get that far I can see myself taking a quick trip over there (on a trailer of course) and getting them to let me know what the balance actually is.

At least that way I'll have some hope of getting through

Matt

thats rubbish.

simple physics here the action of the proportional valve will be relative to the inertia/mass of the vehicle. the iva man asked me why i didnt fit the ford valve to my car so its quite apparent that its not an issue to use them.

if it were me knowing what i know now i would be fitting the valve to avoid the roller test. much simpler to drive the car round the iva station and slam the brakes on and see if it locks up at the back first than it is for them to mathematically calculate it on the rollers over 4 points. you can also test it at home easily by driving down the road and slamming the brakes on while a mate watches :D

No need for the limiter
 

Hi Ash
I am not sure what you mean by rubbish? Further discussion with a few other builders and then your goodself it looks there is no need for the limiter at all, on either disics or drum system. Do you agree and hope Matt can prove this when he takes this to his Mot station?

Cheers

No maths involved,brake tester does it all for you and on average I use one up to ten times a day testing vehicles.

At the end of the day if the mate who is watching which wheel locks first is as good as the roller tester in the IVA he is wasted standing on the side of the road.

the iva man doesent use mot spec brake testers for a start
also the foot pressure on the pedal is monitored along with braking effort at all wheels totaly diffrent kettle of fish to the mot brake test im afraid

Cheers Ash. that's good to know

Thanks to kj71 I now have a Sierra valve so I'm going to fit that and move on.

Matt