IVA Test Fail

[Joseph.Ryan1]

Hi Folks,

Can anyone offer advice as to how I can overcome the problem with my test fail. On the test my 2 Ltr Romero failed mainly on two points.

1. Rear brakes - too much fluid presssure. (Sierra 10" Drums). I did fit an adjustable Brake Bias Valve but had to remove this before submitting the car for the test.

2. The Smiths Speedo clock (new) showed at speeds 30 & 40 mph as accurate, 50, 60, 70 mph as 2 mph slow. Effectively the car would have been travelling at 52, 62, 72 mph.

Any help with the above would be very greatly appreciated.

[dogoncrazy]

Re: IVA Test Fail

Joe
what size bore are your wheel cylinders? I believe there may be 2/3 options depending on engine capacity/rear brake size [Sierra donor]. Speedograph Richfield should be able to recalibrate your instrument .personally think they are being 'picky' for 2 mph , but I suppose those are the rules.

[cameronfurnival]

Re: IVA Test Fail

Well done on almost getting through Joe!
As I understand it you can fit the adjustable brake bias valve if it works on twin master cylinders, however you are unlikely to have taken that approach.
The sierra comes with a gravity operated bias valve (basically a ball-bearing in a pot) which works by rolling forward as the car dips at the front under braking. It can be set by adjusting the angle of it so the ball rolls forward more or less quickly. This type of valve is permitted under section 9b note 4/5(below) as I understand it.
hth

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.

[cameronfurnival]

Re: IVA Test Fail

and here's a picture of the valve...ebay Item number: 180500879599

[cameronfurnival]

Re: IVA Test Fail

BTW The speedometer must not indicate a speed less than the true speed (Section 17 note 4) but you should be able to calibtrate it easily enough

[keith_h]

Re: IVA Test Fail

How soft were your tyres. Just an off the wall thought but would blowing them up really hard eat up the 2mph difference. Can you borrow a good GPS device (I used my son's orienteering one) as it will tell you pretty acurately wat speed you are doing)

[macdonald.dm]

Re: IVA Test Fail

I love off-the-wall ideas!

I think that in the this case, however, increasing the pressure - hence radius, rolling circumference etc. - would actually worsen the situation as the actual road speed would then increase further.

I wonder if air could be let out... Or lower profile tyres fitted. :-(

Good result tho', Joe. Two relatively easy things to overcome - well done.

[keith_h]

Re: IVA Test Fail

Ooops ! It's all well and good having of the wall ideas as long as they end up approaching a solution. I guess the rebound off the wall came nearer