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IVA set up

SteveWallace - 26/12/13 at 10:41 AM

I'm getting close to going for IVA and my thoughts have turned to stuff that its hard to set up or predict without test drives and/or rolling roads. What is the best way to set up the car to maximise my chances of passing.

The things that I'm thinking about are

I) self centring - I understand that neutral or a little bit of toe-out is best for IVA, but not how you would choose to drive normally. Is this correct? Also, what tyre pressures and camber (for IVA)? My caster is already adjusted as far as it will go.

ii) Brake bias - I know that the backs have to lock before the fronts, but presumably there is a limit on how much you can adjust the bias to the rear and still have the fronts perform well enough for the test. How have others set this up without being able to drive the car in anger.

iii) Bedding the brakes in - do people just do this driving to the test? I'm thinking that I could lift the rear end with an engine hoist, put it in gear and then gently apply the brakes to bed them in a bit (obviously only works for the rear!)

iv) speedo accuracy. I can do the maths and I guess that I'll just make minor adjustments at the test if its a bit out. I have to drive past one of those automated speed signs on the way, so I should have a good idea if its right before I get there.

There is an MOT garage next door to the place where I'm going to have the exhaust made, so I'm thinking that I could get them to do some testing, but if they won't do it, is it legal to book an appointment at a garage and drive the car to it pre-IVA. I know that its allowed in order to fix things on an IVA fail list, but not sure about pre-IVA.

[Edited on 26/12/13 by SteveWallace]

snapper - 26/12/13 at 10:56 AM

IMPORTANT. Fronts have to lock before rears or you spin this is the IVA requirement
Tyre pressure should be near 30psi for IVA 20 or less for road
A bit of toe out helps for IVA neutral or a bit of toe in for road

Not bedding in rear means fronts have a bit more bite could help front rear bias

Speedo can be corrected at IVA if to far out

Most stations are flexible and will allow you to fix little things

sdh2903 - 26/12/13 at 10:57 AM

I trailered my car to a nearby industrial estate car park on a Sunday to do most of the bits you mention.

Self centering, I ran iirc about 1 degree toe out and tyre pressures up to 32psi.

Drove the car around said car park to start bedding the brakes in then did a couple of emergency stops to check brake bias. Was well out at first with the rears locking first, tweaked so that fronts lock just before rears.

Used a gps speedo App on my phone to calibrate the speedo, surprisingly accurate, calibrated to just read over as per Iva spec.

Not saying the car park was legally ideal but I didn't really have anywhere else to do it.

SteveWallace - 26/12/13 at 11:04 AM

quote:
Originally posted by snapper
IMPORTANT. Fronts have to lock before rears or you spin this is the IVA requirement

I did know that (honest), I blame the excesses of yesterday for the typo.

Acc8braman - 26/12/13 at 12:49 PM

Remember to lock off your adjustable shocks.

Also head light aim

deeceee09 - 26/12/13 at 01:55 PM

For brake bias, get the car up on stands then adjust (a friend/WAG helps here) bias so the with the front wheels just locked up the rears can turned by hand.

davidimurray - 26/12/13 at 04:48 PM

For Iva I set the car up with 1 deg toe out, made a big difference from neutral. If you got the space, car stationary, full lock, hands off the wheel and start to move off the wheel should try and straighten out of its own accord. Also set tyres to 30+ psi. After IVA I am running 20psi and 1 deg toe in and it has next to no self centring!

For the brakes don't fit performance front brake pads, fit the cheapest standard ones you can get.They will bed in quickly and be good enough for iva then swap for better ones later. That was the advice from my iva examiner.

To setup the speedo measure the wheel circumference and work back through all the gear ratios to work out the speed for a particular engine rpm in a particular gear. From the iva manual find the mid range of the tolerance band and use that to set your speed. Then put the car up on axle stands and run it up to your rpm for a particular speed - e.g. if 3500rpm in 4th is 70mph then set the speedo to read 73mph. I did this and it was spot on during the test.

loggyboy - 26/12/13 at 05:33 PM

quote:
Originally posted by Acc8braman
Remember to lock off your adjustable shocks

Really? Not heard this before.

joneh - 26/12/13 at 08:59 PM

quote:

To setup the speedo measure the wheel circumference and work back through all the gear ratios to work out the speed for a particular engine rpm in a particular gear. From the iva manual find the mid range of the tolerance band and use that to set your speed. Then put the car up on axle stands and run it up to your rpm for a particular speed - e.g. if 3500rpm in 4th is 70mph then set the speedo to read 73mph. I did this and it was spot on during the test.

Don't fancy trying this in the garage!

Acc8braman - 26/12/13 at 11:01 PM

quote:
Originally posted by loggyboy

quote:
Originally posted by Acc8braman
Remember to lock off your adjustable shocks

Really? Not heard this before.

Sorry, didn't mean permanently,

davidimurray - 26/12/13 at 11:24 PM

quote:
Originally posted by joneh

quote:

To setup the speedo measure the wheel circumference and work back through all the gear ratios to work out the speed for a particular engine rpm in a particular gear. From the iva manual find the mid range of the tolerance band and use that to set your speed. Then put the car up on axle stands and run it up to your rpm for a particular speed - e.g. if 3500rpm in 4th is 70mph then set the speedo to read 73mph. I did this and it was spot on during the test.

Don't fancy trying this in the garage!

No need to worry as long as the car is supported on a good set of sturdy axle stands and slowly increase/decrease the speed, car doesn't even wobble or rock. If worried you can always do it with rear wheels off ( but out nuts on to hold the drums) and chuck the wheels under the car just in case.

loggyboy - 26/12/13 at 11:30 PM

quote:
Originally posted by Acc8braman

quote:
Originally posted by loggyboy

quote:
Originally posted by Acc8braman
Remember to lock off your adjustable shocks

Really? Not heard this before.

Sorry, didn't mean permanently,

Not heard of even a temporary lock off being required, are you sute your not confusing with brake bias?

Acc8braman - 27/12/13 at 08:10 AM

What I meant was and excuse my terminology the two adjusters on the shock need to be tight together so that the cannot self adjust over time, one of mine wants and he picked that up. School boy error but sometimes these things can be missed

loggyboy - 27/12/13 at 09:06 AM

ahhhh, u mean the spring seat adjusters.
I can't say I've ever heard of then being mentioned by anyone when reporting IVA failures, but its certainly a valid point and worth checking.
I thought you were talking about the shock firmness adjusters!
mine have a single adjuster with a grub screw to lock them off.

[Edited on 27-12-13 by loggyboy]

Acc8braman - 27/12/13 at 09:35 AM

I see, sorry that's me not knowing all the terms of a shock lol

davidimurray - 27/12/13 at 10:17 AM

My IVA examiner asked me if the adjustable springs seats were locked. I explained to him that they were not, but they were always under spring pressure, even at full droop. He was happy with that.