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NCT test figures - ovality

  • 13-03-2021 9:58pm
    #1
    Sam Russell
    Moderators, Science, Health & Environment Moderators Posts: 20,144 Mod ✭✭✭✭


    The car passed, but puzzled by numbers.

    What does this mean? 50% for both front wheels but a pass.

    Also 'side slip' Front 3.0 m/km but rear -3 m/km. Was the steering wheel crooked.

    Do I need to get the alignment checked?

    Car is just 4 years old and very low mileage. Only done 500 miles in the last year due to Covid.


Comments

  • #2
    greasepalm
    Registered Users, Registered Users 2 Posts: 5,582 ✭✭✭greasepalm


    Sam Russell wrote: »
    The car passed, but puzzled by numbers.

    What does this mean? 50% for both front wheels but a pass.

    Also 'side slip' Front 3.0 m/km but rear -3 m/km. Was the steering wheel crooked.

    Do I need to get the alignment checked?

    Car is just 4 years old and very low mileage. Only done 500 miles in the last year due to Covid.

    Ovality is to do with brakes possibly warped discs with high spots or brake drums with uneven wear / warped.

    Side slip is a way of measuring alignment of front and rear wheels and yours are well within the limits printed on your form.

    If alignment was way out you will get a fail and tyres eaten / worn.


  • #3
    Sam Russell
    Moderators, Science, Health & Environment Moderators Posts: 20,144 Mod ✭✭✭✭Sam Russell


    The car has only 4,500 miles on it. How could the disks be warped? The car has not been driven hard at all, or hardly at all. 50% and 50% ovality is on the front axle and 13% and 17% on the rear. 50% of what? I'm confused.

    Does the car weight include the tester?


  • #4
    greasepalm
    Registered Users, Registered Users 2 Posts: 5,582 ✭✭✭greasepalm


    Its just wording on the form as if yours were bad you would have a hoppy pedal.

    Cant remember what the limit is as dont have a form here to hand.

    All the forms have a limit on each wheel which is tested.

    Even garages can be scratching their head with what has been written on the report.


  • #5
    Sam Russell
    Moderators, Science, Health & Environment Moderators Posts: 20,144 Mod ✭✭✭✭Sam Russell


    greasepalm wrote: »
    Its just wording on the form as if yours were bad you would have a hoppy pedal.

    Cant remember what the limit is as dont have a form here to hand.

    All the forms have a limit on each wheel which is tested.

    Even garages can be scratching their head with what has been written on the report.

    It does not mention the limits for ovality. How can you get a figure of 50% - that would suggest the disk is buckled.

    I checked the NCT manual and was no wiser.


  • #6
    CJhaughey
    Registered Users, Registered Users 2 Posts: 14,907 ✭✭✭✭CJhaughey


    It could be as simple as a rust spot on a disc or more commonly after a run at speed braking to a stop and holding the brake pressed deposits a film from the pad on the disc, that leads to a spot that will gather more material and have different friction characteristics to the rest of the disc.
    Take it for a spin and some high speed driving and a few hard stops almost to 0 but not stopped.
    Then drive it for another 5km and do the same, a few runs like this will usually smooth it out a bit.


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