Dodgy ABS sensors and MOT

[jonnyporsche]

If you have a failed abs sensor, meaning if the warning light goes out after starting the engine but comes back on when moving it is NOT AN MOT FAIL .........untill next month when the rules are changing.

 

[Lowtimer]

How would they know the ABS light comes on when moving- rolling road brake tester?

Yes. Or the road test for limited slip diff equipped cars.

 

[944 man]

Id heard that it was supposed to be all brake testers now, and no inertia meter road tests. I have a Subaru with two limited slip differentials in it and a single wheel tester will damage both in short order...

 

[Lowtimer]

ORIGINAL: rsmithholmfirth

are they doing road tests now?

They can and always have done for vehicles with mechanical LSDs which can't have brake testing done on roller type testers. Such as all late 944 Turbos for example.

 

[Lowtimer]

ORIGINAL: 944 man

Id heard that it was supposed to be all brake testers now, and no inertia meter road tests.

Yes, a lot of people have heard fantasy versions of the new test procedures. There is a lot of nonsense and disinformation being put about. The facts are all here:
http://www.motinfo.gov.uk/htdocs/index.htm


Part 3.7
Method of Inspection

The brake performance test must be carried out on a properly calibrated and maintained slow-speed roller- brake tester designated as acceptable for the statutory tests, except:
· vehicles for which a roller brake tester is not appropriate, or
· at premises without a roller brake tester where approval has been granted for the test to be carried out by other means.

Certain vehicles may not be suitable for testing using a roller brake tester. Testers should take account of the vehicle's drive configuration, transmission type and any Vehicle Specific Information before deciding whether a full or partial roller brake test is appropriate. If additional information is available from the vehicle manufacturer, then this should also be taken into account. Unsuitable vehicles should be tested using a properly calibrated and maintained decelerometer or a plate brake tester designated as acceptable for the statutory tests, see Sub-Section 3.7B and C

 

[TTM]

ORIGINAL: Lowtimer
They can and always have done for vehicles with mechanical LSDs which can't have brake testing done on roller type testers. Such as all late 944 Turbos for example.

Sorry for being thick but do you mean the LSD will add braking force in addition to the service brake in case rollers do not rotate at the same speed?
Or perhaps the LSD will be damaged in case of imbalance between rear brakes?

 

[944 man]

ORIGINAL: Lowtimer

ORIGINAL: 944 man

Id heard that it was supposed to be all brake testers now, and no inertia meter road tests.

Yes, a lot of people have heard fantasy versions of the new test procedures. There is a lot of nonsense and disinformation being put about. The facts are all here:
http://www.motinfo.gov.uk/htdocs/index.htm


Part 3.7
Method of Inspection

The brake performance test must be carried out on a properly calibrated and maintained slow-speed roller- brake tester designated as acceptable for the statutory tests, except:
· vehicles for which a roller brake tester is not appropriate, or
· at premises without a roller brake tester where approval has been granted for the test to be carried out by other means.

Certain vehicles may not be suitable for testing using a roller brake tester. Testers should take account of the vehicle's drive configuration, transmission type and any Vehicle Specific Information before deciding whether a full or partial roller brake test is appropriate. If additional information is available from the vehicle manufacturer, then this should also be taken into account. Unsuitable vehicles should be tested using a properly calibrated and maintained decelerometer or a plate brake tester designated as acceptable for the statutory tests, see Sub-Section 3.7B and C

I spent ages trawling through the new testers manual (in a .pdf) trying to establish whether it was fact or not.

 

[Lowtimer]

ORIGINAL: TTM

ORIGINAL: Lowtimer
They can and always have done for vehicles with mechanical LSDs which can't have brake testing done on roller type testers. Such as all late 944 Turbos for example.

Sorry for being thick but do you mean the LSD will add braking force in addition to the service brake in case rollers do not rotate at the same speed?
Or perhaps the LSD will be damaged in case of imbalance between rear brakes?

The usual brake testing machine tests one wheel at a time, spinning in up using a heavy roller to put some inertia into the spin, and then using the wheel brakes to stop it while the other wheel on the same axle is held immobile (as are the wheels on the other axle). You can't get an accurate reading of the braking effect available to that wheel if an LSD is inhibiting its movement, and the car is also likely to try to climb out of the rollers when the machine spins up the wheel it is testing, and the diff transfers torque to the wheel which is not being tested (which is being at that point held in braked rollers).

 

[944 man]

The real issue is that brake rollers break limited slip diffs.