Tooth discrepancy on ABS tone wheels?

Hi everyone,

My Hyundai Coupe is in need of a new rear hub and, to cut a long story short, my local garage (non-Hyundai) says he can get me an unbranded replacement hub (a sealed hub/beating unit with ABS ring attached) for half the price of the genuine Hyundai unit.

However, he has pointed out the the ABS ring, whilst being the same size as the genuine Hyundai unit, has fewer teeth on it. I'm not sure how many fewer - my current wheel has 44 teeth.

He is adament that he's fitted many to other Coupe's and can confirm that the ABS functions fine afterwards, and indeed does not trigger the self-test fault system. With regards to this latter point however I've examined the fault codes/diagnosis and have found that no such fault condition for mismatched tone wheels exists - the closet fault matches are for missing teeth detected by irregularities in the sine-wave.

So, my question is thus: Whilst it appears, based in his evidence, that this teeth discrepency does not pose a problem I have learnt from searching the web of cars where this has indeed posed a problem - usually in the form of the self-diagnosis failing.

My theoretical ABS knowledge, whilst limited, leads me to believe that a wheel having fewer teeth would give the impression of that wheel turning slower relative to the others on the car (assuming the state of rotational velocity for for all wheels being the same). It is this theory that worries me - could it lead to incorrect operation of the ABS... ...particularly when I need it most?

I would be grateful from feedback from anyone else that has, for whatever reason, experienced trouble from a mismatched tone wheel arrangement. Or indeed if anyone works directly with the design of ABS systems could comment that would be great. The manufacturer of my system is the Japanese company Mando - I've e-mailed them for comment and await a reply.

I'm well aware a topic like this could provoke all sorts of

*theoretical* predictions of how the system *could* behave and hence I would particularly appreciate input that could be backed up with experience/authority!

Regards,

Mat

Reply to
Mathew J. Newton
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You let him do the work, if it triggers the self diag, then you don't pay him till hes sorted it, by fitting the proper hub :)

Reply to
Dan405

If it really is half the price, why not have both sides done and keep the good one as a spare. Then you wont end up forking out for the dealer part now, and potentially the same amount again for the other side in the future?

Reply to
P Latham

The unbranded unit is not half the price as some sort of 'special offer' - it's half the price because OEM parts are a rip off!

With regards to Dan's suggestion to getting the garage to do it and seeing if the ABS self-diagnoses a fault - I know this won't happen... I've examined the control module's fault code sheets and it doesn't check for anything like 'fitting of tone wheel with wrong number of teeth'.

Furthermore, I'm sure the ABS will still function but can I *really* be confident it will perform exactly to spec, in all conditions, as per expected if using *identical* parts?

Mat

Reply to
Mathew J. Newton

That's why you pay extra for OEM parts - by fitting them you know that they will work as the manufacturer intended. If a replacement OEM part goes wrong within its warranty period, then you go to a main dealer and the part will be replaced under warranty at no cost to your self. If you use pattern parts, then you get a replacement part, but have to stump up for the fitting yourself. This has been my experience.

Look at it this way:- you could go for the pattern hub, and then find that the ABS picks up the discrepancy in the number of teeth on the sensor. You will then have to stump up for the OEM sensor to correct the problem, as well as another lot of labour to fit the part.

I have experienced some ABS systems that a very sensitive to changes in the system. Vectra's in particular, would bring up a code due to a difference in tyre depths (3 part worn tyres, then using the new spare on the other).

Anthony Remove eight from email to reply.

Reply to
Anthony Britt

I'd be concerned as to whether it effected the ABS performance, rather than just if a light comes on or not. And I suspect it would.

Reply to
Dave Plowman

The message from Dave Plowman contains these words:

You'd think so, wouldn't you. The toothcount is how it determines relative speed - if one appears to be going slower I'd expect it to trigger unreliably.

Reply to
Guy King

How fussy an abs system may be depends on it's strategy to detect a wheel slowing to quickly. It's no it good looking at relative wheel speeds if all the wheels are locked, the abs would just detect the vehicle had stopped and not that it is sliding out of control.

I doubt the simpler ones use tooth count. Just use the sine wave frequency to produce a voltage, if rate of voltage reduction is greater than a set amount trigger abs for that wheel. A few teeth less will just trigger the abs for that wheel a bit earlier.

I have managed to freak my ABS out and get the 'abs' light on by doing a three point turn, applying the brake lightly while turning the steering quickly to opposite lock so one front wheel stops and revolves backwards while the other goes forwards quicker.

-- Peter Hill Spamtrap reply domain as per NNTP-Posting-Host in header Can of worms - what every fisherman wants. Can of worms - what every PC owner gets!

Reply to
Peter Hill

Most ABS systems cut out at low speeds. ;-)

Reply to
Dave Plowman

'..will just...'?! That's exactly what I want to avoid! :-)

Since my first post I've managed to find a couple of other suppliers - I've asked them to confirm their teeth count, and will go with whoever can supply the 'proper' part for the job...

Given the jury is out on whether tooth discrepency is a problem I may end up going back to Hyundai for the OEM part if the above queries don't result in anything in which case so be it - I see no point in skimping if I'm unsure of the impact on safety.

Mathew

Reply to
Mathew J. Newton

Well, the only reason to use teeth is to give a pulsed output from a sensor - in other words to tell a computer how fast it's turning relative to the other wheels - and to give an indication of the rate of deceleration. Either way, altering the teeth number must upset something. But it may not in practice make a difference. Have you checked to see if they changed the number of teeth during the model's life? It's possible this was changed to cure something, but the pattern part is only available for early/late cars.

Reply to
Dave Plowman

I find this amazing as when a car is going around a corner the wheels are clearly turning at very different speeds ( Thinks back to dad explaining why only one rear wheel was driven on my first go kart) so why does this not trigger off fault codes?

Phil

Reply to
Phil

The message from snipped-for-privacy@yahoo.co.uk (Phil) contains these words:

They're different - but not /very/ different. It's only on very tight corners than the differences are large - and few people can take them at speeds likely to bother an ABS system.

Reply to
Guy King

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