I recently purchased some new rims and tires that I really liked for a great price. However the new combo has an overall different diameter and the rims are also staggered. This has led to two new dash lights... Abs off and traction control off. I cant tell any difference in the performance of the car. Is this a serious issue or just new annoying dash lights to tolerate or can the sensors be recalibtated?

 

Hello Speed,

Anti-lock braking is pretty important. Traction control less so, although you won't notice any difference in performance unless you get into a wheel slip of some kind.

The traction control won't work if the anti-lock braking isn't working, so the issue is probably with the abs. Not uncommon. I would say that likely one of the abs wheel sensors was somehow disturbed when the wheel changeover was made. To start, inspect the four abs sensors and their wires. Maybe you will find one with obvious signs of trouble. You will want to clean the face of the sensor and make sure the rotating toothed wheel (attached to the hub) looks ok. Do this before you buy anything. If the wheel sensors are working properly, they will be calibrated each time you drive the car. So if the abs and traction lights come on every time, there is a problem.

You say the rims are staggered. The width of the rims and tires wouldn't matter, but the overall diameter might. If the front tires are much smaller diameter than the rear tires, the traction control system might see too much of a difference in the rotational speeds, and shut off. But I really don't think it would be all that sensitive.

Unrelated:
Does your XJ6 also have front heated seats? An option called "All Weather Package" was available for the XJ6 and included traction control and heated front seats. Probably an expensive option. Hence fairly rare on an XJ6.

 

Sounds like diameter front and rear are not the same so the computer is freaking out.

Unlikely that you will be able to reprogram it.

Best bet is to find a size that fits and has same diameter front to rear.

Check sites like this:

https://robrobinette.com/tire_diameter.htm

 

Yes, I should mention that I did a rear shock replacement while I was replacing the wheels, and if you have done that job you know what a booger that can be! It is definitely a possibility that I did some damage or something to the ABS sensors. I will be pulling the wheels today to check for obvious signs! Ric ... I really don't want to get rid of these wheels as of yet... They were an investment and I quite like them but I will definitely keep you posted! Thanks to the both of you. Also Sleek, I do have the heated front seats.

 

Given you changed the shocks, it would be worth checking the wiring for damage, and also the connector under the rear seat, which doesnt take much of a pull to disconnect.
That said, unless the difference in rolling diameter is marginal, my guess is that the system is rejecting the readings from the wheel sensors because in a straight ahead, no brakes applied situation, it has two pairs of wheel speed readings which are different, when they should be the same. The ABS and traction control systems basically work by monitoring the individual wheel speeds and intervening where there is an individual wheel getting out of kilter with the others. In your case there will be a pair permanently out of kilter with the others , which the system wont like.
Are you not able to fit different profile tyres to make the rolling diameters the same, while still using staggered wheels?

 

We need pictures too. What size wheels and tires are on it now? You should be able to vary the width and height to get similar rolling sizes. Almost every BMW, Vette, Porsche, etc has different sized wheel widths front and rear but use the right tires to equal out rolling diameter.

 

OK, the rear tires are 5.5 mm larger in diameter. This seems nominal to me.

 

I can't imagine a 5.5 mm larger diameter on the rear tires would make a difference. There has to be some amount of acceptable error between wheel readings, or else the abs would fail to calibrate too often. That error or difference in tire diameter could be caused by different tire brands (even of the same size), differences in tread wear, and inflation pressure. 5.5 mm is about the depth of a tread. I don't think the ABS would come on if a tire was very low on pressure (hence rotating slightly quicker I think).

I would hope that the system design would allow for a plus one or minus one tire size to be used, namely for the purpose of staggering the rears. But I suppose it is discouraged by manufacturers because it could become a safety issue if taken to extremes.

If no damage is noted and everything checks out with the abs sensors, you could always put the old rims & tires back on - if you still have them - and see what happens.

 

I would struggle to imagine such a small difference being the cause of your problem. From memory, there is a tolerance of +/- 3% when comparing circumferences (NB rather than diameter) of wheels and tyres.

 

Our original thinking proved to be accurate. During the wheel fitment and the rear shock replacement (which was much more difficult than anticipated), I nicked a sensor wire which was grounding against the hub. By the way, if your xj shocks are original, save yourself some time and just cut the bottom mounting bolts out. Thank you guys so much for the responses and advice!

 

BTDT....nice short metal saw blade on a sawzall. After much thrashing and heating and cursing.


Glad you sorted the bad wire.