Cruise control reads which wheel speed sensor?

[Pancho]

Cruise control reads which wheel speed sensor? Which one does it read to dtermine speed? Thanks

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[MarcusF]

To calculate vehicle speed, all four wheel speed sensors are used. If one sensor supplies a number that's far enough off from the other three, the speedometer uses the left front sensor and the cruise is disengaged.

[OGCLK320]

My cruise control only works at 65mph and below, anything above 65 it will turn off on its own, I know this is because I am running staggered rims and tires and the reading on the sensors are different, Because I have a 98 and my car did not come stock staggered like the 430 and 55, Is there anything I can do to get the cruise control to work at all speeds with the staggered set up, would I need 430 sensors? or when I buy new tires, I was trying to get all four with the same speed rating, Im not sure if this is possible with staggered, but maybe get as close as possible to have it hopefully work? Any ideas on this MarcusF?

[MarcusF]

You’re interested in a spec called "revs per mile". You want to get that spec for the front and rear tires as close as possible. I run Conti ExtremeContacts; 225/45-17 up front and 255/40-17 in the back. Why? The revs per mile rating for both tires is 828. Years ago a Tire Rack guy told me I didn’t want this combination (on another set of tires) because the car would push (too much rear grip). I ignored him because matching the revs per mile allows me to set the cruise at any speed I want. If I followed the Tire Rack guy’s advice I’d be running a 245/40-17 in the back. Those have a rev per mile rating of 811. It’s only a 2% difference from the front, but no thanks. 2% coupled with bends in the road where the inside and outside tires rotate at slightly different speeds - think about a right hand curve picturing the right fron and left rear. That might be enough to disengage.

[OGCLK320]

I just bought two rear conti extremecontact DW 235/35/18 because my car is pretty low in the rear and I am also running 15mm spacers, so i bought a smaller tire to prevent rubbing, I just found the spec page for the tire, thanks for your help. what do you think about 834 and 848? will I have problems, what is the % that it will still read correctly with out shutting off.

[OGCLK320]

I ended up going with the hankook v12 ventus 215/40/18 for the front with a rpm rating of 840, and the rears are the continental extreme contact dw 235/35/18 rpm of 848. The car rides like a cadillac now, and the cruise control works at all speeds! No more rubbing in the rear with a smaller tire and the steering on the front, feels much more solid with the hankooks. I could not be more satisfied, also had the steering gear bolts torqued to 51lbs and they all were a little loose. New tires= New car! haha

[Pancho]

Originally Posted by MarcusF

To calculate vehicle speed, all four wheel speed sensors are used. If one sensor supplies a number that's far enough off from the other three, the speedometer uses the left front sensor and the cruise is disengaged.

Revs are not the problem:
Front: 828
Rear: 831

So, a couple of questions:

One:
How can I bench test a speed sensor?
Ohms, continuity?

Two:
Would the cruise control behave the same way, ie. test speed, then in a minute or two disable itself,
if a wheel rev. mismatch,
and
if a wheel sensor is broken,
and
if a wheel sensor were totally removed?
In other words, by observation, determine if rev or sensor problem.

Thanks.