Has anyone out there with larger tires recalibrated the ABS wheel speed sensors on a Grand Vitara?  When I change my gear ratio (from 4.3 to 5.12) real soon, my speedo should be back to normal, or pretty close.  However, the ABS sensors are on the wheel.  Does anyone know about recalibrating them?  Thanks.

Dave

After a little more research, I really wonder how much of an impact bigger tires have on ABS.  I had a Suzuki mechanic at a dealer tell me it didn't really matter (and yes, he went on to give me his opinion on why), and reading the service manual and some other things online seem to confirm this.  The service manual states that the ABS controller gets its info from the four individual wheel speed sensors, the stop lamp (I'm assuming this means the "brake lights"), a G sensor (located on the body of the vehicle), and the 4wd switch.  Here's my theory....and I'd love to hear others, so feel free:

The stop lamp a.k.a "brake light" is not affected by larger tires....you apply the brakes and it comes on.  So far, so good.

The G sensor also is not affected by tire size.  When you brake hard the G force sensor will kick in and send info to the ABS controller, no matter what size your tires are.  Still good.

4wd switch??  I'm not sure how this affects ABS.  But I'm assuming it's just to tell the ABS controller whether or not you're in 4wd.

Individual wheel speed sensors- Yes....I'll admit that they are reading the wrong speed.  HOWEVER, from everything I've found online, they are using an algorithm that is basically looking for "severe" changes in rotational speed that would indicate very hard braking, and subsequent locking of the wheel.  So...it seems that even if your speed sensor is reading 10-12% high from oversized tires, it will still detect a sudden change in speed.  In other words, a locked 31" tire is still traveling at the same speed as a locked OEM 27" tire....... zero miles per hour!  I just don't see the bigger tires having a major effect on the ABS.

Any gearheads out there want to comment?  Is there anything I'm not considering, or that I'm oversimplifying?  Thanks.

Dave

Larger tires, as long as the same size is on all four corners, won't make a bit of difference.

Larger tires, as long as the same size is on all four corners, won't make a bit of difference.

Agreed.  It works on difference between wheel speeds.

As mentioned above bigger tires do not effect the operation of the ABS 

If you want to see how it works put a space saver spare on and hit the brakes! I agree with all the above.

Here's what I found on my '00 GV.

In stock form, the friggin ABS went off all the time.  Wet roads at 15 mph, snow, and gravel, and at relatively slow speeds.

Not that I'm at a 31" tire, the ABS behaves nicely, and only comes on when it is actually needed.

Best thing I ever did regarding the ABS was ADD bigger tires.

Actually, with bigger tires, you need less rpm to go the same speed, so your actual axle rotation that the sensors pick up will be slower, not faster.  The speed sensor is likely connected to the speedo, so that will read as slower than actuall real speed, again because of the larger tires. If you re-gear the diffs for the larger tires, then everything should be back to spec for real speed versus axle speed, but those should not affect the ABS in any way.  I am by no means a certified mechanic, but this is how I think everything will work. 

Also, the 4x4 switch that connects to the abs system is for the Electronic Traction control (ETC) system that seperately locks and unlocks the wheels that are spinning faster to distribute traction to the other wheel.  Kind of like a limited slip without the clutches in the diffs. Still not as good as lockers.  I think there is a Stability Control System on the Grand Vitara also that works through the abs system.

Actually, with bigger tires, you need less rpm to go the same speed, so your actual axle rotation that the sensors pick up will be slower, not faster.  The speed sensor is likely connected to the speedo, so that will read as slower than actuall real speed, again because of the larger tires. If you re-gear the diffs for the larger tires, then everything should be back to spec for real speed versus axle speed, but those should not affect the ABS in any way.  I am by no means a certified mechanic, but this is how I think everything will work. 

Also, the 4x4 switch that connects to the abs system is for the Electronic Traction control (ETC) system that seperately locks and unlocks the wheels that are spinning faster to distribute traction to the other wheel.  Kind of like a limited slip without the clutches in the diffs. Still not as good as lockers.  I think there is a Stability Control System on the Grand Vitara also that works through the abs system.

The ABS speed sensors are not connected to the speedo - they are individual tone rings (one for each wheel) and usually mounted on the hub close to the brakes (some live axle RWD/4WD vehicles will only have one sensor at the back) - they look for two conditions, the first being the "rate of change" - if the vehicle is slowing down too quickly - and the second is a speed difference between the individual sensors - which would indicate that one wheel, or one end of the vehicle has or is about to lock(ed) up.

Dittoes.  No negative effects.  Mine works fine with the larger tires although I've never "needed ABS".  I have induced the ABS in the snow to check it once in awhile.

Also, the 4x4 switch that connects to the abs system is for the Electronic Traction control (ETC) system that seperately locks and unlocks the wheels that are spinning faster to distribute traction to the other wheel.  Kind of like a limited slip without the clutches in the diffs. Still not as good as lockers.  I think there is a Stability Control System on the Grand Vitara also that works through the abs system.

That MAY be so on Gen 3, but not Gen 2 (99-05).