Stelvio ABS and tire size ?

[Peter949]

I will be taking my 2012 Stelvio to the Guzzi dealer to repair the ABS. The dash light for the ABS stays on continually indicating a fault in the system. I was also going to have the dealer install a reduced aspect ratio rear tire ... going from 150/70 to the 150/60 size. I was hoping to reduce the ride height. However a member on another Guzzi forum indicated that this could be a problem for the ABS, as it senses wheel speed.

Has anyone here changed the tire size from stock, and continued to have the ABS system work normally?

[pete roper]

No, it won't affect the ABS at all.

[randy yocum]

I went with a narrower profile front tire on my 2012 Stelvio NTX ,a Pirelli Scorpian 100/90-19 ,It's like a 150.00 tire and it was given to me,so I'd be crazy not to use it.I can't tell a difference in ride or handling verses the stock size, and it made no difference with the ABS.

[rocker59]

I will be taking my 2012 Stelvio to the Guzzi dealer to repair the ABS. The dash light for the ABS stays on continually indicating a fault in the system. I was also going to have the dealer also install a reduced aspect ratio rear tire ... going from 150/70 to the 150/60 size. I was hoping to reduce the ride height. However a member on another Guzzi forum indicated that this could be a problem for the ABS, as it senses wheel speed.

Has anyone here changed the tire size from stock, and continued to have the ABS system work normally?

The sensor notes changes in wheel speed, while comparing both wheels.  The ABS will not fault on a different tire size.

Example/Question:  Have you ever had the ABS fault in a car or on a bike when one of the tires' pressures went low, thus affecting the functional diameter of the tire?  No.  You haven't.

[Lannis]

The sensor notes changes in wheel speed, while comparing both wheels.  The ABS will not fault on a different tire size.

Example/Question:  Have you ever had the ABS fault in a car or on a bike when one of the tires' pressures went low, thus affecting the functional diameter of the tire?  No.  You haven't.

Well, don't let an AWD Subaru's tires get low on you, or accidentally put on a slightly wrong diameter, because the car will start setting off warning fireworks that will swamp any ABS issues.   Our Outback is very sensitive to tire pressure, or uneven wear, because it affects the drive system and probably the ABS by extension ....

Lannis

[rocker59]

Well, don't let an AWD Subaru's tires get low on you, or accidentally put on a slightly wrong diameter, because the car will start setting off warning fireworks that will swamp any ABS issues.   Our Outback is very sensitive to tire pressure, or uneven wear, because it affects the drive system and probably the ABS by extension ....

Lannis

AWD issue.  Not an ABS issue.  Thanks, Subaru...

[Huzo]

I accept the couple of opinions expressed, that it will not affect the ABS (or traction control where applicable), although I thought it would have...
Question is, why ???
In the case of a smaller rear tyre on a TRACTION CONTROL equipped bike, how does the system know that the increased rotational speed of the newly fitted tyre (for a given road speed), is due to reduced diameter and not a permanent loss of traction condition ?
Is it because an alteration in rotational velocity is not the only parameter that is being read ? I’m guessing this might be so, because clearly the system can cope with a slowly wearing tyre which will by itself, alter the rotational velocity of the wheel. This one has got me rooted.
If you were cruising along in the mud on your TC equipped bike and instantly lost traction, the rear wheel would speed up relative to the front and TC would set things right, yet if you instantly reduced the rear wheel size to cause the same increase, there’s no predicted TC issue...
Again, please no poorly conceived analogies, we need science and math..
I’ll bet Tusuyan will have a good handle on this..

[Kiwi_Roy]

I will be taking my 2012 Stelvio to the Guzzi dealer to repair the ABS. The dash light for the ABS stays on continually indicating a fault in the system. I was also going to have the dealer install a reduced aspect ratio rear tire ... going from 150/70 to the 150/60 size. I was hoping to reduce the ride height. However a member on another Guzzi forum indicated that this could be a problem for the ABS, as it senses wheel speed.

There should be a calibration procedure in the owners manual
This will reset the ratio between front and rear wheel pulses
At least that's what the V7iii has.

[Ryan]

Front tire speed steady, rear tires speed increasing, rear has broken traction. Rear speed slowing, front slowing faster, or stopped, and the front tire is locking up. Steady spinning at two different speeds is not an issue.

[Huzo]

Front tire speed steady, rear tires speed increasing, rear has broken traction. Rear speed slowing, front slowing faster, or stopped, and the front tire is locking up. Steady spinning at two different speeds is not an issue.

Oh I see.
So TC will allow you to break traction on the rear wheel and hold the rpm higher, as long as it’s not increasing ?
Nup..
But there’s got to be something I’m not grasping.

[rocker59]

Oh I see.
So TC will allow you to break traction on the rear wheel and hold the rpm higher, as long as it’s not increasing ?
Nup..
But there’s got to be something I’m not grasping.

Geez, d00d.  If the rear tire breaks loose (or is breaking loose), the system notices the dramatic acceleration of the rear, as compared to the front, and will either apply brake or cut power (depending on how the particular TC is set up).    The system is reading the the ABS senor rapidly, over and over, and can notice the rear wheel breaking loose under power before you are able to notice it.  They TC systems usually also read throttle position, so it knows that Throttle + spinning rear = loss of traction, and does what it's programmed to do, so you don't go down.

[rocker59]

If you were cruising along in the mud on your TC equipped bike and instantly lost traction, the rear wheel would speed up relative to the front and TC would set things right, yet if you instantly reduced the rear wheel size to cause the same increase, there’s no predicted TC issue...
Again, please no poorly conceived analogies, we need science and math..
I’ll bet Tusuyan will have a good handle on this..

You're leaving out the part where the ABS/TC recalibrates itself at startup each time, and for the first few feet that the vehicle is in motion, to get a baseline on the ABS tone rings.  On some vehicles, the ABS light flashes during this calibration phase.

[Kiwi Dave]

But not on the Cali 1400, the V85 or the V7-III.  These need to be calibrated manually, by (quoting) riding along a flat straight road in second gear at a speed of 30 +/- 2 km/h (18.64 +/- 1.24 mph) for about 10 seconds until the message "Calibration running Hold speed" appears on the digital
display.

So how can the Stelvio get away with not having to do this.  I searched the owners manual and found nothing.

[pete roper]

It's a much cruder system. I can't remember the details but it simply retards spark I believe.

[Ryan]

Math: the rear tire on the Stelvio has about a 25 inch diameter. If you reduce sidewall height by 10% on a 150, that means you are reducing the overall diameter of the tire by 30mm. Roughly an inch and a quarter. 1.25x3.14=4.25, so your shorter tire is covering 4.25 inches less ground per revolution. That's about a 5.7% difference. Should not be enough to cause you a problem. Pi x diameter says that every inch you increase diameter, you travel 3.14 inches further per revolution. The larger the starting diameter, the lower the percentage change this makes. So dropping your front tire diameter by an inch has "less effect" than dropping the rear.

[Kiwi Dave]

It's a much cruder system. I can't remember the details but it simply retards spark I believe.

Yes, I remember my Norge put out a helluva racket when the ABS was activated.  Crude is too polite.

[Huzo]

You're leaving out the part where the ABS/TC recalibrates itself at startup each time, and for the first few feet that the vehicle is in motion, to get a baseline on the ABS tone rings.  On some vehicles, the ABS light flashes during this calibration phase.

Ok then..
Is that what my Norge is doing when the light flashes for the first few metres at startup ?
This is the stuff that I know exists, but don’t understand..

[Huzo]

. I can't remember the details but it simply retards spark I believe.

Are you referring to TC or ABS ?

[pete roper]

TC

[pauldaytona]

With the RSV4 and Tuono v4 you have to calibrate for wheelcircumference when changing tyres. This for the traction control that is a level more sophisticated there. The ABS of the 180 and 150 stelvio tyre work with same abs unit without change

 A lower tyre with same width, gives a flatter rounding of the profile, and might corner less good.

[Kiwi Dave]

But is there a calibration option somewhere in the menu?  I couldn't find any in the owner's manual.

[Tusayan]

With the RSV4 and Tuono v4 you have to calibrate for wheel circumference when changing tyres.

Just kill me now.