Taller tires - computer recalibration

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M

mxz1972

Guest
2000 GM 4x4 - switched from 265/75/16 to 285/75/16. Want to reset parameters
for speedo, abs etc... Been to a few dealers today and they are making it
sound like quite a process. Have to call Oshawa, Ontario (in Canada) and
find out if it can be done. At least two hours time involved. Might have to
burn new program in computer?
Can anyone explain to me what is involved?

Thanks in advance
Danno


 
"mxz1972" <[email protected]> wrote in message
news:abvwb.485055$6C4.57759@pd7tw1no...
> 2000 GM 4x4 - switched from 265/75/16 to 285/75/16. Want to reset
parameters
> for speedo, abs etc... Been to a few dealers today and they are making it
> sound like quite a process. Have to call Oshawa, Ontario (in Canada) and
> find out if it can be done. At least two hours time involved. Might have
to
> burn new program in computer?
> Can anyone explain to me what is involved?
>
> Thanks in advance
> Danno
>
>
Slap a power programmer (you +about$300) or their computer (them + whatever
they decide to charge) into the diagnostic terminal on your truck, inputting
tire size change at appropriate prompt, wait a couple minutes, drive away
calibrated.


 

"mxz1972" <[email protected]> wrote in message
news:abvwb.485055$6C4.57759@pd7tw1no...
> 2000 GM 4x4 - switched from 265/75/16 to 285/75/16. Want to reset
parameters
> for speedo, abs etc... Been to a few dealers today and they are making it
> sound like quite a process. Have to call Oshawa, Ontario (in Canada) and
> find out if it can be done. At least two hours time involved. Might have
to
> burn new program in computer?
> Can anyone explain to me what is involved?
>
> Thanks in advance
> Danno

Danno,

I saw a recalibration gizmo in either Jeg's or Summit's catalogue.

Call em' and see what they can do. IIRC it was around $149.

www.jegs.com or www.summitracing.com

Doc

>
>


 
I would find someone with a GPS and clock it to see.

When I went up from the stock 215's to 235's, my speedo was right on. it
was off before...

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

mxz1972 wrote:
>
> 2000 GM 4x4 - switched from 265/75/16 to 285/75/16. Want to reset parameters
> for speedo, abs etc... Been to a few dealers today and they are making it
> sound like quite a process. Have to call Oshawa, Ontario (in Canada) and
> find out if it can be done. At least two hours time involved. Might have to
> burn new program in computer?
> Can anyone explain to me what is involved?
>
> Thanks in advance
> Danno
 

"Mike Romain" <[email protected]> wrote in message
news:[email protected]...
> I would find someone with a GPS and clock it to see.
>
> When I went up from the stock 215's to 235's, my speedo was right on. it
> was off before...
>
Going up from a 215 to a 235 will not change the speedo. That is the width
of the tire in millimeters. The second number is what determines how tall
the tire is.


 
On Mon, 24 Nov 2003 20:40:01 -0500, Jason Cothran wrote:
>
> Going up from a 215 to a 235 will not change the speedo. That is the width
> of the tire in millimeters. The second number is what determines how tall
> the tire is.

Going from 215/75 to 235/75 *will* change the calibration because 75% of
215 is not the same as 75% of 235.

I agree with another suggestion, find a GPS and try it before sweating the
issue too much. My Toyota Avalon indicates a bit slow, my Sonoma is maybe
1 MPH fast, and I'm very unhappy my Honda GL1800 Goldwing indicates over 4
MPH fast.

About the only issue you will have with ABS is if all wheels are not of
the same size, or if the size changed so much that it moved the low speed
disable-ABS point.

 
Maybe you should explain that the width of the tire is 235mm and that the
height is an aspect ratio of 75% of that width.

~KJ~

"David Kelly" <[email protected]> wrote in message
news:p[email protected]...
> On Mon, 24 Nov 2003 20:40:01 -0500, Jason Cothran wrote:
> >
> > Going up from a 215 to a 235 will not change the speedo. That is the
width
> > of the tire in millimeters. The second number is what determines how
tall
> > the tire is.
>
> Going from 215/75 to 235/75 *will* change the calibration because 75% of
> 215 is not the same as 75% of 235.
>
> I agree with another suggestion, find a GPS and try it before sweating the
> issue too much. My Toyota Avalon indicates a bit slow, my Sonoma is maybe
> 1 MPH fast, and I'm very unhappy my Honda GL1800 Goldwing indicates over 4
> MPH fast.
>
> About the only issue you will have with ABS is if all wheels are not of
> the same size, or if the size changed so much that it moved the low speed
> disable-ABS point.
>


 

"David Kelly" <[email protected]> wrote in message
news:p[email protected]...
> On Mon, 24 Nov 2003 20:40:01 -0500, Jason Cothran wrote:
> >
> > Going up from a 215 to a 235 will not change the speedo. That is the
width
> > of the tire in millimeters. The second number is what determines how
tall
> > the tire is.
>
> Going from 215/75 to 235/75 *will* change the calibration because 75% of
> 215 is not the same as 75% of 235.
>
thats right, but just going the 215 to 235 will not, no aspect ratio was
listed.


 
Mon, 24 Nov 2003 23:00:36 -0500 "Jason Cothran" <[email protected]>
wrote:

> thats right, but just going the 215 to 235 will not, no aspect ratio was
> listed.

If not listed, I assume it to be the same for both 215 and 235.
Same aspect ratio (say, 70%, 75%, 80% or whatever) and tire
height changes when the width changes. This is by definition.

Here's a decent calculator:

http://www.miata.net/garage/tirecalc.html

--
Jukka
 

"Jukka" <[email protected]> wrote in message
news:[email protected]...
> Mon, 24 Nov 2003 23:00:36 -0500 "Jason Cothran" <[email protected]>
> wrote:
>
> > thats right, but just going the 215 to 235 will not, no aspect ratio was
> > listed.
>
> If not listed, I assume it to be the same for both 215 and 235.
> Same aspect ratio (say, 70%, 75%, 80% or whatever) and tire
> height changes when the width changes. This is by definition.
>
> Here's a decent calculator:
>
> http://www.miata.net/garage/tirecalc.html
>
> --
> Jukka

I understand completely how tires are sized. I was just stating the 215 and
235 say nothing of the tire height without the profile listed.


 
Jason

Taken from the original post.. '2000 GM 4x4 - switched from 265/75/16 to
285/75/16. Want to reset parameters'

I would think that a 285/70/16 would be closer to the original size..

--
History is only the past if we choose to do nothing about it..

"Jason Cothran" <[email protected]> wrote in message
news:[email protected]...
>
> "Jukka" <[email protected]> wrote in message
> news:[email protected]...
> > Mon, 24 Nov 2003 23:00:36 -0500 "Jason Cothran" <[email protected]>
> > wrote:
> >
> > > thats right, but just going the 215 to 235 will not, no aspect ratio
was
> > > listed.
> >
> > If not listed, I assume it to be the same for both 215 and 235.
> > Same aspect ratio (say, 70%, 75%, 80% or whatever) and tire
> > height changes when the width changes. This is by definition.
> >
> > Here's a decent calculator:
> >
> > http://www.miata.net/garage/tirecalc.html
> >
> > --
> > Jukka
>
> I understand completely how tires are sized. I was just stating the 215
and
> 235 say nothing of the tire height without the profile listed.
>
>


 
On Tue, 25 Nov 2003 08:07:29 -0500, "Jason Cothran"
<[email protected]> wrote:

>I understand completely how tires are sized. I was just stating the 215 and
>235 say nothing of the tire height without the profile listed.
>

What's funny though is how everybody else knew what the original
poster meant without the mention of aspect ratios........

Matt
99 V-10 Super Duty, Super Cab 4x4

 
Jason Cothran wrote:
>
> "David Kelly" <[email protected]> wrote in message
> news:p[email protected]...
> > On Mon, 24 Nov 2003 20:40:01 -0500, Jason Cothran wrote:
> > >
> > > Going up from a 215 to a 235 will not change the speedo. That is the
> width
> > > of the tire in millimeters. The second number is what determines how
> tall
> > > the tire is.
> >
> > Going from 215/75 to 235/75 *will* change the calibration because 75% of
> > 215 is not the same as 75% of 235.
> >
> thats right, but just going the 215 to 235 will not, no aspect ratio was
> listed.


I didn't bother to list the aspect ratio, it was the same, that's why it
changed my speedo.

In order for those tires to be the same, the aspect ratio would have to
be radically different, something like a 75 series and a 50 series.

If I did that, it really wouldn't make any sense to post about it would
it?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
 
Jason Cothran wrote:
>
> "Mike Romain" <[email protected]> wrote in message
> news:[email protected]...
> > I would find someone with a GPS and clock it to see.
> >
> > When I went up from the stock 215's to 235's, my speedo was right on. it
> > was off before...
> >
> Going up from a 215 to a 235 will not change the speedo. That is the width
> of the tire in millimeters. The second number is what determines how tall
> the tire is.

It sure will unless you radically change the profile.

I went from P215/75's stock to P235/75's.

It is a lot taller tire.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
 

"Mike Hall" <[email protected]> wrote in message
news:[email protected]...
> Jason
>
> Taken from the original post.. '2000 GM 4x4 - switched from 265/75/16 to
> 285/75/16. Want to reset parameters'
>
I am not speaking of the original post, I am speaking of one deeper in the
thread. Obviously, the profile was stated in the original post


 

>
> What's funny though is how everybody else knew what the original
> poster meant without the mention of aspect ratios........
>


Whats even funnier is I'm not speaking of the original post. I am speaking
of the one to which the response was to.


 

"Mike Romain" <[email protected]> wrote in message
news:[email protected]...
> Jason Cothran wrote:
> >
> > "Mike Romain" <[email protected]> wrote in message
> > news:[email protected]...
> > > I would find someone with a GPS and clock it to see.
> > >
> > > When I went up from the stock 215's to 235's, my speedo was right on.
it
> > > was off before...
> > >
> > Going up from a 215 to a 235 will not change the speedo. That is the
width
> > of the tire in millimeters. The second number is what determines how
tall
> > the tire is.
>
> It sure will unless you radically change the profile.
>
> I went from P215/75's stock to P235/75's.
>
> It is a lot taller tire.
>
A lot taller? 15 mm (just over 1/2 inch) is a lot taller?


 

"Mike Romain" <[email protected]> wrote in message
news:[email protected]...
> Jason Cothran wrote:
> >
> > "David Kelly" <[email protected]> wrote in message
> > news:p[email protected]...
> > > On Mon, 24 Nov 2003 20:40:01 -0500, Jason Cothran wrote:
> > > >
> > > > Going up from a 215 to a 235 will not change the speedo. That is the
> > width
> > > > of the tire in millimeters. The second number is what determines how
> > tall
> > > > the tire is.
> > >
> > > Going from 215/75 to 235/75 *will* change the calibration because 75%
of
> > > 215 is not the same as 75% of 235.
> > >
> > thats right, but just going the 215 to 235 will not, no aspect ratio was
> > listed.
>
>
> I didn't bother to list the aspect ratio, it was the same, that's why it
> changed my speedo.
>
> In order for those tires to be the same, the aspect ratio would have to
> be radically different, something like a 75 series and a 50 series.
>
> If I did that, it really wouldn't make any sense to post about it would
> it?
>
In order for the heigth of a 215 and 235 to be the same, there be by no
means a radical difference. Maybe 5% at most.


 
Ok - so i have been to 3 gm dealers today and they all told me it is not
possible to recalibrate for 285/75/16 tires. So what is the deal - the hand
held aftermarket power programmer will work but the dealer says impossible.
Can anyone shed some light on the topic for my feeble brain. Is it even
really necessary except for the speedo and maybe the shift points? The tires
are only about 1 - 1.5" larger in diameter. What are the consequences of
leaving it as is?

Thanks
Danno
"Jason Cothran" <[email protected]> wrote in message
news:[email protected]...
>
> "Mike Romain" <[email protected]> wrote in message
> news:[email protected]...
> > Jason Cothran wrote:
> > >
> > > "Mike Romain" <[email protected]> wrote in message
> > > news:[email protected]...
> > > > I would find someone with a GPS and clock it to see.
> > > >
> > > > When I went up from the stock 215's to 235's, my speedo was right
on.
> it
> > > > was off before...
> > > >
> > > Going up from a 215 to a 235 will not change the speedo. That is the
> width
> > > of the tire in millimeters. The second number is what determines how
> tall
> > > the tire is.
> >
> > It sure will unless you radically change the profile.
> >
> > I went from P215/75's stock to P235/75's.
> >
> > It is a lot taller tire.
> >
> A lot taller? 15 mm (just over 1/2 inch) is a lot taller?
>
>


 

"mxz1972" <[email protected]> wrote in message
news:ZzRwb.495942$pl3.333975@pd7tw3no...
> Ok - so i have been to 3 gm dealers today and they all told me it is not
> possible to recalibrate for 285/75/16 tires. So what is the deal - the
hand
> held aftermarket power programmer will work but the dealer says
impossible.
> Can anyone shed some light on the topic for my feeble brain. Is it even
> really necessary except for the speedo and maybe the shift points? The
tires
> are only about 1 - 1.5" larger in diameter. What are the consequences of
> leaving it as is?
>
> Thanks
> Danno

work out the Pi R squared formula from high school and work out how long the
circumferance of the 285s are and the originals there will be a difference,
divide the number of feet in amile by the circumferance in feet and thats
how many times the wheels turn in a mile. the smaller wheels will turn more
often and the mileometer will be out by however many turns of the wheel the
285s differ from the originals.

fun maths. not sure if it will help.

rhys


 
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