Any pics of upsized tires instead of a drop?
Originally Posted by khsonic03
OK Smarta$$. Sorry to break it to you, but rotational diameter most definitely affects ABS/speedo/VDC. The systems are designed to detect a certain rotational diameter (within certain limitations/variances). If you change that diameter, you are throwing off the calculations that have been programmed into these units. The biggest factor is related to ABS and speed. Not saying that your speedo will blow up, rather read incorrectly and affect odom readings. VDC is more affected by front to rear ratio changes. It's not rocket science. But hey, since you are such a knowledgeable mechanic, how does it work? Please enlighten the rest of us.
Putting 4 taller or 4 shorter tires will create discrepancy between your "land" speed(as measured by outside device-like radar or GPS) and your gear driven speed sensor reading. But VDC and ABS are not that smart to know your "land" speed and thus they don't care. 4/4=8/8.
Now with staggered set up-there's a "dead zone" in the system. Car wheels(even stock size) will rotate with different speeds in corners and VDC is fine with that. As long as front/rear difference is small, VDC will not care. Making it big will screw up your handling anyway.
And I didn't say that I am a knowledgabel mechnic, I said that I try things and post based on my experience and not theoretical reading.
Registered User
Joined: Aug 2003
Posts: 1,112
Likes: 2
From: New England
Well, again...My post (before you attacked me) was indicating the POTENTIAL for problems. I then stated that there are LIMITATIONS on the increases or decreases you can/should make. You should stay within 3% of the original tire size. Why do you think that manufacturers create these recommended sizes? Each vehicle is designed to operate properly around a specific sized rotating diameter. If the computer recognizes more or less revolutions than was programmed into it, it can prematurely trigger the ABS system (or trigger it too late). And again, I said that the VDC system is more contingent on front to rear ratio changes. The speedo/odom thing is obvious.
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Joined: Dec 2005
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From: Edmonton, AB
When i put 245/45/18F and 275/35/18R i thought i would have VDC issues because of the difference in spin rates of front and rear wheels. But that didnt happen...In this particular setup, the front is -1.4% slower than stock, and the rear is +2.8% FASTER than stock... total of 4.2% difference...
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Joined: Apr 2006
Posts: 348
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From: Sacramento, CA
Originally Posted by Nickk6
damn those are big tires...looks like a 4x4
Originally Posted by khsonic03
OK Smarta$$. Sorry to break it to you, but rotational diameter most definitely affects ABS/speedo/VDC. The systems are designed to detect a certain rotational diameter (within certain limitations/variances). If you change that diameter, you are throwing off the calculations that have been programmed into these units. The biggest factor is related to ABS and speed. Not saying that your speedo will blow up, rather read incorrectly and affect odom readings. VDC is more affected by front to rear ratio changes. It's not rocket science. But hey, since you are such a knowledgeable mechanic, how does it work? Please enlighten the rest of us.
Actually the other user is right and your wrong. It doesn't read it from the WHEEL/TIRE it reads it from the hub itself. Changing the tire size to a truck tire will not make any difference in the way VDC/ABS will work on our cars. If you have a different size tire front and one in the rear then yes it will cause a problem because the hub will be turning faster on one corner than the other.
No its not, but you definitely should not try correcting someone with info that you have wrong yourself.
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Joined: Aug 2003
Posts: 1,112
Likes: 2
From: New England
Originally Posted by G35_TX
Actually the other user is right and your wrong. It doesn't read it from the WHEEL/TIRE it reads it from the hub itself. Changing the tire size to a truck tire will not make any difference in the way VDC/ABS will work on our cars. If you have a different size tire front and one in the rear then yes it will cause a problem because the hub will be turning faster on one corner than the other.
No its not, but you definitely should not try correcting someone with info that you have wrong yourself.
No its not, but you definitely should not try correcting someone with info that you have wrong yourself.
"Some types of ABS problems may not set a fault code or turn on the ABS warning light. These include intermittent faults or problems that may be due to environmental factors (heat, cold or moisture), or other problems that are not in the ABS control electronics. These problems include dirty brake fluid that contains debris, a sticking, dragging or leaking brake caliper, warped rotor, variations in rotor thickness, wrong brake linings or contaminated brake linings, changes in wheel and/or tire sizes, electrical glitches in the wiring or charging system, etc."
"Every ABS system is calibrated for a specific vehicle application (a specific size and class of vehicle, a specific weight range, a certain tire and wheel size, and the individual braking characteristics of that vehicle).
Any modifications that may have been made to a vehicle that significantly alter any of these basic parameters may upset the normal operation of the ABS system. Replacing the brake linings with ones that have a higher or lower coefficient of friction than the original linings may affect the operation of the system. Raising or lowering the vehicle's ride height can also change the chassis dynamics and loading on the front and rear brakes."
And the link:
http://www.babcox.com/editorial/ic/ic20636.htm
And another:
Question:
When I replace the tires on my vehicle, do I have to use the same size as the originals?
Answer:
On ABS-equipped vehicles, all vehicle manufacturers recommend using the same size and aspect ratio tire as the original. ABS systems monitor the rotational speed of the tires through individual wheel speed sensors. Changing to an oversize tire with a taller diameter than stock would cause the tires to rotate at a slightly slower speed relative to vehicle speed than the stock tires. Changing to a low profile tire with a shorter diameter would cause the tires to rotate at a slightly faster speed relative to vehicle speed. Though the difference either way isn't much, it may be enough to upset the calibration of the ABS system and have an adverse effect on its ability to detect and prevent skids.
Another reason for not changing tire sizes is because it can affect the speedometer, odometer and transmission shift points on a vehicle with an electronic automatic. Oversize tires will make your speedometer read slower than normal (which may get you a speeding ticket unless you have the speedometer recalibrated to compensate for the change in tire size!). Smaller diameter tires will make the speedometer read faster than normal, and increase the mileage readings on your odometer at a faster than normal rate.
And the link:
http://www.aicautosite.com/garage/repairqa/ques151.asp
And yet another:
"What is the right size for my vehicle?
Buying the correct tire size can get complicated, especially if you decide to upgrade from your vehicle's Original Equipment size. The expert sales team at The Tire Rack is always ready to offer performance and fitment advice. Call 888-541-1777.
A tire's first requirement is that it must be able to carry the weight of your vehicle. No matter how good a tire you select, if its capabilities are "overworked" just carrying the load, it will have little reserve capacity to help your vehicle respond to quick emergency. So when you are in the selection process, make certain that your new tire's size is designed to carry the weight of your vehicle! Don't undersize.
The other size consideration is overall tire diameter. Since many of the functions of today's vehicles are highly computerized, maintaining accurate speed data going into the computer assures accurate instructions coming out. And an important part of the speed equation is your tire's overall tire diameter.
For cars and vans, staying within a 3% diameter change is desirable. Pick-ups and sport utility vehicles (SUVs) are usually engineered to handle up to a 15% oversize tire. Most tire dimensions can be calculated. For more information review the Tire Tech article, "Calculating Tire Dimensions." While at first a 3% diameter increase or reduction in tire diameter may sound very limiting, in most cases it allows approximately a 3/4" diameter change.
Additionally to help with the selection of substitute sizes, a system called "Plus Sizing" was developed. We use Plus Sizing to take into account the diameters of the available tires and the wheels, and then helps select the appropriate tire width that ensures adequate load capacity. Maintaining the tire's overall diameter helps maintain accurate speed data going into the computer."
And the link:
http://www.tirerack.com/tires/tirete....jsp?techid=31
You obviously have no clue how things work in this area. 
If you have the same size tire and wheel on all four corners, if its a truck tire or a go-cart tire it will not make any difference. The only thing different is the speedo will read either faster or slower than what you are actually going. But all the sensor/ecu know is your going 55mph per the HUB but you are actually going faster or slower than 55mph. If there is a different size wheel/tire in the rear than the front yes it will cause a problem. But there is no change in hub speed if you switch to taller tires or smaller tires. The car has no clue how fast its going without reading the HUB, and the HUB will turn no matter what size tires you have on the car.
Think about it. If you put truck tires on the car, and you drive 55mph. The hub will actually be spinning FASTER than it was before so your 55mph per your speedo is actually 45 mph per a GPS.
Like I said before, your car has no clue what size tire and doesn't CARE as long as they all match. The ABS/VDC system will not be affected in anyway.
If you have the same size tire and wheel on all four corners, if its a truck tire or a go-cart tire it will not make any difference. The only thing different is the speedo will read either faster or slower than what you are actually going. But all the sensor/ecu know is your going 55mph per the HUB but you are actually going faster or slower than 55mph. If there is a different size wheel/tire in the rear than the front yes it will cause a problem. But there is no change in hub speed if you switch to taller tires or smaller tires. The car has no clue how fast its going without reading the HUB, and the HUB will turn no matter what size tires you have on the car.
Think about it. If you put truck tires on the car, and you drive 55mph. The hub will actually be spinning FASTER than it was before so your 55mph per your speedo is actually 45 mph per a GPS.
Like I said before, your car has no clue what size tire and doesn't CARE as long as they all match. The ABS/VDC system will not be affected in anyway.
Originally Posted by khsonic03
Hmmm...I'm the one with the wrong info? I know that the ABS reads off of the hub, and there is no magical sensor in the tire. But thanks for that bit of info. That's not my point. It's the fact that the tire/wheel will be rotating at a different speed relative to the speed of the vehicle. This, in turn ALSO makes the hub sensor read a different speed (the hub is connected to the wheel--crazy stuff, I know) The ABS sytstem is calibrated to allow certain variations in the speed, BUT there is a limitation to those variations. I am not going to touch on the VDC thing because I stated numerous times that the biggest variable is front to rear ratio changes. Check these articles out, apparently I am not the only one who believes this. I made it easy and provided the pertinent quotes and then the links:
"Some types of ABS problems may not set a fault code or turn on the ABS warning light. These include intermittent faults or problems that may be due to environmental factors (heat, cold or moisture), or other problems that are not in the ABS control electronics. These problems include dirty brake fluid that contains debris, a sticking, dragging or leaking brake caliper, warped rotor, variations in rotor thickness, wrong brake linings or contaminated brake linings, changes in wheel and/or tire sizes, electrical glitches in the wiring or charging system, etc."
"Every ABS system is calibrated for a specific vehicle application (a specific size and class of vehicle, a specific weight range, a certain tire and wheel size, and the individual braking characteristics of that vehicle).
Any modifications that may have been made to a vehicle that significantly alter any of these basic parameters may upset the normal operation of the ABS system. Replacing the brake linings with ones that have a higher or lower coefficient of friction than the original linings may affect the operation of the system. Raising or lowering the vehicle's ride height can also change the chassis dynamics and loading on the front and rear brakes."
And the link:
http://www.babcox.com/editorial/ic/ic20636.htm
And another:
Question:
When I replace the tires on my vehicle, do I have to use the same size as the originals?
Answer:
On ABS-equipped vehicles, all vehicle manufacturers recommend using the same size and aspect ratio tire as the original. ABS systems monitor the rotational speed of the tires through individual wheel speed sensors. Changing to an oversize tire with a taller diameter than stock would cause the tires to rotate at a slightly slower speed relative to vehicle speed than the stock tires. Changing to a low profile tire with a shorter diameter would cause the tires to rotate at a slightly faster speed relative to vehicle speed. Though the difference either way isn't much, it may be enough to upset the calibration of the ABS system and have an adverse effect on its ability to detect and prevent skids.
Another reason for not changing tire sizes is because it can affect the speedometer, odometer and transmission shift points on a vehicle with an electronic automatic. Oversize tires will make your speedometer read slower than normal (which may get you a speeding ticket unless you have the speedometer recalibrated to compensate for the change in tire size!). Smaller diameter tires will make the speedometer read faster than normal, and increase the mileage readings on your odometer at a faster than normal rate.
And the link:
http://www.aicautosite.com/garage/repairqa/ques151.asp
And yet another:
"What is the right size for my vehicle?
Buying the correct tire size can get complicated, especially if you decide to upgrade from your vehicle's Original Equipment size. The expert sales team at The Tire Rack is always ready to offer performance and fitment advice. Call 888-541-1777.
A tire's first requirement is that it must be able to carry the weight of your vehicle. No matter how good a tire you select, if its capabilities are "overworked" just carrying the load, it will have little reserve capacity to help your vehicle respond to quick emergency. So when you are in the selection process, make certain that your new tire's size is designed to carry the weight of your vehicle! Don't undersize.
The other size consideration is overall tire diameter. Since many of the functions of today's vehicles are highly computerized, maintaining accurate speed data going into the computer assures accurate instructions coming out. And an important part of the speed equation is your tire's overall tire diameter.
For cars and vans, staying within a 3% diameter change is desirable. Pick-ups and sport utility vehicles (SUVs) are usually engineered to handle up to a 15% oversize tire. Most tire dimensions can be calculated. For more information review the Tire Tech article, "Calculating Tire Dimensions." While at first a 3% diameter increase or reduction in tire diameter may sound very limiting, in most cases it allows approximately a 3/4" diameter change.
Additionally to help with the selection of substitute sizes, a system called "Plus Sizing" was developed. We use Plus Sizing to take into account the diameters of the available tires and the wheels, and then helps select the appropriate tire width that ensures adequate load capacity. Maintaining the tire's overall diameter helps maintain accurate speed data going into the computer."
And the link:
http://www.tirerack.com/tires/tirete....jsp?techid=31
"Some types of ABS problems may not set a fault code or turn on the ABS warning light. These include intermittent faults or problems that may be due to environmental factors (heat, cold or moisture), or other problems that are not in the ABS control electronics. These problems include dirty brake fluid that contains debris, a sticking, dragging or leaking brake caliper, warped rotor, variations in rotor thickness, wrong brake linings or contaminated brake linings, changes in wheel and/or tire sizes, electrical glitches in the wiring or charging system, etc."
"Every ABS system is calibrated for a specific vehicle application (a specific size and class of vehicle, a specific weight range, a certain tire and wheel size, and the individual braking characteristics of that vehicle).
Any modifications that may have been made to a vehicle that significantly alter any of these basic parameters may upset the normal operation of the ABS system. Replacing the brake linings with ones that have a higher or lower coefficient of friction than the original linings may affect the operation of the system. Raising or lowering the vehicle's ride height can also change the chassis dynamics and loading on the front and rear brakes."
And the link:
http://www.babcox.com/editorial/ic/ic20636.htm
And another:
Question:
When I replace the tires on my vehicle, do I have to use the same size as the originals?
Answer:
On ABS-equipped vehicles, all vehicle manufacturers recommend using the same size and aspect ratio tire as the original. ABS systems monitor the rotational speed of the tires through individual wheel speed sensors. Changing to an oversize tire with a taller diameter than stock would cause the tires to rotate at a slightly slower speed relative to vehicle speed than the stock tires. Changing to a low profile tire with a shorter diameter would cause the tires to rotate at a slightly faster speed relative to vehicle speed. Though the difference either way isn't much, it may be enough to upset the calibration of the ABS system and have an adverse effect on its ability to detect and prevent skids.
Another reason for not changing tire sizes is because it can affect the speedometer, odometer and transmission shift points on a vehicle with an electronic automatic. Oversize tires will make your speedometer read slower than normal (which may get you a speeding ticket unless you have the speedometer recalibrated to compensate for the change in tire size!). Smaller diameter tires will make the speedometer read faster than normal, and increase the mileage readings on your odometer at a faster than normal rate.
And the link:
http://www.aicautosite.com/garage/repairqa/ques151.asp
And yet another:
"What is the right size for my vehicle?
Buying the correct tire size can get complicated, especially if you decide to upgrade from your vehicle's Original Equipment size. The expert sales team at The Tire Rack is always ready to offer performance and fitment advice. Call 888-541-1777.
A tire's first requirement is that it must be able to carry the weight of your vehicle. No matter how good a tire you select, if its capabilities are "overworked" just carrying the load, it will have little reserve capacity to help your vehicle respond to quick emergency. So when you are in the selection process, make certain that your new tire's size is designed to carry the weight of your vehicle! Don't undersize.
The other size consideration is overall tire diameter. Since many of the functions of today's vehicles are highly computerized, maintaining accurate speed data going into the computer assures accurate instructions coming out. And an important part of the speed equation is your tire's overall tire diameter.
For cars and vans, staying within a 3% diameter change is desirable. Pick-ups and sport utility vehicles (SUVs) are usually engineered to handle up to a 15% oversize tire. Most tire dimensions can be calculated. For more information review the Tire Tech article, "Calculating Tire Dimensions." While at first a 3% diameter increase or reduction in tire diameter may sound very limiting, in most cases it allows approximately a 3/4" diameter change.
Additionally to help with the selection of substitute sizes, a system called "Plus Sizing" was developed. We use Plus Sizing to take into account the diameters of the available tires and the wheels, and then helps select the appropriate tire width that ensures adequate load capacity. Maintaining the tire's overall diameter helps maintain accurate speed data going into the computer."
And the link:
http://www.tirerack.com/tires/tirete....jsp?techid=31
Registered User
Joined: Aug 2003
Posts: 1,112
Likes: 2
From: New England
LOL. Check when I became a member. I know how things work around here. August 2003. Just because I don't have as many posts as you doesn't mean I don't check this site everyday like the rest of you. Apparently you didn't read any of the articles and quotes I posted. Let me guess....you know more than them, right? That's fine. I am going to agree to disagree.
Registered User
Joined: May 2006
Posts: 185
Likes: 0
Yeah but he is right. As long as the wheels and tires are equal the VDC and ABS doesn't care. It looks at wheel speed differential only to determine if a wheel is slipping or locked. Most of the time it is anything greater then 5 mph is required to activate either.
And yes I am a noob but I am speaking from knowledge and experience, not what I read on the internet.
And yes I am a noob but I am speaking from knowledge and experience, not what I read on the internet.
Originally Posted by Incaico
Just put in 255/45/18 on the rear. Ride seems quieter on my '04 5AT. May go with 235/45/18" on the fronts.
Originally Posted by khsonic03
LOL. Check when I became a member. I know how things work around here. August 2003. Just because I don't have as many posts as you doesn't mean I don't check this site everyday like the rest of you. Apparently you didn't read any of the articles and quotes I posted. Let me guess....you know more than them, right? That's fine. I am going to agree to disagree.