Will 18's in the back and 17's in the front mess with ABS
02-07-2003, 10:01 PM
#16
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Location: DeKalb, IL
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Here's the thread I was talking about:
me:
Guys,
how do you figure out how to adjust your speedo when you have a 255 tire in
front and a 265 tire in the back? (40%, both 17s)
Do you just use the 265, or average the two?
Steve Walker:
use the 265. That's the one that would be inline with the reluctor gear in
the tranny for your speedometer.
Honestly it isn't the manufacturer's tire sizing though. You should look
for the rated "Rotations per mile" for the tire instead (then calculate the
functional diameter).
the difference between 265 and 255 tires on the same rim width will be
minimal. If anything the 265 will just bow the sidewalls more and give you
a more "loose" feeling. We're only talking about 4 millimeters here.
Dave Akins
Since the speedometer sender is reading the driveline, you want to use
the rear wheels, the front ones are irrelevant.
me:
Guys,
how do you figure out how to adjust your speedo when you have a 255 tire in
front and a 265 tire in the back? (40%, both 17s)
Do you just use the 265, or average the two?
Steve Walker:
use the 265. That's the one that would be inline with the reluctor gear in
the tranny for your speedometer.
Honestly it isn't the manufacturer's tire sizing though. You should look
for the rated "Rotations per mile" for the tire instead (then calculate the
functional diameter).
the difference between 265 and 255 tires on the same rim width will be
minimal. If anything the 265 will just bow the sidewalls more and give you
a more "loose" feeling. We're only talking about 4 millimeters here.
Dave Akins
Since the speedometer sender is reading the driveline, you want to use
the rear wheels, the front ones are irrelevant.
02-07-2003, 10:06 PM
#18
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Location: DeKalb, IL
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Well that's what I was saying, I doubt the ABS has anything to do with the values you set in the pcm for recalibrating the speedo and proper tranny shifting. Otherwise, why wouldn't it cause ABS problems when you change the gears and don't reprogram the new gear size. The speed the pcm figures is different than the actual speed, but it doesn't cause ABS problems....
02-07-2003, 10:07 PM
#19
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Location: Ware, Massachusetts
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hmm....Maybe the ENGINEERS who CREATED the Corvette took this into account, being that this is the only vehicle to my knowledge available with two different rim sizes. The biggest rims that the Z28s, SSs etc were available with 17" which had P275 40 ZR17's for tires. I have recalibrated many PCMs being that I work for at a Chevrolet Dealership. All the GM cars that I have noticed only have an input for ONE tire size in the calibration. The ABS/PCM looks at ALL available wheel sensors. The ring gear passing over the magnet (aka wheel sensor) creates an AC current. The PCM monitors ALL OF THEM! What would be the purpose wheel sensors on the front of the car if it wasn't going to use them!?! If you monitor your PID data on your scan tool, you can see each sensors voltage it is producing AND the current wheel speed. Josh-97WS6 is correct is stating that something as small as a 5 mph difference can trigger ABS operation once the brake switch is activated. HOWEVER, a constant difference will trigger intermittent false cycling, AND set a DTC for the rear abs sensor being different from the front. Once a DTC is stored in the ABS module, the pretty little light we all dread on our dash comes on, and ABS function is disabled.
Last edited by NtenseZ28; 02-07-2003 at 10:14 PM.
02-07-2003, 10:10 PM
#20
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Location: Petersham, MA
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Originally posted by NtenseZ28
[B HOWEVER, a constant difference will trigger intermittent false cycling, AND set a DTC for the rear abs sensor being different from the front. [/B]
[B HOWEVER, a constant difference will trigger intermittent false cycling, AND set a DTC for the rear abs sensor being different from the front. [/B]
02-08-2003, 01:20 PM
#21
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Location: Sterling Hgts, Mich
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1=..not to sure it will cause problems(BUT I 'v been wrong once or twice
),on the road,all 4 wheels tend to rotate at diff.speeds if slightly..ie..going around corners or driving in a circle will not trigger an abs code,....hey that was easy!
2=..the abs sensor is in the pumkin,the harness plugs into the top of the center diff. vss signal is sent by the trans,
3=..the computer see's and uses both vss. and abs sensors to monitor abs operation.
),on the road,all 4 wheels tend to rotate at diff.speeds if slightly..ie..going around corners or driving in a circle will not trigger an abs code,....hey that was easy!2=..the abs sensor is in the pumkin,the harness plugs into the top of the center diff. vss signal is sent by the trans,
3=..the computer see's and uses both vss. and abs sensors to monitor abs operation.
02-08-2003, 02:55 PM
#22
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Originally posted by WP
1=..not to sure it will cause problems(BUT I 'v been wrong once or twice ),on the road,all 4 wheels tend to rotate at diff.speeds if slightly..ie..going around corners or driving in a circle will not trigger an abs code,....hey that was easy!
2=..the abs sensor is in the pumkin,the harness plugs into the top of the center diff. vss signal is sent by the trans,
3=..the computer see's and uses both vss. and abs sensors to monitor abs operation.
1=..not to sure it will cause problems(BUT I 'v been wrong once or twice
),on the road,all 4 wheels tend to rotate at diff.speeds if slightly..ie..going around corners or driving in a circle will not trigger an abs code,....hey that was easy!2=..the abs sensor is in the pumkin,the harness plugs into the top of the center diff. vss signal is sent by the trans,
3=..the computer see's and uses both vss. and abs sensors to monitor abs operation.
Did you bother reading the rest of this thread?
02-08-2003, 03:09 PM
#23
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Location: Middle Tennessee
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From what I have learned about tire sizes, as long as the overall diameter or the tires are the same size, regardless of wheel diameter, then they turn at the same speed.
For example: a 245/50 ZR 16 is the same size as a 275/40 ZR 17 from MOST tire manufactures (assuming both tires are made by the same manufacturer).
If you use a site like www.tirerack.com to choose a set of wheels for your car and you pick a set of wheels larger than stock, their site automatically shows the proper size tire for the larger wheel.
I don't see any reason you would have to worry about the ABS system if you are using the properly sized tires for the vehicle and the chosen wheels.
For example: a 245/50 ZR 16 is the same size as a 275/40 ZR 17 from MOST tire manufactures (assuming both tires are made by the same manufacturer).
If you use a site like www.tirerack.com to choose a set of wheels for your car and you pick a set of wheels larger than stock, their site automatically shows the proper size tire for the larger wheel.
I don't see any reason you would have to worry about the ABS system if you are using the properly sized tires for the vehicle and the chosen wheels.
02-08-2003, 03:10 PM
#24
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Location: Canada
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Originally posted by WP
1=..not to sure it will cause problems(BUT I 'v been wrong once or twice ),on the road,all 4 wheels tend to rotate at diff.speeds if slightly..ie..going around corners or driving in a circle will not trigger an abs code,....hey that was easy!
2=..the abs sensor is in the pumkin,the harness plugs into the top of the center diff. vss signal is sent by the trans,
3=..the computer see's and uses both vss. and abs sensors to monitor abs operation.
1=..not to sure it will cause problems(BUT I 'v been wrong once or twice
),on the road,all 4 wheels tend to rotate at diff.speeds if slightly..ie..going around corners or driving in a circle will not trigger an abs code,....hey that was easy!2=..the abs sensor is in the pumkin,the harness plugs into the top of the center diff. vss signal is sent by the trans,
3=..the computer see's and uses both vss. and abs sensors to monitor abs operation.
1) you are right - the computer is looking for an RPM difference front/rear/side. But high speed corners won't give you much side-to-side differences. Low speed corners... the RPM for all the wheels will be lower.
2) non-ASR f-bodies get 3-channel ABS with one rear (center) speed sensor. ASR cars get 4-channel with a sensor at each wheel.
3) see 2).
DaveH
02-08-2003, 03:30 PM
#25
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Join Date: Dec 2002
Location: Ware, Massachusetts
Posts: 165
As long as the diameter of the rim and tire assembly remain the same, it will cause the center hub that the rim is attached to turning at the same RPM. As for the going around corners not causing ABS operation. HOW OFTEN DO YOU DRIVE IN CIRCLES WITH YOUR BRAKES ON?!?! That is why the ABS system has a brake switch. If you look at ur brake pedal assembly, you will have 2 switches, one for the brake light, and one for the ABS system. A brief difference in wheel speed while the brakes ARE NOT applied will not cause any change in the system. However, if you drive around when the ABS module goes through it's duty cycles, and you have a difference in wheel speeds all the time, it's gonna set a code. PERIOD. Why do you think that have DTC's that point that out? False cycling is when the brakes are applied, and the PCM sees that one or more of the wheel speeds are different from the rest of them, and the VSS. A chipped exciter ring will cause this because it will change the voltage BRIEFLY, therefore telling the computer that this wheel is spinning at a different speed than the others. No matter the cause, if it senses at ANY point that the wheel is slipping (i.e different wheel speed), and you happen to be using the brakes, the ABS is going to activate.
If you really have a difference of 5" in diameter of ur tires, ur ABS light is probably burnt out from being on for 2 years. Were you running your drag slicks while skidding down the snowy road? Five inches difference would cause the front hub assemblies to be spinning considerably faster than the rear axles.....
If you really have a difference of 5" in diameter of ur tires, ur ABS light is probably burnt out from being on for 2 years. Were you running your drag slicks while skidding down the snowy road? Five inches difference would cause the front hub assemblies to be spinning considerably faster than the rear axles.....
Last edited by NtenseZ28; 02-08-2003 at 03:37 PM.
02-08-2003, 10:09 PM
#27
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Join Date: Dec 1999
Location: Petersham, MA
Posts: 1,697
Originally posted by Pro/Street SS
Quote :
PS- LEARN TO READ ....
You see that my sig is to many lines....try READING it !!
" Almost A Daily Driver "
Quote :
PS- LEARN TO READ ....
You see that my sig is to many lines....try READING it !!
" Almost A Daily Driver "
I did....I'm still not impressed. You should ask your "friend" Brent how many sig lines you're supposed to have if you don't believe me. But I'm sure you already knew that.
02-08-2003, 11:33 PM
#28
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Join Date: Mar 2000
Posts: 186
When I dyno, sometimes the ABS light comes on, so I'd say there is some sort of check. I'm not sure how much different they have to be to cause trouble though.
The answer is just make sure the tire diameters are the same front and back. It would look stupid if they weren't.
-Alex
The answer is just make sure the tire diameters are the same front and back. It would look stupid if they weren't.
-Alex
02-09-2003, 04:17 AM
#29
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Join Date: May 1999
Location: Inverness, FL
Posts: 4,060
Josh,
You may not believe him about it being able to be a daily driver but he is correct. He runs high octane av gas in it right now but with about 3 minutes to change the tune it'll run very good on pump gas. Him and I went to Atlanta last year. The drive took about 9 hours. We were both stuck in a traffic jam on the interstate for 2 hours and his car did just fine. In fact, his car got a little over 20 miles to the gallon on the trip. It is an incredible car... you should see it and ride in it. It rides very good for being a tubb'd car! Heck, it doesn't even do that bad in the rain. He had tires on there before that made it extremely difficult to drive in the rain but the tires he just got do surprisingly well in the rain. So, you can raise the BS flag if you'd like but you'd be wrong.
There is nothing stopping him from driving the car every single day right now other than the fact he keeps the thing absolutely spotless and I know he doesn't like to drive it in the rain because it gets too dirty. Other than the rain (for appearance issues!) nothing is stopping him from hopping in that car and driving it to Orlando, Daytona, or even Atlanta as he did last year... as he dilutes the av gas, he changes the program in the parking lot of the gas station to account for the dilution. We did it twice on the way to Atlanta.
Oh, and Pro Street Johh, he is correct in that we ask people to keep their sig length to around 5 lines. You don't post often and you must have just changed your sig because I don't recall it being quite that long before
As for the discussion about what causes to ABS light to come on... I don't really know. I do know that Pro Street John has all his sensors hooked up, ABS computer intact, and has no codes. It's not his light being out either because he has access to a high dollar Snap On scanner on a daily basis and the scanner shows nothing wrong.
You may not believe him about it being able to be a daily driver but he is correct. He runs high octane av gas in it right now but with about 3 minutes to change the tune it'll run very good on pump gas. Him and I went to Atlanta last year. The drive took about 9 hours. We were both stuck in a traffic jam on the interstate for 2 hours and his car did just fine. In fact, his car got a little over 20 miles to the gallon on the trip. It is an incredible car... you should see it and ride in it. It rides very good for being a tubb'd car! Heck, it doesn't even do that bad in the rain. He had tires on there before that made it extremely difficult to drive in the rain but the tires he just got do surprisingly well in the rain. So, you can raise the BS flag if you'd like but you'd be wrong.
There is nothing stopping him from driving the car every single day right now other than the fact he keeps the thing absolutely spotless and I know he doesn't like to drive it in the rain because it gets too dirty. Other than the rain (for appearance issues!) nothing is stopping him from hopping in that car and driving it to Orlando, Daytona, or even Atlanta as he did last year... as he dilutes the av gas, he changes the program in the parking lot of the gas station to account for the dilution. We did it twice on the way to Atlanta. Oh, and Pro Street Johh, he is correct in that we ask people to keep their sig length to around 5 lines. You don't post often and you must have just changed your sig because I don't recall it being quite that long before
As for the discussion about what causes to ABS light to come on... I don't really know. I do know that Pro Street John has all his sensors hooked up, ABS computer intact, and has no codes. It's not his light being out either because he has access to a high dollar Snap On scanner on a daily basis and the scanner shows nothing wrong.
02-09-2003, 06:56 AM
#30
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Location: Petersham, MA
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If the car is that driveable, then kudos.
I would surmise that his car doesn't not see ABS conditions very often. I would question how well it works up here in New England, where, unfortunately, we get to use it all the time.
I think this thread got confusing when it got brought up that the PCM monitors and compares all the wheel sensors. Perhaps it is different on a car without traction control like Prostreet SS's car?
I would surmise that his car doesn't not see ABS conditions very often. I would question how well it works up here in New England, where, unfortunately, we get to use it all the time.
I think this thread got confusing when it got brought up that the PCM monitors and compares all the wheel sensors. Perhaps it is different on a car without traction control like Prostreet SS's car?