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| istter1 | ABS over size tires | ||
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Elite Guru
 
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On my 87 Vett I have 19" tires and I think 17" in the front. We have checked out throughly the system and it works perfectly during testing. It does not work when driving the light comes on. The brakes with the Hawk pads works great stock brakes. Takled to a lot of brake people and they say it is because of the tire size. I am not that worried about it. Does anyone elese have a simular problem.
Attach file:  IMG00044-20110204-1658.jpg (171.03 KB) IMG00045-20110204-1658.jpg (229.75 KB) IMG00055-20110314-1521.jpg (306.77 KB) |
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Posted on: 2011/7/9 16:58
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| BillH | Re: ABS over size tires | ||
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The Stig Moderator
 
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That does sound strange to me however, my FSM (92) does state: Use of any other tire size or type may seriously affect the ABS/ASR system operation.
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Posted on: 2011/7/9 18:08
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| Matatk | Re: ABS over size tires | ||
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Webmaster
 
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I'm confused as to what doesn't work. What testing did you do? You need a kent moore abs diagnosis tool for testing on car.
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Posted on: 2011/7/9 18:11
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| BrianCunningham | Re: ABS over size tires | ||
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Senior Guru
 
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the ABS system counts the wheel rotations.
stock size, the wheels turn the same rpm for a given speed on that setup they do not |
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Posted on: 2011/7/9 18:59
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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The ABS light is off for about the first 50' then stays on until you shut it down and starts again. What Brian said is what was told to me at the tire shop which makes the light come on.
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Posted on: 2011/7/9 19:22
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| bogus | Re: ABS over size tires | ||
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Grand Imperial Pooh-Bah
 
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yea, Brian is right. The wheel size difference is throwing the computer off.
17" to 19" is the problem here. If you had 18" wheels in the front, you would be better off, because the tires could be the great equalizer. You can get tire sizes that would compensate for the wheel difference. As it is, 17 to 19 is just too damned much for a tire size to compensate for. |
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Posted on: 2011/7/9 19:46
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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When I bought this 87 two years ago from a friend that had injured his back rims and tires had 10 miles on them. A few grand invested. I paid less then $5 grand for it. He paid a few grand for just the tires. Like we talked before the only major problem has been the hydrolic clutch system. Replacing the entire clutch have it done next week if all the parts show up. On trips 24-28 miles per gallon love it.
Thanks Attach file: IMG00040-20100810-1641.jpg (273.99 KB) |
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Posted on: 2011/7/9 20:43
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| BrianCunningham | Re: ABS over size tires | ||
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Senior Guru
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you can have different size wheels provided you have different size aspect ratio tires
what matters is that the TIRE diameters match. IE on my race setup I have 18's in the front but 17's in the back but the tire diameter is about the same since they are different aspect ratio tires  |
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Posted on: 2011/7/9 21:19
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Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/ 383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes NCCC Governor: http://BayStateCorvetteClub.com |
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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makes sence
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Posted on: 2011/7/9 21:27
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| SpectatorRacing | Re: ABS over size tires | ||
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Elite Guru
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Not to ask a stupid question, but are you sure they are 17" fronts? Those look like stock C6 rims, which are 18" front and 19" rear.
Just wondering. Regardless, when you are up for new tires I'd switch the front rims (you can find the stock ones CHEAP) or get higher profile tires as already suggested. |
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Posted on: 2011/7/9 23:14
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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Vehicle is at our shop I beleive you are right they are stock C6 rims. 18 and 19 my son just reminded me. it will be a while before I replace them only have about 5000 miles on them
Sharp eyes lol Never mind being corrected cool |
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Posted on: 2011/7/9 23:27
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| SpectatorRacing | Re: ABS over size tires | ||
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Elite Guru
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Quote:
I have the same rims on my car  |
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Posted on: 2011/7/9 23:37
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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I like the way they look. Front is also lowered 1"
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Posted on: 2011/7/9 23:53
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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Scaryfast It just hit me the guy I bought the Vett from said that the orginal spare tire would not work as it is set up. I haven't been in that situation yet. Do you know the answer or what do I do beside the tow truck? LOL
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Posted on: 2011/7/10 0:01
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| bogus | Re: ABS over size tires | ||
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Grand Imperial Pooh-Bah
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when you get the car back, check all four tires and post their sizes. Well, front and rear cause I expect the fronts to match and the rears to match...
I am wondering if the wheel speed and VSS are not matching... I am trying to remember, but I think VSS data is sent to the ABS computer. If the tire/wheel combo is too big, then problems will occur. Or if the rear diff was changed and the gears not changed in the transmission tail housing. |
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Posted on: 2011/7/10 2:49
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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Good food for thought. Thanks
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Posted on: 2011/7/10 2:56
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Only I can change my life. No one can do it for me. Carol Burnett |
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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" Bogus"
More math time! Your current rear tire is: 275/40/19 To derive overall nominal height: 1. 275 x 40% = 110mm 2. 110mm / 25.4mm (1 inch) = 4.3" 3. 4.3" + 4.3" + 19" = 27.6" This works out to an overall nominal height of 27.6" Now, for the stock 255/50/16: 1. 255 x 50% = 127.5mm 2. 127.5mm / 25.4mm (1 inch) = 5" 3. 5" + 5" + 16" = 26" Well you already have a speedo error - 1.6" is rather significant. At 60mph, you are off by 4 mph slow! 60 really means you are doing 64. So don't let the ratios worry you. I would stick with the .64 OD. If you want to correct the speedo error, there are other ways to do it. The .64 will help of you decide to go nuts with gearing down the road. " Just for kicks we put stock tires on the 87 and drove it and the ABS light stayed off. When we went back to the tire set up Andy explaines above it would do as was described as above threds. Question Might sound dumb! When we install the new transmission and calibrate correctly the speedo error to the computer can that correct the tire rotations to the ABS. Or just the correct size tires combonation correct the light staying on? Does the ABS interact with the other systems? Brakes work fine hate the light being on. Have about 40,000 left on tread. Steve |
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Posted on: 2011/8/3 4:22
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| Matatk | Re: ABS over size tires | ||
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Webmaster
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The VSS/gears in the trans is for speedo. The ABS system is separate and changing the VSS/gears won't affect that.
Matthew |
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Posted on: 2011/8/3 11:46
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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I assumed it would be that way.
Thanks Steve |
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Posted on: 2011/8/3 13:42
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| vette079 | Re: ABS over size tires | ||
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Guru Newb
 
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Quote:
This is correct, the abs computer starts to interfere when it senses different wheel speeds when rolling, slowing down or applying the brakes. If the total tire/wheel hight is different (more then 5%) between front and back, you get into trouble. You can have 15 inch in front or rear, and 20 in front or rear, but as said before, then you need different aspect ratios (80´s 70´s 60´s 50´s and so on) so you will end up with the same height front and rear... At least on the C4´s. Other cars/makes may have their abs computers programmed with different heights front and rear. In that case they still have to end up with the same differences in height as the originals front and rear. |
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Posted on: 2011/8/3 19:51
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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I was fairly certain that the person that told me different was wrong. Per eairler discussions here.
Thanks Steve  |
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Posted on: 2011/8/3 21:23
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| vis_croceus | Re: ABS over size tires | ||
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Senior Guru
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C4 ABS is very forgiving of height differences.
Tons of us have run 1" or more stagger front-rear (i.e., >7%) with no problems. |
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Posted on: 2011/8/4 4:19
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| Jagdpanzer | Re: ABS over size tires | ||
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Guru Newb
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The ABS system takes wheel speed information from speed pickups located on each wheel spindle. The front wheel speed sensors are integral within the wheel bearing hub assembly.
 The rear wheel speed sensors are attached to the suspension knuckles and generate a speed signal from the 47 tooth count reluctor wheels pressed on each axle spindle as seen here:   I also recently changed to a staggared wheel/tire setup of 26" tall fronts and 27" tall rears on my 94 ZR-1. This setup now triggers the "Check ABS" and "Check ASR" lights on the dash alarm panel. The alarm lights come on after driving a mile or two, otherwise the brake system seems to work fine. To fix setting off the alarm lights I am machining two new reluctor wheels for the rear spindles with 49 tooth count which should compensate for the taller rear tires. |
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Posted on: 2011/8/13 0:52
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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So does that mean they work simular to a crank sensor. In that they pick up the signal in the same method.
Steve  |
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Posted on: 2011/8/13 3:14
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| Strick | Re: ABS over size tires | ||
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Guru
 
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Not to rain on your parade, but because of a larger diameter rear wheel, your odometer will register less mileage than actually travelled. So it will calculate out as better gas mileage, but not really. |
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Posted on: 2011/8/14 12:24
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| istter1 | Re: ABS over size tires | ||
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Elite Guru
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Quote:
Andy did the math for me . I off about 4 mph. A lot better than my F150. I enjoy the fact I can drive from Bakersfield to Pismo Beach, stay for a couple day, and then drive back on a on one tank. Cool Steve |
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Posted on: 2011/8/14 12:48
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