What happens when you run shorter rear tires?
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Senior Member
Joined: Apr 2000
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From: Allen, TX, USA
What happens when you run shorter rear tires?
For those that run shorter than stock rear tires (whether on the street or at the strip):
1) does the computer make the trans shift prematurely? I know on some of these late model vehicles, the trans will be programmed to shift based on MPH as much as RPM. So, if you had a shorter tire, in theory, it might shift at too low of an rpm.
2) any thing else happen with the trans shifting differently than normal when you run shorter tires?
3) can the EEC be reprogrammed for a shorter tire, or can a chip take care of this...like if you installed different rear gears? I'd hate to have the speedo off that much.
I would really like to do something with a wheel/tire package on my truck, but a 345/35-18 is a full 1" shorter than stock.
Thx.
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Wes Tarbox
90 LX 5.0 (10.69 @ 134.7)--597rwhp/590rwtq
96 Cobra (12.34 @ 115.8)--392rwhp/433rwtq
99 Lightning (13.20 @ 103.8)--364rwhp/444rwtq
00 Expedition XLT 5.4
http://members.aol.com/Wa2fst/index.html
1) does the computer make the trans shift prematurely? I know on some of these late model vehicles, the trans will be programmed to shift based on MPH as much as RPM. So, if you had a shorter tire, in theory, it might shift at too low of an rpm.
2) any thing else happen with the trans shifting differently than normal when you run shorter tires?
3) can the EEC be reprogrammed for a shorter tire, or can a chip take care of this...like if you installed different rear gears? I'd hate to have the speedo off that much.
I would really like to do something with a wheel/tire package on my truck, but a 345/35-18 is a full 1" shorter than stock.
Thx.
------------------
Wes Tarbox
90 LX 5.0 (10.69 @ 134.7)--597rwhp/590rwtq
96 Cobra (12.34 @ 115.8)--392rwhp/433rwtq
99 Lightning (13.20 @ 103.8)--364rwhp/444rwtq
00 Expedition XLT 5.4
http://members.aol.com/Wa2fst/index.html
Senior Member
Joined: Aug 1999
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Wes
I know for a fact the the 2000 EEC can be reprogramed for both a gear change (3.55 to 3.73) and tire size. I have done both. If you have a tire disparity of 1 inch or greater front to rear you can set off ABS codes. Yes I would like to have run 345's but I would prefer a 40 series. Running a lowered Lightning with 35 series in the front here in Michigan would be a JOKE. We have the worst roads in the nation. Whole cars fall into pot holes and are lost for days. You only find out about it when you hear of the missing persons report. I quess if I wanted to turn my Lightning into a static work of art I could put 35 series tires on it. I envy those of you that have nice highway conditions.
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BABolt
SVT#290
I know for a fact the the 2000 EEC can be reprogramed for both a gear change (3.55 to 3.73) and tire size. I have done both. If you have a tire disparity of 1 inch or greater front to rear you can set off ABS codes. Yes I would like to have run 345's but I would prefer a 40 series. Running a lowered Lightning with 35 series in the front here in Michigan would be a JOKE. We have the worst roads in the nation. Whole cars fall into pot holes and are lost for days. You only find out about it when you hear of the missing persons report. I quess if I wanted to turn my Lightning into a static work of art I could put 35 series tires on it. I envy those of you that have nice highway conditions.
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BABolt
SVT#290
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Joined: Jan 2000
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From: Houston, Tx, USA
BABOLT. Do you or anyone know if you can reprogram a 99 for different tire sizes. I am in the process of changing tires to one that is 30.4, 2 inches taller than the f1s but with a 10" rim. (See, I do listen). 
noelvm
noelvm
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Senior Member
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From: Allen, TX, USA
Thanks guys.
BABolt, thanks for the info about the 1" disparity b/w front and rear. I was considering the 345/35 in rear and 295/35 in front, but that's a full 1.5" difference. Didn't think about the ABS.
And, yes, we have awesome roads down here in the N. Dallas suburbs. I will never complain about how the roads are kept here.
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Wes Tarbox
90 LX 5.0 (10.69 @ 134.7)--597rwhp/590rwtq
96 Cobra (12.34 @ 115.8)--392rwhp/433rwtq
99 Lightning (13.20 @ 103.8)--364rwhp/444rwtq
00 Expedition XLT 5.4
http://members.aol.com/Wa2fst/index.html
BABolt, thanks for the info about the 1" disparity b/w front and rear. I was considering the 345/35 in rear and 295/35 in front, but that's a full 1.5" difference. Didn't think about the ABS.
And, yes, we have awesome roads down here in the N. Dallas suburbs. I will never complain about how the roads are kept here.
------------------
Wes Tarbox
90 LX 5.0 (10.69 @ 134.7)--597rwhp/590rwtq
96 Cobra (12.34 @ 115.8)--392rwhp/433rwtq
99 Lightning (13.20 @ 103.8)--364rwhp/444rwtq
00 Expedition XLT 5.4
http://members.aol.com/Wa2fst/index.html
