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Joe
Dodge Dakota
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10/13/2002
16:46:10
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 Subject: Tire change
IP: Logged
Message:
I have a question about changing from stock 215/75R15 to 235/75R15.
I have a V8 4.7L auto 3.55.
I pull a light travel trailer just fine with this truck. But it has only passenger tires on it and was told that you should subtract 9% off tire weight if using passenger P-series tires. I should be using 6 ply LT-series tires.
Fine, no problem. I can have the dealer program the rear end for whatever tire size you get.
Every tire dealer I go to says they either don’t carry my 215/75R15 in 6 ply and cant get them or say they can special order and be here in 3 days. (I don’t want to be on vacation needing a replacement and have to wait 3 days due to a blowout).
Some tire dealers say to go up to 235/75R15 since everyone carries the tires and have Dodge reprogram the rear for speedometer, odometer, auto trans shift points, etc.
Here’s the problem: Some tire dealers say don’t go larger, it will dramatically cut my towing power making my 3.55 rear seem like 3.40. Others say I wont even notice that little change. Some say, “I build gear boxes all the time at the race track, you wont notice that little bit”.
Can you tell me how much of a change will really be felt if I change?
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smittyt2
Dodge Dakota
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10/13/2002
18:13:23
| RE: Tire change
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Message:
I may be wrong but I thought that the first set of numbers in the sizing is for the width of the tire. I thought the overall height of the tire and wheel is what would affect your speedo and such, not the width. Once again, I could definitely be wrong.
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Joe
Dodge Dakota
JOIN HERE
10/13/2002
19:03:41
| RE: Tire change
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Message:
215/75R15 = overall height of 27.6 in
235/75R15 = overall height of 28.9 in
The other thing I dont understand.
If you can order the Dakota with either of the
2 above tire sizes and both rear ends are 3.55,
which is really running at 3.55?
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POWER HUNGRY
Dodge Dakota
JOIN HERE
10/13/2002
21:33:21
|  RE: Tire change
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Message:
The gear ratio is only the mechanical number of the ratio in the rear-end. The ratio that changes when switching to a tire with a different diameter is the final drive ratio. This ratio is only a theoretical ratio comparing the leverage change the new tires make compared to the old ones. Since the change isn't mechanical people usually say," the tires make my truck act like it has 3.73 gears."
As for the question sa to how much tire dia. will I feel a difference. I have 3.55 and went from 215/75/R15 to 265/75/R15 and noticed a big difference. It feels at full throttle what it use to full like when at 60% throttle. The tire change made it feel like I had the stock tires with a 3.21 gear in the rear. To restore the feeling of acceleration of the stock combo I would need to change the rear gear to 3.92's.
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Cotharyus
GenIII
 
10/14/2002
07:05:51
| RE: Tire change
IP: Logged
Message:
Consider this:
215*.75=161.25
235*.75=176.25
235*.70=164.5
The result of these equations is the hight of the sidewall in millimeters. See if you can find a 235/70R15, and you won't need to change anything, because the overall difference in size will be less than one cm. I did something similar to my truck going from the stock 235/75R15 to 255/70R15.
2001 QC 4x4, 4.7,5 spd, LSD, 255/70-15's, K&N Gen II Intake, Robert Shaw 180 Stat, Hanson Industries custom front bumper, Highflow cat
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Demon Dakota
DakotaEnthusiast
10/14/2002
09:13:24
| RE: Tire change
IP: Logged
Message:
I'm doing the same thing, only I'm going from 255/65-16 to 275/60-16. Same overall diameter, just wider tires.
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Mig
Dodge Dakota
JOIN HERE
10/11/2010
16:09:16
| RE: Tire change
IP: Logged
Message:
I have a 99 dodge dakota sport (3.9L - club cab) 2WD and just put 235/75/15 tires on it. It came with 215/75/15 tires - OEM. Is there any concerns I should have about upsizing the tires?
I got it in March of 2008 with only 15K miles on it (seriously) and it now has 35K and I want to make sure I don't mess anything up just because I thought the OEM tire sizing looked weak!
Thanks!
MR
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daddio
Dodge Dakota
JOIN HERE
10/11/2010
17:20:51
| RE: Tire change
IP: Logged
Message:
I did the same thing on my '00 QC when I got it. 235/75/15 is an optional size and no problems. Speedo isn't off enough to worry about.
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