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#1 |
Gettin It One Pice At A Time
Join Date: Oct 2004
Location: everett, washington
Posts: 2,688
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tires
hey guys, got a couple questions about tires. I HAVE to buy 2 new rear tires for my 79 and the ones I have now are 30 x 9.50 R15 LT's and I looked at the tag on the door and that says that the truck needs LR 78 x 15 C's is that the same? do they make the latter anymore? one reson is that Ive always suspected that my spedo was off, and I noticed that my odmiter is also off, because Ive checked it useing the mile markers and when it came to the same number on the od its ether been befor the mile marker or after it by a few 100 feet. and sometimes notices it run fast or slower. but this was going between 60-70 so I dont know if that makes a diference. Ive been told that the 30 x 9.50 's are a harder size to find. is this true? if so what is a good size to put on the back. I cant aford alot. around $100 per tire is about max. I've been quoted for a used pair of tires that in realy good shape that are a lill biger for 80 out the door. so that seems best for right now. its ok to me if I get biger in the back for now. I happen to like the rake stance anyway lol. thats what it is now I think. thanks for your help!
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RIP ELJAY ![]() ![]() Getting the truck done, one piece at a time. “You can tell a lot about a fellow’s character by his way of eating jellybeans.”Ronald Reagan “I don’t know the key to success but I know the key to failure is trying to please everybody.” Bill Cosby Last edited by 79gmcc15; 11-19-2004 at 11:10 PM. |
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#2 |
State of Confusion!
![]() ![]() Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,858
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In today's tire size your truck probably would have come with 225-75x15 as the standard tire. Most would run 235-75x15 as that is what the standard tire for today is. If you want a regular tire to replace your current tire a 255-75 will be about the same size as your current tire. That is about a 2" height difference (taller)which means your speed is off maybe 3-5 MPH (faster)at Highway speeds.
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Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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#3 |
Gettin It One Pice At A Time
Join Date: Oct 2004
Location: everett, washington
Posts: 2,688
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would it realy efect the speed diference if they go on the back? I also have I think 3.73 gears and a 350 trany, what would that do to performance?
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RIP ELJAY ![]() ![]() Getting the truck done, one piece at a time. “You can tell a lot about a fellow’s character by his way of eating jellybeans.”Ronald Reagan “I don’t know the key to success but I know the key to failure is trying to please everybody.” Bill Cosby Last edited by 79gmcc15; 11-20-2004 at 07:35 AM. |
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#4 | |
Active Member
Join Date: Feb 2004
Location: Atlanta GA
Posts: 174
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Quote:
PFJI, I checked with a website on tire heights, and your old L78's are (per them) equal to 235/75x15's. That tire is 28.9 inches tall; it's also a very common, readily available (read: cheap ![]() ![]() Being on the back will make all the difference on the speedo readings, since that's where the speedometer gets its information (back of the tranny). The taller tire that you're running now will slow acceleration (compared to the original size) and also throw off the speedo/odometer readings. You can mentally compensate for that to avoid tickets ![]() ![]() One more bit of minutia: that taller tire would have made it appear your gas mileage got worse, since the taller tire is making fewer revs per mile, making the odometer take longer to clock a "mile". Your mileage isn't worse, and may be a bit better for the engine turning slower. Using the more correct size will give you a better idea of actual gas mileage. One caveat: I talking sizeable tire height differences, not a half-inch or so. If you go from the 30 x 9.50's you now have to 29's the difference would likely be quite noticeable, both for acceleration and accuracy. Hope this helps. Brian |
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#5 |
Mudslides 'r my specialty
Join Date: Dec 2003
Location: STL
Posts: 1,106
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30x9.5's aren't hard to find.
My truck came with 225/75-15's and I plan on installing 31x10.5's. I'll just figure to multiply my speed by 31/28.29.
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Always on the lookout for old cars and parts...(20s, 30s, 40s, 50s, 60s, etc.) http://www.cardomain.com/memberpage/500339 |
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#6 |
Registered User
Join Date: Jun 2004
Location: South Carolina
Posts: 419
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Or just figure up your tire size (which ever you decide on and buy) and your gear ratio, and then buy another gear for the speedometer. That should make it more accurate, but if you dont want to do that just remember that you will probally be going 5mph difference.
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#7 |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Man you guys make it hard. To figure out if your speedometer is off just put the truck at 60 MPH and drive a couple of miles per some mile markers. At 60 MPH it should take 60 seconds, at 65 MPH it should take 55.5 seconds, at 70 MPH it should take 51.5 seconds, at 75 MPH it should take 48 seconds. Time the distance from one marker to the next and then calculate. The formula is simple 60 MPH x 60 seconds equals 3600; so for any reading other than 60 seconds divide it into 3600 and get the speed you are going. REMEMBER Not all mile markers are the same exact distance and you should be on a level area to figure this out. Taller tires will make you go faster than your speedo shows and shorter tires will make your speedo faster than you are going.
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