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| Tire size and RPMs https://slantsix.org/forum/viewtopic.php?t=18319 |
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| Author: | RDJ [ Fri Jun 30, 2006 12:30 pm ] |
| Post subject: | Tire size and RPMs |
My 73 Swinger needs new tires bad, so I am buying new rims also. Currently the car has the stock 14x4.5 inch rims. It has 195/75/14 (26.6 inches diameter) on the back and bald 185/65/14 on the front. I have no idea what size tires came stock on these cars. The car has 3.21 gears, 904 torqueflite, 2800 rpm stall converter, an engine cammed where the power range is primarily 2500-5500. The rims I am getting are 15X7, 4" backspace, zero offset. What I was going to get are 235/60/15 (26.10 diameter) all the way around. 1) do you think these will these fit? 2) How will the extra diameter affect the power? The 225/60/15 are 25.60 diameter (same as the 195/75/14), but I have to order them special. It seems that the 235 is a much easier size tire to get with more variety, and is part of my decision to get that size. Or, would going even smaller, like a 215 be the way to go. I don't mind having to order the tires if there is a big difference, but getting the standard stuff in the beginning usually makes things easier in the future. |
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| Author: | Super6 [ Fri Jun 30, 2006 12:44 pm ] |
| Post subject: | |
Using This Calculator at RCC, it looks like you turn around 2750 rpm @ 65 mph with your current tires (need real world check here, I believe the calculator assumes no slippage in the torque converter, so your actual rpms may be higher) With your new tire selection (the 235's), rpm at the same speed would be a touch under 2700 rpm (again, assuming no slippage). Not much change, but then neither is the change in tire diameter. 
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| Author: | vynn3 [ Fri Jun 30, 2006 1:02 pm ] |
| Post subject: | |
235/60-15 should fit fine in back, but you'll be pushing it up front. I think it will all come down to build tolerances and brakes. You might have to tweak the wheel openings a bit. I might try 215's on the front and see how close they are, then go bigger on your next tire purchase if you have the room. VM |
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| Author: | Joshie225 [ Fri Jun 30, 2006 1:20 pm ] |
| Post subject: | |
FWIW I would run 225/60R15 all around so you can rotate them and keep the same overal diameter. If you look at a place like The Tire Rack you'll actually see more choices in that size than the 235s. You can also buy better tires in 225/60R15. |
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| Author: | ryandcovalt [ Fri Jun 30, 2006 8:23 pm ] |
| Post subject: | |
I just bought a set of 235, 60 R15's yesterday. We mounted the one up front on my 72 dart, and it is gonna be extremely tight. the car is currently on jack stands, so I havent been able to test it on the road yet, but from the way it looks, it is questionable if they are going to rub or not. if it does I think we will be able to modify the front fender to give it enough clearance. If I was you I think I would go with the next size smaller, at least up front, but it is nice having all the same tires for rotation purposes. |
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| Author: | RDJ [ Fri Jun 30, 2006 8:50 pm ] |
| Post subject: | |
Thanks for the replys. Ryan, let me know how it goes. I think I will go ahead and order the 225s though. I would like to rotate them so they last as long as possible. |
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| Author: | RDJ [ Fri Jun 30, 2006 9:13 pm ] |
| Post subject: | |
By the way, do you know what your backspace and offset are on your rims? and, are you using a 15X7? |
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| Author: | emsvitil [ Fri Jun 30, 2006 10:09 pm ] |
| Post subject: | |
The original size tire was either a 695-14 which is 25.30" diameter or D78 -14 which is 25.50" diameter So a 225/60 15 or a 205/65 15 would work. Either works on a 15 x 7 |
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