| [GMCnet] Tire size opinions for Alcoa rims [message #301808] |
Tue, 07 June 2016 20:56  |
RicksGMC
Messages: 145
Registered: May 2012
Karma: 0
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Hi All,
Looking for opinions on tire sizes, I know that LT225/75R16 are the usual size used on Alcoa's but my GMC had 245/75R16's on it when I got it. I like the look of the 245's but if 225's are better for the ride/handling or clearance then now is my chance to pick the right ones.
Rick
Rick&Tammy Drummond
Prior Lake MN
'74 (re)Painted Desert
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Rick
Rick&Tammy Drummond
Prior Lake MN
'74 (re)Painted Desert
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301810 is a reply to message #301808] |
Tue, 07 June 2016 21:11  |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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The 225/75s are the closest to the diameter as the original 8.75/16.5s IMO, the 245 75 or 235/85 will gear the coach up too much. It is already geared too high with the stock 3.07. I DO run oversize tires on the front (255/70R 16 BFG All Terrains) on 8" wide rims, but I also have a 3.70 final drive. Next tire change on the front I will be switching to 245/70s. They are closer to the diameter of the 225/75s. Some people run the 245/70s on the rear successfully, but my thinking is that they are a little too big and can come awefully close to the fenders etc.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301826 is a reply to message #301808] |
Wed, 08 June 2016 08:37 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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You just gave me an idea for the gas mileage (poor) I'm getting from the new used coach. Bigger tires. The ratio will certainly pull therm.
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301828 is a reply to message #301808] |
Wed, 08 June 2016 09:21 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I like my all terrain tires on the front, you can really feel a traction improvement. as far as tire size, I think most people have stated the reasons, and the choice is really up to you. I thought you had an improved final drive.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301829 is a reply to message #301826] |
Wed, 08 June 2016 09:32 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Johnny,
Running the bigger tire, say a 235 or 245 tire will not necessary improve your fuel milage and actually could make it worse. By going to the bigger tire you change your ratio in the final drive so the engine has to work harder to pull the coach down the road. An example would be is that if you have a 3.55 gear set and you go with the 245 tire your ratio will change to aprox. a 3.39 to a 3.42 ration depending on tire manufacturer. I ran the 245 tire with a 3.66 ratio which change my effective ration to a 3.50. Went back to the 225 tire and the coach woke up and the milage was slightly better. Just my personal experience, yours may vary!
JR Wright
78 Buskirk Stretch
75 Avion
Michigan
> On Jun 8, 2016, at 9:37 AM, Johnny Bridges via Gmclist wrote:
>
> You just gave me an idea for the gas mileage (poor) I'm getting from the new used coach. Bigger tires. The ratio will certainly pull therm.
> --
> '76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301837 is a reply to message #301808] |
Wed, 08 June 2016 11:15 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Mine has a 3.70:1 and it's overkill for the southeast. Neil hauled a trailer load of Harleys around the northern CA mountains and to the East, he needed the 3.70. I don't and don't. Somewhere around 3.5 ought to get where I need to be. If I can get there with tires I'm going to have to get anyway, it seems a cost effective solution.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301838 is a reply to message #301808] |
Wed, 08 June 2016 11:18 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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JR, the engine will do the same amount of work pretty much regardless the drive ratio - It's hauling 11,000 pounds along into the wind regardless. Based on engine - to - road ratio (regardless where you get the ratio) you may well move the rpm at a given speed to a more efficient or less efficient rpm for the load being hauled - but the load won't change.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Tire size opinions for Alcoa rims [message #301862 is a reply to message #301838] |
Wed, 08 June 2016 14:10 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Johnny,
You're mistaking the term load. It is not the weight of the coach but the required torque to move the coach down the road and in your area in is not flat country, you have a lot of hills and some mountains in your area. The bigger tire will cause the motor to work harder at lower rpm to move that same weight and you could lug the motor real bad and hurt something. The 455 and 403 really don’t get on the cam until about 2650 to 2750 RPM and they really pull beyond that point. There is no free lunch.
JR
> On Jun 8, 2016, at 12:18 PM, Johnny Bridges via Gmclist wrote:
>
> JR, the engine will do the same amount of work pretty much regardless the drive ratio - It's hauling 11,000 pounds along into the wind regardless.
> Based on engine - to - road ratio (regardless where you get the ratio) you may well move the rpm at a given speed to a more efficient or less
> efficient rpm for the load being hauled - but the load won't change.
>
> --johnny
> --
> '76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
>
> "Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon
>
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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