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Old 07-10-2016, 07:41 PM   #241
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Many truck tire sites give a rolling circumference dimension which is more important for the calculation you are doing.
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Old 07-10-2016, 07:59 PM   #242
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Ok, one *perhaps* stupid question, anyone know what the height of an 11R22.5 tire and a 12R22.5 tire should be and what the differences in height are?

I'm trying to see if I can bump up the top end while keeping the engine turning @ 2K rpm. Preferably getting Heavy to get up to 65 mph by changing tire size. So far with the help of Tango's calculator I have figured going from 11R22.5 to 12R22.5 gets me close to 60 mph from 48 mph. Yes, a big jump, but not quite big enough. The question is am I using the right calculations such as tire height and (I believe) the 643 tranny having a 1:1 final ratio going to the drive shaft. I do know I have a 5.29 gear ratio in the rear axle, but the rest I can use a little bit of help on to be sure I can get 65 mph @ 2K rpm with 12R22.5 tires. Just trying to save some $$$$ before spending any........

Thanks all!!!!

M1031
The 11R22.5 tires are very common and easy to find. The 12R's, not so much. Personally, instead of spending well over $1000 on new tires (and still not getting much over 60 MPH), I think you'd be better served by changing the rear-gear ratio. If you plan to put a lot of miles on it, you'll likely save that much in fuel over time. I looked into this for mine; removing and replacing the axle "chunk" myself, having the gears professionally changed (and warrantied) will set me back around $900 ... plus gaskets (I forgot to ask if the swap would include them), and of course a gallon or 2 of gear oil.

My Volvo runs something like 3.53 gears, Lo-Profile 22.5 tires, ISX Cummins and 10-speed trans; it has a top speed well over 80. It turns around 1600 RPM at 70 or so.
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Old 07-11-2016, 11:04 AM   #243
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Yeah, I did some number crunching and I'll get a better bang for the buck by swapping out the gears for 4.11s. Thanks for all the feedback!

M1031
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Old 07-11-2016, 11:51 AM   #244
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the other thing to rtememberr is driveability changes the bigger the tires you go on the same size rims.. taller tires are usually wider so you'll have a little more feet on the street... plus there is more flexible material between the road and your steering wheel.. so you may have the tendency to get the bus in a sway motiomn a bit as the steering responses become slightly dampened with each tire height increase...

getting new gears has the advantage that you have a fresh set of gears in the rear... plus when the driveshaftys are down id have the U-joints changed in those too...

-Christopher
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Old 07-11-2016, 05:51 PM   #245
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Originally Posted by M1031A1 View Post
Yeah, I did some number crunching and I'll get a better bang for the buck by swapping out the gears for 4.11s. Thanks for all the feedback!

M1031
Hey M1031A1, I have the same set up as you, did you eve find out where to get the gears?

J
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Old 07-11-2016, 10:52 PM   #246
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Hey M1031A1, I have the same set up as you, did you eve find out where to get the gears?

J
J,

I'm STILL looking! I'm calling Eaton tomorrow as well as Spicer to see IF they have ANYTHING I can use to get the 4.11 conversion done. Short of that I'm now starting to seriously consider an axle swap from a semi-truck. That may be the way I finally go. Have some more calling to do tomorrow. Will have results from my search tomorrow evening. On a more positive note Blumenthal's has my sheet metal work ready for the windows I'm blanking out! Pics to follow when the blanks are up and secured!

Oh yeah, before I forget (again) Brian called me about his problems breaking drill tips. I got the message, but without a phone number, it's kinda hard to call back......... So, Brian, PM me when you read this.........
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Old 07-12-2016, 12:00 AM   #247
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No worries... I had someone else bring me some more bits! They were closer than Texas!
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Originally Posted by M1031A1 View Post
J,

I'm STILL looking! I'm calling Eaton tomorrow as well as Spicer to see IF they have ANYTHING I can use to get the 4.11 conversion done. Short of that I'm now starting to seriously consider an axle swap from a semi-truck. That may be the way I finally go. Have some more calling to do tomorrow. Will have results from my search tomorrow evening. On a more positive note Blumenthal's has my sheet metal work ready for the windows I'm blanking out! Pics to follow when the blanks are up and secured!

Oh yeah, before I forget (again) Brian called me about his problems breaking drill tips. I got the message, but without a phone number, it's kinda hard to call back......... So, Brian, PM me when you read this.........
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Old 07-12-2016, 12:19 AM   #248
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Originally Posted by M1031A1 View Post
J,

I'm STILL looking! I'm calling Eaton tomorrow as well as Spicer to see IF they have ANYTHING I can use to get the 4.11 conversion done. Short of that I'm now starting to seriously consider an axle swap from a semi-truck. That may be the way I finally go. Have some more calling to do tomorrow. Will have results from my search tomorrow evening. ...
I simply called Atlanta Gear (I think that's the name of them); they are a heavy truck axle/transmission shop in Atlanta. I'd look for something similar in a major city near you. Doing the actual gear swap yourself is *NOT* recommended unless you really know what you're doing, something about adjusting the spacing on the ring gear, adjusting something on the pinion, adjust, adjust, adjust. Bah! Let the experts do all that, I'll just unbolt the "chunk" and bolt in the new one (plus they warranty it if they do the work). Yeah. I can manage that.
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Old 07-18-2016, 06:43 PM   #249
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Well, I've been trying to update my thread. Got my locking cargo bay door handles Friday. Third time trying to post the pic... So here it goes.....
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File Type: jpg P10100110.JPG (71.6 KB, 9 views)
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Old 07-29-2016, 10:41 PM   #250
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I'm a newbie and was reading another conversion that had a rear end problem. He has a source that you can exchange pumpkins. Hope it helps. Louis


http://www.skoolie.net/forums/f11/the-wait-is-over-5819-13.html
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