| Author | Message | ||
| captain ron (Captain_ron)
Rating: N/A |
I thought my speedo would be way off also. but I hade a friend drive along beside me and clock me and it was only about 2 mph off. and driving on interstate I would check mileage with mile markers and it seemed dead nuts. not exactly precision measuring but the best I had to work with. I'm going to try driving about 60 and check fuel mileage. also compare my wheel hub to my odometer. the wheel hub is for the old tires. | ||
| Brian (Bigbusguy)
Rating: N/A |
What size tires did you have and what size did you buy I missed the post on the tires. Brian 4905 Klamath Falls Oregon | ||
| captain ron (Captain_ron)
Rating: N/A |
I had 1100 r 20 went to 11r24.5 If any body knows how to figure the mileage or how much difference my odometer changed pipe up. | ||
| Sojourner (Jjimage)
Rating: N/A |
Diesel owner & driver drive by exhaust tell-tale smoke grayness via outside mirror. The lighter the better. Never black for good economy. So while going thru gear shift always feather throttle enough to minimize black smoke. So if keep RPM in good torque range to avoid lugging equal black smoke (unburned fuel & damaging). If no RPM gauge (most not equip), compare or watch speed gain. If it black & slow gains (acceleration), than shift to next gear lower until reach govern limit. Whatever you do keep exhaust to lightest gray equal best fuel economy. Better yet if engine good compression and tune to spec (including proper thermostat temp and clean-very-low restricted air filter). A rule of thumb for internal combustion engine, the hotter the better fuel economy, HOWEVER engine not design to LAST at above recommended operating temp. Keep hill climbing temp gauge reading no more than thermostat setting. If you have automatic fan clutch it will engage to rob torque while climbing. That is nearly impossible to avoid. Another word keep it rev in upper range and sable temp reading. So view rear v-mirror often to maximize economy. It fun to own & drive a bus. FWIW Sojourn for Christ, Jerry | ||
| RJ Long (Rjlong)
Rating: N/A |
Capt'n Ron - At this point it might be hard to actually figure out the difference, but if you somehow had access to your old 11.00x20 tires, it can easily be done. (Your spare??) What's needed is the tire's diameter in inches, both old and new. For the new tire, it should be available from the dealer, as well as this important little number - how many revs/mile it turns. Don't measure the tire vertically on the vehicle, measure it horizontally, in order to come up with the diameter. GM engineered the stock highway coach powertrain around tires that turn 495 revs/mile. Thirty-five foot models use a 4.125:1 rear axle ratio, forty-foot models are geared slightly lower, at 4.375:1. You must also factor in the bevel gear ratio in order to come up with the actual overall final drive ratio (rear axle ratio x bevel gear ratio = overall final drive ratio). Manual gearboxes use an 0.808:1 ratio, V-730s are 0.87:1. Armed with all this info, you can go to Daris Boutillier's site, and use his little MPH Calculator to figure out the difference. Here's the link: http://www.freewebs.com/darisb/ Understand that if you mount tires that turn MORE than 495 revs/mile, you'll lower your top speed and increase your fuel consumption somewhat. If you install tires that turn LESS than 495 revs/mile, the opposite will be true. The "tallest" 11R24.5 that I'm aware of at the moment is a new Bridgestone model drive tire that turns 470 revs/mile, which is about a 5% difference. If you have a transmission-driven speedometer/odometer, I'm not sure if a different drive ratio for the unit is available any more. You may just have to figure out the difference and live with it. Isn't this hobby fun!?!?!  HTH, RJ PD4106-2784 Fresno CA | ||
| Brian Brown (Fishbowlbrian)
Rating: N/A |
Many speedos, even from the factory, aren't quite right. The best way to know exactly what the accuracy is: go on a LONG trip down the superslab. The first mile marker you come to write down the mile marker # and the odometer reading, up to tenths if you have those. The longer you drive, the more accurate the figuring will be. And don't get off the road and get fuel, etc. before writing down the final numbers. At the last mile marker, write 'em both down again. Do the math, and use that ratio now for distances, MPG, etc. CR: I'd be surprised if taller tires did not change your indicated MPH and odo. And I really don't think an alt. would change you economy that much. My old Chevy van reads 9% too low... speedo indicated is lower than actual speed. And miles travelled are less than real life. I obviosuly have to watch myself around radar traps! Someone must have bought bigger tires at some point. But, I'm sure it gets better mileage than stock tires would because of less RPMs per mile. My Ford Taurus wagon reads almost 2% too high... which is safer when a Smoky's nearby. And close enough for most things. Keep us posted. BB | ||
| Brian (Bigbusguy)
Rating: N/A |
I think if you got the tall 11- 24.5 not the low profile 11-24.5 its about 2" taller setting them side by side to the 11- 20's. Im looking on geting the same but if your fuel mpg droped that much I dont know . Your spedo will show you going less miles then you did with the taller tires. Im looking for a used 11.00-20 tire near me for free. Brian 4905 Klamath Falls Oregon | ||
| Doug Dickinson (Dougd470)
Rating: N/A |
I use a GPS to check my speedo. It is more accurate than other methods, and will let you use check in all situations and speeds without any assistance. It is accurate to 1/10 MPH even with the introduced error. My way. Doug St Louis MC9 | ||
| Al Newell (The_peregrine)
Rating: N/A |
I find the best way to figure all of this is with a GPS. Even a hand held will read out to a 1/100th of a mile. Mine will figure top speed, average speed, time moving and time stopped. I found out my big wheeled jeep Wrangler is 14% faster than the speeometer. My bus, GM 4502, is right on with front wheel odmoter driven. Good Luck, Al | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
Captain Ron, the stock alternator on a 4106 runs 220 amps, which is 3 kw. That means that it uses about 4 or 4 1/2 horsepower going full blast and would only require less than 1/3 of a gph with a good engine. Since normal consumption at 65 mph is around 7 gph, your mileage would drop only about 1/2 mpg and only while producing maximum output. With a converted coach, that is only going to last as long as it takes to get your batteries back up. We get our average of 9.5 mpg even with all of our electrical needs included, so you probably need to figure out if your new mileage is here to stay or only something that was caused by this particular trip's conditions. Good luck getting it figured out. Tom Caffrey PD4106-2576 Suncatcher | ||
| Henry R. Bergman, Jr. (Henryofcj)
Rating: N/A |
Using a GPS will work, but one must understand that the distance OBSERVED will NOT be the distance TRAVELED because of the suck of gravity of the earth resulting in the world being round kinda and the actual distance traveled as indicated by a GPS will not allow for the curve of your path from point A to point B because the earth is not flat but curved kinda soooss you are actually traveling more distance than you think. This error would be compounded if we were on mars and even more compounded if we were on the moon, but less if we were on Vulcan. Can i have more wine now? | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
We've just got a cheap Magellan hand-held unit that tracks the speed and distance in curves quite well, Henry. When we hit a curve when on cruise control in the car, the speed readout does not change, as it would if the unit was reading between two points, regardless of where they are. It kind of surprised me, because I thought it would not do well on that sort of thing. For what it's worth. Tom Caffrey PD-4106-2576 Suncatcher | ||
| R.C.Bishop
Rating: N/A |
Salud, Henry!!! RCB |