What do you want? - Fiberglass RV

Thread Tools Search this Thread Display Modes
Old 02-04-2009, 08:44 AM   #1
Senior Member
Kevin K's Avatar
Name: Kevin K
Trailer: 17' Casita
Posts: 3,040

Click image for larger version

Name:	gearchart.gif
Views:	56
Size:	49.4 KB
ID:	17751

Chart- Numbers on top = tire height
Chart -Numbers on the left = gear ratio

Change either gear ratio or tire height .

If you want better gas mileage, find your gear ratio on the left and pick a new tire height to lower the rpm to get better mileage.

If you need more power, pick your gear ratio on the left and pick a smaller tire height to increase your rpm.

Don't go to far either way.

More information at http://www.4lo.com/calc/geartable.htm

Kevin K is offline   Reply With Quote
Old 02-04-2009, 09:09 AM   #2
Senior Member
Trailer: Casita 17 ft Spirit Deluxe
Posts: 509
You didn't mention transmission ratio in selecting a RER and tire size. This also effects fuel milage and engine RPM.

In the case of the Escalade the final transmission ratio is 0.7.


CD and Joyce Smith - Lily, Violet, and Rose
1999 Casita 17' SD - "The Little Egg"
2007 Escalade - 6.2L V8 - 6L80E Trans - 3.42 Diff
CD Smith is offline   Reply With Quote
Old 02-04-2009, 07:38 PM   #3
Senior Member
Pete Dumbleton's Avatar
Trailer: Scamp
Posts: 3,072
Send a message via Yahoo to Pete Dumbleton
Actually, the tire size is part of the total drive ratio, that starts with engine rpm and ends where the rubber meets the road -- Swapping tire size when the tires need replacement is the least expensive way to change the ratio -- The gears in your transmission also make a difference, esp the tasks of moving slow on rough ground, backing into campsites, etc. -- That can really challenge a clutch or auto trans and is where 4WD-Low is very handy
Pete Dumbleton is offline   Reply With Quote
Old 02-04-2009, 08:45 PM   #4
Senior Member
Dan Meyer's Avatar
Name: Dan
Trailer: Scamp
Posts: 546
Don't forget to recalibrate your speedometer if you choose to do this.

-- Dan Meyer
Dan Meyer is offline   Reply With Quote
Old 02-04-2009, 09:10 PM   #5
Senior Member
Raya's Avatar
Name: Rachel
Trailer: 1974 Boler 13 ft (Neonex/Winnipeg)
Posts: 3,014
Don't forget to recalibrate your speedometer if you choose to do this.

-- Dan Meyer
I thought of that too, Dan, and noticed that they have a conversion function on the page for that.

Tangential story:
My car takes a European sized tire, which is 185-R14. Well, once I went in to get tires (on my way out of town on a cross-country trip), and as I headed east I noticed that a lot of people seemed to be passing me. Well, long story short, the tire place had decided to put on tire size 185-70R14, which is not the same at all. ARGH! Once I figured that out, I did some timed mileage runs and figured out that my speedometer/odometer were about 10% off, and so I was driving 10% slower than I thought. That explained all the passing.

So I went back in to the tire shop (and it was a tire shop, specifically!) on my way home and explained the problem. They refused to believe that the two tires could be different sizes How exasperating! I pulled some circumference figures that I had written down out of my pocket (I had a feeling they wouldn't believe me), but still no dice ("But we put this size on someone else's Volvo and they didn't mind"). They actually made me drive around with one of their technicians and a handheld GPS. Lo and behold.... about 10% off. When they ordered in the proper tires.... my, my, right on!

Since that tire size is hard to find, I've since done some calculations and found that the much easier to find North American size of 195-75R14 is almost exactly the same circumfrence as the 185-R14, so that's what I get now.)


Raya is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Upcoming Events
No events scheduled in
the next 465 days.
» Virginia Campgrounds

Reviews provided by

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 03:22 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.