Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 05-30-2009, 09:29 PM   #1
RJG
Member
 
Join Date: May 2009
Posts: 48
Question More questions of tires

Hello all, I'm looking to replace my toyo 8R-19.5 tires but would like to go with Michelin's, they do have an XZA of this size, However, I would like more of a foot print, so I'm thinking of a XZE 225/70R-14 19.5 or XRV 225/70R 19.5, the latter have a dual spacing of 9.7 opposed to 8.7 of the XZA. load range of the XDE is greater due to the 14 ply these tires are shorter in stature and will affect speedo and odometer readings a little. this coach has a cummins 230 HP and allison 3060 push button auto trans, so I'm wondering if there could be a shifting problem?? and if there could be some other reasons not to make the tire size change. and perhaps some different prefrences of the "X" tires. anyone might have. Thanks so much for your thoughts.. Ray.. P.S. 6 XDEs @$2536.32 XRVs @ $2016.00 XZAs a little less..
__________________

__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 05-31-2009, 02:36 AM   #2
Senior Member
 
DAN L's Avatar
 
Winnebago Owners Club
Workhorse Chassis Owner
Join Date: Sep 2007
Posts: 2,898
Quote:
Originally Posted by RJG View Post
Hello all, I'm looking to replace my toyo 8R-19.5 tires but would like to go with Michelin's, they do have an XZA of this size, However, I would like more of a foot print, so I'm thinking of a XZE 225/70R-14 19.5 or XRV 225/70R 19.5, the latter have a dual spacing of 9.7 opposed to 8.7 of the XZA. load range of the XDE is greater due to the 14 ply these tires are shorter in stature and will affect speedo and odometer readings a little. this coach has a cummins 230 HP and allison 3060 push button auto trans, so I'm wondering if there could be a shifting problem?? and if there could be some other reasons not to make the tire size change. and perhaps some different prefrences of the "X" tires. anyone might have. Thanks so much for your thoughts.. Ray.. P.S. 6 XDEs @$2536.32 XRVs @ $2016.00 XZAs a little less..
i still have the original mich xrv 245/70 19.5 tires on my moho. they only have 9k miles on them. the tread and the sidewalls look like new.
they hold air really well. they loose maybe 1# in 3 months. i have the tst truck tire pressure and temperature monitor system and thus can keep track of the exact pressures.
they ride well and handle well also.
__________________

__________________
01 WINNEBAGO 35U W20.8.1L SW Wa, Hi. Good Sam, SKP. AMSOIL fluids. BANKS ecm program. SCAN GAUGE II w/ Ally temp. 2 LIFELINE GPL-6CT AGM Batts on their sides. TST tptts. K&N panel air filter. AERO mufflers. TAYLOR plug wires. ULTRA POWER track bar. KONI fsd shocks, toad '14 smart car
DAN L is offline   Reply With Quote
Old 05-31-2009, 06:58 AM   #3
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,060
Carefully calculate the change in rolling circumference if you change tire sizes. A change in circumference changes the number of rotations per mile and is in effect a change in gearing. This affects your speedometer, odometer and performance.

For example, a 245/70 will be taller than a 225/70 as well as wider and thus have a greater circumference. A greater circumference means you travel further on every tire revolution and you will be going further and faster than your odometer 7 speedometer indicate.

The tire manufacturer usually has all this calculated out if you can find it online somewhere.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is offline   Reply With Quote
Old 05-31-2009, 04:51 PM   #4
RJG
Member
 
Join Date: May 2009
Posts: 48
Thanks for the information, in my case the 8R's are 33.6 and the Xrv's are 32.0 and XZE's at 32.2, so around 1.5" difference I defenitly would rather be going in the other direction though. I don't know what this will do to trans shifting if anything ? Has anyone made this change?? Thanks everyone Ray..
__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Old 06-03-2009, 10:23 AM   #5
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,060
Quote:
in my case the 8R's are 33.6 and the Xrv's are 32.0 and XZE's at 32.2, so around 1.5" difference
That sounds more like the tire diameter rather than the circumference, so the 1.5" difference is multiplied by pi (3.14) to yield a 4.7" difference for each revolution of the tire. You will be going that much LESS distance per revolution with the smaller tire, so your actual speed will be lower than your speedo shows and your odometer will record more miles than you actually went. That's because the speedo and odo count RPMs and convert to miles assuming your original tire size. As for gearing, this is equivalent to using a large gear ratio (higher number), which means better acceleration but poorer fuel economy.

The difference in size is a bit under 5%, so that will be the effect on speedo and odo. Hard to say what the mpg effect will be, but probably very small. Maybe not even noticeable.

You can probably have your speedo recalibrated for the different tire size. Some are adjustable via dip switches while others require a different gear.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is offline   Reply With Quote
Old 06-04-2009, 10:54 PM   #6
RJG
Member
 
Join Date: May 2009
Posts: 48
Gary, your definitely smarter than me!! So let;s say with the smaller diameter tires with a 5% decrease in spedo and increase in odo, what if : I increased my speed 5% to compensate for the spedo based on the posted speed, and in most cases I do drive at the posted speed, would this increase the odo mileage to 10% ??.. And to turn the tires faster, will this, therefor, increase the RPM 10% or will it be affected ? because of the decrease in diameter of the tire, less effort or more effort,? to turn them round, the weight being the same to push ? (I'm in way over my head here) Just trying to figure if the gearing of trans will be affected ? one allison fellow say's 1.5" probely not, one other would not commit and says to ask another, whom I have not been able to contact yet. as far as mpg dont think I have enough Brain cells to go there now, and perhaps EVER. And after reading this I wonder if it makes any sense at all ?? But I'll send it anyways.Thanks very much for your replys. Ray..
__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Old 06-05-2009, 03:44 PM   #7
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,060
Your speedo and odo are driven off the same RPM counter, which works on the output shaft of the transmission. If you change the rear axle gearing or the tire size, the distance traveled per RPM changes. You, of course, set your speed based on your feeling of safety, visual comparison with surrounding traffic, and the feedback you get from your speedometer. If your speedo reads low, you will likley push the pedal down a bit more, increasing engine RPMS until the speedo says you are going the speed limit.

No, the rate of error doesn't change if you speed up. It is still 5%, but it is 5% of a slightly large number.

It doesn't change your transmission gearing - those are physical gears. What is does change is the effect of that gearing. In the amouts we are talking about, you won't likely notice any effect on performance.

If you could get a .75 profile tire instead of .70, the 225 width would put you closer to the original tire height and circumference. I'm talking about a tire size of 225/75R19.5. If you can't, well, you have a decision to make. Personally I would not be trying to increase the tire footprint and would stay with the 8R19.5 size, which you say is available in the XZA. What do you expect to accomplish with the added complication of a size change?

Don't get me wrong - I'm not totally opposed to tire size changes. I recently did it myslef on my car to save $300 on a set of 4. But I used a tire size that was barely 1% different in circumference, so the effect of the change was neglible (I'm going 79 when my speedo says 80).
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is offline   Reply With Quote
Old 06-05-2009, 08:04 PM   #8
RJG
Member
 
Join Date: May 2009
Posts: 48
well, I was thinking a wider footprint might offer a little more stability, and I don"t like the looks of the sort of "u" shape tires that are on this coach,
However, I am beginning to see the complications associated with the change. Not knowing for sure what these tires have been through I thought it might be prudent to get new tires in view of the posts I have been reading and the life span of MH tires, although ,there is no visible signs of cracking, checking or wear. The mf dates are, I think, ok on 4, those being, 3505,3405,2@ 2405 with the spare @1105, the other two @ 2603,1504. The tires are TOYO's and from what i have been reading they have stopped recomending their tire for MHs, so if I replace the older tires with new same brand & size and use them for steer tires it will be around $800.00 and in a year possibly two replace them all. and perhaps put some koni fsd's or some other type on with the $ saved to help the stability, if they make those for Oshkosh chassis ?? With all this being said, when I started thinking about tires I was thinking of taking a job in AK, so new tires seamed the way to go. and considering this, I was trying to find a MS rated tire and having no luck. haven't decided yet on the job, thinking mabey next year to give me time to get this coach in order.. also I can't seam to find 75R in this size so far, I didn't think of it untill you suggested it. and as always, all suggestions are much appreciated. Thanks very much Gary. Ray..
__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Old 06-05-2009, 10:36 PM   #9
Senior Member
 
slabman's Avatar
 
Join Date: Oct 2002
Location: Plano TX
Posts: 2,217
Gary's giving you good info. I recently changed tire size on my TOAD, increasing the diameter. I can tell when going up a hill under cruise control, it kicks into a lower gear to maintain the revs. As for your rig, I doubt you'd feel this difference, esp. since you are going DOWN in size. But I'd be more concerned about increasing the tread width. I doubt that you'd improve lateral stability and would think rolling resistance would increase, impacting mileage by a miniscule amount. If a harsh ride is your concern, do get a set of Koni fsd shocks on the front axle. I did and the ride softened so much the DW even noticed!
__________________
Slabman
2014 Newmar Essex 4544
2007 Lexus LX470 Toad
slabman is offline   Reply With Quote
Old 06-06-2009, 02:14 AM   #10
Senior Member
 
DAN L's Avatar
 
Winnebago Owners Club
Workhorse Chassis Owner
Join Date: Sep 2007
Posts: 2,898
Quote:
Originally Posted by RJG View Post
Hello all, I'm looking to replace my toyo 8R-19.5 tires but would like to go with Michelin's, they do have an XZA of this size, However, I would like more of a foot print, so I'm thinking of a XZE 225/70R-14 19.5 or XRV 225/70R 19.5, the latter have a dual spacing of 9.7 opposed to 8.7 of the XZA. load range of the XDE is greater due to the 14 ply these tires are shorter in stature and will affect speedo and odometer readings a little. this coach has a cummins 230 HP and allison 3060 push button auto trans, so I'm wondering if there could be a shifting problem?? and if there could be some other reasons not to make the tire size change. and perhaps some different prefrences of the "X" tires. anyone might have. Thanks so much for your thoughts.. Ray.. P.S. 6 XDEs @$2536.32 XRVs @ $2016.00 XZAs a little less..
will 245/70- r19.5 tires fit on your rims? how about the dual spacing? they should be close in rolling circumference to your current size.
__________________
01 WINNEBAGO 35U W20.8.1L SW Wa, Hi. Good Sam, SKP. AMSOIL fluids. BANKS ecm program. SCAN GAUGE II w/ Ally temp. 2 LIFELINE GPL-6CT AGM Batts on their sides. TST tptts. K&N panel air filter. AERO mufflers. TAYLOR plug wires. ULTRA POWER track bar. KONI fsd shocks, toad '14 smart car
DAN L is offline   Reply With Quote
Old 06-07-2009, 02:32 PM   #11
RJG
Member
 
Join Date: May 2009
Posts: 48
245's

Hi Dan, I have 6" rims so I can't run the 245's I think they require 6.75 / 7.50 unless I replace the rims, that I wouldn't mind doing if I had the $$. However you raised a question that has been on my mind, about dual spacing;I'm guessing that is the space between the duals? how does one determine what is available on an existing rig? if I look between the duals it looks like 2+" without measuring, The XZA's are 8.8 8R's, XZE's 9.7 XRV's 9.7 I think the Toyo's are 8.something. What do you think of running 2 new XZA's on the steer and moving the Toyo mid 05's to the rear. and later replacing the rear toyo's with the XZA's ?? Thanks Dan and all, Ray..
__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Old 06-07-2009, 06:58 PM   #12
Senior Member
 
DAN L's Avatar
 
Winnebago Owners Club
Workhorse Chassis Owner
Join Date: Sep 2007
Posts: 2,898
Quote:
Originally Posted by RJG View Post
Hi Dan, I have 6" rims so I can't run the 245's I think they require 6.75 / 7.50 unless I replace the rims, that I wouldn't mind doing if I had the $$. However you raised a question that has been on my mind, about dual spacing;I'm guessing that is the space between the duals? how does one determine what is available on an existing rig? if I look between the duals it looks like 2+" without measuring, The XZA's are 8.8 8R's, XZE's 9.7 XRV's 9.7 I think the Toyo's are 8.something. What do you think of running 2 new XZA's on the steer and moving the Toyo mid 05's to the rear. and later replacing the rear toyo's with the XZA's ?? Thanks Dan and all, Ray..
new michelin tires on the steer axle sound like a good idea to me. i would use the 225x70 xrv for longevity, better ride and handling. your ride height will be about .8" lower in the front.
mark your toyo front tires for rotation direction before removing. install them the same way on the rear axle.
maybe michelin will have the new "super singles" available in 19.5 size for your rear axle in a couple of years. i am hoping for this also. then you only have to buy 2 wheels and 2 tires. check out:
Accuride Corporation: All Around Leader in Wheels for definitions including wheel spacing. the measurement is to be taken "from the center of one wheel to the center of the other wheel". i guess from the center of one tire to the center of the other tire is a pretty close measurement. you can use spacers between the wheels.
check the michelin rv tire website:
Michelin North America RV Tires Page for required rim width and dual spacing.
__________________
01 WINNEBAGO 35U W20.8.1L SW Wa, Hi. Good Sam, SKP. AMSOIL fluids. BANKS ecm program. SCAN GAUGE II w/ Ally temp. 2 LIFELINE GPL-6CT AGM Batts on their sides. TST tptts. K&N panel air filter. AERO mufflers. TAYLOR plug wires. ULTRA POWER track bar. KONI fsd shocks, toad '14 smart car
DAN L is offline   Reply With Quote
Old 06-12-2009, 12:12 AM   #13
RJG
Member
 
Join Date: May 2009
Posts: 48
Thank you all very much, Ray..
__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Old 06-17-2009, 11:15 PM   #14
RJG
Member
 
Join Date: May 2009
Posts: 48
Well, I made the plunge and ordered 6 XZE LRG Michelin 225/70R/19.5 load range G, 14 ply from Costco beat the other dealers by about $70.00 per tire $2,093.55 mounted, balanced, and tax, still need to get spare and shocks, soon I hope, will have to have speedo/ odo re caibrated. decided to go with all new for peace of mind. Thanks to all for your help.
__________________

__________________
94, 34' Itaska turbo DP lots of new stuff. 2011 Jeep Wrangler unlimited Rubicon.
RJG is offline   Reply With Quote
Reply



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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Balancing Tires with Powder/Firestone FS 560 CARVAL Motorsports MH-General Discussions & Problems 9 07-20-2009 08:16 PM
Trailer Tires K-Star Travel Trailer Discussion 28 07-13-2009 09:39 PM
Best price is not always the BEST on tires supercub Workhorse and Chevrolet Chassis Motorhome Forum 4 07-18-2007 07:44 PM
Onboard compressor to fill up the tires gMw Winnebago Industries Owner's Forum 9 05-08-2007 05:42 PM
Nitrogen in tires The Shadow MH-General Discussions & Problems 11 04-17-2006 05:29 AM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 12:44 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.