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Old 08-29-2013, 08:15 AM   #1
Andymon
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Tire size upgrade

I have 205/75R-15C tires as of now. Is it ok to go to a 225/75R-15D and use the same wheels? Going to Maxxis tires.

thanks!
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Old 08-29-2013, 08:39 AM   #2
JRTJH
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Two factors must be considered. If your wheels are rated at 50PSI then no. If they are rated at 65PSI then you'd be OK. ASSUMING that the weight rating for your wheels is adequate for your RV. You won't be carrying any added load over the original RV configuration so you should be good on weight, but just adding it as a double check since you're upgrading tires, you may need to upgrade wheels also.

NEXT: Carefully measure the clearance in your wheel wells. You may find that the 225/75R series tires are too big to clear the top of the wheel well when you're "bouncing" down the highway. Better to remain with the original size tire and upgrade to a heavier ply (if the wheels can hold the pressure) than to create another problem with wheel well damage from "too big" tire problems.
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Old 08-29-2013, 01:47 PM   #3
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JRTJH.

thanks! I think I'll stick with the size I have. In the maxxis I see they are load rated D. I can't find any marking on the wheel.
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Old 08-29-2013, 04:27 PM   #4
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Often times the max pressure or max load is stamped on the "non road side" (inside) of the wheel hub. Unfortunately, sometimes it's stamped INSIDE the wheel and can't be seen until the tire is dismounted. If you can't find the information on the back side of the wheel (sometimes on the supporting rim, sometimes on the wheel proper) then best guess is that it's inside under the tire.

Your wheels are 5 lug bolt pattern and my best guess would be that you have Dexstar wheels. Usually (emphasis on usually) they are rated at 1820 lbs and 50 PSI. Occasionally you will find some rated at 1870 and 65 PSI, but not often. The only way to know for sure is to visualize that stamp.

Since your RV is a "previously owned" model, visualize each wheel individually. It's very possible that a previous owner had tire issues and may have replaced one or more wheels so they may well not all be the original wheels. Check each one to be sure !!!!!
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Old 08-30-2013, 02:59 AM   #5
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clearance issues

as was said to check the height but also check tire closeness. I went with 235/85-16e on my 3912. I have a 3/4 inch gap between my tires now. its close but they don't rub. also you could consider new rims to carry the pressure.
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Old 08-30-2013, 07:37 AM   #6
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Quote:
Originally Posted by abneynormal View Post
as was said to check the height but also check tire closeness. I went with 235/85-16e on my 3912. I have a 3/4 inch gap between my tires now. its close but they don't rub. also you could consider new rims to carry the pressure.
Here is a list of tips from Dexter axles. Item 24 is about spacing between tires.

http://www.dexteraxle.com/running_gear_tips

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Old 08-30-2013, 10:07 AM   #7
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I looked at this http://sitesource.rvusa.com/demo/201...le-s1506-t1146 and in the section about tire size, it says that the "C" indicates speed rating. does that mean that a "D" rating is not only an 8 ply but also indicates that the tire is rated for higher speed?
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Old 08-30-2013, 10:31 AM   #8
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Go here for "CORRECT" information: http://www.tirerack.com/tires/tirete....jsp?techid=55





ST-Metric sized special trailer service tires will be branded with their load range (Load Range D or LRD) on their sidewalls and list their appropriate load range letter in their descriptions as ST205/75R15 LRD.

Near the bottom of that page you will find a chart specifically outlining ST tire designations. I'll try to reproduce it here, but the spacing may not come out correctly.

ST-Metric Trailer Service Tires

Load Range Ply Rating Markings Max Load Pressure

B 4 B 35 psi (240 kPa)

C 6 C 50 psi (350 kPa)

D 8 D 65 psi (450 kPa)

E 10 E 80 psi (550 kPa)


The website you listed is an RV dealer's site outlining the data for a specific RV he has for sale... The information he listed is "suspect" at best and an "outright lie" in some areas.... If you notice, he doesn't list the "front tires" on that RV, only the "rear tires" And he has the designation for load range listed as speed range...

Go to an "expert" in tires not an RV dealership ad when you're looking for information on tires.... The link I listed above is from Tire Rack, Inc. a well known and respected tire authority on the internet.

If you have quesitons about what to best install on your RV, you've been given reams of information on this website already. If you can't interpret the data you have available, please contact an expert in tires (a respected tire dealer) in your area... Looking for "conflicting information" on various websites on the internet will only serve to confuse you and make your decision much more difficult... It was my understanding from your previous posts that you were buying Maxxis 8808 tires in the same size as your existing tires (ST205/75R/15 LRC) these are 6 ply radial tires with a standard inflation of 50 PSI. Have you changed your mind? or have you not decided on those tires?

I think you are overanalyzing the data and coming up with conflicting (incorrect) information from suspect internet sites and that you're becomming very confused... Talk to an expert, you'll get much more accurate data and help with your tire choices.
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Old 08-30-2013, 11:07 AM   #9
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I have been trying to read as much as I can about which tires to get and yes, I still want the Maxxis M8008. I have asked two different tire dealers. One, performanceplustire.com and onlinetires.com have both indicated that 205/75R-15D would be fine. I guess my main concern is the C rating is 1820 lbs which right at the end of the max TT weight. That's why I was wondering if the D would be a better choice. sometimes it takes a while for things to get in my thick skull.

thanks for the reply.
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Old 08-30-2013, 11:23 AM   #10
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That question was answered for you by Diugo in post #3 of another tire thread you started: http://www.keystonerv.org/forums/showthread.php?t=12928

You asked about LRC vs LRD in that thread and received an answer. Nothing has changed in tire manufacturing since then.

Again, much of the internet searching you are doing leads you to "less than correct" websites. The data you find there is usually not only incorrect and misleading, it also will lead you down a pathway to making wrong choices. Stick with the advice and documentation you find at your local "tire expert" or from reliable internet sites, not sites listed by Google or Bing on a generic websearch.

Again, if you want Maxxis ST tires, then the 205/75R/15 LRC will require 50 PSI wheels to support 1820 lbs each and the 205/75R/15 LRD will require 65PSI wheels to achieve maximum load rating of 2150 lbs each. The only step you need to do at this point is verify what PSI rating is on the wheels you own and buy the appropriate tire of your choice, as both will support your RV weight adequately. If you have 50 PSI wheels and want LRD tires, you'll need to buy new wheels rated at 65PSI as well. Otherwise, its simply a matter of making your decision.
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Old 08-30-2013, 05:11 PM   #11
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st tires

NOTE: st or special trailer tires are rated for a maximum speed of 65 MPH. I went to LT tires on my 16 inch rims. they are rated 106 MPH. the D you talked about is the load range.
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