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Old 05-17-2009, 06:05 AM   #1
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Classic Motorhome Tires

Has anyone converted from their original size 8R19.5 to 225/70R19.5 Tires. I am particularly concerned with the clearance between the tag axle tire and the inner fender since it is minimal now with the original size tire. I believe there is sufficient clearance between the duals.
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Old 05-17-2009, 11:44 PM   #2
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Gunter,
Nope...I run Michelins...tires are more important than the engine, to me...can always find a 454, but replacing a 345 is getting harder to do.
mike
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Old 05-18-2009, 04:14 PM   #3
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What I want to put on are Michelin XZE, but I am concerned about the clearance since these are 8.9 wide.
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Old 05-18-2009, 05:38 PM   #4
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Not sure about the extra inch, if the front bonnet has ever been compromised(read hit something hard enough to bend it...we have 8.0 XZA 19.5>...since I don't do my tires on the MH, I don't know about clearance, but someone out there HAS to have thought about this before. I would want to know a couple or so things before I jumped...
Will the suspension be affected? Will this have any effect on the airbags(I know, part of the suspension, but maybe another can of worms)? What will the effect on the steering be?
I'm curious about your plan to go a little bigger on the tires...is there something you have heard, or is this a personal knowledge kinda thing?
m
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Old 05-19-2009, 12:33 PM   #5
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Quote:
Originally Posted by gunner View Post
Has anyone converted from their original size 8R19.5 to 225/70R19.5 Tires. I am particularly concerned with the clearance between the tag axle tire and the inner fender since it is minimal now with the original size tire. I believe there is sufficient clearance between the duals.
Gunter, I'm curious as to why you want to change from the 8R19.5 to the 225/70R19.5 tires. What are the advantages and disadvantages?

Brad
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Old 05-19-2009, 02:41 PM   #6
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Hi Gunter

What we have been doing on Classic Motorhomes for the last 15 years or so is running the 225/70 19.5 tires on the front but staying with the 8.00 19.5's on the rear. The reason for this is the 225/70's have a more precise steering feel.

On the rear the 8.00's ride smoother and because of their larger diameter you don't increase the engine RPM.

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Old 05-19-2009, 09:30 PM   #7
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I have new Bridgestone 8R19.5 on the front, a friend of mine gave me 7 new Michelin 225/70R19.5 that I want to put on the rear and the spare when my current tires either wear out or the sidewalls start to deteriorate. The only concern I have is the tag axle tires due to the clearance to the inner fender.
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Old 05-20-2009, 07:21 AM   #8
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Hi Gunter

If you use the 225/70's on the duals you will increase your engine RPM by 5% or 150 RPM at 60 MPH. I always felt the 454 was spinning plenty fast on the pre overdrive coaches.

As well the 225 has less sidwall roll and more traction so it will put more pressure on the tag axle bearings and the axle itself. The tag axle bearings do not have a lot of margin for additonal load.

The shorter sidewall also rides firmer so you will get more pounding through the duals into the body of the coach.

They may work ok but those are the reasons we only use them on the steering axle.

Andrew T
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Old 05-20-2009, 09:51 AM   #9
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Stick with the 8R19.5, I've been running Goodyear G647 RSS tires for years and get great performance out of them.
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Old 05-20-2009, 01:52 PM   #10
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Hi Gunter

If you use the 225/70's on the duals you will increase your engine RPM by 5% or 150 RPM at 60 MPH. I always felt the 454 was spinning plenty fast on the pre overdrive coaches.

As well the 225 has less sidwall roll and more traction so it will put more pressure on the tag axle bearings and the axle itself. The tag axle bearings do not have a lot of margin for additonal load.

The shorter sidewall also rides firmer so you will get more pounding through the duals into the body of the coach.

They may work ok but those are the reasons we only use them on the steering axle.

Andrew T
I run Michelin 225's on the front and 8R's on the back. Thus I don't increase RPM but do get a wider stance in front. I carry an 8R spare.

So far, so good.

The Michelins made a huge difference in the ride.

Oops, Andrew I didn't see your earlier post on this same configuration, oh well, great minds etc.
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Old 05-20-2009, 04:12 PM   #11
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It is hard to turn down new tires at no charge.
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Old 05-20-2009, 10:02 PM   #12
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Tnstaafl

Quote:
Originally Posted by gunner View Post
It is hard to turn down new tires at no charge.
- there's no such thing as a free lunch!

I have 8r19.5 Dynatracs on my front wheels - last digits on the dot #'s are 02207 which I assume means manufactured in February, 2007?
However on the remaining 6 I have the Michelin 8r19.5's, but with dot #'s ending in 0300 and 0700!

I know they need replacing, but what with, Dynatracs or Michelins?

On size, the consensus appears to be, keep the 8r19.5's for the duals and tag and something with less diameter and more width up front like 225/70R19.5
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Old 05-29-2009, 04:23 PM   #13
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This is strange. I recently had a 345 in for UK preparation, and that had the larger tyres all round. After my 310 with the standard tyres the cornering was phenomenal, despite the front steering and suspension being totally shot away. I replaced the bell cranks, suspension arms and others, and the road holding was far superior to my 310.

I take the point that these bigger tyres do run the engine faster due to the smaller radius, hence my wishes to GV overdrive - OR even fit the 4 speed gear box. Has any one any thoughts on that?
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Old 09-13-2009, 09:23 AM   #14
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I am asking for your input in regard to this possibility. Since I have limited clearance between the inner fender with the current 8R19.5 Tires on the Tag Axle, I am thinking of installing the 225/70R19.5 on the Front and the other four on the drive axle and leaving the 8R19.5 on the Tag. The difference in diameter between the two tires is 1" or between the center of the tire and bottom .5 inches. I would believe there is that much difference in road surface and this wouldn't be a issue. This way I would have the stability of wider tires on the front and drive axle and still maintain the original clearance between the inner fender and tire on the Tag axle. The only other alternative is to machine a .5" aluminum spacer between the wheel and drum to achieve additional clearance.
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