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Old 02-16-2014, 02:59 PM   #1
Join Date: Nov 2010
Location: Mashpee, Ma.
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New tires and horrible handling?

Hello, Im looking for some advise. I have a 04 Coachmen Mirada 300qb with no slides on a 18k F53 chassis. It had Continental tires from the factory and performed fine. I installed a Blue ox rear track bar when I bought it back in 2010 to help performance and it was well worth it. Well I just had 6 new Continental HSR 225 70R 19.5 tires installed and man the things all over the road. The shop aired them up to 95 psi. Any thoughts or suggestions?
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Old 02-16-2014, 03:05 PM   #2
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The first thing I would do is get the rig weighed, go to the tire mfgr's inflation tables, and make sure you have properly inflated the new tires.

If they're over inflated I believe it can make you feel like you're driving on ball bearings.

Best of luck.

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Old 02-16-2014, 03:07 PM   #3
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Is 95 lbs psi the recommended air pressure for the tires and did you have the front end inspected?
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Old 02-16-2014, 03:23 PM   #4
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Was all the shop do was the new tires? Or did they align too?

For sure, use your previous four corner weight numbers and go the the chart for that specific tire to get the specific PSI for that tire. If you do not have the weights, then as mentioned, do go and get them. (Search on how to do four corner weight, if you are not familiar with this.)

I also have heard of defective tires causing problems. Broken bands for example. Not familiar with these, and don't recall ever hearing of, 'directional' RV tires. Wonder if they exist, and if so are these some, and if so did shop mount them wrong?

If PSI settings do help, go back to the shop and talk with them. If they don't see any problems, and Continental can't give them any ideas. Then ask them to swap them out with a different brand... Most tire shops will do this, if you have not run too many miles on them. (And, I feel if the tires were not defective, it's fair to pay them for mounting the new tires a second time.)

Best of luck, and please let us know what you find out. Continental gets good feedback, so hope this is just a PSI adjustment!
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Old 02-16-2014, 03:29 PM   #5
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The tires say 110 psi max when cold. No, I did not have the front end inspected but she handled fine with the 10 year old set. I had them set at 85 psi.
Regarding how she handles the steering wheel needs to be corrected constantly and when the unit sways she feels top heavy, almost like I broke a swaybar link. Although I didnt I checked.
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Old 02-16-2014, 03:34 PM   #6
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1st try going to 85psi,

But I would weigh all 4 corners than you know if it's something else
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Old 02-16-2014, 03:40 PM   #7
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I am 300 miles from the shop so it would be 600 round trip. They were not the kind of guys who would provide service after the sale. They were pretty shady, told me a $2400 out the door. Tax, mount, balance, take the old tires, everything. When it was time to pay the bill they said, oh that was a cash price. Auto 1 plaza 3045 fowler st. Fort Meyers Fla. The got me for another $150. I guess its a tourist tax. Should have stuck to the large rv shop.
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Old 02-16-2014, 03:41 PM   #8
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Lowering to 85 psi concerns me, dont want to blow another
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Old 02-16-2014, 03:46 PM   #9
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I weighed my Winnie 35P, checked the tire site, and set the pressure at 85 lbs. Works fine.
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Old 02-16-2014, 06:25 PM   #10
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Originally Posted by marcdohc View Post
Lowering to 85 psi concerns me, dont want to blow another
If it was mine I'd try the 85psi as well you don't have to travel hundreds of miles to check them.

How long did you travel with the set at 85 on the old set? You could also split the difference and set them to 90.

The best bet as already mentioned is get it weighed and adjust the pressures according to the manufactures air chart.

Page 28 for pressures.
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Old 02-16-2014, 07:07 PM   #11
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Weigh your coach. You are likely running too much air. I would do this before taking any other action.
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Old 02-16-2014, 07:16 PM   #12
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Yep, I agree it sounds like over-inflated tires on the front. Front and rear PSIs are normally different, but need to be adjusted per axle/four corner weight of the coach. I've been running Continentals for over 7 years now and they have been great.
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Old 02-20-2014, 10:52 AM   #13
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Confirming the real load on each corner then consulting Load/Infl charts for Continental HSR 225 70R 19.. With the MINIMUM cold inflation established I suggest you run all tires on each axle to minimum + 5 psi based on heaviest loaded tire.

You didn't say how much wear on the old tires but two things will affect steering.
1. Old rubber is stiffer than new so new tires will not be as responsive as old.
2. Shallower tread tires will respond better than deeper tread tires so again your worn tires will respond better than new.
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Old 02-20-2014, 01:14 PM   #14
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You've gotten great advice so far...
Are the new tires the same size and profile as the old tires or are they more narrow or wider or taller or ?!?!? ....

if you cant get a 4 corner weigh, spend the $10 and 10 minutes at a cat scale to at least get a 2 axle weight... then you can divide by the # of tires on each axle to see the load to calculate your correct psi...

New tires also have much 'square-er edge' and have a tendency to 'follow' the road when the edge catches the side of a rut' or just an indentation... until worn in a bit...

the old ones probably had 'rounded edges' and would not be as affected by the road.
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