I bought new tires on Friday for my 1999 3500, and am having some heartburn with them. The old tires, (Goodyear MTs) were about worn out but still rode good and were very stable. I replaced them with Goodyear HT radials (235-85/16). They are scary unstable! Wiggles all over the road, and will sometimes change lanes on it's own. I've tried full inflation (80lbs cold) and it helps a little. Should I try to lower the pressures?

Jim

 

What size were the tires that you replaced?

 

Same size. 235-85-16.

 

Is your 3500 dually? 235's in my oppinion are not wide enough for our trucks. Even if you had good luck with the previous 235's. I bet you will find more 235's being unstable then stable. I had a set of 235/85/16's on my truck and it did the exact thing you are experiencing.

Dave

 

I think 235's are about as wide as I could go on my truck without the rears rubbing. (The manual calls for 215's) My truck has the narrow spacing on the rears, unlike the newer ones. A quick check with 3 of my buddies with 3500's (they were all duallies) run 235-85-16s, some over 200k miles towing heavy. Thanks for your answer, but I think the size is OK.

 

The tire size is fine. I would think full inflation will only make it worse.

 

alignment or loose lugs nuts, IMO.

unless they are a directional tread pattern........

 

No alignment issues or loose nuts. The truck drove like a dream ten minutes before I put the new Goodyears on. This is a tire issue. Has anyone ever seen this?

BTW: These are highway rib type tires. Not directional. E-Rated.

 

this may totally irrelevant but have you check to make sure they gave you a load range E and not a D or C? i don't know if you can or not get the 235 85 16s in D or C ratings but if so its possible the week side walls are weak.

 

No they are full E-rated heavy duty truck tires.

 

I have seen and experienced that after driving on worn tires, putting fresh ones on (same size, load range, manufacturer, and tire pressure) will give you an eery feeling as the additional tread will 'give' more than the worn tread.
Miight be what your feeling.
Or it could be the tires aren't running true.

 

Try lowering your tire pressure to 65 front and 55 rear.
Last time I changed tires they didn't listen to what I asked and put in 80 psi all around. Truck was all over the place and even hopped around on rough roads.

 

Thanks Infidel, that's what I was looking for! Jim

 

I agree with Shovelhead. It could be the fact that you now have deeper tread that will squish more than the old worn out tread. Also, A rib type tire would be more succeptible to this side to side squishing than your mud tires you had before, even at full tread. Hopefully playing with the air pressure can make it more stable for you.

 

After a terrifying 400 mile round trip to East Texas this weekend, I swapped the tires for Cooper Discovery AT's. Problem solved!