QuestionQUESTION: Barry - I purchased a set of Cooper Discoverer AT tires for my 2000 Jeep Grand Cherokee. I found that they rode very hard on small highway cracks and such, though they wore very well. 60,000 miles later, I need new tires and want to see if there is a more comfortable tire that has the grip to get me around a very hilly wet and snowy property in Upstate, NY. The dealer recommends I go with the same Cooper tire but in an LT version, rather than the P rated Cooper, stating that the LT is a softer ride. I am struggling with this given that the LT is a "heavier duty" tire and that passenger tire were softer. Does an LT tire offer a more comfortable ride? I am considering the Toyo Open Country given its traction and comfort ratings.
ANSWER: Jared,
There are so many variables involved here that we need to start with the basics:
1) Did you use the original tire size?
On every vehicle sold in the US, there is a sticker - commonly called the placard - that will list the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box, but sometimes it is located in the trunk or on the fuel filler door.
If you did not use the original tire size, what size did you use?
2) What inflation pressure did you use?
To gauge this, I need to know both what you used and what the placard says.
3) Inflation pressure is the largest single contributor to ride quality. The problem is that inflation pressure is also the largest single contributor to load carrying capacity (aside from tire size). So you need to use enough pressure to hold up the vehicle (as indicated by the placard in the form of tire size and inflation pressure). More pressure helps load carrying capacity - and therefore resistance to load related tire failures - but hurts ride quality.
Side note: "LT" tires need to use more inflation pressure than the same sized "P" tires. This is certainly the opposite of what you have been told.
So to proceed further I need to know those things listed above. But to be fair, I should advise you that I just don't have a feel for differences in ride quality for different tires.
1) There are so many different tires, it's impossible to stay up to date.
2) As I pointed out, inflation pressure is more of a factor.
3) My expertise is more in the engineering side of things. Differences in ride quality is just not something I would keep tracked of. - even if I had access to evaluations of this type.
4) Since I work for a major manufacturer of tires, I really shouldn't make brand specific comments.
Nevertheless, I will try to help you sort out what I can.
---------- FOLLOW-UP ----------
QUESTION: Than you so much for your quick response. Ok, it IS a little more complicated. The Jeep has a 2" "budget boost" lift and stiffer Bilstein shocks, though I wouldn't think this would effect the hardness - shock play/travel perhaps, be I do see a difference. With the lift and new rims, I put slightly larger tires than the factory size. The factory size was 245/70/HR16 (Goodyear Wrangler). The Cooper tires on there now are 255/70/R16. The Wranglers had a PSI of 33. The Coopers were 44. Maybe THATS the difference??? Should I be looking for a tire with a smaller PSI? I am not carrying heavy loads in my Jeep. Thanks again for your attention.
AnswerJared,
I just read up Rubicon's Budget Boost and if you used that - or something similar - that will cause the vehicle to ride stiffer.
But there is no question the 44 psi in the Coopers will cause a stiffer ride!!
No, the tire size is OK, it's the pressure. You could have used 33 psi in the Coopers and the ride would probably have been fine!
