QuestionQUESTION: We have a 07 Toyota Highlander AWD that has standard load P 225 70 16 tires on it. We live and drive on Rock Limestone roads and wish to upgrade to a heavier load range D or E tire that is more suited for the abuse. We wish to keep tire diameter close to the same. Would a P 235 65 16 load range D tire work. Any other suggestions? Thanks
ANSWER: Dear John,
Thank you for using AllExperts.
I'll try to keep my answer as simple as possible, but you've presented some complexities.
Gravel roads can certainly wreak havoc on tire tread wear...especially in wet conditions. I've checked the common original equipment fitments (P225/70R16)for the '07 Toyota Highlander and the original tread depth is typically 10/32nd" of an inch; not much. I wouldn't recommend changing from your original size...and I've checked (as an example) the BFG All Terrain T/A KO, size LT225/70R16 Load Range 'C'. BFG shows the original tread depth as 16/32nds". Other 'LT' (light truck) offerings (tread depth) may be similar. This additional tread depth may provide more tread life on your limestone roads. There is no need to go higher than load range 'C.' There will be trade-offs in going from P-metric to LT-metric:
1. Since 'LT' tires are designed to a completely different formula compared to P-m tires, and are more robust in their construction, you will have to apply MORE air pressure to achieve equivalent loads compared to the P225/70R16, for example:
P225/70R16 load capacity at 30 psi = 1,701 lbs/tire
LT225/70R16 load capacity at 45 psi = 1,710 lbs/tire
If your current tire information placard recommends 30 psi, you'll have to apply 45 psi to the LT225/70R16.
2. Another trade-off is speed rating. Using the BFG All Terrain T/A as an example, its speed rating is 'R' (max 106 mph), whereas your original tires may have been rated at 'S' (max. 112 mph).
Overall, you will sacrifice ride comfort with the LT tires due to the higher air pressure requirements.
If you have any questions regarding the (above), or if anything is not clear, don't hesitate to contact me again.
DT
---------- FOLLOW-UP ----------
QUESTION: Thank You DT
Additional tread depth may extend the tread life on limestone reads, however tire punctures and breaks, requiring patches or replacement, seem to be a more common occurance. My thought was a tougher tire ( higher load rating ) would reduce these occurances. We are not as concerned with tread wear, I am concerned with wife and kids stranded on some road with a punctured tire.
Thanks for your thoughts.
AnswerDear John,
I can understand that this may give you some peace of mind, however I note that size LT225/70R16 is only available on the market in load range 'C' according to my records. Even if it were available in 'D' for example, I've never seen any evidence that higher load rated tires offered additional puncture or rock penetration resistance; only a higher load capacity. The key point to driving on gravel roads is to NOT OVER-INFLATE the tires beyond what is necessary for the vehicle load.
DT
PS...having said (the above), most light truck tires have two steel belts and many have an additional one or two nylon reinforcing ply on top of the belts. Larger size LT tires may have three steel belts, and this may aid in resisting rock penetration...but these are not available in your size and are not suitable for a crossover/SUV such as yours. The number of steel belts, or nylon reinforcing plies is not necessarily directly related to the load range...C, D, or E.
DT
