Hi all,
Info for anyone considering purchase of Cooper ST tyres.
I am thinking of fitting STs to my GU Patrol. Last week went through the archives and found a thread (19Feb) where Slunnie refers to side lug failure on STs fitted to a DiscoII. I followed this up with Coopers Oz distributor, who provided reply below. I was really pleased with the reply and they also phoned me to discuss - great service. I have had ATs before and will likely fit STs (though will wait for the new STC, due mid year). I think the bottom line here is selecting the correct tread pattern for intended application - such a subjective topic but one needing objectivity.
Hugh
We have just had a visit from the technical people from Cooper USA so I am up to date with all the information about changes in Cooper product etc. As you may be aware Hugh our company has been the Australian importer of Cooper Tires for 13 years and we work with distributors in each state as
well as having a retail store in
Brisbane that specializes in 4x4 tyres. So we have seen a lot of tyres over the years and all the brands which has given us the ability as a wholesaler to see first hand the effects of the Aussie conditions on tyres, in fact we have had input into the design on some of the Cooper patterns in recent years.
The comments you have read on Explore OZ website on Cooper ST's chipping and tearing of lugs. Yes we are aware of it, and yes it has happened more than we first expected, however most of the people who experience this and feel that it excessive, have been comparing to other mud pattern tyres. You see Hugh the Cooper ST is a unique pattern and is designed to fit between a mud pattern and an All Terrain pattern and for people looking for more traction than other All Terrain tyres. The only trade off is that it is still an All Terrain pattern and does have limitations. What I mean by that is the ST has Sipes or tiny cuts in the tread blocks. These sipes are designed to squeeze water out form under the tyre on the black top, however on sharp dirt roads the tyre chips away as it does with all siped all terrain patterns. It is just that people think that it should not chip, however whenever we have seen a direct comparison between a Cooper ST and other brands of AT patterns the ST does better
miles in the long run and does chip less in the same conditions. Remember that the mud patterns do not have sipes (even the Cooper Mud pattern) and that's why Mud pattens do not chip and do better in sharp or gravelling conditions. Also remember that many people that should be using mud pattens for these reasons and have switched to Cooper ST's to reduce tyre noise and improve on road performance have been the ones to notice the difference (many of these people that come through our retail outlet we have changed back to Cooper STT's and they have now realised that their application does require the Muddy's).
Tearing lugs is for similar reasons. The Cooper ST has a small but sharp
shoulder lug with a fine split or sipe in the middle of it and if you compare with the Cooper Mud pattern in the same size the Mud pattern lug is at least 3 times the size. It is obvious to us now why the ST lugs tear. Put simply, they are doing the job. What I mean is they are getting traction, to much traction, and because of the small lug they can tear. Now when given the same condition with a Muddy they don't tear and get the same grip, whereas if the same tyre had of been an All Terrain pattern it may have not torn, however it also would not have gripped like the ST (they probably would of got stuck). The people that
buy the ST for more traction than the average AT have been happy, it has only been the Mud tyre buyer that has bought ST's or people that use them for the same sort of work that have concerns.
Now the good news as some people have heard is Cooper are improving the ST compound. In late may we are expecting our first shipments of the new compound (the pattern name with be STC standing for Chip Resistant). Now all tests show a huge improvement with a 90% improvement in tear resistance and 40% improvement in chip resistance. Remember Hugh that although it will be improved it will still chip as the sipes are still in the design as
well as the small shoulder lugs, so it will be far better that any other All Terrain but still not as resistant as a Mud pattern given the same conditions.