Discussion in 'Renegade Wheels & Tires' started by fred, Oct 25, 2016.
Give us a progress report on those tires! Looks great!
I'm Sitting on 235/70 R16's, no Rubbing, these
are 29X9.3 in size. I'll post some better pictures in the morning
Installed KO2s 225/65/17 on Stock Rims, Stock ''16 Trailhawk, without a lift and without spacers. No Rubbing ~1/2 clearance to struts and ~5/8 to the Weld Seam dimple when the tire is turned to the where it comes the nearest.
My question is air pressure. The shop put 35PSI in the tires. I found by watching my gauges they tires where heating up way too much and way too fast. I was seeing 6 to 8 degrees after twenty five minutes of highway speeds. Also my gas mileage that is normally 25 mpgg to 27 mpg on that stretch of road had dropped to 19 to 21.
Based on the sidewall rating of 65psi cold at max load and that its an 8ply tire I shot for 55psi. This brought my MPG back in line. I still think this is might be the right pressure. Ambient was 74 degrees. I was a little gun shy so I dialed back to 48psi. I did a chalk test today and the patch looked good if not a little on the low pressure side. I'm starting to think 50psi to 53psi might be correct. I haven't been able to get access to the engineering load temp curves for this tire toactually do the calculations.
I would be interested in any opinions. I'm positive running these at the door sticker of 35 PSI is going to mean the tread life is going to be more like 30k to 35k verses the advertised 55k. I do have anengineering background in automotive. I just can't find the load / Temp curves to determine the actual correct tire pressure for a GVW of ~4500. Maybe if someone know an OEM application for this tire and what the door sticker says for that OEM use, I can back door the math to get the correct pressure for us. Anyway Here is what my Reny looks like with these. This is right after I did the patch test. The tires were warm at about 52 psi in 79 degrees ambient.
UPDATE: I did some additional road tests andchalk tests. Currently I'm running at 54psi. I drove twenty minutes at 75mph and only saw 3psi to4psi which I think would be a normal heat up. Chalk tests looks good also. There might havebeen a little lifting on the outside edge of the tires in the front, but that could be some camber offsetas well. 52psi might be good too, I'm going to runa few hundred miles like this.
UPDATE: I experimented with multiple locations of the roof rack on the roof, and yes it does matter, to minimize the losses. At dead center I lost about 2.5 mpg at highway speeds.
Recently, I removed the air spoiler that mounts to the front of the rack. I've attached the before and after pictures. With the spoiler removed I'm not losing any MPG, but there is noticeable winded noise through the bars with the rack mounted in the middle. On the plus side I've now moved the rack to the rear were the noise is less, and it makes it much easier to load the rack since I can now stand on the rear tires. Best of both worlds.
Interesting... Please keep us posted.
Looks great! I put these on my wife’s Pilot. I found the best ride is at 45psi. With the high load rating 65 gives you a harsh ride on a light weigh vehicle. At 45 we also had a much better feel while turning and better traction.
got some wheels of a Chrysler 200 for a winter set up. tires are 215/60-17. wheels are 7.5 x 17 with a 41 offset..tires rub rear strut. had to add .25 inch spacer and get longer stud bolts, hope this info can help some one else
I thought that it was supposed to be 38 psi for the ko2's thats what ive been running. So I should go higher then?
If you never exceed 35 mph, then you are fine running less than 45 psi, but if you run highway speeds the tire will heat up and you'll lose mileage on the tire and MPG on your gas tank. This is born out by those who say they love the tire, but only get 35k out of the tread.
There are lots of tests and indicators, the best is having access to the manufacture tire load charts. I haven't found them for this tire. Without charts, I most trust two indicators, the chalk test and, since we have live pressure monitoring, tire heating. You can Google how to do a chalk test, it's really simple. For the pressure test the rule of thumb is at ~65°F to ~75°F if you check the tire pressure after at least a three hour rest , cold state, then drive at highway speeds for 1 hour, you should not see a pressure increase of more than 3 psi max, hot state. I also watch my mpg. You will get the best MPG at higher tire pressures. Be careful, mpg alone should not be used. At the best MPG, the tire will be over inflated.
I just got the KO2's on a few days ago. Asked the tire guy what he put the PSI at and he said 35, wouldn't recommend any higher. I'm running em at 43psi cold, after 25 minutes of 65mph they get up to 46. My MPG has been shit in the winter even before theses tires.. can't say I've noticed a huge change but I'm currently getting around 20mpg highway.. maybe I was getting 21-22 with the falkens.
A installer is limited by their legal policies to only inflate to the pressure on the OEM Tire card on the vehicle.
Tire inflation is directly related to the load carrying capacity of the tire as you under inflate you reduce the capacity. At 65psi cold the tire is rated at 2150 lbs which would support a gross vehicle weight of 8600 lbs. Now our Reny's only have a GVW of 4586 lbs. Now I've seen enough load inflation tables in my 25 year engineering history to be confident that at 35psi there is just enough air to support the load on the axles. However, as you noticed mileage will be terrible, and it is possible that once you start running on hot pavement in the summer you will see 4 psi to 6 psi pressure increases. If you have significant miles on the tires you may be able to start seeing evidence of poor tread wear. Use a tread gage plunge micrometer or the end of a pair of calipers to measure the depth of the tread from the outside to inside of the tire. If you are running correct inflation the depths should be consistent to within +/- .015" if you see more than .030" from the center to within .250" from either edge of the tire you have a problem. Center high means over inflating. Center low means under inflating.
You should also look for evidence of " Cupping" this is where the top of the tread starts to get a scalped appearance, like the tread pattern itself wore unevenly within the shape of the Z patterns.
Do you know exactly what the relation between PSI and load is, or is that the missing piece of information because we don't have access to the graphs?
If it's a linear relationship between PSI and GVW and PSI should be 65 at 8600lbs, that equates out to about 34.6 PSI @ 4586 GVW.
What you're saying makes sense, which is why I increased my PSI from 35 to 43.
If we don't have the graph for this tire, maybe we could go off the graph of a similar tire or if anything it would give me a better understanding of the relationship between PSI and GVW.
Kevin, given that the GVW for the Reny is substantially less than the target load for the BFG KOs, the load charts would be useful at knowing the minimum tire pressure we could run and safely operate the vehicle. Using the Chalk test combined with looking at the side wall flex, watching the pressure increase while driving, and gas mileage analysis are a better method of determining the best operational pressure. I have seen on the Toyota Tacoma and the Landcruiser forums that some people have been sucessfull at emailing Goodrich Customer Support for pressure values. What they get back are the pressures that correspond to the equivelent axle loads for the vehicle.
When it is said that they don't rub or hit anything.....has the tire/wheel set-up been FULLY flexed and turned lock to lock?
You got the set up I’d like to put on..Have you noticed any rubbing?
Very little rubbing. Only on certain turns under certain suspension conditions. Not enough rub to warrant the seam modification.
Thanks for the reply!
Last question..have you put spacers on the front?
Yes. 1.25" spacers on all 4.
Sorry..I just red you have 1,25” spacers
Would 1 inch spacers have worked on your set up?
Separate names with a comma.