35s to 37s, rough ride

[Turning Blue]

Have you considered having your shocks rebuilt? It may be time?

 

[HulkHartman]

Quick update. Had the other 2 tires balanced last week, drove 700 miles this weekend. No change. Some sections of road it smoothed out but for the most part, rough. Im swapping the stock wheels and tires on either tonight or tomorrow morning to get a comparison. If the stock tires feel great, ill be selling these 37s and finding new tires lol.

I've considered it may be time for a shock rebuild. Whats the best route for this nowadays? I've seen rebuild companies, or just replacing them. I haven't looked into the costs though

 

[Barclay]

Is there any chance that these new tires are of a higher load rating than the stock tires? The stock KO2s are load range C. I had devoured six of them (I had to replace one in the middle of a cross-country trip due to a massive blowout) and turned them essentially into slicks, with as many as 12 patches in each tire by the time the odometer reached 11k miles. It was ridiculous, haha, with some of my neighbors even joking about our nearly constant flat tires. So when I replaced them, I went with the load range E KM3s due to their tougher 10-ply rating, compared to the stock tires' 6-ply rating (the KM3 switch was due to living in Texas and being surrounded with seemingly bottomless clay mud, haha). I can say it was definitely the right call, since I am now at almost 33k miles (so I've used the new tires twice as long as the old ones), and I still have about 50% of the initial tread remaining, and haven't had to patch a single tire yet. I popped a bead while wheeling twice, but none of them have required repair. But I digress.

The reason for bringing them up is that when I first got them, I was disappointed with the ride quality. On the highway, I was previously running 35-38 psi (sometimes 33 or 34 psi in the rear if I wasn't carrying much weight in the bed). I tried dropping the KM3s down to 32 front and 30 rear, and the truck immediately rode so much closer to how it felt originally. Smoother, more planted, and more stable, especially over rough pavement, which tended to be where I had seen the largest degradation in ride quality. After running lower pressures on the pavement for a while, I noticed the tires were still wearing a little faster toward the center than they were toward the outsides, seeming to imply that 32/30 psi was still overinflated for those tires on the truck.

Experimenting with chalk (coating the threads with chalk at different inflation pressures, driving over the chalk, and inspecting the chalk print to find where the pressure between the inner and outer treads is most even), I found that around 28-30 psi was the ideal paved road pressure, depending on how much weight I was carrying (I wasn't testing to max, but between the different amounts of weight I commonly carry). The stiffer tires are designed to be able to carry a much heavier vehicle at a given pressure, so you don't need as much pressure for a lighter vehicle to maintain the ideal contact patch, and it was a larger difference than I expected.

As others have mentioned, switching to 37s also adds another dimension to finding your ideal psi. Tires with a larger volume of air (I'm assuming these 37s are also made for 17" rims, so they're definitely larger inside?) don't require as much pressure to support a given weight. I've heard from Jeep guys who run 37s on 17" wheels that their ideal on-road pressure is around 25 psi. Obviously, the Raptor is heavier than your typical Jeep, but it wouldn't surprise me if you'd fare better with something around 26-30 psi? It would be worth experimenting with, I think.

 

[HulkHartman]

They are load C also. They are essentially the gen3 stock 37 tire. I havent swapped back top the stocks yet, been a little too busy. I have them at ~30/31 cold and the ride is much better then 35+. ive gotten used to the ride quality in town, interstate still suck. I may drop the psi down a bit for testing though based on your suggestions.

How do the Load E km3s do on the road comfort wise?

 

[Badgertits]

They are load C also. They are essentially the gen3 stock 37 tire. I havent swapped back top the stocks yet, been a little too busy. I have them at ~30/31 cold and the ride is much better then 35+. ive gotten used to the ride quality in town, interstate still suck. I may drop the psi down a bit for testing though based on your suggestions.

How do the Load E km3s do on the road comfort wise?

I’d try going to 29/30 - it’s either the pressure or the balance, what about the rims, are they OEM? A rim could be bent too btw….

Id imagine if the shocks were starting to get to the point of rebuild then the 37”s may show it sooner/be more noticeable

 

[dsiggi]

I'm going to guess you have a tire that has a separated belt or similar problem. You should be able to see a wobble if you could spin each tire up using a spin balancer or maybe that road force balancer. It's likely going to be one of the tires that didn't get the road force balance on your last visit. Find that tire and replace it.

Have you considered having your shocks rebuilt? It may be time?

This. You have 55k miles on the truck , you need a rebuild it will be night and day with the shocks. You also just put a much heavier tire on that wasnt in the design spec for the stock suspention setup. Its a heavier tire and more for the suspention to control. Rebuilding the shocks should help a ton, but don't expect it to be the same when the truck was not designed with those tires.

 

[HulkHartman]

Been a minute for an update, short update: Problem still exists and is unknown.

However, i swapped stock wheels and tires back on, still very rocky/bumpy at in city speeds, highway felt much smoother. I swapped back to the new wheels and tires until i was able to get new tires. I ended up getting Toyo at3 315/70/r17 load d tires (stock size but 4 lbs heavier). Definitely better riding on highway, but almost more "Bouncey".. My Mechanic buddy took it for a ride and definitely noticed what I was talking about and did a Suspension look over and said every looks and feels (idk what that means) like nothing is wrong when inspecting it. To go over the symptoms again: Intermittent as in sometimes very subtle and sometimes horrible bouncey/kick in seat/feels like being lightly bumped from rear. Sometimes on highway feels like wheels are all shaking/out of balance, without stopping on same road will go away and be much smoother ride. This happens at random spots on the interstate, tried to correlate to rough road but its not. It almost feels like driving down a gravel road constantly. Big bumps/speed bumps feel easy like brand new, its basic driving on smooth-appearing roads that makes me crazy haha.

Truck is at 60k now. Im going to look around locally for a suspension shop to service the shocks. I asked my local Ford about it and they said "raptor shocks dont ever need to be rebuilt" I chuckled and didnt even bother referencing the manual that recommends shock service...

 

[rschap1]

Sounds like the dealer/service dept. needs some edumacation.

 

[Badgertits]

Well you’re on 18”s right? You had 17”s on w/ the 35”s right? So basically didn’t gain any extra sidewall height for one, I have heard the 37”s are very tough to balance- as others have said, maybe mess w/ different psi’s

Also (shot in the dark) wonder if your rear leafs are very worn - probably are if original- & im sure that wouldn’t help ride quality

 

[Swaddict]

My 37" KM3's balanced fine and run very smooth for a mud tire at 33 psi