JK shock valving

[bae146]

Does anyone know the difference in shock valving on a four door  2007 sahara vs a  4 door 2007 rubicon?  The reason I ask is my friend has a 2007 sahara with som 33X12.5 toyo open country mt's on it and he is not happy with the ride.  He is running about 32 psi on these on the street. (sad but his jeep is always on the street, MALL CRAWLER)  Anyway I have a set of slightly used rubi shocks and I was wondering if it would be worth the effort to swap shocks in the hopes of better wheel control and ride?

[w squared]

I have heard on one of the US "JK" boards that the Rubi shocks are "better". Nobody has ever gotten specific about how or why they are better.

Depending on what load range those 33's are, 32 psi may still be too high.

Before you invest any effort in doing a swap, I would do a chalk test on the tires. It may well improve the ride, and may also improve tire life.

[FiEND]

the tires are tough (solid, hard), 32 is too much.  25 to 28 max.  as for shocks.  might help if they are softer since he isn't getting much cushion from the tire's sidewalls.

[w squared]

I just took a look at the Toyo sizing chart, and I be surprised if those 33's were not a "E" rated tire. On a vehicle as light as a JK (even a 4 door), they're going to be bone-jarring at 32 PSI.

I think that if he drops ate least 5 psi off the hop and then does a chalk test he'll find that his ride quality will once again be similar to the stock ride (which is pretty good on a 4 door JK)

[Zombie]

I will try to copy the aome of the charts that I have at work that relate to air pressure and tire sizes/load ranges.
it has some good detail in relation to what weight a specific tire is able to carry at what pressures.

works good in my opinion.
on a buddies tj, the stock size was 215/75r15 at 33psi
with some 33x13.5r15's we ran them at about 25psi and it held the weight of the jeep no problem, and ran well, considering we didn't balance the tires because they needed 12-14 oz of weight on each wheel. (TSL swampers, bias ply I think)
we tried 30, and it ran like a rock.

[w squared]

14 ounces per wheel 

I guess that's what you get for bias play swampers.

Did you try rotating the tires on the wheels?

[Zombie]

nope, he wasn't planning on running them too long and he didn't care, he only drove it in the city, and 2 times on the highway to hit the trails with them on.
said it sucked at highway speeds anyway, sold it after about 8 months.
I think he is on vehicle #16, and he is 22

drove in the city, and at 25 psi it ran great, and that was in a 4 banger

[bae146]

The first thing I'd do in support is say: "You need to be more specific about the problem you are trying to solve."   "not happy with the ride" really leaves us to make assumptions.

I agree, larger tires don't need as much pressure as I found out on my 04 Rubi... I'm running about 25 right now, may be prudent to do less, but I have yet to do a chalk test or any other test. (I had interesting results from a temp measurement after driving in to work, but I want to do it a few days over to see if it remains the same.)

The Toyos are a "truck tire" I'm fairly sure and have substantial sidewalls, so they are going to pass all the bumps through to the suspension.  Softer shocks may help a bit, but then he may find it dips and dives more and may "bottom out" when he hits things like parking lot entries to malls etc. depending on how soft.

Granted, if you are talking about going to Rubi shocks, I'd assume they are a stiffer shock, so perhaps he wants a stiffer ride than the Toyos are providing?  Perhaps there is too much suspension movement for his taste when he does hit bumps etc. due to the increased inertia at the wheel/tire?

Perhaps it's the handling?

As Far as ride is concerned he just said it rides to harsh.  I will try to get him to change his tire pressure, and I will take it for a drive and try to discern where his problem lies.  My only question was on shock valving, I was not wanting to go into the whole tire pressure debate.  I do thank you for your suggestions, but tire pressure can be one of those debates that gets overinflated in a forum (ha ha  )

[Zombie]

nice
if you let me know what tire size and pressure the jeep originally had, I can tell you what pressure it should be based on the new tire size and load rating.

[Bnine]

The only people that would debate tire pressure would be those that dont understand it.

Even contact is all that matters. If he is running a E rated Toyo, a contact pattern will show that 32lbs is over inflated. 20-24 should be more then enough.

[w squared]

The only people that would debate tire pressure would be those that dont understand it.

Even contact is all that matters. If he is running a E rated Toyo, a contact pattern will show that 32lbs is over inflated. 20-24 should be more then enough.

I think that Bnine is saying the same thing that the rest of us are on this thread...he just does a better job of it. 

[BlackYJ]

As Far as ride is concerned he just said it rides to harsh.  I will try to get him to change his tire pressure, and I will take it for a drive and try to discern where his problem lies.  My only question was on shock valving, I was not wanting to go into the whole tire pressure debate.  I do thank you for your suggestions, but tire pressure can be one of those debates that gets overinflated in a forum (ha ha  )

I notice a big difference in ride quality on my YJ when I go from 25 psi to 30 psi.  Especially since he is running E rated tires, I would try lowering the pressure first before he start messing around with shocks.  The tires sidewalls do a lot to absorb shock from the road.

[bae146]

I think that Bnine is saying the same thing that the rest of us are on this thread...he just does a better job of it. 

Yup this is good info.  I have done the chalk test with him and told him to run abou 26 psi but he has not listend to me.  Of course now he has had enuf of the rough ride and is now willing to listen.  It would be nice to throw it on a dyno and do it so you can bring it up to hwy speeds and see how much affect centrifugal force has on the contact patch........

[w squared]

Yup this is good info.  I have done the chalk test with him and told him to run abou 26 psi but he has not listend to me.  Of course now he has had enuf of the rough ride and is now willing to listen.  It would be nice to throw it on a dyno and do it so you can bring it up to hwy speeds and see how much affect centrifugal force has on the contact patch........

There's actually a low-dollar solution to that too. Once you've gotten in the ballpark with the chalk test, try the "paint test".

Apply a good, thick coat of a light coloured paint the same way you would with chalk. Then drive on it for long enough that it starts to wear off. This will give you a good indicator of highway performance if you're about to start a road trip when you do it. If you do it over a period of days of "normal" driving for you, it will be based on the cross-section of your normal driving patterns. 

[Zombie]

i do like the contact patch thing Bnine, I have to try that one day.

what I was trying to get at is that actually finding out what the jeep weighs front and back will give a good indication of where to start.
I wouldn't want to run too low either. alot of it would be dependent on what how wide the wheel is too.
it is is out of spec, it would change how the tire contacted the road too.