Unsprung wght vs Sprung Wght

[AJeepZJ]

was it someone here that had the calculation to what additional unsprung weight translates to in sprung weight. Ive postedl in 3 different forums for 3.7's with 33's or larger - The posts were a ghost town. So it appears I am the only 3.7 with 33's.

In my first drive with them, it was great, Gville is flat so it doesnt drop gear much. That was untill I drove to Raleigh. Raleigh is hilly it drops sgear to hold 65. I want to discuss ways to better manage the unsprung weight, what to watch for in terms of wear on the vehicle, and the cheapest and most effective mods to deliver power in order of prioritization.

And please do not comment 'engine swap'. It will just make me dislike you, lol.

[Matt]

Seems like there's a few different questions in this post...

1) managing larger tires with the 3.7L
Not really much you can do there until gears become available IMO. Most of the "power" mods on the market squeak out a small performance gain at the peak levels... this doesn't often translate in actual power gains since the gain % diminishes as the RPM's lower and it's minimal in the RPM range that you normally drive at (ie: 10hp increase at peak 5000RPM may only be 1.5hp increase at 2500RPM)

2) the effect of larger/heavier tires on the suspension system
Inertia is the issue with unsprung mass. A simple way to think of it is when the tire hits a bump in the road it must move upward, it's motion must then stop and move back downwards- changing directions of a heavy object is much more difficult than a light object... think of a soccer ball; someone rolls a soccer ball to you and you kick it, no problem... but what if someone rolls a bolling ball at you and you try to kick it? >>>> well the bowling ball is the heavier tires and the shock/spring is your foot. The offroad oriented suspension systems are better at handling the unsprung weight, but also firms up the ride in the cab.

3) trade off between unsprung weight from tires and ride quality
The best thing you can do to account for the unsprung weight of the tires for both ride quality and efficiency is to find your optimal tire pressure. Too much pressure increases the effects of the "bowling ball" since the tire must react to almost every road imperfection (hence why everyone complains about E-rated tires because they don't realize that the pressure stamped on the sidewall is waaaaay too much for their application). Too low of a pressure however will reduce MPG and may also overheat the tire. So there's a balancing act there.

Hope that helps some

[AJeepZJ]

Pretty helpful... So of the list of performance mods I want to do - none will give me the edge I need aside from regearing? Also, with respect to the drivetrain, what do I need to keep an eye on as far as wear. Do I need to beworried about the tranny.... And what about a tuner to modify some of these gear changes?

[Lt_JWS]

The cheapest thing you can do is port and polish your throttle body, easy and free if you have some tools! That combined with an intake or DIY intake might help off set the tires... When i had my 08 WK i had an intake and an airram powerwire(simple IAT mod) that helped it out, got me mpgs and some extra power! As for the transmission it should be the least of your worries, its practically the same thing they use in the 300C with hemis and the srt8s..... WA580 is a Mercedes designed transmission, wish mine had it to be honest.....

[Matt]

In terms of "performance", there's not much to be had- especially for the price. The only thing that will help is a tuner that can correct your speedometer since your shift points are off due to the increase in diameter. But don't expect an intake/exhaust/ported throttle body to have a significant change (normally people "feel" a change from the placebo effect... kind of like how your vehicle "feels" like it runs better after you wash it. They feel better performance because they expect to feel it. So be wary of dropping $400+ for these types of mods. $.02)

As far a wear goes, just keep an eye on everything as you normally would. These vehicles can handle 33s pretty well (in terms of suspension), i think the weakest link is the steering rack.

Tranny.... yes. Make sure you keep up with maintenance on it since the tranny will be getting a workout. Only thing that will help the tranny is regearing the axles which, unfortunately, is not much of an option right now. The other thing that helps the trans is an external cooler... so if yours isn't already equipped with one, that would be a good mod. Or, if it is equipped, a larger one would help.

[NeilSmith]

A.J. , I have to deal with hills and small mountains on a daily basis and I too have the 3.7 . I am running 245/75s which I guess are like 31.5 " tall. My XK shifts out of overdrive at the very least incline but its just something you have to get use to. Eventually you will become use to it and ignore it. I've been running these for almost two years now with no issues what so ever when it comes to suspension or drive-train. Sometimes I wish my area was flat so I could get better mileage but then it wouldn't be as beautiful. This is what I have to deal with daily, its so sad.

[Sal-XK]

Just hit the tow/haul button


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[criket]

Just go ahead and do that t case swap that you've been talking about, lol.

[AJeepZJ]

Ive been wanting to do an another fan for some time, that wouldnt be a bad idea at all, will look into that tomorrow... Yeah, I definitely need to fix the gear chamges..

[hoaxci5]

Turbo! Supercharger! (hey it's not an engine swap)