The I-15 bounce!

mbryson

.......a few dollars more
Supporting Member
I’ve noticed it even in my ‘98 Cummins long bed extended cab just as you come down the hill from the overpass over the train tracks southbound on i15. Don’t notice it on the CCSB
 

Hickey

The Dark One
Supporting Member
After seeing Glockmans mod and the previous link with all of the animations, I can totally understand how the frame is flexing on the long bed trucks and causing the bounce. If I still had my long bed, I would be in the garage building a crossmember immediately.

Great work, gentlemen!
 

jeeper

Currently without Jeep
Location
So Jo, Ut
I just picked up a small load of drywall. Ticket says it’s 510lbs. The drive home was worse than my drive there ‍:mad:

I’ve never had weight make it worse before.
After I hang this drywall, I think I am going to make a cross member.
 

jeeper

Currently without Jeep
Location
So Jo, Ut
I added some rancho adjustable shocks front and rear about a year ago, and thought I had solved my bounce for the most part. It was really neat to be able to make an adjustment and see the immediate change in the was the truck handled.

However, a few weeks ago one of the Hankooks on my truck separated a belt and bulged. I replaced them all with a set of Cooper ATP’s. Immediately after while diving home, I had the worst bounce ever, and it was just on the surface streets near my house.
I guess I could have thought it through, but I didn’t think tires would make such a big difference.
 

Tonkaman

Well-Known Member
Location
Taylorsville
I added some rancho adjustable shocks front and rear about a year ago, and thought I had solved my bounce for the most part. It was really neat to be able to make an adjustment and see the immediate change in the was the truck handled.

However, a few weeks ago one of the Hankooks on my truck separated a belt and bulged. I replaced them all with a set of Cooper ATP’s. Immediately after while diving home, I had the worst bounce ever, and it was just on the surface streets near my house.
I guess I could have thought it through, but I didn’t think tires would make such a big difference.
So you think it’s the ATP’s??
 

Hickey

The Dark One
Supporting Member
Did you check the air pressure? Do both sets of tires have the same load rating? I've had great results with all of the Cooper tires I've had, but they were all truck tires.
 

jeeper

Currently without Jeep
Location
So Jo, Ut
This will be my 3rd or 4th set of the ATP's and I've been happy with all but the smaller light-duty set I put on the colorado a while back, and that's because they wore out quicker than I thought they should. traction, ride, and noise level have all seemed good with them.

I changed air pressure from 70 down to 60, and it didn't make a big difference, then went up to 80psi to get my sensor alarms to shut off.
I played with the adjustments on my shocks a little today, and going 2 clicks softer seemed to get rid of most of the hop.. but every time I was in the truck it had a different load in the trailer or bed.. so not really good comparisons. I will keep playing with it. I am not concerned.. I was just surprised at how BIG of a difference it made from the tire change
 

mbryson

.......a few dollars more
Supporting Member
Just thought of this thread this morning. Had a southbound newer Tundra come past me just as you come down from the railroad overpass just before the Warm Springs Rd exit this morning. That looked pretty uncomfortable but the lady driving it just seemed to treat it as normal?
 

Herzog

somewhat damaged
Admin
Location
Kamas, UT
My taco gets the I15/I80 bounce pretty bad. I actually think it's a little bit of axle wrap mixed in with the fact that I haven't tuned my rear shocks. It's not fun.
 

I Lean

Mbryson's hairdresser
Supporting Vendor
Location
Utah
It definitely feels resonant. (which is why it doesn't happen when I have a load in the bed)
 

Spork

Tin Foil Hat Equipped
It definitely feels resonant. (which is why it doesn't happen when I have a load in the bed)
Thinking those that have added a cross member have changed the vehicle enough to get out of the affected frequency. My VW has issues on California Ave in salt lake, the seams make it start bouncing around 30-40.
 

RockChucker

Well-Known Member
Location
Highland
Thinking those that have added a cross member have changed the vehicle enough to get out of the affected frequency. My VW has issues on California Ave in salt lake, the seams make it start bouncing around 30-40.
I think EVERY vehicle has problems on California Ave. That road is the worst. I've been wanting to add a new cross member on my truck right at the front spring hanger for the rear springs. I think the outside spring mount creates a moment on the frame rail that is magnified by the fact that my truck's frame isn't fully boxed.
 

Hickey

The Dark One
Supporting Member
I think EVERY vehicle has problems on California Ave. That road is the worst....

I think the outside spring mount creates a moment on the frame rail that is magnified by the fact that my truck's frame isn't fully boxed.
California could be a decent offroad race course.

Your description of the frame issue is the most plausible to me. Fitting a crossmember in that area on the bottom of the frame looks like a difficult task. Between the exhaust and driveline, there is a bunch of crap in the way. A crossmember on top of the frame might be easier, even with pulling the bed off.
 

I Lean

Mbryson's hairdresser
Supporting Vendor
Location
Utah
California could be a decent offroad race course.

Your description of the frame issue is the most plausible to me. Fitting a crossmember in that area on the bottom of the frame looks like a difficult task. Between the exhaust and driveline, there is a bunch of crap in the way. A crossmember on top of the frame might be easier, even with pulling the bed off.
Yep. My 2012 does not look reasonable to add one here.
IMG_20201008_085533083.jpg

And looking at the inside of the frame/spring hanger, there is already a cross member there, so adding one on top of the frame wouldn't be worth it, probably?

IMG_20201008_085555809.jpg
 
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