Dangerous condition...rear tracking??

[Duke Mk1a]

I would call it rear tracking with the road or wallowing but driving down to Houston and back up I had issues with it. To the point that the car felt like I could lose control if I did not counter the rear end movement. Was really bad in corners with road deviations. Also during hard acceleration at speed the rear wheels seemed to shift right and left. Downright scary.

I checked everything in the rear suspention and nothing is loose. Axle shafts, axle connection to leaf springs, U bolts, leaf spring connection to body, body mounts, rear leaf connection. I pulled the wheels and pushed and pulled on the axle and there is no movement.

The shocks are crap Monroe. I pulled them off and replaced them with new crap Monroe shocks.....this seem to fix the problem but the problem returned on the way home. I did expose these new shocks to many hard launches over a couple of days.

Now, would the TOYO RA1 tires cause this? They are rated to 149 MPH so I should hope not.

I plan on getting some of Dale A's rear shocks but have a few items to fix right now. I am just wondering if I have checked everything or am barking up the wrong tree.

 

[Cal44]

Duke,
are the tires directional only?

When you changed the shocks last time did it completely remove the bad behavior of the car then did it slowly come back?

Mike

 

[Duke Mk1a]

Duke,
are the tires directional only?

When you changed the shocks last time did it completely remove the bad behavior of the car then did it slowly come back?

Mike

Yes, they are directional and they are installed in the correct direction.

I want to say that yes, the condition was gone. Conditions were not that same as when I was doing 75 mph on the interstate though. It did slowly come back and was fully as bad on the return trip about 400 miles into it. But......it seemed to get better for the last 80 miles. It had cooled off a lot then too. It has me stumped. I am going to pull the shocks and see if they still self expand like they did when I put them on. The old shocks were dead fish and did expand, they still had resistance when pulling and pushing on them.

 

[hottigr]

I have the Toyo Proxes RA-1's...running 185/60 in front and 205/60 on the rears. Never had anything happen resembling what you are describing. I have had it to about 120 on these tires and have run 12 second quarters...straight and true. I don't think it's a design problem with the tires, although I suppose it could be a manufacturing issue with one of the rear tires (steel belt slipping or ?).

 

[BillRo]

I have the Toyos with no problems. Panhard Rod?

BillRo

 

[Duke Mk1a]

Panhard Rod?

Removed. I have Dale A leaf springs.

 

[michael-king]

Duke,

I was going to ask about the panhard rod.. thats your issue. Dales springs do nothing to assist axel location, they will help with tramp. The panhard rod locates the rear end laterally. Your rear end is actaully moving side to side.. and given your increase in HP the torque reaction from the engine now is probably making it MUCH worse.

You are likely stressing your spring hangers with the lateral movement. You need to install the panhard rod again or use a watts linkage.. you need to locate the rear end. The springs/shocks/tyres have nothing to do with the issue.

 

[Duke Mk1a]

Duke,

I was going to ask about the panhard rod.. thats your issue.

This is under cruise conditions when I am using ~30 HP. I have had the panhard off for years. I drove to Maine and back (3200 miles) and this did not happen with no panhard installed.

If I did install the rod, I would rip out the first time I launched hard. I am installing a torque arm as soon as it gets to the house. I just don't think it is the issue.

Dale told me to remove the rod and traction bars (they were both bent anyway) with his springs.

 

[TigerBlue]

Puzzle

This is a tough problem. Solid rear axle. Each rear wheel is perfectly aligned (solid!) and on the same axis as the other.

The rear axle may be steering the car but it would have to be moving. It is mounted tightly on stiff springs... that is not possible. The rear shocks likewise cannot steer the car. Even if it is moving? not likely at cruise only hard acceleration/braking.

A tire which has de-laminated in the cords or belts could? Might be aggravated by heat? Look for irregularities or bumps in sidewalls and tread.

I agree that the panard rod is useless. The only thing lost in removing it is about ten pounds.

What else did you work on when the engine was changed. The crossmember was out of the car. Is it tight?

I would like to drive it but that is not likely. Geographically unlikely. I am not in KS. (or OZ)

Be safe.

Rick

 

[michael-king]

This is under cruise conditions when I am using ~30 HP. I have had the panhard off for years. I drove to Maine and back (3200 miles) and this did not happen with no panhard installed.

If I did install the rod, I would rip out the first time I launched hard. I am installing a torque arm as soon as it gets to the house. I just don't think it is the issue.

Dale told me to remove the rod and traction bars (they were both bent anyway) with his springs.

I know the panhard rods have a habbit or removing the face of the rail, but thats why there is the brace modification. As for Dales springs.. again, they are gogn to help with axel tramp, not lateral location (i have dales tough springs too, but i have a 340hp motor and can wind them.. your video shows your 400+ doing it easily too.

I suggested in your traction post to go the torque arm route, but again, thats stooping tramp, specifically the rotation of the axel as the spings load up.. if you look at the mounting to the X frame it would allow for some lateral movement, so .. dont think thats going to help sove your problem.

Its a good suggestion re checking the front X member if you had it removed for the motor install, if thats not aligned or tight enough might give you some wandering. If you drive down the road at say 40mph or 30mph is it moving around, or is it just at higher speeds? Are there any noises creaks from the front end when going over bumps, any slack in your steering UJ's?

The only way i could see the rear steering if its not moving laterally would be something like a spring or shock on one side that was significantly weak compared to the other but that would be perceptable at all speeds and likely have the car sitting a little lop sided. Perhaps a faulty tyre with significant psi difference.. maybe check the inside tyre wall on the rear and see they dont have any buldges that might be trhwoign the balance out? Seems an odd issue... what speed does it start at?

 

[Duke Mk1a]

Great points and things to look at guys,

I am most curious about the front cross member. I thought I tightened it down but you never know.

Have a business trip then family vacation, will get a chance to look at everything in a couple of weeks.

You will be the first to hear of my results.

 

[Duke Mk1a]

UPDATE

Hello all,

Back from vacation and feel great........felt so good, the first thing I did was get the Tiger's front end off the ground to check the crossmember as it has been at the back of my mind for over a week now.

The crossmember was not loose but was not torqued to 62 ft/lbs. Each bolt took a 1/2 to 3/4 turn to reach the torque spec. So, I loosened them all, gave both tires a big kick to set the crossmember to the rear and then evenly torqued the bolts to 62 ft/lbs.

Gotta fix the front main seal leak before any more driving. More soon.

 

[0neoffive]

Logic ain't working ?

The only time I ever had "rear steer" was when something broke. My aged gut says something is moving around that should be fastened solid. Upper shackle bushing ? Front spring eye not snug & happy. Wandering brake shoe ? Methinks the thing with the shocks was happenstance, and not directly related. Like my old Huey crew chief once said (at 2500 feet!), "Ain't nothin' worse than a part time problem. Couldn't find the break, so I put it all together and we're flying with it till I can spot it". Be safe & careful, amen

 

[Duke Mk1a]

Like my old Huey crew chief once said (at 2500 feet!), "Ain't nothin' worse than a part time problem. Couldn't find the break, so I put it all together and we're flying with it till I can spot it".

Thank you sir,

I have ~300 hours flying a UH-1H and from all the helos I have flown, to include the AH-64, enjoyed that old bird the best.

Huey crew chief's are the best.


"ABOVE THE BEST"!

 

[Duke Mk1a]

FOUND THE PROBLEM

First of all, thanks to all who suggested I look at the front end for my problem.

Turns out that the passenger side upper A arm rear bushing "self locking" nut worked its way loose by a good 1/4-3/8". There were no threads of the fulcrum pin exposed. This allowed quite a bit of movement of the A arm on the pin. So I tightened it down, with loctite blue, and gave all the other nuts a go. Two others were not completely tight.

Getting ready to road test it but I am sure that was the problem.


**Road test complete. Problem is fixed and car is rock steady at speed again. I have an issue with reaching redline in 4th way too fast. I need two more gears.