Our township grader, a John Deere 670CH with 7400 hours on it has a problem (not new) that is causing us problems. When making a final pass on the roadbed, using a blade with carbide bits on the cutting edge, (just trying to "rake" the windrow in the middle of the road to put the aggregate back onto the driving lanes, very light blade loads) using 5th gear, running around 9 MPH, I get a serious wheel hop out of the rear tandems on both sides of the machine, so severe that you almost have to come to a complete stop to eliminate the hopping. This is not "wheel bounce", but "hopping up and down". We have had the blade tightened up to eliminate any "slop", it seemed to help some. Have adjusted air pressure, running from soft tires, to hard tires, different pressures in diagonal tandems, but nothing seems to solve the problem. Have been wondering if putting heavy shocks on the tandems would solve it, or maybe air shocks with an electric compressor so you could adjust the pressure on the bladders? Looking at other threads, I see that we are not the only ones with a problem like this... Help !!!
Check your toe in on your front axle. I had a 12G I cut two inch's out of the cross bar to get it to stop that dreaded hop... its almost like a 4 wheel drive pickup when you lock it in and turn on asphalt. It binds and then release's,. Im not saying that's your problem, but it'd be worth looking into.
did you try unlocking front front drive?
This machine doesn't have front wheel drive. I have tried unlocking rear axles and that don't help either.
Are the tires the same size and worn the same or are they different?
Tires are all the same size, tandems are equal in wear and front ones basically new. 1400X24 bias tires.
Toe in on front tires is pretty good, caster/camber not so much, when you get one tire vertical the other is tilted outboard... Would this create the problem with the rears hopping up and down ?
Something as simple as a bad tire ?
I'd say you're trying to go to fast. With an empty board I slow to 5 or 6 mph.
I'm betting you have nothing wrong with your machine it's just your trying to go way to fast with a bias type tire we had bias ply on one of our old machines and you could only blade 4 to 5 if lucky we switched to all radial tires now and we can go much faster with them I genrely pull windrow on to the middle of the road in 4th gear about 5mph and blade off in 5th gear at 6mph and that's running a 2004 deer 772ch.I never go any faster figure I get paid by the hour why hurry.
Bias ply tires don't like speed. Fine grade work doesn't like speed. Either for that matter. As the others said, try slowing down to 5mph or less. Switching to radials should also increase tire life from what I've seen.
I agree, 4-5 mph when spreading if your machine will let you, your machine is telling you to slow down.
What is the ideal toe in angle of the front tires on a grader that doesn't have front wheel drive??
About 1/4" of toe-in is about right. Here's the procedure. Install the lockpin in the tie bar of wheel lean. Make a mark in the exact center of the tread on each tire at the 3 o'clock & 9 o'clock positions on each tire as viewed from the side. Center the steering and lift the front wheels off the ground. Measure the distance from the mark on one tire to the mark on the other tire at both the front and at the rear of the tires. Toe-in is correct when measurement at the front tires is 1/8" - 1/4" less than the measurement at the rear of the tires. Once you have the toe-in adjusted correctly the ball joints that screw on to the ends of the steering cylinder rods may require adjusting so that the steering cylinders are the same extended length on both sides.
I've run into this problem with the A,B,C and D series Deere graders the only solution I've found is to slow down 4th gear half throttle is about all the faster we can go without the machine hopping.