reb78 Posted March 1, 2012 Share Posted March 1, 2012 Right. As a result of some twitchy steering that i talked about here http://forums.lr4x4.com/index.php?showtopic=74788, I changed the bushes on the passenger side trailing arm today as the rear one had a lot of play (in fact, the inner metal sleeve just dropped out when i removed the arm ). It was a bitch to get the old bush outer sleeve out and i was running out of time, so i removed the other arm, but the bushes were good, so they havent been replaced yet. The probem for today is that when i ran string around the wheels to double check the tracking , it doesnt touch the front side of the rear wheel on the passenger side (its about 2-3 mm off of the tyre) - it suggests to me that the axle is slightly too far forward on this side? Is this possible? (it was like it before i changed the bush and i put it down to the bush allowing the axle to sit a bit further forward - its marginally better now though. On the drivers side, the string touches the side of the rear tyre on the front and back, as it runs forward round the front tyre. I suppose another explanation that could cause this could be if the front axle or wheel on the passenger side is a couple of mm more lateral than the rear wheel/axle? Could/should i adjust the rear arm at all? Can i put a spacer washer at the front of the trailing arm, behind the bush to push it back? Or, can you get triangular spacers that go between the metal in the centre of the bush and the chassis? (i presume the front bushes are symetrical and can be fitted with either side facing forwards?) Quote Link to comment Share on other sites More sharing options...
bluespanner Posted March 1, 2012 Share Posted March 1, 2012 I'd be happy that the distance is only 3mm :-) Quote Link to comment Share on other sites More sharing options...
mmgemini Posted March 1, 2012 Share Posted March 1, 2012 The only way to check this correctly is to do a "drop check" Don't even think about packing, VOSA would take a great interest if you were involved in a serious accident. Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted March 1, 2012 Share Posted March 1, 2012 Is your truck lifted..?????? if it is, i would suggest that the issue is the fact that the lift has effectively vis the panhard rod pulled the front axle off centre, hence the 3mm gap at the front of the rear wheel....! This has lead to the two axles not being in line as it were...... Quote Link to comment Share on other sites More sharing options...
reb78 Posted March 1, 2012 Author Share Posted March 1, 2012 No. No lift, all standard. It's puzzling, but it must have been like it a long time. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted March 1, 2012 Share Posted March 1, 2012 The probem for today is that when i ran string around the wheels to double check the tracking , it doesnt touch the front side of the rear wheel on the passenger side (its about 2-3 mm off of the tyre) - it suggests to me that the axle is slightly too far forward on this side? Tyres can be pretty oddly shaped things, I would not trust one for taking important measurements from. Chris Quote Link to comment Share on other sites More sharing options...
Giles Posted March 2, 2012 Share Posted March 2, 2012 Tyres can be pretty oddly shaped things, I would not trust one for taking important measurements from. Absolutely. As I live surrounded by piles of carp (spares dear, spares), I keep a matched set of rims w/o tyres for the very purpose. 3mm out don't sound too bad really; but perhaps you should replace the other bush too as it might have compressed a bit over time?? giles Quote Link to comment Share on other sites More sharing options...
GBMUD Posted March 2, 2012 Share Posted March 2, 2012 Even rims can have a lot of run-out and remain in tolerance. I recently had the tracking set on SWMBO's Freelander. The 4-wheel tracking kit mounts such that it contacts each rim in three places and the tracking details are then readout on a computer screen - in degrees and minutes. Now, 2 wheel tracking used to be done in just degrees, and I think a degree is a reasonable amount to try to measure in such a way, but trying to set tracking to the minute seems daft when the allowable run-out on a wheel rim must make the results so variable. Daft? Chris Quote Link to comment Share on other sites More sharing options...
mmgemini Posted March 2, 2012 Share Posted March 2, 2012 Chris Yes. I prefer to check tracking on the tyres at their widest point using trammels.Although I too wouldn't bother about 3mm.The other thing about tracking is not to bounce the car on the final run to the tracking station. Reb. Have you thought of measuring the wheelbase. How accurate is that ? Quote Link to comment Share on other sites More sharing options...
reb78 Posted March 2, 2012 Author Share Posted March 2, 2012 Thanks all. I wonder if a hunter type alignment might show up any problems. it should take away the potential tyre error anyway. I could measure the wheel base, but I wonder how accurate the tolerances were for that! Part of the reason that i didn't change the other bush was that it would have to compress in order or pull that side of the axle forwards, to correct the error on the other side, so I figured the new bush wouldn't change that. Are the front trailing arm bushes sided at all? If one was longer one side compared to the back and the pair are fitted the opposite way on one side, that might explain 3mm (I'm away from home so can't measure them now). Mike - what's a drop test? Quote Link to comment Share on other sites More sharing options...
mmgemini Posted March 2, 2012 Share Posted March 2, 2012 I doubt if the wheel base will be equal each side. Try a tape measure....Or make a trammell from a length of wood. Drop test. I'd rather explain to your face but here goes. Flat floor. Plumb bob and chalk. Now walk round the car and drop the plumb bob from the outside of the front dumb iron. Then the axle center. Then the rear axle center.Outside rear crossmember Out side rear of chassis. Take as many points as possible with the plumb bob and mark the floor with a cross. Push car out of the way. Now join every cross to every cross. You should have a nice pattern on the floor. Now take a chalk line down the center where the lines cross. Everything should be withing 2mm. Drop test, you drop the measurements using the plumb bob. The point is, did you understand. If not try and catch me at a show. Quote Link to comment Share on other sites More sharing options...
pat_pending Posted March 3, 2012 Share Posted March 3, 2012 Even rims can have a lot of run-out and remain in tolerance. I recently had the tracking set on SWMBO's Freelander. The 4-wheel tracking kit mounts such that it contacts each rim in three places and the tracking details are then readout on a computer screen - in degrees and minutes. Now, 2 wheel tracking used to be done in just degrees, and I think a degree is a reasonable amount to try to measure in such a way, but trying to set tracking to the minute seems daft when the allowable run-out on a wheel rim must make the results so variable. Daft? Chris 4 Wheel alignment systems allow for run out during the set up stage (or they should if the operater knows what they're doing). reb 78, So the alignment has been checked with a bit of string, and you're worrying about 3mm ? Does the string have a valid calibration certificate? 3mm is nothing on a Land Rover. Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted March 3, 2012 Share Posted March 3, 2012 Rich, I wouldn't even think about it as a problem until you have changed the bushes on the other trailing arm and even then it's less than an 1/8 of an inch. If you measured the brackets on the chassis from a datum you'd probably find more varience Mo Quote Link to comment Share on other sites More sharing options...
reb78 Posted March 5, 2012 Author Share Posted March 5, 2012 Thanks for the tips chaps. I'll change the other bushes as you suggest Mo and then see what it looks like (might take the arm on that side to my local garage though and get them to press out the old bush and put in the new one though!) I understand what you mean Mike - basically a set of measurements from each side using a plumb line hoping that the result is symmetrical. As for setting the tracking with string, i bet it's more accurate than some of the garages I've used in the past with all of their certified laser equipment! I've seen some people make a right mess of the alignment when using the correct equipment. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted March 5, 2012 Share Posted March 5, 2012 Reb. I bet the string is too. I have a set of small trammel bars. Like a long shallow U that adjusts. Simpl;e and easy. Another way is a telescopic car aerial Quote Link to comment Share on other sites More sharing options...
reb78 Posted March 6, 2012 Author Share Posted March 6, 2012 Reb. I bet the string is too. I have a set of small trammel bars. Like a long shallow U that adjusts. Simpl;e and easy. Another way is a telescopic car aerial I like the idea of the aerial. I was trying to adapt an old track rod to do the job - with the threaded part of the old TRE (ball joint cut off) forming the adjustable section that could be screwed up to the wheel rim. Trouble is, its too thick and the radius arms are in the way, so i think fabricating a sort of 'U' out of it like your bars is the way forward. Am i correct in thinking that the measurement between the rims needs to be taken at the level of the axle (i.e. half way down the rim) and that taking it at other points on the wheel would not be correct? Quote Link to comment Share on other sites More sharing options...
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