After a 20 year restoration, my '69 Series 2 OTS is finally ready for a first test drive. The bonnet is not on nor does it have an interior, but mechanically it should drive. Over the years this forum has provided innumerable numbers of tips and how-to’s - thanks everyone for helping me with this project.
Unfortunately, I think I have a somewhat serious IRS alignment problem. During restoring of the body, I had to replaced both sills and the left side radius arm cup. I spent considerable time make sure that it went back in the same place as it was originally installed, but maybe I missed something. Yesterday, when I did a simple string alignment test I noted that the IRS seems to be rotated slightly clockwise (when viewed from above). The front sidewall of the drivers side rear tire does not touch the string, and the rear sidewall of the passenger side tire also does not touch the string. This implies miss-alignment by 0.34 degrees.
What to do?
Options as I see them:
Remove the radius arm cup and remount it. This is a massive job, as some of the fasteners are under the curved plate behind the seat.
Mechanically lengthen the radius arm - cut and weld a piece in the arm, or rebuild the mounting point where it attaches to the wishbone.
Since you said ‘any’ input I’ll offer my 2 cents worth, can you adjust it at all with the shims holding the four rubber IRS /frame mounts? Your other options sound terribly drastic to me.
Good luck,
Cheers,
LLynn
This is definitely a case of measure twice (actually, a lot more than twice) before you “cut” once. In my experience “simple string” tests are very prone to errors, and should be repeated multiple times with movement of the car in between, before any conclusions are reached. The compliance of the rubber bushings in the suspension, when combined with a contact point between the tyre and the floor which resists slip can cause measurements to vary a lot. The archives contain quite a few suggestions on how to limit this friction in the context of wheel alignment measurements. This may help to get repeatable measurements. When I was measuring the IRS location points on my car I did it using a plumb bob hanging from each point and marked the location on the flat level floor below. You might want to do something similar to mark and measure the locations of the center of the radius arm cones, and some fixed datum points at the front of the car to verify if you really have a mis-alignment. Once you are sure what (if anything) is misaligned, it may be easier to determine if a correction is necessary, and how to do it. Good luck!
Have someone follow you and closely observe the front vs. the rear wheels. They are looking to see if the car is “dog tracking”. You can also tell by driving over wet pavement and observing if the track of the rear tires follow the fronts or if they track to one side.
I wouldn’t worry too much at this stage. A third of one degree would be within your measurement error and I doubt of any great significance when driving.
I would get the car complete and on the road, and as suggested get your error checked professionally.
If it is still there you could probably correct it with shims, as suggested.
I don’t think that the shims will help at all. They merely help centre the cage. There’s no fore/aft adjustment allowed for to alter the tracking.
I would want to fix that right now, before any interior goes in. You can’t live with it because you’ll probably have significant oversteer cornering left. I’d get a four wheel alignment done, then decide what to do. I definitely wouldn’t mess with altering a radius arm or factory mount point.
Sorry but .3 deg is insignificant IMHO my XJ40 had <>3mm toe on the left rear and there were no handling problems, and I didn’t pussy foot around with that car.
A string box set up around the car can give quite acurate measurements providing its done correctly…you dont measure to the tyres…these are just moulded rubber that will alter with air pressure…the measurements need to be taken from the wheel rims…however dont measure untill the suspension has been settled which means getting the full weight on the ground and moveing the car backwards/ forwards. …preferably driving for a short distance…Steve
Thank very much for the excellent suggestions. My takeaway: Get the car on the road, drive it a bit, make better measurements of the potential problem and consider a fully alignment check using a modern, laser-guided test rig. I appreciate you all talking me away from the edge of doing something drastic!
To that end, I took the car for a short test drive yesterday, the fourth of July. It was really great to have the car on the road again after 22 years! This car has been in the family since new, I took it to my high school prom, it was my Dad’s pride and joy. Lot’s of nostalgia here! The first test drive went very well. Braking, clutch, ignition, carburation - all working well. It won’t idle, but that’s a carb adjustment yet to be made. Cooling fan(s) is not coming on - perhaps a relay problem. A dripping water leak from the rear of the engine - couldn’t pin point that while in the street. Will have to run again and jump to some jack stands to see where that one is coming from. But, otherwise, considering I’ve taken every nut and bolt off of this car (as you all have, I’m sure, in a proper restoration) and then reassembled, this seems a good result.
Here’s a link to the video of the first engine start two months ago. I’ll post another of the first drive in the not-too-distant future.
WHAT IF: you put the rear on stands, loosened all the cage mounts, used ratchet straps to exert tension in the correct direction. retighten the mount bolts. Then released the strap tension. There’s a lot of rubber and slotted metal back there. Maybe…if you don’t pull the car off the jack stands you could find some adjustment.
I remember taking my 69 to the alignment shop after years of work & 300 “smiles” of driving. The alignment guy called me in and grabbed the top of the rear tire and rocked it in and out a ridiculously large amount. It did feel a little “imprecise” in the corners. The output shaft flange ball bearings were self destructing. Great disappointment, but I re-geared to 3.07 in the process. The point is all the" sorting" out issues will be in the rearview mirror…soon.
Didn’t Enzo draw his race car chassis in chalk on the shop floor? Did he use the real thick chalk or thin blackboard chalk. Anyway it worked out well for him.
An interesting suggestion. I needed straps to pull the bottom of the IRS cage forward enough to engage the radius arms to the cups, so perhaps I did something there that was not quite right. More investigation needed, for certain.
Took the car for a first drive around the block on Saturday. The car drove beautifully, didn’t notice ANY issues with the IRS, but 1/2 mile is too short a distance and not enough straight line to really determine anything. Found a water leak, fixed that and figured out why my electric fans weren’t working properly. Now, my clutch won’t disengage…this has me a bit concerned. But hoping it’s something simple as I can see the clutch fork moving as well as the pressure plate inside the bell housing…
