Morgan +8 Forum

Duncan. Great explanation. I am still constantly learning about these cars. Based on your explanation It seems that trail braking would help to move the tire into a better grip situation on top of adding more weight for better cornering. Does that make sense?

I am thinking about adjusting the camber this winter. I know Morgan Spares sells blank plates that you can drill to get the camber you desire. Without a $300+ camber set up tool that might be kind of tricky. Does someone sell predrilled plates that will get me into the neutral camber area?

---

'73 4/4 "Henry A"
'53 +4 Flat Rad "Pug"
'84 Citroen 2CV6 Special "Bebe"

https://morgan34.org/

Hi Paul,

I think your car should steer with throttle alone, as does our Plus 8. Getting the front/rear pressure balance right will help with that. Trail braking does the same thing as (to a greater degree than) lifting throttle when entering a corner, transferring weight to the front, thereby increasing grip there, so that should help rotate the car.

Does your car have brake reaction stays? If not, you can make up a pair by using some 3/4" EMT (a.k.a. metal conduit tubing). Figure out where you'll mount the rearmost end to the chassis (there was a bolt in the right place on my car). Flatten that end and bend it to the right angle before drilling. Flatten the forward (upper) end and drill a hole to take the one-shot oiler fitting receiver bolt. That will stiffen up the upper tube and keep it from flexing forward under braking.

If the kingpins are at matching angles, you could just do the trig calculation (hmm... don't ask me how to do it -- it's been too long since I calculated sines and cosines but "b adjacent" is what you want to calculate, changing the yellow angle on the left) or just lay it out on a piece of paper, using a protractor to figure out how much to move the bottom of the kingpin outboard to achieve the camber angle you want. Use a stock kingpin bottom plate to mark the outer bolt holes on the new plate, and mark the old kingpin hole centerline. Move the new kingpin centering mark outboard by 90˚ and drill there. By memory (not a reliable source, these days) it takes about a 3/4" move outboard to attain zero degrees camber.

Duncan

That brings up another question. Tire pressure. For the autocross. We usually kick around numbers like 32 or 24 psi so that the tires don't try to leave the wire wheels. But it seems to me that would be more important in the front than the rear due to increased forces when turning the wheel into a corner. It seems that I can get the car to rotate, but if I adjust the camber the front should stick more, in theory making the car more prone to oversteer. I guess.

I do have brake reaction bars, AVO's up front, and the Rutherford kit in the rear.

---

'73 4/4 "Henry A"
'53 +4 Flat Rad "Pug"
'84 Citroen 2CV6 Special "Bebe"

https://morgan34.org/

Tim,
You might get a tiny bit of caster change by moving the hole forward slightly but the bottom if the kingpin is restrained fore and aft to some degree by the existing lower mount, even if you cut the projecting "ring" to allow outboard movement of the bottom of the kingpin. I think you'd need 3/16" to get just one degree and I doubt there is enough room for that. However, theoretically one could remove material from the forward side of the kingpin, near the base, to allow it to shift forward. I think I would rather take my chances with bending the upper tube rearward and then cinching it down with a new brake reaction stay. If and when I get the 4/4 racer back together I'll change the mounting holes for the cross tube assembly to make sure I get at least 4 degrees of caster. Peter Egan's description of this car (driving it at Hallett Motor Racing Circuit) was that the steering would "dolly" the car around until you got on the power.

Whether that meant it didn't have sufficient caster, I'm not positive, since I didn't measure that before I disassembled the chassis. The modified TR3 rear axle currently has a Detroit Locker limited slip and I imagine that would try to keep the car going straight under power and transition to a bit of oversteer once turning under power. I think I'm going to put in a stock axle and worry about adding a clutch-type LSD later (the '52 Plus 4 racer had that setup ia modified Studebaker axles built by Fred Sisson) if it has traction problems, although a guy in the Northwest Pacific said his Detroit Locker cut a full second off his lap times at a particular track in that part of the country.

Duncan



Edited 1 time(s). Last edit at 2023-10-09 05:59 PM by DuncanCharlton.

Paul,

If you change the camber I think you'll just have to experiment with tire pressures. Some racers use a thermal probe to check tire temperatures across the tread. I use an infrared non-contact thermometer to check inside, center and outside of each tire tread but that has to be done very quickly once off the track because the tire cools quickly -- and an autocross may not put enough heat into the tire to really tell you much. Others will put chalk marks that run from the tread onto the shoulder. Then look where the chalk rubs off. You'll see of the shoulder is doing no work or if the tire is rolling over onto the sidewall. That will at least tell you about the load bearing ability of the tires during cornering. I would use that mainly to tell me what the front tire is doing and then use whatever pressure in the rear allows the car to behave the way you want to. When you determine pressure for the front tire, make note of whether the figure was obtained when the tires were cold or hot and whether it is hot weather or cold, so the pressures are repeatable. The pressure might vary 4 to 6 psi from cold to hot. I have no idea how hot your tires will be at the start of each session, but I imagine they cool off completely between each session. Again, I think it's the front/rear pressure differential that matters the most.

By the way, I know of some racers who decrease their tire pressure when running in the rain, reasoning that it adds more traction. That doesn't quite add up for me, since in the rain the tire will never reach the temperature, and therefore working pressure, that it would on a dry track. It makes more sense to me to raise the pressure for rainy conditions so that the wet-track colder working pressure is similar to the hotter working pressure that would normally be caused by driving on a dry track.

Duncan

It appears that bump steer is a built in feature of the sliding pillar setup. Bump steer was actually a feature of most suspensions prior to the '50s, when it became fashionable to try to reduce it as tires became wider, which finally filtered down to road cars. Porsches had lots of bump steer, all the way into the 80s. 'Part of the charm, I guess.
Bump steer is a common problem today with lowering spring kits on modern cars, and is seldom corrected.

The Morgan front end is full of compromises. Bump steer, limited travel, camber problems, and friction. Did I mention frame flex? Play in the old style worm and peg steering box? Changing the camber may introduce some bump steer, but will I notice it with all the rest of the noise? Will it make any sort of difference? My guess is it will be more of the same, but with more front end grip, and better tire wear in normal driving. All my cars are set to negative camber, and all of them get even tire wear across the tread. Heavy steering? What else is new? Duncan has the physics down, but there is little to do with that suspension. Too many problems, all at once. So, we do what all racers do. Lower the car, stiffen the springs, put a bunch of negative camber in it and add as much power as is possible. Your Morgan can corner harder, even with the compromised suspension, because it is lighter, and accelerates quicker because it is lighter and has more power. Geometry? We don't need no stinking geometry!

On my Morgan, the rebound springs are completely crushed when the car is lifed. They are not stiff at all. Some here have recommended some soft, cheap springs from Suplex. Maybe when I get around to rebuilding the front suspension.

The camber plates with the slots should not slip. Use some good serrated washers, some safety wire on the fasteners, maybe make a stop for the slots if you think that you need it. I am going to set mine up, and put a stop in the slot to make sure, but my other cars had similar slotted plates and never slipped.

Alignment Tools:
You can get the smart camber tool frame, and add you own level (you can find the one in the correct size for around $17, or you can pay the full price (do some shopping, Pegasus is not the least expensive). However, if you pay $200, that is the cost of two or three alignments at a reputable shop on a 4 wheel rack. Once you go to an adjustable camber plate, you will be taking temperatures with a contact pyrometer (around $100), and you will want to make changes to get the adjustment just right.

Getting blank plates and drilling them is difficult, as you will have to do the setup with the car weighted, have the alignment shop set everything up and drill the plates, with may not actually give the precise setting. Adjustable is the way to go, but you may have to do more than one adjustment. You can get pre drilled plates, which may be accurate. Depends on how accurate your frame and cross head is. Slotted plates allow for correction.

Greetings...Duncan, I think you are right about a limited possibility in making a caster change this way. I was just thinking-often a dangerous pastime. Bending the top tube would be the best way. Someone - Mulfab maybe - makes an adjustable brake reaction bar. I wouldn't try this on my 66 +4 as sometime in its past it took pretty good hit to the right front. The top tube was repaired by welding somewhat inelegantly a new foot of tubing. I don't know how long its been that way but it hasn't been a problem.

Jan, have you ever measured camber on an unmodified car? I'll bet it varies side to side.

Tim

I made up camber plates years ago by measuring with a string and level and I forget what else, my goal was 0 degrees and I probably got close to that.

Boyohboy -- Jan brought up the rebound springs. There has been lots of discussion on those. For a while I was a non-believer even though Hooke's law explains what's going on, which is that the spring rate of the rebound spring is added to that of the mainspring as long as both springs experience compression at the same time -- and it doesn't matter that they seem to be opposing each other (and Bob Nogueira rigged up a scale and two springs in series to test the idea himself). In other words, at static height, if the rebound spring can't be turned by hand, the suspension will feel stiffer, creating roll resistance, which creates relatively level cornering but also causes low-speed understeer and makes the springing feel much stiffer, particularly over small road bumps. Corner harder and faster, and the outside sliding axle assembly lifts off the rebound spring, dropping the spring rate to that of only the mainspring (which is lower than that of the rebound spring) while the inside axle compresses the rebound spring further, resulting in a different spring rate on each side. This limits body lean and cornering feels more neutral at speed. It acts a bit like an anti-roll bar for each side, neither connected at the opposite wheel.

John S. Sheally II insisted he always removed 1-1/2 coils from the rebound springs. Some made the rebound spring short enough to allow it to be turned by hand when the car is at its static ride height. The Suplex ones might be an attempt to remove or minimize this step in the overall spring rates. Bill Button drove around with his rebound springs removed for a while. I don't recall what he learned from that (but do recall that he reinstalled the rebound springs) but surely there was lots of crashing and banging going on whenever the axle assembly bottomed out, and static ride height at the front would have risen. Someone reported that the works had tried using rubber snubbers in place of rebound springs many decades ago.

The system with softer rebound springs (didn't that also involve progressive rate mainsprings?) was tried. That would have minimized this stepped change in spring rate but some didn't like the way the cars drove. I never drove a Morgan so equipped, but imagine that while some appreciated the softer suspension feel over small bumps, that others found the increased body roll undesirable.

I measured the camber on my car, at precisely 2º left and right.. Caster was 4.5. No variation. The car is amazingly straight. Repeated measurements are always within .1º on my garage floor using my Smart Camber tool. Toe settings are done using the toe plates. I have not made any changes to the chassis setup since I brought the car home.

So much discussion about the rebound springs! I remember that there was a You Tube video of the front suspension under load, on a road. the most noticeable thing about the video was how the uprights were not in contact with the rebound springs at all, except for brief moments of suspension rebound. Basically, all spring rate theory aside, are there just as rebound buffers, quieting any metal to metal contact between the upright and the king pin base. On my own car, they are not engaged when the car is at rest. What this gets down to, on my car, is "how many Morgans an you park on the head of a pin" sort of discussion. The suggestion of using the looser fitting Suplex springs is certainly valid if one needs new rebound springs, based on price and perhaps the loose fit.

The bump steer question is something that I will have to deal with later, once the camber is adjusted. I don't intend to change the ride height (a whole different can of premium sized worms), so I am figuring that the bump steer may not be a huge problem.

Bump steer. Could the future be steer by wire, to eliminate all the linkage?

---

'73 4/4 "Henry A"
'53 +4 Flat Rad "Pug"
'84 Citroen 2CV6 Special "Bebe"

https://morgan34.org/

Jan, I imagine my rebound springs weren't touching the hubs when I bought my Plus 8 with 189,000 miles on it. I installed new springs, the free length of which was now significantly longer than the old springs, so I think that either your springs have sagged a bit or someone already modified the rebound springs.

I'm not convinced the Morgan factory hadn't lost the thread on how the front suspension works by the time my car was manufactured.

Duncan

Ps: steering and suspension by wire could conceivably eliminate all the drawbacks of current mechanical designs. You first!

Oh, it'll come. One day. Not on my '73 though.

---

'73 4/4 "Henry A"
'53 +4 Flat Rad "Pug"
'84 Citroen 2CV6 Special "Bebe"

https://morgan34.org/

My car has about 80K on it, so sure, the rebound springs have probably been hammered a bit shorter, along with the main springs above. I have plans for the dampers up front (the rears are already selected), but nothing other than the bearings to reduce steering friction. I have not thought much about the damper blades, either. I might eliminate them and fit the steering damper on the linkage. I have been told by a few owners that the damper blades are not really necessary. In any case, they will have to be modified once the camber change is done. I have a feeling that Morgan had it right the first time, and I may keep them, or mount the hydraulic damper or... never mind... Let's do this later...

Steering by wire? If it were to eliminate the linkage between the steering box (actuator?) and the hubs, maybe. Otherwise, the latest steer by wire just eliminates the steering column, and conventional type linkages still exist between the actuator (steering box?) and the hubs. I can see where putting the steering actuators at the hub, but this might have an effect on unsprung weight. Interesting as to how this might go in real life. I suspect the first application would be on an autonomous vehicle, where such things as steering feel and feedback along with unsprung weight might not be a concern.

Bump steer is as big a problem as one might want to make it. Some cars have handled the problem well, while others cam with it from the factory, and nobody seems to mind much, other than racers. The Morgan has so many things that are out of date, and the car's feel so raw that a little bump steer is pretty much lost in the noise from frame flex, steering friction, suspension friction, king pin angle... But that's what I bought the car for. All that delightful noise (except for the steering friction, as it filters out the delightful noise). What does it have going for it? Limited suspension travel (the less bump, the less steer), light weight and lots of power 'Works for me.

I have driven some "steer by wire" cars, most notably a BMW that could (sort of) correct itself out of a slide or spin. Very strange feeling when we tested them at Albecete race track in Spain. Full steer by wire and hydraulic steering have been around for a while, but the systems are rather conventional other than the installation of the electronics to control the steering box. Steer by wire is even easier with electronic power steering, as the actuator problem is already solved.
I mentioned earlier of how the system might eliminate bump steer using separate actuators at each hub (Hmmm. 4 wheel steer by wire, of course!), but in reality, Bump Steer is really not much of a problem on a modern car with a properly set up suspension. I have successfully corrected bump steer on my street race car with a couple of bushings, and other systems offer up spacers to relocate any pivot points that are problematic.

Bump steer is often brought up as a big problem, but it really isn't on modern cars. Most people, even enthusiasts are not aware of the problem, or have even heard of it with any understanding of what is going on. Sure, our cars with the early 20s suspension might have the problem, but you know... The '69 +8 is what it is...

I say "NOT MY PROBLEM".