MG Sports Cars

Hi Jim,

Good to se you making such impressive progress, I been looking in on a regular basis and am in awe of your engineering abilities.

Re; the coil spring damper units, don't know if the figure mentioned was for 2 or 4 units but 2 should be fine and possibly Bill Guzman could advise what spring and damper rates he is using on his four link rear end which should be pretty close apart from more unsprung weight.

My new 4.35 engine is now built and apart from some fine tuning on the the valve gear geometry, is ready to go into the car which should happen fairly soon.

Good luck on your continuing progress with the Roadmaster.

Kevin Jackson.

I've been following this for a while as I'm in the process of putting a narrowed Jag rear in my B. I had the axles, lca and the cage narrowed. I recently bought a rusty rear B clip so I could fit everything together with the clip turned upside down as your doing. As your about to shorten the axles I have to pass on this little bit of information. I used tubing that had a 1.125 ID. The wall is about 1/4 in. During the welding process of having the ends welded on, the turned down yokes turned in the tubing. This caused the yolkes to be out of phase. I had some shafts made before the welding, that slipped through the yokes and set the whole thing on a thick piece of steel channel. You could see the yoke start to rotate as it was being welded, even if it was tacked in different spots. A solution was to drill a hole through the tubing into the yoke stub and then plug weld the hole. The axles were then secured using the made up shafts through the yokes. This should minimize the shifting. This may not happen to you. This is just to make you aware of a problem that may arise. I discovered that when I put these shafts through the u-joint holes on an unmodified axle, the factory axle ends were slightly out of phase. This might have been about 7 degrees. I checked 5 different axles and they all had a twist in them. They were also checked on a level, flat steel plate with known shims to check if my finding was accurate. I got the same results the second method and that the factory axles were out of phase a little. This could be caused by the torque of the Jag engine and the weight of the car. Hope this info helps and keep up the good work. Willy in Winnipeg.

Jim,
We have $450 and change in the account.
Jim Thompson from Mauldin,SC donated the Jag hub that is needed. I plan to bring it with me. It will need new bearings.

Steve

Good to hear from you Kevin, thanks for the kind sentiments and I'm really interested in seeing how your upgrade turns out. That price was for 2 units, but we'll have to do some figuring to get the right springs. I'm sure Bill's input would be helpful. I'll try to call him as soon as I get a chance.

Willy, what a timely post! It's pretty normal for welding to cause some distortion but that twisting you reported is certainly something I wouldn't have expected. I definitely appreciate the heads-up. The stock shafts being twisted is a bit of a surprise as well. But I just wonder if it might have been caused by hard braking rather than engine torque? Really hard to say. But if we find it to be a problem I suppose we can go to larger diameter tubular half shafts later on.

Citron Wrote:
-------------------------------------------------------
> Jim,
> We have $450 and change in the account.
> Jim Thompson from Mauldin,SC donated the Jag hub
> that is needed. I plan to bring it with me. It
> will need new bearings.
>
> Steve

Another timely post! Steve, is there any chance you could also get the washer that the inner seal rides on?

We're missing one of these and the hub can't go together without it. We have new bearings and seals courtesy of Dan M. We also need four rotor shims but that's not so critical. Your timing couldn't have been better. After test assembly with the arms and such of the IRS for my roadster I realized that I couldn't get an accurate width measurement because the vette wheels won't fit the jag wheel center pilot. So I cut down the pilots on the two hubs we have and began the upright assembly by pressing the races into place.

I got to the point of pressing the bearings on and quit because I didn't feel like packing them. A very lucky thing as it turns out.

I have another question, maybe Willy or someone else can answer it. The hubs for my roadster appear to have a dust shield behind the hub flange:

which the ones for the Roadmaster do not have:

This seems to be a part that is commonly left off, though it does appear in the parts diagrams. Anyone know what the story is with those?

I have more photos for you also.

Jim

As mentioned I did a test assembly to get width measurements. As mentioned the arms aren't parallel, though at first glance it might seem like they are, especially at full droop:

or at normal ride height:

But at full compression the picture is obviously much different:

Note what happens with the camber changes. Under compression the contact patch moves outward as the wheel angles in at the top, and when unloaded the opposite occurs though the effect is not so pronounced. But if you can visualize the car leaning and both tires still in contact with the ground, it would appear that the outside wheel is still relatively square with the pavement with the outside edge loaded more heavily than the inside. The inside wheel on the other hand is angled in relative to the pavement, tending to lift the outer edge of the tire off the ground first. None of this seems particularly troublesome, but it's graphically obvious that we do have camber changes with body lean due to the unequal lengths and offset pivot points of the arms. You would intuitively think that shortening the arms would exaggerate those camber changes, but at this point I can't say exactly what happens, since I've not made a study of unequal length suspensions. The easy choice would be to shorten each one by the same amount. Anyone care to step in here and help us out with an informed explanation? I'm all ears.

Jim

Finally, I have the shots I know you all really want to see.

This first shot, featuring all sorts of stuff stuck to the gas tank, shows the full width axle with the vette wheels and tires, and how far they stick out on both sides. Well, actually they would stick out maybe 3/8" less per side because of the hub pilot mismatch, but it gives a pretty good idea.

Here we have the left side

and the right. You've noticed I'm sure that the tire sticks out further on the left, this was a direct result of centering the pinion in the transmission tunnel and means that the left side will need to be shortened more than the right. How much? Roughly 3" on the right and 4" on the left, though those numbers will be much more accurate once we have the uprights with the machined hubs fitted. I'll try to get one pressed up tomorrow and fitted. Stay tuned!

Jim

Jim, check out Art Morrison.com catalog on page 42. Coil over poly bushed street shocks $210 a pair with springs. They also have a 160# - 250# variable spring available. They use Gabriel adjustable shocks inside.I tried to scan a picture but could'nt.



Edited 1 time(s). Last edit at 06/11/2008 01:06AM by mgb260.

[www.uk-hotrods.co.uk]

I'm sending this attachment in regards to your concerns about the control arm and the axles not being parallel. The UK hotrodders have shortened many Jag rear ends and it seems what your encountering is not unusual and not really a worry.

Jim, those look like a good deal, provided we can use that style top mount. I'll call them later today and ask about them. Thanks a lot.

Willy, thanks for the link. I saw some good discussion of the radius and torque arms but wasn't able to find anything about the LCA's or half shaft shortening. Is it there and I just didn't look in the right place? Also on the radius arms I was sort of waiting on Rob to send me a pair of MGB spring eye bushings (but he's had trouble removing them from the springs) before making up the radius arms. The plan is to run a cross bar between the front spring hangers and locate the forward end in the center of that bar intersecting the inner pivots. By using longer rod for the pivots enclosed in a tube for the extension, this addition can be welded solid to the LCA and act as both the radius rod and the torque bar. But that may have to wait until after the meet. What I really want to concentrate on right now is the narrowing of the track.

Jim

But, but, wider is better! Leave the track, widen the body!!!! ;-)

Looks good Jim. Good to have Willy's input on the rear end, experience is always appreciated. Remind me again why we're using a big block Buick instead of something more exotic? I see you have the Florence anti gravity machine working again, so some power source using dilithium crystals should be easy! ;-)
I think we need to leave the body width alone, I don't think I can find any flares wide enough to cover those meats unless the rear axle is narrowed, we were just lucky with the Omni flares showing up at the right time, don't press our luck.
Looks like I'll be able to make the trip to Port Washington after all, so seats will be delivered for the car there. Anything else I can bring up from KC?

Jim,
I was in Mauldin yesterday. I can not get the seal washer.
Had scare here over the weekend. I was loading the wheels and tires in the trailer and something in my right arm popped. Lots of pain, many phrases used that I learned in the Navy. Sore all weekend. DR. says I have a ruptured bisept tendon. They don't usually fix that sort of thing. Just leave it alone. Arm now feels fine. I may not be able to leap tall building anymore.

Steve

"I think we need to leave the body width alone, I don't think I can find any flares wide enough to cover those meats unless the rear axle is narrowed"

I wasn't talking about bigger flares. Split the whole thing right down the middle. Hand me a chop saw! ;-D

It's OK about the washer Steve, it turns out it can go in later by unbolting and removing the spline. I can maybe find something for a temporary spacer. It'll be late tonight before I can look at it. Sorry to hear about your arm. Won't that make driving painful? I wouldn't expect you to make the trip in your somewhat weakened condition.

I'd respond to Carl but that might only encourage him. Bill, I'm sure glad you can come, and not just because of the seats either!

Jim

Jim,
Arm does not hurt, but is not strong yet. I will be albe to drive with no problems. I will leave in the morning, not sure what time.
Should reach you by late afternoon or early evening.
Can't wait to see the progress. Really want to see it on it's wheels.

Steve

Steve, we'll do it if we can.

I put the one good hub assembly together and installed it on the car with the vette wheel and 315/35-17 tire. Now bear in mind that we're planning to use 275/35-17 tires on the car, so that means we have an extra 40mm to play with, or about 3/4" per side, inside and outside. With that in mind I've taken measurements on the long side (right, or passenger-US spec) at various points in the suspension travel. Droop is limited by LCA interference with the brake rotor and beyond a certain point has no bearing on track width, but at a point somewhere in the neighborhood of 3" below nominal ride height it does limit track by interference with the inner shock mount bolt head and with the frame section lower seam. This seam can be folded inward somewhat but clearance to both it and the bolt head with these tires is almost exactly 2", measured on an axis roughly parallel with the half shaft.





The other limiting factor is in compression, at the point where the tire would contact the inner fenderwell. Because we have not yet cut the fenders for clearance we cannot take a direct measurement of this so it must be measured indirectly with the tire removed. Luckily I can do this. You will recall there was a single vette front wheel that came with the two rears which was not used. This wheel is the same diameter but is 1" narrower and has 1/2" less backspacing. Taking the 5/8" that the tire protrudes beyond the rim, adding that 1/2", plus our 2'' dimension for narrowing gives us 3-1/8" for our dimension from the rim to the inner fender at full compression.

Maximum compression is limited by u-joint interference with the LCA which occurs just beyond 6-1/2" of compression from our nominal point where the tire is resting on the existing fender lip. However, at this point even including our 3/4" of extra clearance we are into the inner fender some 1/2". At 5" of compression though the picture is much rosier and we have exactly 3-1/8" which is our target dimension.

This tells me that we can compress the suspension 5" and allow considerable droop as well, for a potential total suspension travel of around 10-12 inches! Too bad we can't hope to match that on the front. It also tells me that a 2" narrowing of that side of the car is appropriate. The other side should come in about 1-1/4" more for a total of about 3-1/4". Not bad, and mostly made possible by the deeply offset wheels.

More photos coming.

Jim



Edited 1 time(s). Last edit at 06/12/2008 01:44AM by BlownMGB-V8.

Here is a side view of our compressed distance of 5". Looks to me like that should be adequate upward travel, I have yet to see if the differential clears the ground at that point, but it looks as if it would.

Here is our nominal ride height.

And here is maximum droop.


Now I know what you're thinking, this isn't an off road machine. And you are right of course. We will plan to set the ride height 1-2" lower than nominal which will cut our jounce to 3-4 inches, a very workable range, and then allow another 3-4 inches of droop for a total travel of 6-8 inches, very very respectable in a car of this type.

Jim

The other side checks out. In fact the 3-1/4" dimension is right on the money. Now the question must be asked, do we wish to "cheat" by stealing some of the 20mm clearance we will have on the inside with 275 tires? The question is a very valid one because at nominal ride the tire sticks out past the fender about 2-1/2 inches. Even subtracting the 20mm there (3/4") that's 1-3/4" that we're asking the Omni flares to cover, plus they don't do a whole lot for us as we move on up into the well. So things could get real tight on the outside.

The counter arguments would be that first off, what if we go to a 285 tire due to availability problems? Now we just have 15mm. Plus, how much is the tire going to deflect under hard cornering? 5mm? 10mm? 15mm? 20 even? (Personally I doubt that last one but I certainly do not know.) Some of you guys with tight tire clearance should weigh in here, especially if you run a panhard. Tell us if you've had tires rub and at what clearance distance. If we have to go 20, we'll go 20. But it may impact our tire choices.

Jim

Oh, and I did get to thinking about what Carl said. You know, that would give us a little more room in the driveshaft tunnel so that we could keep both sides the same length... and we could have enough room in the engine compartment for conventional headers... and wider seats... But Nah!! Just the windshield alone would be problem enough to say faggidaboutit. But maybe someday...

J



Edited 1 time(s). Last edit at 06/12/2008 01:38AM by BlownMGB-V8.

One more thing before I call it a night. Is it just me, or do you guys think those tires just don't look right from the side? Tomorrow I'll look to see how much clearance we have inside the rims and shoot a photo or two of it. We may be able to get by with 16" rims. I doubt we could go 15 but won't know until then. Of course that will make tire choices more of a challenge and we've been through this already, but we may as well make it look as good as we can, within reason.

Jim

I agree Jim, something doesn't look right with those 17s. We should be able to use a 15" rim, that's what Jag used with those rear uprights. I realize that the sill is missing and that would add a bit of depth to the body, but the photo of the car at nominal ride height looks pretty high with those tires and wheels. We probably need to find something a little smaller that would tuck up in the wheel wells better. I realize the limitation is with finding tires these days in a 15" rim with any width, but I think we could get by with a lot less width if we want and still have a car that hooks up pretty well. Of course from the onset of the project I've leaned towards the "sleeper" look so smaller tires fit right in there.