MG Sports Cars

Donations to the Roadmaster Project can be made to:

Bill Davidson, Treasurer
7208 W 54th Terrace
Overland Park, KS 66202

913 677-0884
Bill74mgb@yahoo.com

Checks should be made out to:

British American Deviant Automotive Sportscar Society
or
BADASS

Yes, and we need donations to get the car back on the road and keep it there. Currently we need to replace the coil-over suspension units on the rear, at a cost of around $500. Auto insurance renewal will be coming up soon as well and we'll need some money for that.

Remember that this project generates a good bit of visibility and good will for our sport while we pursue our stated goal of investing in the future of our young people by encouraging them to take wrench in hand and build their own car. Your small contribution added to those of others can make the difference between having the car out on the road where it can be seen or sitting idle. And also remember that you too can drive the car.

Jim Blackwood, former BADASS President.

OK guys, we need some help here. Jim S. and Jim N. and maybe Fred and others, we are trying to come up with a part number so we can order the coil-over units. Here are our requirements:

-Street coil-over units with 5/8" diameter shock rod (shaft)
-1/2" diameter mount, both ends
-urethane bushing mounts, both ends
-adjusting nut which accepts a wrench (we also need the part number for the wrench so we can get that too)
-400mm (15-3/4") extended length eye center to eye center
-265mm (10-7/16") compressed length
-23mm (7/8') tall bump stop or rubber snubber on shaft inside spring
-internal travel limit stop (extend)
-spring length, 12"
-spring rate, 375 lbs/in

The length requirements can vary a little but the OAL should not be made any longer.
I confirmed the spring rate, it is etched on the end of the spring. Damping is pretty light. It's no wonder we broke one of these, the neck at the end of the threads on the shock rod is only .390" diameter.

Using urethane mounts may mean we have to bump the floor up a tiny bit to fit them in, if that part is larger than the heim joint ends but this can be done if necessary.

So, guys, can you check your resources and find something that matches these requirements?

Jim

Last call, yes or no, QA-1 not designed to limit rebound travel ? I suspect this may have caused the problem ? Cheers, roverman.

Would it be a good idea to add an external rebound stop? Perhaps "Strapping Lad" type straps could be mounted behind the lower control arms, where some Jag IRSs have a second pair of shock absorbers.

Road Master is running (2) coilovers on rear, instead of (4) ? Is this a proven conversion ? Will the lower a-arms long endure, additional torsional loads, of 1 shock per side ? Good Luck, roverman.

unfortunately you are right Art, unless it gets converted to a four link like the Satchell link design which would be difficult at this
point.
Dave



Edited 1 time(s). Last edit at 08/20/2013 08:45PM by Preform Resources.

No, not a problem. The torque loads on the LCA are at least one order of magnitude greater than the suspension loads.

Jim

ERA Cobra's use single shock each side about the same angle. They are usually 350lb springs compared to the stock Jag 200lb dual springs.

I don't see a problem with a single coilover per side either.
Any tangential load that shock will impart on the LCA will easily be handled by the forked mount at the diffy.
Which is designed to handle much higher loads than the shock could ever impart due to its need to "twist" the diffy as the suspension moves..
The Jag design is really very clever and poorly understood by most.
The toe and camber changes as the suspension moves are very carefully calculated and are only now being utilized by other manufactures.
A 4 link design doesn't really apply to this type of suspension and would destroy the "rear steer" that is built into the design.
Cheers
Fred

Jim B, A guy on the Locost site says the stock XJ6 has 175lb rate springs and stock compressed length 9",extended length 13". XKE had around 200lb rate springs

That seems to fit Jim N, double that brackets the spring rate we are using exactly.

I haven't heard back from QA1. I hope they are taking the request seriously and it hasn't gotten lost. But at this point I'd probably just buy another shock and the 12" springs and put the car back together, send the old shock back to QA1 for rebuild, and put it in the boot as a spare.

Jim

Good morning Jim,



The small body shocks are only available with the ½” piston rod. To get a larger diameter rod you would need to get a large body shock like the Alumamatic shocks which use a 2 1/2” ID spring and not the 1 7/8” springs. Part number ALN4855P has a compressed length of 10 1/8” and extended length of 14 ¼” and come with poly bushings. The part number for the spring is 10-375 for silver power coat or 10CS375 for chrome. Let me know if you need anything else.



Have a good day,



Damien Brase

Technical Sales and Support

…………………………

QA1 Precision Products, Inc.

A: 21730 Hanover Ave, Lakeville, MN 55044

D: 952.985.6433 | P: 952.985.5675

F: 952.985.5679 | W: www.qa1.net


Those appear to be our choices at this point.

The distances from shock to outer pivot and shock to inner pivot are as follows:
Driver's side, 6-1/4:11 ratio is 1.76
Passenger's side, 6-1/14:12-1/4 ratio is 1.96

So with the extended length being 14-1/4 instead of 15-3/4 we lose 1-1/2" of shock extension and 2.64" or 2.94" of droop. Considering we have 8" of droop now we can probably live with this. The shorter compressed length means that we will either have to have a taller bump stop (external in addition to the internal one), stiffer shock settings or stiffer springs to keep the tires from hitting the inner wheelwells, or a combination of the three. We can try just the stiffer settings initially and if that isn't enough stiffen the springs and/or add the external bump stop inside the spring.

To fit the larger diameter spring we will need a spacer at the top of the shock (1/8 to 1/4") and a longer top shock bolt. I used stainless so we would not have future problems with corrosion making the bolt impossible to remove (and requiring removal of the entire suspension). The tab for the brake line will also have to be bent or relocated.

If nobody can come up with a better option, then these are your two choices. You need to decide.

Bill Davidson is the treasurer. He can pay for them. Somebody needs to order them. Probably somebody close to Dave K.

Jim

OK, since nobody has done anything about this, I've gone back to QA1 with a request for a racing shock with the same length dimensions as the QA1 #28020931 8252 that is on the car now, but with a larger body and rod. If they can do that I'm thinking that might be a better solution since the ALN4855P will probably need an external compression bump stop anyway. (It is 5/16" shorter in compression.) All we'd be giving up is the extension bump stop and the cushion mounts (maybe). Nobody has admitted jumping the car so I can't see the extension stops being much of a concern. I'll let y'all know what they say.

Jim

Dave K sent me the broken coil over and I've inspected it and talked with him on the phone.

I just got off the phone with Damian at QA1. They do not have a 5/8" rod shock that comes any closer to matching the shock we are using. If anyone knows another coil-over maker that does we should look at it.

In the meantime, I reviewed all of the parameters with Damian including suspension travel, shock travel, ride height, shock ratio, shock angle, angular misalignment, remaining travel at ride height, spring rate, spring length, location of adjuster nut on the shock barrel, appearance of the fracture, orientation of the fracture, appearance of metal fatigue/tensile failure and a few other factors, including over extension. Am I wrong in thinking that the car has never been jumped? If it has we really ought to know about it and no repercussions to anyone who jumped it, you have my word on that. Personally, I think with the rear suspension travel we have the car would have to be seriously launched before the rear wheels came off the ground and if anyone did that they would know it, if only because the front would come down very hard. I don't see how you could miss it.

Damien did not feel that the spring length contributed to the failure. He said using a 10" spring on that shock at that spring rate and with that loading should not cause any problems. I will be sending him some photos so they can look at it and see if they can come up with any other ideas as to why it might have broken.

Honestly, the overall wear patterns seem to indicate to me that the car was driven for some time with the shock broken. But on the Omaha trip we had no indication of any problem.

So here is what we are going to do, unless somebody is dead set against it and offers an acceptable alternative. I have left a voice mail for Ted and will get in touch with him and see if he will order us another shock and spring assembly just like the one that failed. I have contacted Bill Davidson about paying Ted directly. I will see if the new unit can be drop shipped directly to Dave K. He will reinstall the new unit and we will get the car back on the road.

Then we will look into rebuilding the old unit to carry as a spare. If we feel it is warranted we might at that time consider buying a set of longer springs and/or adjusting the damping. However any adjustment requires the shock to be disassembled at least partially, which requires a pin spanner and I've mislaid mine and the pins are probably too big anyway, so a new tool will be required to do that. IIRC they are only adjustable in rebound anyway and that doesn't do anything for us. So if we go to a longer spring we will also increase the spring rate.

Jim

Pardon my ignorance.....but just what is "jumping" and how would one do this to the Roadmaster. Wheel hop???

re: Honestly, the overall wear patterns seem to indicate to me that the car was driven for some time with the shock broken. But on the Omaha trip we had no indication of any problem.

I don't agree with your theory. I think it was a catastrophic failure. The car was under my guard from the time you dropped it off in St.Joseph until the time that it left the trailer to be parked on Dave's driveway.

I drove it to town twice...and drove it to Indianapolis. You know my driving habits....I respect my vehicles, especially the Roadmaster.

Had the shock been broken while I was driving it at any point in time during my guard, I would have noticed a change in handling. I would have also noticed a change in its stance.

FWIW - YOMV.

Rick, I suppose "THE JUMPING" would be incidents similar to events in the movie "Bullitt' where Steve McQueen's Mustang and the Black Dodge Charger became air bore on the jumps in San Fran. This is just a thought I had . I have probably been incorrect before, but it was a trivial thing. :) PS, don't suppose Vin Diesel had a chance to drive the Roadmaster?

I was thinking Dukes of Hazzard. :) The General Lee spent more time in the air than any other car I know of.

I seriously doubt the Roadmaster has been impersonating the General. It broke. Let's put another one on like Jim suggested & see how it lasts.

I agree Rick, we had no indication anything was amiss.

But there is a rather large flat spot on top of the top spherical rod end. And that really makes no sense to me at all. But it had to get there somehow. A clue perhaps?

Jim



Edited 1 time(s). Last edit at 09/04/2013 09:26PM by BlownMGB-V8.