930 trailing arms on a G50

[j911brick]

I have something of a problem.

I'm doing a 930 trailing arm conversion on a g50 torsion tube. As far as I can tell nobody makes a weld on adapter. I bought the adapters for the earlier torsion tube and thought i could do a mock-up to make a jig to get proper location of the trailing arm mount, but they fit so poorly they need a jig themselves. So barring getting good adapters or a jig, a need a method of locating the mounting holes in the correct location. Can anyone help with that or set me in the right direction?

TIA

[j911brick]

What I need is this:

[gled49]

I’ve posted this before, and the 930 trailing arms are the same from 930 to G50. Maybe the dimensions can help you with your project.

[AlBackus36]

Not trying to derail, OP. Hope you don't mind if I ask a couple questions.

How much of an improvement in lateral stability does this provide?

The forward end of the trailing arm is a single pin joint with either a rubber bushing or sometimes a spherical bearing. This joint will flex or swivel as opposed to dumping a 'kick' into/or 'bending' the tube.

Does the 930 run faster lap times than a carrera?

[Duc Hunter]

I just asked a similar question in my own thread. I was asking if I could move a narrow body car to a 930 trailing arm without chasing wheel offset, so I could leverage the stronger wheel bearings vs eating the narrow body wheel bearings every 3,500 miles or so. They said the only way was weld in a 930 torque tube.

For your issue I think you need the alignment drawings for so the its glide a Cellette Bench. The chassis measurements for the 930 to “straighten” the frame would probably give you what you needed.

[r lane]

Originally Posted by Duc Hunter

I just asked a similar question in my own thread. I was asking if I could move a narrow body car to a 930 trailing arm without chasing wheel offset, so I could leverage the stronger wheel bearings vs eating the narrow body wheel bearings every 3,500 miles or so. They said the only way was weld in a 930 torque tube.

For your issue I think you need the alignment drawings for so the its glide a Cellette Bench. The chassis measurements for the 930 to “straighten” the frame would probably give you what you needed.

Make 3d drawings of the G50 tube and the earlier tube and then you can figure the difference in pickup point location. Not an easy assignment but what else to do. The 930 arms do push the hub out about 20mm I have just discovered. Bruce Anderson's book has information and a company called John James racing may have done this job. Good hunting. Bob

[r lane]

I track a 78 911 with 930 arms, didn't replace the tube but calculated the location of the pickup point and built camber boxes. A fairly common conversion. Bob PS My understanding of their different geometry is that they facilitate a more even camber change matching the car's roll. That should allow you to run less static camber in the rear. You will need turbo brakes now.

[r lane]

Originally Posted by Duc Hunter

I just asked a similar question in my own thread. I was asking if I could move a narrow body car to a 930 trailing arm without chasing wheel offset, so I could leverage the stronger wheel bearings vs eating the narrow body wheel bearings every 3,500 miles or so. They said the only way was weld in a 930 torque tube.

For your issue I think you need the alignment drawings for so the its glide a Cellette Bench. The chassis measurements for the 930 to “straighten” the frame would probably give you what you needed.

Make 3d drawings of the G50 tube and the earlier tube and then you can figure the difference in pickup point location. Not an easy assignment but what else to do. The 930 arms do push the hub out about 20mm I have just discovered. Bruce Anderson's book has information and a company called John James racing may have done this job. Good hunting. Bob

[j911brick]

Thanks for your reply. I seen the photo but never read the caption. Thanks again. At least gives me something to work with.

[j911brick]

Originally Posted by AlBackus36

Not trying to derail, OP. Hope you don't mind if I ask a couple questions.

How much of an improvement in lateral stability does this provide?

The forward end of the trailing arm is a single pin joint with either a rubber bushing or sometimes a spherical bearing. This joint will flex or swivel as opposed to dumping a 'kick' into/or 'bending' the tube.

Does the 930 run faster lap times than a carrera?

My understanding is it reduces the amount of camber change under squat as well as reduced toe changes.

[j911brick]

Originally Posted by AlBackus36

Not trying to derail, OP. Hope you don't mind if I ask a couple questions.

How much of an improvement in lateral stability does this provide?

The forward end of the trailing arm is a single pin joint with either a rubber bushing or sometimes a spherical bearing. This joint will flex or swivel as opposed to dumping a 'kick' into/or 'bending' the tube.

Does the 930 run faster lap times than a carrera?

Originally Posted by Duc Hunter

I just asked a similar question in my own thread. I was asking if I could move a narrow body car to a 930 trailing arm without chasing wheel offset, so I could leverage the stronger wheel bearings vs eating the narrow body wheel bearings every 3,500 miles or so. They said the only way was weld in a 930 torque tube.

For your issue I think you need the alignment drawings for so the its glide a Cellette Bench. The chassis measurements for the 930 to “straighten” the frame would probably give you what you needed.

With the specs posted above I think I can 3d model it and print an alignment jig ( once I learn how to do these things of course).

[j911brick]

So not being able to locate a jig, design, or parts, I have been working the past few weeks on learning enough CAD to do this. I just got a 3D printer and I have been fine tuning the jig. What I have learned is even the factory didn't get the right and left sides perfectly symmetrical. The weld on adapters sold by Partick Racing and others (they are all the same) are worthless and aren't even close to actually fitting anything, except maybe a Camero. The jig and parts I made only fit the G50 mounting system. Now I have to someplace that can actually make the parts. I also need to figure out the relocation of the transmission mount.




All that just to make this:

[j911brick]

Parts are back from the CNC shop.

[j911brick]

Originally Posted by r lane

Make 3d drawings of the G50 tube and the earlier tube and then you can figure the difference in pickup point location. Not an easy assignment but what else to do. The 930 arms do push the hub out about 20mm I have just discovered. Bruce Anderson's book has information and a company called John James racing may have done this job. Good hunting. Bob

I was finally able to get some measurements. From the inside of the inside pick-up points it measured ~310mm vs ~285mm on a regular torsion tube. Moving the pickup point directly out the specified 47mm lands it pretty damn close to the correct spot.