Merits of Studs for rear subframe mounting?

[Mr & Mrs Shrek]

My E36 M3 has studs on the rear sub-frame mounts ( 2 studs at front and 2 bolts at back) which really helped with locating to refit the sub-frame so I am thinking about doing the same thing for the Mustang rear sub-frame when I put poly bushes in given the problems some people have had with cross threading the factory bolts with the thread cutting ends and it allows dropping down the sub-frame somewhat while still being located.

Any thoughts on this?

Does anyone know the length of the bolts so I can get some studs made without having to pull the bolts to check? I am going to cut the head off a M14 12.9 bolt and get the end threaded.

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[HoosierDaddy]

 

[Norm Peterson]

I have a feeling that the threads on the OE bolts may be rolled rather than cut (rolled being better). Never mind that putting a nut on the bottom would probably make future removal more difficult.

I think what I'd do would be to make up a pair of studs, somewhat longer than OE, that you'd screw into the car after removing the OE bolts (removing and replacing one at a time). These would be temporary studs, for locating only (you'd remove them in favor of the real bolts after getting the cradle properly located and a couple of the bolts at least started/snugged), so these studs wouldn't need to be 12.9 material.

Grinding a pair of flats in each so you could run them down in their threaded holes with a wrench if necessary, and putting a little taper on the unthreaded ends would help.


Norm

 

[mikeD4V]

Steeda offers some inexpensive delrin sleeves for those bolts to ensure the IRS is correctly located every time.

https://www.steeda.com/steeda-s550-mustang-irs-subframe-alignment-kit-2015-all-555-4438.html

 

[Mr & Mrs Shrek]

@HoosierDaddy, thanks that is very helpful and covers what I need. So it looks like the shank is about full length of the bush.

 

[Mr & Mrs Shrek]

I have a feeling that the threads on the OE bolts may be rolled rather than cut (rolled being better). Never mind that putting a nut on the bottom would probably make future removal more difficult.

I think what I'd do would be to make up a pair of studs, somewhat longer than OE, that you'd screw into the car after removing the OE bolts (removing and replacing one at a time). These would be temporary studs, for locating only (you'd remove them in favor of the real bolts after getting the cradle properly located and a couple of the bolts at least started/snugged), so these studs wouldn't need to be 12.9 material.

Grinding a pair of flats in each so you could run them down in their threaded holes with a wrench if necessary, and putting a little taper on the unthreaded ends would help.


Norm

@Norm, thanks I have read many of your posts, quite insightful! I think the temp stud option you suggest might be the best of both worlds. Do you think, cost aside, replacing the factory bolt with a 12.9 ZP socket head would offer any benefits or stick with factory bolt?

 

[Mr & Mrs Shrek]

Steeda offers some inexpensive delrin sleeves for those bolts to ensure the IRS is correctly located every time.

https://www.steeda.com/steeda-s550-mustang-irs-subframe-alignment-kit-2015-all-555-4438.html

@mikeD4V, I forgot to mention I have these sleeves sitting around uninstalled as well as BMR poly bushes. I am going to put the poly bushes in hence tackling the studs question so I can do it as a part of the install. I might do the sleeves first to check whether all 4 points will align ok beforehand given this is a simple install.

 

[KellTrac]

Here ya go:

http://kelltrac.com/IRS-Subframe-to-Chassis-Stud-Kit_p_24.html

 

[Norm Peterson]

@Norm, thanks I have read many of your posts, quite insightful! I think the temp stud option you suggest might be the best of both worlds. Do you think, cost aside, replacing the factory bolt with a 12.9 ZP socket head would offer any benefits or stick with factory bolt?

I'd stick with the factory bolts, as I would expect Ford to have more stringent corrosion resistance requirements.


Norm

 

[Mr & Mrs Shrek]

Decided to go with permanent studs. Got my 4x M14 x 150mm (6") bolts @ 12.9 (total ~US$20) and head machined and threaded (total ~US$30). Now off to be Zinc-Nickel plated and passivated (maybe Olive Drab) to make sure Norm's comment is suitably addressed, although no salt roads to worry about here.

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