[mike082802]

so as the title says, after dropping the rear subframe a few times for bushing inserts, then sways, then full bushings i stripped the driver rear subframe. it started 2 years ago when i must have misaligned the subframe while tightening so i ordered a tap and a new blot. this saturday while i was swapping out bushings for a firmer poly it started to rain so i rushed and stripped it. i has a M12x1.5 tap so sunday i tried to clean the threads and i had a brand new subframe bolt. no dice, wouldn't tighten past 50 ft/lbs. i now i was thinking about my options and this is what i came up with:
1. get a 1/2-13 tap from home depot and 5' bolt there
2. get a 1/2-20 tap online and order the associated 5" bolt
3. get a M14x1.5 tap and rethread and pick up a VW/Audi subframe bolt.

i dont know if the 1/2 bolt size will work since it is close in size to the old M12, i dont know if it matters much if i go with the coarser 13 threads per inch then the finer 20 threads per inch? i dont know if i should just jump to the M14X1.5 or start with the smaller bolt first.

any advice is appreciated.

[feuer]

I'm not sure m14 will fit into the bushing. The best is to holicoil and use same bolts all around.

[BB_cuda]

The thing about helicoil is you're really tapping it to a larger size. The helicoil kit typically comes with a tap that fits the OD threading of the helicoil. Then in your case, the original M12 is the ID threading of the helicoil. I had stripped M8 and was contemplating using helicoil. I ultimately went with M10. Feuer does make a great point that M14 might not go through which ever bushing you are securing.

If you think using the original M12 bolt is warranted (to be able to use the factory torque) then helicoil is thing to do.

By the way, belmetric.com sells all sort of metric bolts in 10.9 grade too. I used this for my rear diff support bolt as I needed to go longer.
https://www.belmetric.com/?gclid=CMT...FY5WDQodL7QPlg

Where on sub frame is the threading stripped? You might be able to just run the correct size of tap unless you ground the threads off. Maybe that is what you mean by in only holds up to 50 lb-ft torque.

Public service announcement: units of torque is force times distance not distance divided by force. It can be in either order lb-ft or ft-lb. Metric is always shown as N-m though.

[mike082802]

i already cleaned the threads with a m12x1.5 tap, i must have really fcked them up. i use belmetric for all my bolts, but in this case its cheaper if i go to the local vw dealer and pick up the m14 bolt if thats the way i go as its 6$ and no shipping.
i know what ft-lbs are, dont know why i wrote it that way, im a licensed professional engineer.

[BB_cuda]

Originally Posted by mike082802

i know what ft-lbs are, dont know why i wrote it that way, im a licensed professional engineer.

Cool, I'm a mechanical engineer.

[mweisdorfer]

Originally Posted by mike082802

i already cleaned the threads with a m12x1.5 tap, i must have really fcked them up. i use belmetric for all my bolts, but in this case its cheaper if i go to the local vw dealer and pick up the m14 bolt if thats the way i go as its 6$ and no shipping.
i know what ft-lbs are, dont know why i wrote it that way, im a licensed professional engineer.

Are you sure it was m12 x 1.5!?

It could be m12 x 1.25...

If the original was m12 x 1.25 and you are re-threading it to 1.5??

[mike082802]

realoem says most of the bolts are m12x1.5 and the one i ordered from belmetric went right in the front unstripped subframe hole.

[juld0zer]

The bolts go into the chassis.
Unless you were using power/air tools, they usually are quite difficult to cross thread because of the tapered guides which guide the subframe into position. The other possibilities are you used the bolts to pull the subframe up instead of a jack or the bolt threads picked up some grit on the way up.

Have you tried brake cleaner and compressed air to clean out the hole?