Re-use or replace CV bolts?
 

I'll be replacing the boots on my '88 Carrera soon. Do you guys generally re-use the bolts on the CV joints, or replace them? I thought I once read they were one-time-use bolts.

Generally you can successfully reuse the bolts. However, the Schnorr washers should always be replaced. Also, good practice is to check the bolt torque after a few hundred miles of use. Many guys like to wire the bolts as well.

Stage8 also makes locking fasteners. I used them last year and they are great.

They're not one-time-use bolts. They're just common 12.9 property class socket head screws. The larger 108mm CV joints on your '88 are M10 size screws. I've found that the M10 are more robust than smaller 100mm joints with M8 screws. I've reused the M10 on my former '87 for years and it saw a good amount of driveline stress from track day driving.

As long as the hex in the bolt is not ruined by sloppy wrenching, i'd have no problem reusing them. Reason being is that it's difficult to over-tighten the M10 screws since they're torqued to 60 lb-ft. Whereas the smaller M8 screws are limited to 30 lb-ft and it's not uncommon to find those bolts loose, probably due to yielding from over-tightening them.

Thanks for the replies. I didn't realize they had Schnorr washers with them. I know I have some new ones that I used on my Beetle, but didn't know Porsche used them as well.... will have to look into that.

Well, a 911 is just a beetle with lockwashers!!!

Not all CV's used the Schnoor washers, so don't be surprised if you don't find them in there.

The definitive answer:
http://forums.pelicanparts.com/porsche-911-technical-forum/222537-reconstructing-constant-velocity-cv-joints.html
With info from Grady C.

I have 24 12.9 grade M8x50mm hex socket c/v bolts left from my recent 79 SC CV install project if anyone is interested 15$ /dozen shipped us .
bruce

hbkramer3@gmail.com

I just did an axle on my 87 that has standard Socket Head M10's. My car has no Schoor washers and none shown on the PET. It "does" have 3 double hole C shaped plates, a type of washer. I've removed and replaced the tranny ends many times during misc. maint. activities and never replaced bolts and never had one loosen. Bolts look perfect so why replace ?
The new axle from our host came with new triple square socket bolts which I tossed in the trash, hate those things. That would just make access twice as difficult.

They are not stretch bolts I don't think? Most times they come loose more then break. Be better to use a good same grade bolt with the heads drilled and run safety wire thru them if your worried about them

they can be reused. just clean them very well along with the flange threads. one other thing. make sure the bolts go ALL the way thru the flange. you want a thread or 2 sticking out of the back side. trust me, its not fun or pretty when one comes off.

fastenal has the bolts in 5mm lengths along with the washers. they are the correct 12.9 bolts.
you just have to buy a bag of 50.

You can get a new set of 12 M10x50 grade 12.9 bolts and Schnorr washers for about $8.50 at Fastenal.

Why bother with old hardware?

Why throw away perfectly good fasteners???

Unless the heads are damaged, you can keep reusing the 10mm 12.9 fasteners for a very long time.

Again, I'm in the re-use group. And where does all the wisdom on Schnoor washers come from ? They were not used originally so why are they being suggested here. Is that a racing thing ?
The M10 bolts are at least 50% stronger than M8's (amount of steel in that diameter) so they should be fine as is to me.
FYI, Schnoor is a brand name, they call the washer with the radial grooves their "safety washer".

Grady Clay spent a lot of time explaining all the above questions. As he stated, the price for getting it wrong can/could be extreme. It is a lot of posts and some can be breezed through, but there is a lot of collective knowledge imparted, if you want it....
Safety wire will not prevent the woes....

The M8's would work fine on your car even though you can't use them.

The Grady Clay thread has more info than you will use.

You are talking under $100 for parts if you get schnoors, new bolts with wire holes and moon plates.

Or just do new stock with new M10s and regular washers.

Or just clean up what you got and re-use them. Check them in 1,000 miles and you may find reasons for the voiced concerns. They loosen up. Main thing is to keep on top of them.

Not worth arguing this issue.

Do what you want to do. Report back though as to what you find after 1,000 miles. Then there would be value in this thread.

Well, schnorr washers at a minimum should be replaced each time, as they tend to permanently deform. Personally I prefer NordLocks, as they seem to be good for at least a few reuses.
Having worked on a few cars with stripped CV bolt heads (most were 914s) I dont think the $6 savings is worth the risk of fussing with a stripped out allen hole.

A couple of years ago I installed a new axle on my 964 and it also came with the triple square bolts. I have the proper bits for these, so that wasn't a problem, but the new bolts that came with the axle weren't the proper length. IIRC, they were too long. I just cleaned and reused the Allen head 10mm bolts. When I recently removed the axles to drop the engine and trans, they were still properly tight.

Properly torqued, the 10mm bolts don't need washers.

proper length and clean. oh and torque.