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.

I reuse the 10mm CV bolts all the time. I put Schnorr washers on them.
I don't reuse the 8mm ones. I've seen a several loose 8mm CV bolts and I think it happened to me once or twice. My solution is to use new ones. I don't know if it is the grease in the threads (of the old bolts) or what but it solved the problem for me. These bolts are relatively inexpensive so it's cheap insurance.

Do all M8 bolts have the same thread pitch?

Yes

Thank you. All of mine are loose. I suspect they were over torqued in the past, rendering them over stretched.

No! For the CV joints you want to make sure you get M8 with 1.25mm pitch. The most common alternate pitch is 1.0mm.

That’s one possibility….

Which class of bolt is acceptable for cv joints? And, are the moon washers reusable. Mine “ look okay “?
I’m seeing 8.8 zinc, nothing higher for zinc. Black Oxide 12.9, prone to rust!

12.9 - black oxide is typical and not a problem.

Moon washers are certainly reusable.

Yes Sir. & thanks

most times when they come loose it is because of sloppy assembly and they have CV grease in the threads,,
the very last thing when doing this job is taking each bolt back out one at a time and installing new bolts, or cleaning the old ones with brake clean and an old tooth brush and putting a dab of blue loctite.

recheck after 500 miles, 1k miles and 5 k miles ... good to go ..

i also run a pipe cleaner type wire brush through the holes, but not everyone has one.

This is interesting. And lends to what I suspected. I’m in the middle of this job on my 930. My 10mm bolts had washers on the inside only. And I don’t think the were Shnorr washers. This is the first time the C/V joints have been off in over 15 years. They were all tight. After reading all the threads I got nervous and ordered
Nord-Locks. I’m still waiting on them. The problem is, I’ll need longer bolts for proper thread engagement because the Nord-Locks are over 2mm. longer
I think I’ll just run wut I brung

This is a good point. And should be done to achieve proper torque specs. Regardless of weather or not you’re using Locktite.