CV Joint Bolts?

[scotts216]

Maybe a stupid question, but...... What are correct bolts for a standard duty CV joint? 8mm or 5/16"??? 8mm seems a bit bigger to fill the hole better? Or are they interchangable??? 5/16" came out, but I want to replace them as I have it all apart.

Thanks.......

[D.T. Benner]

The Metric ones as Thats What came in the car when it was new.
Whats most inportant is to use the correct grip length bolt so you have the shear loads on the solid body of the bolts,not the threads.

[ghickman]

Normally the cv bolts are 5/16-24.....however there are also some diffs. and stub axle flanges that take an 8mm x 1.25 bolt.

I own a machine shop and I just happen to manufacture cv joint bolts with a 12 point head and they are also cross drilled for safety wire. I have both sizes in stock. They are MS spec. bolts made to mil. spec. standard.

These bolts are the correct grip length by the way...

You can PM me, email, or call if you need a set.

Regards
Gary Hickman
email gary@bombshellparts.com
phone 619-456-4564

[scotts216]

Thanks for the replies..... It apears that the 8mm bolt is only a couple thousandths bigger. I also figure it is the clamping force of the bolt that keeps the CV joint in place, so maybe that difference in size is not so importnat. I think I'll look for an appropriate sized AN bolt at 5/16".

Working on a RT5 and it's my first CV car. Other two cars use rubber donuts......

Regards, Scott

[D.T. Benner]

Remember that the acceleration and brakeing forces are Always trying to shear the bolts and/or work them loose so always keep checking them. Also don't slop a lot of Silicone saler on the mateing surfaces as that works like a lube between the parts and you will wonder why they keep getting loose all the time.

[Graham Rankin]

Daryll's comment about constantly checking you bolts is very prudent. We check ours after every session.Our Swift 014 was fitted with AN h/w, but after one experience lat year where two bolts actually did shear we opted to try the MS bolts going forwards.Hardware is often one of the most overlooked items on a race car,but often puts a car on the sidelines.
I personally have developed a policy that hardware is consumable.Yes there is a cost (watch out for sticker shock on the MS CV bolts!) but i consider it cost effective in the grand scheme. Just my 02 cents !

Graham

[Paul LeCain]

I use both a lot. You do have to be careful about the radius under the head on these bolts. If you're not using washers (countersunk), you have to make sure the hole the bolt goes in is countersunk.

[ghickman]

I use both a lot. You do have to be careful about the radius under the head on these bolts. If you're not using washers (countersunk), you have to make sure the hole the bolt goes in is countersunk.

To All Concerned
These bolts have a large fillet underneath the head. They must be used with the special washers that we supply with the bolts. The washers have a corresponding fillet that matches the head.

They are also cross drilled for safety wire which is an added exspense but if you want to be sure the bolts never come loose the option is there.

Gary Hickman

[formulasuper]

Safety wire is the key. If they can't loosen up the clamping force will prevent shearing. Also, you won't have to keep checking them. Must be the reason the aircraft industry has been using it since the Wright Bros.

[D.T. Benner]

In this case I don't use Safety wire because these parts are in constant strugle to twist,shear and move around. That and the heating,cooling cycle of the parts create a different set of conditions than just clamping loads. I spent a lot of time working on aircraft and aerospace goodies but in this caes I feel better putting a wrench on the bolts rather than looking at the safety wire. Just MY 2 cents.

[Paul LeCain]

I don't use it either.

Torquing the bolts is just part of the pre-session check.

[Rennie Clayton]

Daryll's comment about constantly checking you bolts is very prudent. We check ours after every session.Our Swift 014 was fitted with AN h/w, but after one experience lat year where two bolts actually did shear we opted to try the MS bolts going forwards.Hardware is often one of the most overlooked items on a race car,but often puts a car on the sidelines.
I personally have developed a policy that hardware is consumable.Yes there is a cost (watch out for sticker shock on the MS CV bolts!) but i consider it cost effective in the grand scheme. Just my 02 cents !

Graham

After 6 years of never having sheared a CV bolt, we lunched one at Portland this past weekend. Must be all the glorious mid-range torque we're getting from our new Loyning engine!

That thing is a real stump-puller, as Keith Lively can attest to... I started race #2 from the 3rd row due to a wee off in qualifying. I got a ho-hum start, but by the time we went barrelling into T1, I was about 2-3 car lengths in the lead. Race over. But I digress...

We've long been in the "no safety wire" cadre for CV's, preferring to torque every session. This Portland weekend we did not find any which had loosened from session to session, with the exception of the sheared lugs, of course, and no evidence that they had loosened. Might have to bit the bullet on MS hardware, but what are the thoughts from the safety wire crowd regarding whether or not that would prevent CV bolt shearing as well?


Cheers,
Rennie

[Brian]

Safety wire keeps a bolt from falling out when it comes loose, it doesn't keep a bolt torqued. So in this case, safety wire might be neat and workmanlike, but it won't fix the problem of the nut/bolt loosening. The torque transfer in the CV joint is supposed to be through the friction developed through the clamp load between the bell face and the face of the CV joint. That's why any sealant there is a problem, it reduces that friction. Clean and absolutely dry is best.

So the bolts are supposed to be in tension, and selection of bolts that can produce the greatest tension load is appropriate, as is checking them often and perhaps lifeing them. Maybe adding dowels would work, in very close fitting holes. Using (or thinking of) the bolts as locating dowels really won't work all that well in this application (if it ever does), since if you use 5/16" bolts they are under-size already, and even the correct metric bolts aren't all that close a fit. For me, a dowel fit that is supposed to transfer torque and not just be a rough locator is less than .001" (and a total PITA to machine).

For me, figuring out how to torque a nut on a bolt to the level of torque required (around 35 ft lbs from memory) is a real trick, and I would be tossing the little jet nuts after every use if I actually managed to get that level of torque on them, I just do the nut up as tight as I can. I do torque the outer bolts, on my cars they are blind-threaded into the outer hub so there is only a bolt, no nut.

My thoughts on this, anyway, for what they are worth.

Brian

[Paul LeCain]

For me, figuring out how to torque a nut on a bolt to the level of torque required (around 35 ft lbs from memory) is a real trick, Brian

AN-5 bolts won't take 35 ft-lbs. They should be in the 12-15 ft-lb range.

NAS 1305 limit is 18-20 ft lbs.

[formulasuper]

Safety wire keeps a bolt from falling out when it comes loose, it doesn't keep a bolt torqued. So in this case, safety wire might be neat and workmanlike, but it won't fix the problem of the nut/bolt loosening. The torque transfer in the CV joint is supposed to be through the friction developed through the clamp load between the bell face and the face of the CV joint. That's why any sealant there is a problem, it reduces that friction. Clean and absolutely dry is best.

So the bolts are supposed to be in tension, and selection of bolts that can produce the greatest tension load is appropriate, as is checking them often and perhaps lifeing them. Maybe adding dowels would work, in very close fitting holes. Using (or thinking of) the bolts as locating dowels really won't work all that well in this application (if it ever does), since if you use 5/16" bolts they are under-size already, and even the correct metric bolts aren't all that close a fit. For me, a dowel fit that is supposed to transfer torque and not just be a rough locator is less than .001" (and a total PITA to machine).

My thoughts on this, anyway, for what they are worth.

Brian

I agree about using dowel pins, I have 3 in each inboard CV. My sprocket is sandwiched in the left side & my single inboard brake disc is sandwiched in the right side. However, I (& the FAA) know that if safety wire is correctly installed per FAA 43.13.1A, the bolt can not turn in the loosening direction.

[Fred Michael]

Correct.
The safety wired bolt cannot turn.....but the nut can!

[Paul LeCain]

I should have said that, on my car, the the bolt head is inside the transmission, captured by a ridge on the output flange - it can't turn.

Then the shank comes out through the flange and through the tripod housing. Then, there's a k-nut on the bolt. That's what gets torqued (obviously).

[Brian]

Couple of points about my earlier post. Holokrome SHCS, which is what I actually use, in 5/16", call out a tightening torque of 460 in-lbs (38.3 ft-lbs) for NF thread and 415 in-lbs (34.5 ft-lbs) for NC threads. I use NF inboard, with nuts, and NC outboard, threaded into the hub. I actually torque the outboard, dry, to spec with a torque wrench. I don't use a torque wrench on the inners, I just use a wrench on the jet nut and do it up as tight as I can. I looked up the torque capability of a jet nut once, when I was researching this the first time, but I forget what it is right now. It's probably lower than what Holokrome bolts can take.

Yes, that is a higher torque than an MS bolt calls out. Hence my comment about searching out and using fasteners designed for tension applications (by and large mil-spec is designed for use in shear applications), and looking for fasteners that develop high clamping loads. Torque is actually irrelevant, clamping loads, in the application, are very relevant.

The total clamping load of the outer CV joint, which I do torque up with the click-stick, is in the neighbourhood of 35,000 lbs.

My point about safety wire is that all it does is keep bolts from turning, it doesn't keep them tight, under tension, producing clamping load. It's belts and braces, fail-safe of last resort. If the bolt stretches, if a nut collapses, if a washer squishes, if the thing being clamped collapses - the bolt is no longer under load and is not clamping. The VW CV joint installation is designed to use clamping force to tranfer it's load. Adding dowels is a good thing, but depending on the bolts in shear is wishful thinking.

Just for fun, I just googled the install instructions for VW axles (I happened to find Type 4) the VW spec for torque on these bolts is actually 50 ft lbs. Yes, 50! The kit I found happened to use something called Nord-lock washers http://www.nord-lock.com/upload/file..._intro_ENG.pdf with supposedly excellent results.

Bottom line - NAS or MS fasteners are way understrength for CV joint applications. Get good bolts. VW bolts are metric and use a funky "triple-square" internal wrenching socket that you have to go out and buy, because nothing in your toolbox will fit...

Edit - it occurs to me that someone should go and get ARP to make a CV joint kit. They could probably engineer something that would actually work and stay tight. It also occurs to me that if you aren't using the funky double hole load-spreaders under the bolt/nut head, you are asking for trouble. The small diameter of the nut/bolt bearing directly on the thin, soft steel of the typical CV joint boot retainer gonna collapse in no time, and hey presto, loose bolt. It doesn't take much to loose the clamping force.

Brian

[D.T. Benner]

Good information here! I'm still learning more everyday thanks to ApexSpeed.

[formulasuper]

Forgot to mention, My bolts screw into my center section spool flanges, no nuts. The safety wire has worked for 3 years, never find them untorqued when I cut off the safety wire. But then my Busa only has about 93 ft lbs of torque.

[D.T. Benner]

Some engines have that much at Idle. But you must make up for it with Horsepuppies! I can see why the Safety wire works fine in your set-up with no nuts and the lower torque load. My Tripods are a 4 or 5 part stack with a flange,1 thin shim and an Alternator pully (right inner only) and the tripod housing then the steel flange that the boot mounts to.

[scotts216]

Lots of good information in the thread. I have learned a lot, thanks to all who replied.......

Scott