What causes torn CV boots?

[jpnovak]

Last fall when I finished building the ST I installed the CV half shafts that came with the 78SC I parted. I drove the car about 250 km and then it was parked while I did some home improvements.

About two month's ago I found a torn CV boot on the pass. outer end. I just thought it was due to handling/storage for the two years they were packed up. No problem, a few hours later new boots were installed, the shafts were repacked with grease and all was good.

I have only driven the car about 300km since the boot replacement. Last night while giving the car a once-over (nut and bolt) for my DE tech inspection on Friday I found that this boot was again torn. The whole outer end section of rubber that bolts to the flange is gone. It looks like it started right next to the metal fixing band on the flange.

Any ideas that would have caused this? The boot was new. This has happened twice with very few miles. Maybe the first boot was bad.

Would a lowered car cause this? I would think there is less angle on a lowered car than a higher car.

I don't mind replacing it and have a spare on the shelf. I just question why.


Share your thoughts...

[silverc4s]

Jamie,
Possibly old stock rubber boots from your source, somewhat decomposed due to storage temp, light. dryness, etc. Just think, they have been making those boots for over 30 years now.
Does anybody know if there is a date code on the rubber somewhere? Probably not, maybe on the packaging they come in..

edit: There are also pretty significant centrifugal forces on the outer diameter. if a lump of grease was lodged there, it could have caused this (??) maybe a combo of both of the above...

[ttweed]

I destroyed boots on a lowered car with insufficient spring rates which allowed them to contact the chassis over a big enough bump.

TT

[kqw]

When you installed the boot...did you make sure that the boot was not stretched a bit lengthwise on the axle?

i.e., allow for that boot to expand outward with centrifical force...If not it's going to pull away and possible tear.

[jpnovak]

I assume that the rubber was not old, it was a new replacement using a reputable local source.

Yes, a lump of grease could do it. I guess it could get squeezed out of theh joint and collect on one side.

Yes, it was installed without stretch, to the inside of the protrusion on the axle.

Tom, I like your idea. My car is quite low and I was infact raising the rear when I found teh boot. I am still going through suspension development. That body seam on the longitudinal is right in line to wreak havoc. I might have to look closer at that.

In the end a new boot will get put in tonight. What a greasy hour long mess.

[Jeff Higgins]

Maybe the "metal fixing band" caused the tear? Do you mean the crimp on "hose clamp" kind of metal bands that attach the boots to the axle and the flange? I quit using those and just put a big heavy duty zip tie around it instead. They have a much "softer" edge and won't dig in to the boot. I have not torn one in those areas since switching.

[zymurgist]

I have the exact same symptom as Jamie.

One of the first projects I did after buying my 911 was replacing the outer right CV boot because it was torn. My car is up on jackstands for other service at this time, and I noticed that the same boot was torn again. Odometer is broken (of course!) but I estimate only about 2K miles (if even that many) since I replaced the boot. The boot came from PP... I imagine that they sell a lot of boots so the rubber can't be terribly old. I installed it up to the protrusion on the axle also.

One thing I noticed on my car... on the driver's side, the boots are both clamped to the axle so they don't extend nearly as far down the axle. I was planning on clamping the new boot to the axle when I replace the boot (actually, nylon tie sounds good to me) to see if I can get this one to last a bit longer.

[DG624]

I was told that silicon spray will help keep the rubber boots pliable.

[ttweed]

Originally posted by jpnovak
That body seam on the longitudinal is right in line to wreak havoc.

That's the thing that cut mine. We had to cross a swale at high speed in an autox one time and my car bottomed out severely over it. The suspension travel on the rear axles brought the outside boots into contact with that seam on the body. This was on a '66 911 with 21mm front and 26mm rear T-bars, but it was pretty slammed.

TT

[ckissick]

I, too, have had the same problem. Torn outer right rear boot, with about 1000 miles. My car is also lower than normal: 22-3/4" measured from top of wheel well. I noticed it when I replaced the leaky oil tank and thought,, "Can I have at least a short respite from more DIY work, please?"

[Sumotang]

Just my limited 2c worth. I recently had my mechanic replace my CV boots. My left hand side inner CV boot was torn where it mates to the flange. I would have replaced them myself but couldn't get the hex bolts undone due to PO DIY work.

The new boots for my 83SC had clamps on the flange side when delivered. I noticed the mechanic didn't put any tie on the axel side and he said that its best not to clamp this side so the boot can move in and out slightly and not bind up on the axel. This could be a cause as well.

But from reading the posts it sounds like these things can tear when the suspension fully bottoms out compressing the boot against the flange.

My new boots have only been on for about 150miles and the rubber looked excellent on them. I will re-post if I have problems.