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Why exactly are CV boots such a common (and costly) repair item?

Can someone point me to what exactly the deal is with these?
Are they just some rubber “bellows” that protect some axle parts?
Why are these such a big cost?
The part is like $10, but is it b/c the entire axle needs to be taken apart to replace them?

For example, why can’t you just duct tape them shut if they tear?

Yes they’re just rubber bellows, almost constantly flexing.
They’re down where sticks and other debris get to them.
and
Because there’s so much work to get to them.
NEVER gauge a job by the cost of the parts.
I’ve sold dollar o-rings to jobs that totaled 600 or so because of the massive puzzle just to get in there.

In addition , most people wait too long to either know they need one or to get around to it. By then too much dirt has gotten in and too much grease has gotten out so as to forever damage the ball bearing joint AND with all that labor already invested…it pays to just replace the assembly.

CV boots protect your CV joints, and keep them covered in grease. The CV joints are what allow your engine/transmission to supply power to the wheels while they are turned, or as your car bounces up and down across the road. If these things break, you’re looking at a loss of power to your wheels at best, and a complete loss of steering which leads to a catastrophic crash at highway speeds at worst.

The CV joints normally have to be replaced after the boots tear, because as ken said, there is a very small likelihood that you will catch the problem immediately - even if you inspect your boots every 1,000 miles, there’s a possibility that it could tear 999 miles before your next inspection. Once even a small amount of dirt and grit get into the boot, it will eventually work its way into the CV joint and cause it to wear. Unless you catch the problem almost immediately, it’s a good chance that simply repairing the boot will have you replacing the joint anyways in the next several hundred miles.

As for expense, you’re partly right. It is time consuming to tear down the axle and replace the individual joint, and there’s always a slight risk that it doesn’t get put back together properly, or that contamination gets into the new boot/joint before it is sealed up. For these reasons, most mechanics will just replace the entire axle assembly - these come preassembled with a CV joint/boot on each end, and are very simple to replace in most cases (i.e., pull out old axle and push in new axle). However, the cost of this part is significantly higher than the individual CV joint, so it normally ends up to be about the same total expense. However, in the latter case, you’re getting an entirely new (or professionally rebuilt) axle, so most people go this route.

It really is just that the cost to get to the boot is high in terms of labor. It can easily be 140$ of labor to disassemble the wheel down to the knuckle and access the outer boot. The two part crimp on boots fail due to being unbalanced they shake apart. Unless the car has been parked for 10 years the rubber wear is similar to the wear on the bearings. If you tear down at 140$ a 60-100 p rebuilt axle is not a bad deal given at least 60k in life.
I used to do these on much older cars with rear drive. When you get to the front wheel drive it is quite a bit more work. Plus Are you really sure it is the outer cv and not the inner? May be a mistake causes the whole tear down again. The inner boot is just as old as the cracked outer boot, it just was not cracked TODAY.

One thing that I did not see mentioned in addition to the hard work needed to access the boot is that you will need a front end alignment or in the case of a BMW, possibly a rear wheel alignment as vital suspension parts need to be disconnected.

I have never had trouble with CV boots on GM cars in spite of driving some of them to ripe old ages. On the other hand, my VW has needed at least two boots and I have recently noted that an inner boot has developed cracks that may eventually open up so I now have time to get mentally prepared to rip it apart again to replace the boot. Possibly the Germans do not use a durable rubber compound for boots.

Something similar happened to a BMW motorcycle that I owned. The air tubes from the air filter to the carburetors had a sharp right angle bend that was completed with a rubber sleeve. The rubber sleeves cracked after a few years and I had to buy new ones.

Another German rubber compound problem involved the first VW Rabbits. They developed an oil burning problem that was due to failed rubber valve stem seals. They sat on the problem for years before VW finally admitted to an engineering defect and fixed it.

CV axles and their protective boots have ALWAYS been a design compromise…It’s an area where manufacturers can save a few bucks on materials and they obviously do that…They could make boot material that would last forever if they wanted to, but THE ENTIRE CAR was designed to last something LESS than forever…What also must be improved is protecting the boots from debris impacts on the highway…At 75 MPH, it doesn’t take much to tear open a CV boot…

I’m SURE they could design a half-shaft with no rubber boots at all, a completely sealed drive system. But it would probably cost 3 times as much money to manufacture. Instead, they will put that money into the GPS,and DVD player, the rear view camera, heated leather, stuff that works in the Showroom…Cars are designed and built from the drivers seating position outwards…The running gear is almost generic…

Caddyman really hit on the problem, has any new car buyer ever asked the salesman how long will the CV boots last? No one does this. When people are shopping for a car, they are only interested in what they see, for the most part.

Sometimes a vehicle comes under fire for reliability in general, as American cars did for so many years. Manufacturers had to respond by making more reliable vehicles, in general. People began to notice that timing belts were an issue when the general population of new car buyers started keeping their cars for more than three years. Now timing chains are more popular, even though a timing belt could be made to last just as long and would be cheaper.

It does seem that CV joint boots are lasting longer than they used to. I remember having to change them about every 4 to 5 years, now it seems like 10 years is the new normal for them. It is just a matter of the type of rubber used. Urethane rubber would last much longer than the buna or latex rubbers often used. Silicone rubber would probably last the life of the vehicle and then some. BTW, I don’t think I have ever seen a boot split from road debris, the lower control arm and steering knuckle pretty much protects them from flying debris. They split from the rubber aging.

When consumers start asking the question, the manufacturers will respond. But keep in mind, if a long lasting boot costs say a dollar more, at 4 per vehicle, that $4 per vehicle. Now multiply that by 5 million vehicles that use these boots in their drivetrain, thats $20 million. If no one is asking the question, then that is not considered added value, only added cost.

If people are asking the question and the manufacturer figures out that advertising long life boots will add more than the $4 per vehicle in added value, then you will see longer lasting boots.

There’s another problem or tow with the issue of asking how long a CV boot will last.
One is how well articulated an answer would be from a salesman and at what point does a customer stop questioning why a car maker did this, that, or the other.

If that extra cost per improved boot was added onto the MSRP then that leads to adding the cost of a 1000 other improved things on also.
At some point a customer might be looking at a Chevy Malibu that has an MSRP of 75 grand.

I’m in total agreement about emphasis being on moving them off of the showroom floor. The only thing the car maker cares about is that the car suffers no CV boot problems during the warranty period…

The only thing the car maker cares about is that the car suffers no CV boot problems during the warranty period..

Thats not completely true, the car manufacturer cares about what the dealer has problems with. The dealers in turn only care about issues that arise with the original customer, the new car buyer. If the new car buyer is not happy, they will not be a repeat customer, and if they are not a repeat customer, then the dealer can’t buy as many new vehicles for their lot.

No one cares about the used car buyer. If a used car needs a new timing belt or CV joint boots, that is not a problem to the dealer or the manufacturer. But when the average new car buyer starts keeping their vehicles longer and these things start to affect them, eventually this feeds back to the manufacturer and things start to get fixed.

As new car buyers began keeping their cars longer, you started seeing timing belts go from 4 year to 7 years change intervals and dealers offering better deals on replacement packages than the independent mechanics. It does seem to me that CV joint boots are lasting longer now too, about 10 years vs. the 5 years I used to get.

Timing belts and CV joint boots have always been the real big ticket items on small FWD cars since they came out. I don’t think there are a 1000 other items, although Honda should really re-engineer their heater control valve too.

I dynno guys. If a 22" diameter wheel goes 100,000 miles, it turns the axle 5,280 x (100,000/69) or 7,652,173 times (that’s 7.6 Million!). That is a whole lot of flexing for any polymer to survive. I’m unaware of any material or design that would allow the boot’s convoliutions to last forever. Frankly, I think the current design and material is pretty darn good.

Good luck expecting your questions to go any further than the salesperson who is going to blow off your inquiry the minute you disappear from view. It’s not like they have an established communication channel for customer inquiries anyway. The last vehicle I bought, I asked if it had a timing chain or belt. I already knew the answer of course, just testing his familiarity with the product. You guessed right if your answer was “a deer in the headlights stare followed by GEE, I DON’T KNOW. Why do you ask?”. What are the CV boots made out of and how long will they last?? Good luck in that quest…

There is a company out there that claims to make a “forever” boot. I don’t know what they’re made of. Factors as important as the elastomer used are the number and diameters of the convolutions, the “normal” amount of articulation in the joints, and the total articulation experienced by the joints. Just the material alone is not enough data to make any assumptions whatsoever.

In short, an inner boot in an assembly that has no articulation in it’s static angle, and little total range in the suspension travel, will last indefinitely. An outer boot, that has to bend much more and much more often, won’t. And if it’s poorly designed, with too few convolutions or too smal a diameter, it’s unlikely to last long. Even if the material is the same.

It does not mean much in this case, but there is a way of eliminating the boots.

I had a 196? Sunbeam Imp. It used a block of rubber, no moving parts. (however some did stretch.) They never caused me any problems. I can’t remember how many miles I put on it, but it was quite a few.

the same moutainbike

“That is a whole lot of flexing for any polymer to survive. I’m unaware of any material or design that would allow the boot’s convoliutions to last forever. Frankly, I think the current design and material is pretty darn good.”

Materials do make a difference, flexing less so. The boots on our 97 Honda split at about 10 years and around 150k miles where my Saturn is just now 10 years old and has 254k miles. So far the boots haven’t split on the Saturn, but I expect it any time now. It seems to be due to age more than miles.

FYI, the boots on my 79 Dodge Colt lasted about 4 years, they lasted about 5 years on my 90 Colt and my daughters 93 Ford Aspire. It does seem like the newer vehicles are using better materials, but I think they could do even better.

"I had a 196? Sunbeam Imp. It used a block of rubber, no moving parts. (however some did stretch.) They never caused me any problems. I can’t remember how many miles I put on it, but it was quite a few. "

The ‘Wheeler Dealers’ TV show did a repair job on an old Lotus Elan (I think), it had that style of joint in the rear independent suspension. One was shot, so they replaced both sides with a newly-designed CV joint-based axle. Had to handle a bit more hp than an Imp, I’d imagine.

Heat and things of that nature also contribute to shorter boot life. Using Subaru for an example, the front boots may fail but the rear ones seldom do.

The rear boots on my old Lincoln and current Lincoln also still look fine at 15+ years of age and the Merkur still has the original boots in good shape at the ripe old age of 25 years.

Dorman sells both “standard” vulcanized rubber and silicone rubber replacement boots. Silicone isn’t affected by oxygen, ozone or heat as much as other rubbers and so they stay supple and last far longer. Some car mfrs might be using silicone and others cheaping out. Personally, I’ve only had one car where a boot cracked (both failed on this particular car). Perhaps the cooler climate is a big factor (or just lucky- maybe go buy megabucks ticket today???)…

Why exactly are CV boots such a common (and costly) repair item?

I have had the same experience as Wha Who? who says, “I have never had trouble with CV boots on GM cars in spite of driving some of them to ripe old ages.” Also, that’s been my experience with all my Chrysler vehicles. I’m talking millions of miles of driving, here.

However, we replaced many split open CV boots on foreign cars when I worked for VW/Mazda dealers.

To me, I don’t consider CV boot replacements common. I think it depends on what you drive.

We sold CV boot kits that were designed to open up and fit over the joint/axle without having to remove the axle. They were quite popular. Do they still make and sell these things ?

CSA

"We sold CV boot kits that were designed to open up and fit over the joint/axle without having to remove the axle. "

They’re called “split boots”.
Still around, but the presence of one was cause for a car to fail Wash. DC safety inspection.
I used one once as a temporary fix until I could put a proper boot on.

Check out these “split boots” made from saran wrap and ziplock freezer bags. Scan down about half way.

http://www.tercel4wd.com/viewtopic.php?f=4&t=6029