Monday, June 23, 2014

How to replace pivot bearings in a Santa Cruz Tallboy 2 Carbon

It's been a year since I got my Tallboy 2 Carbon, and a midseason tear-down a few weeks ago revealed the need to overhaul the pivot bearings. The 2014 model uses eight 7900 bearings: four with rubber seals in the upper pivot, and four with metal seals on one side only, in the VPP linkage. Although six of these bearings looked mint (nice clean grease), the top two bearings in the upper pivot had rusted out and one was completely seized. So no more riding until at least the two rusty bearings were replaced.

One of the details that attracted me to Santa Cruz in the first place was their attention to pivot design. Indeed, the VPP incorporates grease nipples to allow both sets of lower bearings to be flushed out with clean grease. The design works really well, but it can't overcome basic wear caused by hammering little metal spheres into tiny races. Over time, you'll get notchy pivots, which is exactly what I had in all locations. Notchy bearings makes it hard to adjust your pivot axles for that sweet spot between fluid smooth rotation and no side-to-side play. It was time to replace all bearings.

Santa Cruz offers a helpful overhaul guide and even sells replacement parts at a good price. In fact, replacement bearings are free, but you have to mail back your old ones. I ordered the Santa Cruz extraction tool (you only need the 7900 tool for the Tallboy 2), the bearing press, and a full set of bearings. Everything arrived two weeks later and I set to work. In retrospect, ordering new pivots with bearings installed may have been the cheaper option. Read on to avoid the frustration I faced!

First of all, these are the hardest bearings I've had to replace in all manner of vehicles and machinery. Although merely a press-fit, they are so tight they remind me of a certain obsolete submarine hull penetrator design adopted from the Trident missile program. To install the thing, you needed to soak it in liquid hydrogen. The metal absorbs the hydrogen and expands, allowing the parts to be slipped together. The hydrogen evaporates and the metal shrinks, creating an almost-welded level of watertight bond between the components. Clearly Santa Cruz has adopted this technology, because three hours of gentle and then increasingly berserk whacking with a hammer and the Santa Cruz tool did nothing except punch out the inner race. I was being mocked by a piddly bearing! By the end I had a pile of bearing carnage: balls, seals, races--all in a greasy pile.


The guide mentions that "some bearings may be hard to remove..." No kidding. I only succeeded in punching out the centre race, and then only in the four upper pivot bearings, with the Santa Cruz extractor tool. After that, the tool was pretty much worn out (or just badly designed), because there wasn't enough of a purchase on the back side of the outer races in the VPP linkage for the tool to grab.

Basically, the extractor tool is a waste of money. You can't even use a drift to punch out the bearings from behind, because the way the races are seated, there's no outer race visible from behind. Too bad there isn't centering spacer tube like in a few motorbikes I've fixed. Then you can tap from one side to extract a bearing, slide out the spacer, and tap out the other race. Even better would be a needle bearing design for high-impact locations like the top pivot. This is something I'd love to see on mountain bikes. Even bike shops hate replacing pivot bearings because it's such a pain in the ass on most bikes and you can't charge enough for the the hassle. My Santa Cruz dealer said there was a month-long wait to even book an appointment, and then would charge by the hour. This overhaul would've cost around $200-300 given the difficulty.

In this pic you can see the little Santa Cruz extractor and punch in the middle. The press is above. Compare that with the extractor tool below--the real solution.


While a blind bearing extractor is not cheap at $150, compared to paying my local bike shop it was a decent investment. The extractor uses a hardened steel collet that wedges with a threaded piece into the bearing area of the outer race. It doesn't spring out like the Santa Cruz tool. An integrated slide hammer allows you to tap out the race without risking damage to the pivot itself, because you're hammering away from the pivot. With the Santa Cruz tool,  you have to hammer towards the pivot. One slip and you can hit the pivot (or your finger) and damage something.


Installing the new bearings is fairly simple with the threaded press tool, but inevitably one bearing will go in slightly askew and it's hard to straighten. I recommend using an arbor press to push the bearings in square. Each time you press in a new bearing, you stretch the forged linkage slightly and over time it'll loosen up. Then you'll need a Loctite product to bond your bearings in, or have to replace the pivot altogether.

After all this hassle, pressing in the VPP bearings using the threaded tool resulted in a bit of a notchy feeling when I was done. Crap! For my last bike, I had machined a set of presses that pushed on the outer race of the bearing (rather than the centre) to avoid this problem. However, the Santa Cruz stock bearings don't seem to be well designed for this (in fact, some of the seal edges had snapped off during removal), so I'm going to look for some better quality after-market replacements (79002RS) with double seals and a bigger edge on the outer race, and make a press. I've never had these problems with any other bearings I've replaced, even cheaper Chinese bearings when the SKF or FAG models are way out of budget. I've also never had any other bearings blow apart just from tapping them in the centre race.

Update: Having used the blind puller for a while now, it's not grabbing the outer race as well as it used to. I'm looking for a better solution, such as a collet that fits better than the sizes included in the kit. I've also ordered a second set of pivots with bearings pre-installed. Now I can just swap pivots and get back riding quickly, and replace the worn bearings in the other pivots at my leisure.

When reinstalling the pivot axles, Santa Cruz specs tightening them to 35 inch-pounds. I find this is just a bit too tight when using my torque wrench (assuming it's still calibrated) and back them off about 1/8 to 1/4 turn. It's important they're snug but not tight, since the bearings are a radial design that requires preloading just like a headset. Too tight and they grind. When re-installing the centre lock bolts, Santa Cruz recommends 100 inch-pounds of torque. That's actually a lot of force; I just put a dollop of Loctite blue on the end and give them a firm torque by hand. Here's an official vid of the procedure.

To sum up:

1. Use a blind bearing extractor (collet style) to remove your pivot bearings. This reduces the risk of damaging your pivots and saves hours of frustration with the Santa Cruz extractor. The kit I bought is a universal Chinese set you can get from any budget tool supplier.
2. Use an arbor press (if available) to install new bearings. Or ask a machine shop to press them in for you.
3. Use a press that pushes on the outside race rather than the centre race (as with the Santa Cruz threaded press).
4. While Santa Cruz will replace your pivot bearings for free, you can get much better aftermarket bearings (e.g. 2RS for the upper pivots) for not much money. All bearings will wear out from constant impacts over time, but at least the 2RS will resist water ingress better. And all but the cheapest bearings are more likely to come out in one piece when pressing only on the centre race.
5. Consider buying the replacement pivots with bearings preinstalled. Santa Cruz offers these parts at a surprisingly good price. Then you can just swap out pivots and take your time to replace the alternate set of bearings at your leisure. I think I may go this way in the future, so I can spend more time riding and less time waiting for parts.
6. Tighten pivot axles to 35 in-lbs, lock bolts to 100 in-lbs.

Thanks to Joe at Santa Cruz who patiently answered my tech questions.

9 comments:

  1. Thanks, this is very helpful. I'm about to do the same with my identical bike after 6,000km. I agree with your comments about sealing and will look for 79002RS here in Tanzania. In the mean time I have the SC bearing kit but no blind puller. What do you think about using an M6 wall bolt? And what do you think about heating the top link first (boiling water) to loosen the bearings?

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  2. Hi John: Sorry for the late reply--didn't see this until now!

    The trouble with using a threaded extraction method (including what you suggest) is you need to be able to keep pulling on the bearing once it rises above the press-in cavity. Sometimes you can rig a large socket over the hole so you can pull the bearing into it (with the threaded puller passing through the socket hole), but there's a high risk of slippage.

    As for heating, I've never found that boiling water adds enough heat to create enough useful expansion.

    Applying force is OK as long as it's perpendicular to the bearing axis. Any off-axis force on extraction or installation risks ovalizing the bearing or the mount. Over time things will loosen up a bit and become easier to install. By the time they're too loose, it's probably necessary to replace the rest of the bike as well! Especially if you're getting 6,000km out of a set of bearings. Jealous.

    PS: Send pics of where you ride and I'll post them.

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  3. Well I did the top link so far... one out of 4 bearings came out complete with the wall bolt method. The rest collapsed. A large wall bolt didn't work on the outer race. In the end I found a nut of the right diameter, sawed a slot in it, compressed it into the outer race, screwed in the bolt from the back side to expand it again, hammered it out over an appropriate socket and it worked. About 3hours! The pivots are a bit worn in places, I suspect because of stiff bearings or over tightening the pivots. It seems to be quite tricky to get the pivots tight enough that there is no play or flex in the back end but not so tight that it binds the bearings. I am experimenting but have no answer here.

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  4. And I am loving this bike.Used for epic rides and stage racing. About to hit 7,000km
    Almost exactly the same set up as you, XT 2x10 (clutch still working), Hope/Stans Crest wheels, RS SID100mm and some ebay XTR brakes with 203/180 rotors, all v good.
    Steep mountain here, not brave enough to change to 1x10 yet!

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  5. sorry, no idea how to send you a photo!

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  6. Sounds like an epic bearing change! The blind puller really is helpful. Also, just installed bearings with an arbor press and it eliminates frustration on that step as well. Send your feedback to Santa Cruz. They are accessible and responsive, and we're all aiming for the same goal of better riding.

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  7. Wish I'd read this piece first but I wasn't anticipating a battle. Anyway, for what it's worth I substituted the drive pin with a3/8" brick punch to break the outer bearing free. It spread the jaws tightly into the outer bearing wall. I also used a rubber mallet because I knew I was going to have to take a big swing at it and I didn't want to risk damaging the link any more than I already was.
    Th

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  8. PS. Thanks for the piece. I hope my two cents helps some other frustrated SC owner.

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  9. You're welcome! There's gotta be a better way for these. Noticing some creak in my lower link and I just replaced the bearings this spring. Going to order a replacement link with pre-installed bearings this time... hopefully save some effort.

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