Pressure Washing Cassette, Chainrings, Chain

Question

I just took my road bike into the dealer for a tune-up, and told the mechanic that about every 4 months I have been applying Bontrager's degreaser followed by pressure washing the cassette, chainrings, and chain, and then applying Bontrager's chain lube and wiping off the excess. Firstly, he measured wear of the chain and said I need a new chain, and then replied that I should only use free flowing water from e.g. a garden hose to rinse off these items. Apparently, the force from pressure washing can force dirt/dust into the bearings - which is not recommended.

Since he recommended a Level-2 tune-up, I then asked if they'd disassemble the axles and bearings and inspect them, and he said no, but they'll assess bearing wear.

I am wondering if exacerbated bearing wear any by pressure washing(?)

[fyi - specifically, the bike is a 2021 Domane SL7 (Shimano electric) and the dealer is a TREK dealer].

Answer 1

I understand that knowing what needs servicing on a bike is tricky to pick up. It is plausible that you need a new chain. I know newer cyclists might be concerned, understandably, that the bike store's trying to upsell you, but you can actually wear a chain out pretty fast if you don't maintain it.

I'm not sure how often you apply lube, but if it is only once every 4 months, this is extremely unlikely to be enough. I tend to lubricate my chain weekly. If you wait until it starts to squeak (which means direct metal on metal contact without lubricant, which is bad), you'll also accelerate wear.

If you aim your pressure washer away from the bearings (in your bottom bracket and hubs especially), I don't think this is a major problem. It is actually not the best way to clean the chain.

At an absolute minimum, I'd leave the factory lubricant on it, wipe the surface with a rag every ride (aim is to reduce the amount of dirt on the chain), and add lube every week. Avoid Muc Off and White Lightning - if you prefer a detailed rationale, I'll add it later.

Since you have the resources and inclination to clean your chain periodically, that helps, maybe considerably! It's better to get an on-bike chain cleaner. Add some dilute degreaser and run the chain through it. You'll see the degreaser get black. All that was dirt that's inside the chain, particularly in the rollers, and it's accelerating the metal's wear process. If you feel able, you can get some re-usable quick links and a pair of master link pliers, remove your chain periodically, and shake it in a bottle with dilute degreaser. That's likely to get out even more dirt. It's also easier to do than you think, although I can understand the hesitation.

I would inspect bearing wear by just turning the bearings in your hubs and your crank (with the chain off). If worn, you will feel noticeable roughness. Your mechanic is likely to do the same. It's not necessary to disassemble anything to check this. As the mechanic said, it is definitely possible that if you face the bike sideways and spray water at the drivetrain, you'll push some of it past the seals, and you might push some of the bearing grease outside of the bearing.

Most bearings are cartridge bearings, which actually aren't designed to be disassembled. If worn, you'd replace them wholesale. It's not possible to say exactly how long they should last, but in general, decent quality original bottom brackets and hubs should be OK after 3 years, unless it was 3 years of a lot of use and pressure washing. For interest, you can get the seals off a cartridge bearing. If dirt intruded past the seals and contaminated the grease, it would accelerate bearing wear. The issue is that many seals, especially the full contact ones, aren't designed to be removed, and may actually be damaged on removal. And if you replace the grease, you've now got clean grease, but you still had worn bearings, plus your seals may now not fully protect the bearing. Plus you night need to extract the bearing and then press it back in. So, this isn't typically done unless the manufacturer specifically asks you to, and only a few high-end ones do. Cup and cone hubs, which aren't that common these days, are a different story, you do need to service them, but it's not terribly hard.

Answer 2

In my experience, a pressure washer will not "force" dirt and debris into the bearings, especially with a presoak using a degreaser. A pressure washer will either blast the crud away, or knock it loose and it will drip out.

That said, I do not use a pressure washer. I find that the pressure tends to displace and bypass grease and thus accelerate rust and corrosion. Consider that that's a bad enough problem from free-flowing rain.

For cleaning, I'm camp brush. I have the park tool brush sets and work between the cogs and chain rings with hot soapy water - and I recognize even this can ingress bearings and cause issues. But I also trust my ability to feel when bearings start to feel worn and I can repack grease and replace as needed. This is a regular maintenance issue.

For getting LBS service, you might opt for the one higher level tune, and ask for inspection report on the bearings.