Posted on March 11 2020
Getting a nasty scratch on your fresh suspension's stanchion tubes can be very frustrating. And even worse, it often happens when we least expect it, like when your bike falls over in the wind at the local cafe, grinding it's silky smooth stanchions down a rock wall's edge, or just plain and simple - during a crash.
Either way, here's a little insight into what can happen as a result of scratched stanchions:
The Dust Seals:
The dust seals on your forks are designed to keep the oil in, and keep the dust out. With this in mind, any imperfection from either worn or scratched stanchions can quickly do damage to the dust seal, and it can be very difficult to see. The dust seals are not very good at sealing an 'im-perfect' surface, and whilst they may seal the oil in (with the help of gravity), when the surface is imperfect, they'll likely struggle to keep dust from getting in. Hence, many externally 'clean' looking forks with scratches down the stanchions that come in for service, have heavily caked dirt in the foam rings, instead of that silky smooth bath lubricant. This will likely lead to premature stanchion wear (ie, from dirt caked in the bushings), and an almost guaranteed loss of performance.
Bushings are coated with a specific high-grade teflon that is designed to work under extreme heat and force to consistently provide stiction free operation. FOX forks use 'hydrodynamic' lubrication. This system basically force feeds oil into the tall, slotted bushings during the compression stroke. When the fork cycles up and down, the oil is trapped between bushings, upper tubes and seals.
However, bushings can also be held responsible (along with the dust seals) to keep the stanchions clean and operating smoothly, hence why routine maintenance helps to keep them clean and clear of contamination. Ie, when the imperfect dust seals and foam rings are full of dirt, that contamination will sit on or in the bushing/s and will glide up and down the stanchion surface, likely causing further damage in the form of vertical score (wear) marks on the stanchion.
The other scenario is bushing damage. Instead of bushings simply wearing out, Bushings can also be damaged by a raised surface on the stanchion, mostly in the form of a rock strike or scratch like those pictured. The raise surface from the damage area, passes through the bushing during the fork's cycle, and damages the teflon surface of the bushing/s. Damaged bushings can lead to even more severe stanchion wear, as you can see in the pic below:
(Below) Damage to bushings as a result of a scratched stanchion:
(Below) Damage to stanchion as a result of a damaged bushing/scratched stanchion:
We have all seen it before, and whilst most people are concerned with oil loss and appearance, the issue can be far more substantial, and can cause major performance losses. Thankfully, at least with brands like Fox, Marzocchi and a few others, bushings can easily be replaced as part of a service, adding approximately $80 to a service if they're damaged, worn, or over-honed in some cases. Rockshox don't offer new bushings anymore, but a new lower leg (with fresh bushings installed from factory) is another option.
The 'band-aid' or 'short-term' solution:
Here's the 'grey area'. If the scratch on your stanchion is anywhere in the first 70% of your travel, then it's likely going to cause some issues, at some stage. If it's in the last 30%, then not as much as you'll generally spend less time in that area. The quick solution to effectively 'buy time', is to repair the area and reduce its severity to minimise any performance loss, and dust seal or bushing damage like above. Here's a few quick repair tips:
What you'll need:
- Steady hand x 1
- Very fine file
- 400 or more grit emery paper
- Isopropyl or similar alcohol based cleaner
- Clean microfibre cloth
- Anodised aluminium polish, such as 'Autosol'
1) Clean the area with Isopropyl.
2) Very carefully and lightly, file or sand down the scratch marks to reduce any raised surface.*
3) Clean with isopropyl when smooth
4) Using a clean microfibre cloth, polish using Autosol, or something similar.
5) Check the area to ensure there are no raised bumps or scratches.
*If it's a really deep scratch - Add some clear nail polish to your shopping list, and fill the area with an appropriate amount. Wait for it to dry, and continue from step 2.
The real solution - The solution WE recommend.
The best and only way to make it go away completely for the Fork's long term health, performanceand good looks, is to replace the CSU. The CSU (Crown Steerer Unit) and possibly the bushings will need to be replaced, both of which are major parts, and are commonly consumed here in the workshop and or sold online (excluding bushings). They are available for most suspension brands as a replacement part, and whilst it will certainly cost more for a new CSU, your fork will thank you for it and will pay you back with endless hours of unconditional love.
Scenario 1) If the fork has seen minimal or nouse since the damage occurred, then bushings may not need to be replaced. A new CSU like this below, will come in several styles to suit wheel size, axle spacing, model etc.
Scenario 2) If the fork has had a 'short term' repair, and has been ridden for some time with scratched stanchions, there is a chance that bushings may also need to be replaced.
New CSU's (example)
More info on CSU options here:
Q: Can just the one damaged stanchion of the fork be replaced?
A: In theory yes, however none of the big suspension brands offer single stanchion tubes for sale, and hence it's not generally an option. We do press fork stanchions in and out for various reasons in the workshop, and occasionally will have a match for a fork that needs a single stanchion replaced. However, this solution is rarely an available option thanks to the long list of varying stanchion tube lengths, internal bore diameters and sizes.
Q: Does a scratch on my stanchion void my forks factory warranty?
Q: Is there a long term solution, other than replacing the CSU?
Q: Can I purchase bushings from you to DIY install?
A: No, bushings require extensive tooling for installation and the 'bushing sizing' also involves extensive tooling and processes.
Got any further questions? Shoot us an email, or give us a call!