GCN Tech Clinic: Drivetrain lube, Shimano vs SRAM, and leaky tubeless

Alex Paton and Ollie Bridgewood are back once again in the GCN Tech Clinic to shine some light on the cycling and tech-related questions that you are dying to find answers to.

This week, the pair take a look at bottom bracket compatibility, drivetrain lube, and whether you should be filling your tyres with nitrogen.

• Read more: GCN Tech Clinic: Numb hands, swapping tyres, and winter speeds

When freewheeling in my hardest gear, my chain comes off the cassette. What can I do to stop this?

To solve this, you will need to carry about an inspection of your drivetrain. If your chain is loose it will need to be shortened to remove any slack in the system.

To find out if you need to do this, put the bike into the hardest gear and have a look at the chain tension. If the chain is sagging between the derailleur and the chainring then it most certainly needs to be shortened.

When doing this, it is important to check that the chain is still long enough for you to get in to the easiest gear without the derailleur being put under any excessive strain.

What grease do I need to use when fitting a bottom bracket to an aluminium frame?

For this application, as with almost everything on a bike, a standard bike-specific assembly grease will be more than appropriate for the job. The only exception to this rule is when you are clamping a carbon seatpost or when servicing a freehub.

If you are looking for more advice and help when it comes to bike-related maintenance make sure you check out our dedicated how-to page on the GCN website.

What is the process for applying and reapplying a dip on wax chain lube?

We have taken a deeper dive into this subject with Silca CEO Josh Poertner in the past. However, if you are riding around in dusty and dry conditions, using a drip-on emulsified wax lube will last longer and outperform a generic dry lube. If you do decide to use a drip-on wax lube, the first application needs to be done on a clean, degreased chain.

After the first application, you can then move over to a top-up process. When the chain begins to get noisy, give it a wipe over with a microfibre cloth and then simply reapply the drip-on wax lube.

• Read more: Silca CEO shares his secrets on the best ways to wax your chain

When changing between Shimano and SRAM drivetrains are there any third parties that make bottom brackets and freehub bodies that fit both?

There may well be brands that offer this. However we would not advise going for these solutions. As far as freehub bodies are concerned, 11-speed Shimano and SRAM both use a HG body design, it is only for 12-speed systems that the brands went their different ways with Micro Spline and XD.

We would recommend that you fit the correct freehub body and corresponding cassette to the drivetrain you are using for optimum shifting. In regards to bottom brackets, you can use a different crankset from a third party provider that fits your preferred bottom bracket type.

Should I use indoor-specific training tyres on rollers?

Indoor trainer tyres, which reduce noise and are hard-wearing, are used to preserve your expensive road tyres when indoor training. This is because for wheel-on turbo trainers, the clamping force puts a lot of pressure on the tyre.

This is less the case on rollers as it resembles more closely the real-world forces on the tyres. If you are using a set of rollers as your indoor training set-up, then using some old tyres that are past their best can be a great way of getting every last kilometre out of them and saves the need for spending money on dedicated indoor tyres.

• Read more: Which Wahoo smart trainer is best for you?

Would nitrogen in tubeless tyres reduce leaking due to sidewall porosity?

We have taken a look at a similar question to this before in the Tech Clinic, with the original question stemming from motorsport where nitrogen use in tyres is common. Nitrogen molecules are four times bigger than oxygen, meaning that a tyre filled with it wouldn’t leak as fast because it would be harder for the larger molecules to escape. The issue with this rationale is that air is already 78% nitrogen so using pure nitrogen wouldn’t have a massive benefit.

The latest batch of tubeless tyres and sealants are also far less susceptible to this issue than when the technology was brand new. Almost all tubeless systems hold air without noticeable leaking through the side wall. In fact, a latex inner tube will leak at a far higher rate than the latest tubeless systems.

If you have any tech-related questions that you need answering, head over to this week’s Tech Clinic video on the GCN Tech YouTube channel and add your question to the comments along with #ASKGCNTECH. Or leave your question in the comments below.