GCN Tech Clinic: TPU tubes, stem angles, and matte maintenance

Alex and Ollie are coming to us from Mallorca this week as they aim to resolve more of your cycling questions

Clock17:41, Wednesday 18th October 2023

This week, Alex Paton and Ollie Bridgewood are out in sunny Mallorca filming some great content that will be hitting the channel over the coming weeks. That didn’t stop them from sitting down and diving into the tech questions that you need answers to. Here is this week's tech clinic.

Is there anything you can do to protect matte-finish frames from scratches?

Matte frames are notorious for scratching easily, but there are a few preventative measures you can take to keep your frame looking in tip-top, box-fresh condition.

Firstly, look at how you are cleaning your bike. If you are immediately going in with sponges and brushes, any dirt and debris that gets dislodged will then abrade the frame leaving some scratching. Washing your bike down with a hose first to get the grit and dirt off will reduce the contaminants that could scratch the paint.

Much like you would with a car, you can also apply some bike-specific finishing wax. This will not only buff over any surface scratches and restore the matte finish to the naked eye, but it will reduce the amount of dirt and grit that sticks to the frame. This should only be done on a clean frame, with a perfectly clean cloth so as to not risk any scratches through the process.

Can you use TPU inner tubes with rim brakes?

This depends solely on the brand of TPU tubes you are looking to use. Some brands do specify that they are not suitable for use with rim brakes. This isn’t because of some disc-brake conspiracy, but rather that the material is more susceptible to the heat build up experienced from a rim brake. The best solution is to check with individual manufacturers and go for one that explicitly states that it is for use with rim brakes.

Can I fill a butyl inner tube with tubeless sealant?

Although using tubeless sealant in an inner tube will offer some level of increased puncture protection, this will only be from typical punctures from thorns or debris penetrating the tyre and tube, and not from pinch flats. A pinch flat will create two large tears in the inner tube that tubeless sealant will not be able to plug.

The best solution for avoiding pinch flats is to either increase your tyre pressure slightly, or to fit a larger volume tyre. Although there is some benefit to using sealant in an inner tube, it can be messy and a lot of faff. Generally, moving to a tubeless set-up will give you the puncture performance you are looking for.

Is it normal that a more aggressive position feels more comfortable?

Experiencing pain in your lower back when riding a bike with a more relaxed position is something riders can experience. As the position becomes more upright, more of your body weight will be distributed towards the rear of the bike, putting pressure on your spine. In a more aggressive low position, you distribute your weight differently, including putting less weight through your sit bones.

If this aggressive low position is something that you have become accustomed to, your body will have adapted to it, with your muscles used to it. When you rotate to a more upright position, your muscles and body mechanics are not adjusted and will find it more stressful, which could lead to pain on the bike.

What is the difference between a -6 and -17 degree stem and why would I choose one over the other?

Let's get the obvious answer out of the way first… 11 degrees. With that out of the way, we would almost always recommend a -6 degree stem here at GCN in all but the most extreme of cases.

Aggressive negative stems came into fashion largely as compensators to make a bike fit. Some bike brands in the past have produced race bikes with relatively high front ends, in part to make them suited to the consumer rather than the racer. Having a high front end can make getting a super aggressive aero position difficult, so to compensate for this a -17 degree stem will put the bars at a lower height.

Unless you really cannot dial in a bike fit that feels correct for you, going for a typical -6 degree stem will give you more choice as well as a more comfortable fit, that will allow for better power development.

How can I get my bike ready for winter?

The first thing you can do to keep your bike protected from the worst of the winter weather and all of the salt that ends up littering the roads is to fit a set of full-length mudguards. In fact we have actually just done a guide on exactly this topic, so if you want a really comprehensive answer, check out the best ways to get your bike ready for winter.

If you want to thoroughly winter-proof your bike, spend some time cleaning and greasing the bearings in your bike with a thicker grease, like marine grease, which will act as an effective barrier to the elements. Also, always clean your bike immediately after each ride so that any corrosive solutions are not left on the frame or components, eating them away.

What is the best way to clean my drivetrain before I wax my chain?

Most importantly of all, make sure that whatever you are using to clean the chain doesn’t leave any residue behind. This is because for chain wax to work at its best, it needs to have complete and undisturbed coverage of the chain. Any cleaning products that leave a residue will compromise the adhesion between the wax and the chain, resulting in a decrease in longevity.

A good practice is to start with warm soapy water to get rid of the worst of the dirt and grime, using a brush and sponge to work the soapy solution into the hard-to-reach areas. When you are looking to clean the chain of any past lubricants, the best approach is to use an organic solvent, so things such as turpentine or acetone or isopropyl alcohol would all work as a solvent to remove organic compounds.

If you have any tech related questions that you have got to find answers to, head over to this week’s Tech Clinic video over on the GCN Tech YouTube channel and add your question to the comments along with #ASKGCNTECH.

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