GCN Tech Clinic: Deflating tyres, carbon components and cycling clothes

We find ourselves back in the Tech Clinic where Ollie Bridgewood and Alex Paton are looking at solving some of cycling’s great maintenance mysteries. This week we look at how to get the right size cycling clothing, what to look for in a set of budget carbon wheels and power meter discrepancies.

What is the easiest way to remove frame stickers without damaging the frame?

Sometimes it can be nice to update your bike and give it a new lease of life with some fresh graphics. Naturally, the first step in the process would be to remove the existing graphics. However, it is important that you go about doing this carefully so you don't damage your frame.

The first thing you need to work out is whether there's a clear coat over the top of the stickers, which some bike brands apply to protect the graphics from damage. This does make it an impossible task to remove them without going down the rabbit hole of sanding the frame back and then having to re-lacquer it after swapping over the graphics.

My Pirelli P-Zero tubular tyres go down over the course of 2-3 days, is this normal?

The exact tyres in question use a TPU innertube section that should hold air for longer than 2-3 days. If a system was using latex inner tubes then it would be more expected for the pressure within them to significantly decrease over the course of a few days.

If the air is leaking slowly and you cannot see any punctures to the surface of the tyre, the most common cause of pressure loss is that the valve or valve core is not tightened fully and a small amount of air is able to escape.

What am I looking for in a set of carbon wheels?

If you are looking to stray away from some of the more premium carbon wheel manufacturers in favour of a pair of Chinese carbon wheels there are a few things you can do to make sure you are getting a good quality set. Firstly, look at the build of the hubs, specifically the bearings that are fitted inside them and also the seals that are used to defend against water and dirt ingress.

An internal rim width of around 21mm is currently fairly standard in the industry giving you plenty of scope to fit wide rubber to the wheels depending on your frame's clearance. This is also a consideration if you are using rim brakes as the calliper design can struggle to accommodate tyres over 25mm in width. As far as your cassette compatibility is concerned you want to match the freehub body to the drivetrain you would be using, either Campagnolo or SRAM/Shimano HG for 11-speed cassettes or SRAM XD for SRAM 12-speed cassettes.

How is cycling clothing meant to fit, and how do I pick which size is right for me?

Ultimately this is a decision based on what feels right for you. Cycling-specific clothing is designed to fit closely to the body. Not only is this more aerodynamic, but it can also help with better temperature regulation and comfort as it is less likely that clothing will chafe.

With this being said, how closely fitting feels right for you is down to individual preference. Some clothing can be super tight fighting to offer an aero advantage whereas other styles can be a bit more relaxed. So long as the clothing is comfortable and meets your needs the exact fit of it is more of a preference than a science.

What can I do about data discrepancy between a crank-based power meter and an indoor trainer?

When you calibrate, or to give it its proper term 'zero offset' a power meter you are in essence zeroing the effect the weight of the power meter has on giving readings. This takes into consideration temperature as well, however, it is important to understand that this is not actually a calibration. If the power meter came out of the factory incorrectly calibrated, then every zero offset you carry out will be using this as a reference point. The unfortunate reality is that in this setting it is most likely that the crank-based power meter is over-reading.

With single-sided power meters much like a 4iiii or stages unit, you are open to a greater degree of error. This is because to get the rider's total power output it simply measures the power of the left leg and then doubles it. If you have any biomechanical asymmetries this can lead to over or under-reading your actual power output. The only solution to this issue is to fit a dual-sided or spider-based power meter that will measure your total output.

Why are my carbon wheels suffering from water ingress?

Some carbon fibre wheels including those from Zipp do not have drainage holes in the rims. This means that over time, especially through prolonged periods of cold and wet winter riding, water can work its way into the rim without an easy method of escape. Unfortunately, if your rims do not have a drainage hole the only way to get the water out is to remove the tyre and tube or tubeless valve.

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!