Optimal tyre pressure, noisy chains and inner tube repairs: GCN Tech Clinic

The dynamic duo are back in the studio to shine some light on more of your bike tech and maintenance-related questions. Along with the obligatory waxed chain question they also look at minimum tyre pressures and e-bike regulations.

How many times can you repair an inner tube?

So long as the patches you are using cover the puncture and the tube has not perished an inner tube can be repaired countless times. You should only need to replace the inner tube rather than repair it if the patches start overlapping or if a repair patch gets punctured.

Is it possible to get an e-cargo bike that will allow me to keep up with fast-moving traffic?

Although high-speed e-bikes exist, as do retro-fitted modifications that could allow an e-bike to travel at speeds of around 60km/h, most countries have regulations that limit the maximum speeds of e-bikes. In the UK and most of the EU, e-bikes of any description cannot provide assistance above 25km/h. Unless you live somewhere that has no rules governing the use of e-bikes it is unlikely that what you are looking for will be achievable without breaking the law.

An alternative solution would be to look at either travelling at a different time of day when the road is considerably quieter or looking to take a different route altogether. It might add a few kilometres to the journey but feeling safe and confident out on the road is worth a few more minutes of journey time.

What is the best type of laundry detergent to use to keep kit smelling fresh?

The most important thing to look out for with detergent specifically used with sports gear is that it is non-bio. Biological detergents can stick to the fibres in the material and trap the smell on the garment. Biological detergents can also harm the fabrics causing them to break down and lose their colour.

In general, cycling clothing should be treated the same as delicates and washed at a low temperature and on a relatively low spin cycle. If your kit does suffer from retaining the smell of hard workouts, an antibacterial washing fluid can be added as a prewash to help break down the odour-causing bacteria.

Why don’t GPS head units have a bell function incorporated?

Using a bell can be a polite way of alerting other road users and pedestrians of your presence. The unfortunate reality is that for the most part bells are not all that aesthetically pleasing and on bikes with aero profile bars not a viable option. Some brands do make exquisite bells however these are often costly and not worth the investment for a lot of riders.

On the surface it would make sense for head unit manufacturers to add a bell function, however this would not be as easy as a simple software update. Head units are not equipped with the kind of hardware required to produce a sound loud enough to act as a bell — the speakers that generate the key tones are not powerful enough.

Should I fit a harder ratio cassette to my bike whilst training for an event and then use a wider ratio cassette come race day?

The theory behind this is that training on harder gears will force you to work harder and then when the easier gearing is fitted for the event there is a more noticeable benefit to it. The issue with this, especially for an event with a lot of climbing, is that riding harder gears will change your pedalling dynamics and not transfer well to easier gears.

Riding with inadequate gearing that results in you deviating away from your optimal cadence will develop a high-torque pedal stroke if you spend a lot of time riding outside of your preferred cadence come race day it might be hard to reap the benefits of being able to spin in an easier gear. As a general rule of thumb, we would always suggest that you train on the gear you are going to use for the event.

What should I do if my calculated optimal tyre pressure is lower than the lower limit of the tyre?

As much as online tyre pressure calculators can be a real help in determining the best set-up for you they should always be taken with a pinch of salt. Always adhere to the specified limits of a wheel or tyre, even if that means going above the recommendations of a calculator. If your tyre says a minimum pressure of 50psi but a calculator has said you should use 45psi, we'd suggest that you stick to the 50psi limit.

This is the same for hookless systems. It is possible that an online tyre pressure calculator might specify an optimum pressure over the ETRTO safe maximum pressure of 73psi. In this case, you should not exceed this 73psi limit. Instead, either increase the width of your tyres to compensate or switch to wheels with a hooked rim.

When trying to dial in any optimisation on the bike it is always important to stick to manufacturer guidelines over of calculated recommendations.

Why do we not see mirrors being used more on road bikes?

Mirrors on bikes are a great way of keeping tabs on what is going on behind you. Although there are plenty of products on the market for riders that do want to use one they have never really taken off in popularity. Most riders are capable of turning their head over their shoulder to check what is behind them from time to time. For riders with reduced neck mobility, mirrors can be a great solution but for the added hassle of fitting a mirror to your bike, most riders simply don’t see the need.

Cyclist are also a particular bunch, and mirrors are not in keeping with the aesthetic of a beautiful race bike. Whilst there's plenty of options for those of us who do want mirrors, most of us would rather turn our head than spoil the clean, symetrical look of our handlebars.

How can I stop my freshly waxed chain from making a noise?

If you have freshly waxed your chain and it is making a lot of noise when it has been fitted to the bike there are a few different things that could be the cause.

Firstly, if you are new to the world of chain wax, perfecting the process and removing the chain at the right time to get the best wax coverage possible can take a few attempts. There is a sweet spot when it comes to removing the chain from the wax bath. If the wax gets too hot it becomes too fluid and does not properly adhere to the chain. The optimal time to remove the chain from the wax is when a slight skin is present on the surface of the wax. Any hotter than this and the wax will not coat the chain properly resulting in it being noisy.

Secondly, waxed chains have a break-in period before they settle down and go silent. On an indoor trainer this can typically take around 10-15 minutes however if you decide to break your chain in on a ride outside the ambient temperature will have a massive impact on how long it takes. The colder the conditions are the longer this will take.

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.