GCN Tech clinic: Bike size, syncro shift & cheap Chinese products

This week in the clinic we also take a look at bike fit, Di2 and how best to store your bike for winter

Clock13:00, Wednesday 4th October 2023

Alex Paton and Ollie Bridgewood sit down in the tech studio this week to take a look at the questions keeping you up at night. From setting your gravel bike up correctly to fitting larger cassettes to your groupset, the boys have your back as always, providing you with everything you need to know.

Will riding the wrong size bike affect my performance on the correct size bike?

Riding a bike that is far from your optimum size will have an impact on your riding compared to a bike that fits you well. The main concern when riding a bike this size is that your likelihood of injury is far higher as you will have to contort your body into an unnatural position just to ride the bike.

Riding a bike that is the wrong size will also have an effect on your power development. If your saddle height is incorrect, your legs will have to compensate, putting a lot more stress through your knees and quads. This will have a knock-on effect when jumping on to a well-fitting bike, as your muscles will not be trained to be used effectively in this position.

Estimated figures on Strava from phone or head units are wildly different. Why is this?

Quite honestly, here at GCN we aren’t all that sure on the specifics behind why this might be happening. One potential reason could be that your phone might be syncing with a wearable device like a Whoop or a smartwatch that will give it more data to base its calculations from.

Ultimately, calculated data is always going to be fairly inaccurate, with too many variables that cannot be considered playing a factor. The only way to get reliable calorie or power data is to invest in a power meter on your bike.

Is it worth buying a cheaper Chinese carbon fibre bike?

There is a lot to be said for these emerging cheaper and lesser known Chinese brands, with some brands using comparable materials and technologies that you would expect from the more mainstream brands. Part of the reason some of these lesser known brands are offering bikes at what can appear like bargain prices is because they are looking to build their customer base and presence in the market.

Chinese carbon frames have always had a reputation for being unreliable, so today's brands are massively incentivised to produce good quality products and honour warranties. In the modern world we live in, where everyone is connected via the internet, brands cannot hide from poor performing products anymore.

With this being said, there are plenty of cheaper brands out there now that are fairly well-established with plenty of customers riding their bikes. It could be safest to stick to these rather than investing a large amount of money in a completely unknown brand.

How often does Di2 need charging and updating?

This will be different for everyone, as it is dependent on how often and how you ride your bike. If you ride in hilly areas and are constantly changing gears (especially at the front) you will find that you need to charge them more often than someone that lives somewhere flatter and shifts far less often.

Shimano has used a small LED indicator to show the charge status of the battery, and we charge our Di2 when the green indicator light starts to flash. Shimano Di2 uses a large concealed battery to power both the front and rear derailleurs meaning that you can get a longer battery life than the smaller batteries of a SRAM AXS system can offer, with around a month between charging cycles typical.

The need to update Di2 software is fairly infrequent, and can be systematically checked whenever you connect your phone to the bike to change a shift setting or if you are experiencing any problems with your Di2.

Should I set the fit of my gravel bike the same as my road bike?

Whilst you get used to the new bike, setting it up to mirror your road bike will give you a strong base position to get started. It will allow you to understand how the bike is different and how it handles, with any differences being easily attributed to the bike's geometry rather than just a change in position.

That being said, as you progress and find how the bike handles and how it works on the terrain that you are going to ride most, you can then go ahead and tweak the set-up to make it more suited to what you ride, with the most common alteration being to lift the cockpit a little and reduce the reach with a shorter stem. This will give you a more responsive front end and put you in a slightly taller position that works well for descending off road.

Should I remove tubeless sealant before storing my bike for a prolonged period of time?

Although it is not essential, we would strongly recommend that you do clean out your tyres of sealant before storing your bike for winter. Sealant can dry and if your bike is sitting stationary it will dry faster inside the tyre. When this happens it creates a lot of mess and can cause the tyre to get stuck to the rim or for the rim tape to end up peeling off with the tyre when it is removed.

Taking the time to remove any tyre sealant from inside the tyre with a specific tubeless sealant remover will keep your tyres and rims in good working order ready for when the riding season kicks off next year.

Depending on the manufacturer of your tubeless sealant, it is recommended that you replace the sealant every 3-6 months regardless of if the bike is being ridden or not. This is to prevent the sealant drying to the tyre and not operating as it should.

Do pros use syncro shift on 2x setups?

As a general rule in the world of pro cycling riders want to be in total control of their bikes, using a syncro shift feature removes that direct level of rider input that they are looking for so across the peloton it is not being used on road bikes. There is some small-scale use of the syncro shift function in the professional ranks on TT bikes, but it is on a case-by-case basis of what the rider prefers.

One of the notable features of syncro shift is that it can be customised in the Shimano e-tube app to lock out specific gears to prevent cross-chaining. Ollie uses this to lock out his two easiest gears at the back when he is in the big ring at the front. The system will automatically shift up until these gears where it will stop, preventing the chain line from becoming extreme and affecting performance.

Can I fit a larger 11-32 or 11-34 cassette without needing to change anything else on my drivetrain?

This unfortunately isn’t a blanket answer and it depends on the generation of your 11-speed groupset as older models have a shorter cage than the new versions. If you have a long cage rear derailleur fitting a 11-32 or an 11-34 will be possible without the need to replace it. However, if you have a short cage rear derailleur this will need changing to fit a bigger cassette.

Regardless of anything else, when changing the cassette, you will need to change the chain length to accommodate the new bigger sprockets as well as adjusting you b-tension screw on the rear derailleur as it will be sitting at a different relative position.

Have a tech question you need answering? 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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