GCN Tech Clinic: Slammed stems, quick links & charging Di2

It’s that time of week again when Alex and Ollie sit down and answer some of your burning questions

Clock16:10, Wednesday 20th September 2023

This week in the tech clinic Alex Paton and Ollie Bridgewood set out to answer the questions you desperately need answers to. From getting the right type of bike to fit you best, all the way through to asking if it's possible to clean your bike too much. We have you covered in this instalment.

Is it better to get an endurance bike with a slammed stem or a race bike with lots of spacers under the stem?

This is not at all a one-size-fits-all answer, however, there are a few considerations to take into account whilst making your decision. First of all, the biggest deciding factor will be the suitability of the bike as a whole, if you are looking for something that is comfortable for long days in the saddle an endurance bike is naturally going to tick the box, equally if you spend every Thursday evening bombing around a local crit circuit then a race bike is going to be more equipped to handle this.

If you still find yourself sitting on the fence, the big question is what determines ‘a lot of spacers’ to you? Running some spacers under the stem is normal and most bikes are designed to accommodate this up to around the 40mm region.

Once you start needing more than 50mm of spacers under the stem you can start to run into issues with the rigidity of the fork. This is because the effective lever that is the steerer tube is a lot longer and so can experience more flex, especially in sprints when you load the bike up. If you need an excessive amount of spacers to get the correct bike fit, then going for a more relaxed geometry endurance bike will be the better solution.

Does a smaller inner tube offer better puncture protection?

There have been a few comments under our recent 10 types of riders video claiming that running a slightly smaller inner tube than recommended can offer better puncture protection. Unfortunately, there isn’t any truth in this. A smaller tube will need to stretch more to fill the tyre cavity making the tube surface thinner than it should be. If anything, having a tube that is too small fitted will increase your risk of both pinch flats and punctures as the inner tube is under more stress.

The best thing you can do to give yourself better puncture protection is to run wider tyres so long as your frame will accept them, as these can be run at lower pressures and offer a larger surface area contact with the road. Alternatively, if your rims are appropriate, removing the tube altogether and running a tubeless setup will minimise your chances of puncturing even further.

Does connecting my Di2 to my head unit cause more battery drain?

This isn’t something that we have experienced ourselves here in the GCN office. Nonetheless, there are a few things you can try to remedy the battery issue. The first port of call would be to ensure that both the Di2 and head unit firmware are up to date, as software is rolled out there can be bugs in it that get ironed out in further updates. Using the Shimano e-tube app you can check and update your drivetrains software and the same will be applicable for your head unit.

The other thing that could be causing this issue is that the head unit battery has started to degrade. All head units will run off a Lithium Ion battery that has a lifespan normally rated in charge cycles, if your head unit is a few years old it could be that the battery is starting to lose performance. A good way to check this is to go for a ride with your Di2 disconnected from the head unit and see if the battery issue remains. If it does, you know that the issue is purely with the head unit and not with the Di2 connection.

This is a great question and something that anyone who has waxed their chain has probably faced at some point. Due to the very nature of adding a wax coating to a chain, the overall size of the chain does expand by a small amount, however, even this is enough to interfere with the fitment of the quick link.

The first bit of advice is to refrain from waxing the actual quick link itself, doing so will cover the pins in wax making them incredibly difficult to fit through the rollers.

The other bit of advice, if you are still struggling to fit the quick link, is to use something like the park tools pick to remove the wax from where the quick link interfaces with the main chain. This will allow for easier fitting and then you can apply a drip of wax to the area to ensure that the whole chain has an even wax coating.

GCN covers lots of road content and GMBN covers lots of mountain biking however, is there a channel for trekking and bike packing?

Here at GCN we try to appeal to every type of rider out there and although we do not have a dedicated channel to trekking or touring we do have content out there on just such exploits. We also have a mass of touring-related content on GCN+ including the ‘Slow cycling’ series and some amazing adventures such as riding across Iceland.

It is also worth mentioning that although a lot of content might not be targeted solely at trekking, a lot of the principles are relevant, for bike maintenance, how to ride more efficiently and how to fuel for a ride. It might take a bit of reading between the lines in some videos but there is plenty of carryover from our more road-based content to touring.

Can I over-clean my drivetrain components?

The short answer to this question is no. The long answer is a little bit more dependent on how you are cleaning your bike. Using bike-specific cleaning products and low-pressure water will have no negative impact on your components, so long as you also conduct a good after-wash routine where you lube the drivetrain with bike-specific products.

The issues arise if you use very strong solvents or degreasers to clean your bike, although they will do a great job of removing any dirt or grime, they will also remove any protective layers of grease from components. Although there are no issues with jet washing your bike, it is advised that a lower pressure washer is used and the jet is not pointed directly at sealed components like the bottom bracket or headset. If these are avoided you can clean your bike as often as you want to, without a worry about causing any harm.

Can Di2 be charged off a power bank or does it need mains power?

You can indeed charge up a Shimano Di2 system with a power bank, you just need to connect the tube cable to the power bank and away you go. So far as removing the battery for charging purposes is concerned, this is not possible. Shimano Di2 needs to be charged as a whole system rather than removing the battery as you can do with SRAM components.

Are wide tyres more suitable for rough roads and heavier riders?

A wider tyre is going to offer increased comfort and puncture protection for any type of rider no matter their shape or size. You certainly can opt for a narrower road tyre, something like a 30 or 32mm width, this will necessitate upping the pressure in the tyre to compensate for the reduction in volume. This can have a knock-on effect of creating a harsh ride if the pressure is a lot higher in the narrow tyre.

An alternative solution can be to fit something like a file tread tyre in a wider width. This will allow the comfort and puncture protection to remain, however, a file tread is going to roll a lot faster than a knobbly tyre and be more suited to road riding and light gravel sections.

What is meant by Zwift trainer difficulty and how does it work?

One of the features you might stumble across in the settings on Zwift is something called ‘trainer difficulty.’ This controls how much resistance the trainer applies to simulate gradient changes. Setting the difficulty level to 100% will have you changing down the gears the moment the road points uphill with the training adding lots of resistance. Equally, when you get to a descent the trainer will back off and apply almost no resistance at all.

Setting the difficulty to somewhere in the middle, will simulate a more road like feel, with the resistance level allowing you to ride up the hills without needing to mash through the gears quite so much. It will also allow you to have a level of resistance on the downhills that accommodates pedalling.

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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