GCN Tech Clinic: Worn Tyres, Stripped Bolts & Aero Bars

Aug 07, 2023

This week Ollie and Alex are back in the GCN Tech studio taking a look at some of your tech and maintenance-related questions

Junior Tech Writer

This week Ollie and Alex are looking at 11/12 speed cross compatibility, how to make sure you buy the right wheels for your bike and what to do if your steerer tube is just that little bit too long. Don't forget that if you have a question you want the guys to take a look at head over to this week’s Tech Clinic video and add your question to the comments along with #ASKGCNTECH

This is a really good question with a lot of choices for a lot of different aspects of riding. The most important thing to look for in ensuring your wheels will work with the rest of your bike is that the axles your bike uses are compatible with the hubs of the wheels. Typically you can get adapters from the manufacturer to accommodate various sizes but some will be too large by standard to be run in the frame. For example, a hub that is 110mm as standard might not be able to be reduced to 100mm and the same for regular, boost and super boost spacing at the rear.

Once you know the wheels can fit in the frame and fork the next thing to assess is the rim width, this is particularly important if you are looking to run either very wide or very narrow tyres. Most manufacturers will have a recommended tyre size range, if a rim is hookless it is even more important to ensure that this is abided by to prevent the tyre from blowing off the rim.

The only other consideration is that the hubs accept the discs you have (either six-bolt or center lock) or be prepared to factor in the price of some new discs into the cost of the new wheelset.

The compatibility of the tyres you want to fit will be quoted by the frame manufacturer, every frame will have a maximum tyre width that the manufacturer guarantees will fit and work without the issue of catching on the frame.

The simple answer to this question is, yes. Running a 12-speed groupset will mean that anything that your bike is running on will also need to be 12-speed. Not only is there an extra cog to factor in but the chain and cassette for a 12-speed system are also a different thickness than an 11-speed, which means that the chain will not mesh and sit properly on an 11-speed cassette.

This boils down to the cost of the cranks and how much they would cost to be replaced. Unfortunately, this is not going to be an easy fix at the local bike shop and it is going to be a fairly labour-intensive job.

The best bet is to ask them to give you a rough quote for how much a job like this will cost and then decide if that is cheaper or more expensive than cutting the cranks off and replacing them with a new set.

For lower-end cranks and ones that are not also power meters, replacing the cranks might well work out the better option and this way you have a fresh pair of cranks with working self-extracting bolts.

There are a few ways that this issue can be tackled depending on how you want to alter the aesthetics of the bike. The most simple way to remedy the issue of having an ever so slightly too long steerer tube is to add a 2 or 3mm headset spacer above the stem, this will give you enough space for the headset bolt to pull on the star nut and tighten everything up.

If you have enough spacers and want to keep the bike looking a bit sleeker you can equally cut another 5mm or so off and remove one of the current spacers.

It is always better to have a steerer that is just a little bit too long than one that is too short for your headtube. The safer bet is to add a 2 or 3mm headset spacer above the stem to take up the extra.

Changing 11-speed cranks to 12-speed cranks will work, however, this is not endorsed by Shimano. There have been issues with compatibility going the other way, so running an 11-speed crankset with other 12-speed components. In this case, riders have reported an increase in dropped chains running this set-up.

This is a difficult one to give a blanket answer to as it really does depend from case to case and from tyre to tyre. As a general rule, any cut that exposes the threads of the carcass is a risk for future punctures and you might want to look at replacing it. If you have a target event that you have been training for, for a long time, fitting a new tyre prior to the event will give you peace of mind that the tyre will not cause any issues or ruin the event for you.

Flared bars are certainly something that we are seeing more and more in the pro peloton and have long been a staple of the gravel community, allowing for a traditional width at the hoods and a wider stance when on the drops to offer more control and stability.

If you are looking for a narrower bar a flared option could work well as it will give you an aero position on the hoods however for descending you still have a good controllable bar width on the drops.

If you are struggling with rotating your wrists out in an aero position on the hoods you can also look at rotating the hoods a few degrees as this will make the contact point with your hands effectively narrower.

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