GCN Tech Clinic: How much clearance should I have between my tyres and frame?

Alex Paton is reunited with Ollie Bridgewood in the tech clinic this week. With normal business resumed the duo is here to shine some light on your latest bike-related questions, from tyres and wheelsets to how to keep your chain well waxed during the winter months.

Do I need to keep the spacer when I change the cassette?

This depends on the exact setup you have, but if you are using 12-speed Shimano, the answer is yes. A 12-speed Shimano cassette on an 11-speed freehub body requires a thin spacer fitted behind the cassette. If you are changing the cassette this spacer needs to remain on the freehub body.

If you are running an 11-speed setup the spacer might not be needed at all. An easy way to check is by fitting the cassette with the spacer behind it. In most cases, if the spacer is not required the lock ring will not thread onto the freehub body. Equally, if you fit the cassette without the spacer when it is required you will find it impossible to tighten the lock ring enough to take up the play in the cassette.

Is there a way to prevent me from needing to re-centre my brake callipers when I swap wheelsets?

This can be a frustrating issue to deal with every time you swap the wheels over on your bike. Luckily there is a fairly easy solution if you are using rotors that mount to the hub using a six-bolt interface, rather than a centrelock system.

The best solution is to space one of the rotors out from the hub slightly so that they sit in the same location relative to the calliper on the bike. The first thing you need to do is set the calliper up centrally for the wheels that have the discs mounted further outboard. Once you have done this, using some small washers you can space the other disc rotor out until it sits in the brake calliper without rubbing.

If you have a centrelock system, you can get a six-bolt adapter. Once this is fitted you will need to buy some corresponding six-bolt disc rotors but after that, the process is exactly the same.

How do you maintain a waxed chain in the winter?

The best way you can look after your waxed chain through the winter months is to give it a rinse over with clean, low-pressure water to remove any salt that has built up throughout a ride. Once the chain has been rinsed thoroughly the best thing to do is dry it with a clean microfibre cloth. Whilst you are drying it, inspect the chain for any signs of wear that point towards the need for reapplication of the wax.

Can you wax multiple chains at once and do they degrade over time once they have been waxed?

If you are looking to save some time and have multiple chains to wax, treating them all in one go can be a great way to efficiently wax all of the chains. Once they have been treated, the wax coating will not degrade over time, so long as you store them appropriately in a dry, humidity-controlled environment.

If you are going to wax a bunch of chains in a batch, it is worth taking some time to run the treated chains around a metal or plastic bar to loosen the links. If you are going to leave a freshly waxed chain unused it can lead to stiff chain links. Running the chain around a bar by hand will make sure that the chain is good to use when it comes to fitting it.

Is there a way to attach a rack to the rear of a carbon bike that doesn’t have specific mounting points?

There are some solutions out there for this. Both Topeak and a brand called Tailfin offer solutions for bikes without mounting points. It is important to work out what it is you are looking to carry as to what the best option out there is.

Whatever the solution is that you end up going for, make sure that wherever any clamps or straps sit on the bike, you cover these areas with a protective tape to prevent any damage from chafing.

What is the best way to clean and lubricate a rear derailleur?

To clean a rear derailleur the most effective method is to use a brush with some degreaser to remove any built-up dirt from the surfaces. If you are particularly concerned you can clean the derailleur with it set in the highest and lowest settings to make sure all the areas are clean.

As far as lubricating a rear derailleur, once it is dry use a drop of chain lube on each of the pivot points. If you have a sticky derailleur it can be advantageous to manually work the mechanism side to side to encourage the lubrication to work its way into the pivots. When this has been done wipe away any excess with a cloth.

Is there any benefit in waxing a cassette?

Waxing a cassette isn’t necessary and can actually cause more issues than it could solve. A waxed chain running on a cassette has all the lubrication needed for the entire system. The molybdenum disulphide additives in chain wax treatments smooth out the surface of the chain links. As the chain passes over the surface of the cassette it will act as a lubricant in this way. Excess lubrication can cause dirt and grit to build up which can lead to accelerated wear. Only waxing the chain is the best course of action.

How much clearance should I have between my tyre and the frame?

There is no clearly defined measure for tyre clearance. However, you do want to make sure that small stones or debris that might get picked up by the tyre can pass through the gap. If you are running gravel tyres you are going to want even more clearance for mud to pass through, but as a general rule for a road bike, at least a few millimetres on each side and around a centimetre on each side for a gravel bike.

Something else to consider is that the tyre has enough clearance for when the tyres deform in corners. The wider the tyre and the lower the tyre pressure the more this needs to be considered. Although a tyre might look like it fits fine in the work stand, out on the road when the bike, wheels, and tyres flex under load it might be a different story. It is always worth checking with a little test ride to make sure you aren’t going to be damaging your frame.

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.