Cush core is a great product but for new people, there is some confusion related to cush cores and specifically sealants and cush core.
So I decided to write about all the problems that you face with the cush core and provide a better solution or answer to those questions
why sealants do not react with the cush core :
To answer your question fully let me compare the ingredients of the sealants and foam.
the main components of sealants are
Natural latex, propylene glycol, water, adhesives, and some other chemicals.
The main component of the cush core is foam and foam is made of
polyol, polyisocyanates, and water
Polyol is derived from propylene or ethylene and butylene oxides so there’s no way propylene will cause a chemical reaction with the foam because its components are derived from it and natural latex is rubber in simple words so is the foam, so to give you a summarised answer.
Sealants and foam have almost the same ingredients or their ingredients are derived from each other’s elements so sealants will not react with the cush core or other tire inserts and you can use sealants in them with no worry.
Hope this helps you better understand the concept and puts your mind at ease.
Why Tire Inserts Don’t absorb Sealant or let the Sealant pass through them:
I did my own research into why the tire inserts do not absorb sealant because so little information is provided by the tire insert manufacturers on why the inserts don’t absorb sealant because naturally all the foam we usually see either absorbs liquids.
Tire inserts use Closed cell spray Foam these foams are tightly bonded and it’s in a layered structure so they will not absorb water or even let the sealant pass through them but it’s still porous enough to let the air pass through which can act as a double edge sword.
Tire inserts are porous which means that they will let the air through in some proportion if not in large quantity the reason I said double-edged sword is that the area of the tire sidewalls that the cush core or tire inserts cover will not let the sealant reach those spots so if you get a flat in those blind spots the air will leak through.
But on the other hand, the benefits of too much not getting one and you don’t get flats on the side walls so often but it’s still a possibility, and removing the tire can be a pain but I think they are still worth the trouble.
I also did an article on Pinch Flats with Tire Inserts | Can you ride with pinch Flats and some quick fixes
If you had like you can check you my other article on tire inserts as well.
Should you use sealants with cush cores :
Well, the simple answer to this question would be.
Yes, it would be best if you used sealants in your tire despite the fact that you have a such core or other tire inserts inside because you are going to pump up some air inside that tire for the sake of your tire the rim would stay safe with the cush core and it will provide plenty of protection to the rim but nonetheless, you need at least some air inside your tires so that your tire doesn’t wear out too quickly.
So you will still need the sealant inside your tires because you are still using some air inside the tire and no matter the reduced risk of pinch flats you should still top up your sealant so that when you remove a cush core or in the lower part of the bike where cush core cant reach you should be able to still seal the tires.
how much sealant should you use with cush core :
The amount of sealant in general and with cush core or other tire inserts would change depending on the size and width of the tire.
But on practical terms normally you would be using 3-4 oz or 80 to 120 ml of sealant in 29er tires which could be in any width and everyone fills their tires based on their own situations seasonality and other factors.
But the point I am getting at is you wouldn’t need that much sealant with the tire inserters but it depends on personal satisfaction and the trails to ride on as well so there is no given amount to use.
Go with half the amount that you use and if it’s not working in your favor use double the amount it wouldn’t cause any problem as far as the sealant or the tire inserts are concerned.
how to fill sealants with the cush core inside the tires :
There are many different ways to fill the sealants with the cush cores on the real problem occurs when it’s time to refill or clean the old dried sealant but I will get into that in a second.
- Injecting sealant with the tube
- injecting sealant with the bottle
- Injecting sealant by lifting the tire bead
The problem with lifting the bead and injecting sealant is that it’s sometimes hard to remove the bead and with a tire insert or cush core it becomes a pain to remove the bead and inject the sealant.
But it becomes much easier with the sealant tube or with the bottle.
But sometimes the sealant rushes out and the problem around that usually is that you either used the rim tape the wrong way or used the tire insert the wrong way.
And mostly it is the valve that you didn’t adjust properly when you were inserting the tire insert or you didn’t use the valve that came with the tire insert if you correct these mistakes the problem should solve but for the time being if you are in a hurry you can just pull out the bead and fill in the sealant.
Always remember to clean the valve core and valve stem with isopropyl alcohol or wd40 and try not to use too much so it doesn’t mix with the sealant itself it will save you a long term the pain of sealant clogging in the valves.
How to refill or clean tires with cush core (it can be hard to take the tire off or mount it with cush core inside) :
dismounting and mountain g tires can be hard with or without a tire insert bead just doesn’t pop off that quickly and it becomes harder for mountain bikers so here are some of the tricks that I usually use and some that I avoid altogether.
Tricks that you can use to demount the tire.
- Using soap water mixture
- using metallic tools (preferably steel)
- removing sealant and air before doing anything
Things that I don’t recommend or use when unmounting or mounting tires.
- using pointy tools that can harm the tire
- using oils
- plastic tools
these are a brief list of things that I don’t use and use when mounting tires on and off.
If you want to know more I did two wholesome articles on Mountain Bike Tire bead(types,Bead Seating Tricks,Bead leak)
and another article on mounting the tire
using oils is not a great idea to loosen the bead because once you get it on it will slip on the trails along the way and you will be leaking air and the sealant as well.
for plastic tools, I am not a big fan of plastic tools for mounting and demounting mountain bike tires specifically because these tires are much stiffer than road bike tires and most of the time you are going to break plastic tools in the process of mounting or demounting tires so I wouldn’t recommend using them either.
Another thing would be using tools made of aluminum or other material that have a lot of elasticity they will bend straight away but steel tools are much better suited.
You can use pliers (not pointy one) to mount the tires or demounting they can be great but remember not try to pry open the bead with so much force that you end up creating a hole in the tires.
For the tires with the tire inserts using steel tools to unseat or seat the bead would be a much better choice than using any other method or tool.
Tire leaking air with cush core inside :
Cush core or any other tire inserts don’t allow the air to pass through them when you fill up the tires the problem is usually with the rim tape times when you are trying to mountain the tire on you would disturb the rim tape intentionally or unintentionally other than that there should be no problems with the air leakage.
The right way to apply the rim tape with cush core or tire inserts would be to just apply it in the middle and not on the sidewalls because cush core or the tire inserts would take care of the air leakage through the side walls of the rim so you don’t essentially need to apply the rim tape on the side walls.
Another disadvantage of applying the rim tape on the side walls with cush core or any tire insert would be that the bead will not easily break while in normal circumstances you would apply it because it would help in taking the tire off in this situation don’t try it it’s useless it will just work against you.