Do not mix different tubeless sealants unless the maker explicitly approves that combination. Two white liquids labelled “latex” can contain different particles and additives, and a tyre holding air after a top-up does not prove the mixture will seal the next puncture.
For MTB and eMTB riders, the straightforward approach is to top up with the same exact formula. If you do not know what is inside the tyre, open it, remove the old liquid and start with a known product. Our tubeless sealant guide compares the options; compatibility comes before choosing a favourite brand.
The same brand does not always mean the same formula
Silca makes this distinction particularly clearly. Its Ultimate sealant guidance advises against mixing the current product with either its older sealant or another brand. It does allow the new formula in a previously used tyre after cleaning out old material, especially large deposits and residue around the bead.
That is a useful distinction: changing products does not automatically mean buying a new tyre. It means preparing the tyre properly and following the instructions for the liquid you are putting in.
How to change sealant without creating a mess
1. Identify the tyre, rim and sealant requirements. Check the tyre and wheel are suitable for tubeless use. Read the new sealant’s filling method and quantity before opening the wheel. Do not assume every formula can pass through every valve or injector.
2. Deflate fully and collect the old liquid. Remove the wheel, release all pressure, then carefully unseat one bead. Keep the rotor and brake pads clear of sealant. Use a container and follow the product’s disposal guidance.
3. Clean the tyre and inspect the sealing surfaces. Remove loose dried lumps and old liquid without damaging the tyre, bead or rim tape. Follow the sealant maker’s cleaning instructions. Peaty’s, for example, tells users to rinse away old sealant and let the tyre dry completely before adding Holeshot Biofibre.
4. Measure fresh sealant. Shake the bottle as directed so particles are dispersed, then use the stated amount for your tyre. Peaty’s recommends 100–120ml for a 29in MTB tyre, but that is guidance for its formula, not a universal prescription for every tyre and insert combination.
5. Refit, inflate and check. Follow the tyre and rim seating instructions and never exceed the lower of their pressure limits. Distribute the liquid, inspect bead seating and check for leaks before riding. Recheck pressure after the wheel has stood.
An injector is useful, but check compatibility
Adding sealant through a removable valve core can keep a straightforward top-up tidy. Larger particles, restricted valve passages and some inserts complicate the job. Our sealant injector guide explains the useful differences. Pouring through an open bead remains an option where the product instructions permit it.
Frequently asked questions
Can I add water to old sealant? Do not improvise a dilution. Use the maker’s approved replenisher or fresh sealant as instructed; changing the concentration can change how the product behaves.
Can I use CO2 after a puncture? Check the exact formula. Peaty’s lists Holeshot Biofibre as CO2 compatible, while Schwalbe advises against CO2 for its Doc Blue setup. One brand’s answer cannot safely stand in for every sealant.
Will fresh sealant fix a large cut? Not reliably. Carry a suitable tubeless repair kit and a way to reinflate. A damaged bead or carcass needs proper assessment, not simply more liquid.
The practical rule is simple: know what is in the tyre, keep a matching bottle for top-ups and clean the system when you change formulas. For detailed setup requirements, consult Peaty’s instructions and Schwalbe’s tubeless guidance.