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I had two new tires put on my bike and the LBS used Finish Line sealant.

I have managed to puncture after 5 rides. The tire doesn’t lose much air, but air still bubbles out. My experience with Stans sealant on the previous tires is it did a good job.

I was going to syringe it out the Finish Line and replace with Stans, will this compromise the Stans?

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    What kind of bike? Tire sealant is all but worthless on a road bike - the pressure is too high in the small tires used on road bikes. The sealant doesn't stop air from escaping until the pressure is too low for riding. All it does is muck up the tube's valve. Feb 8 at 10:48
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    No idea whether those two sealants will mix well, but relying on sealants is always a bad idea; they can never provide serious puncture protection. That is the domain of puncture proof tires: No mess when installing/taking off tires, no problems with sealant unglueing patches, and a puncture rate of about once in 10000km in my experience. Feb 8 at 10:50
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    Are you referring to tubeless sealant or sealant in tubes? Both the previous comments appear to assume the former, the answer assumes the latter
    – Chris H
    Feb 8 at 12:54
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    Finish Line is a company, not a particular sealant. They make several very different kinds of sealant. What is your actual question?
    – Vladimir F
    Feb 8 at 19:12
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    @MaplePanda to be fair, the appeal of FinishLine's (original) sealant is that it doesn't have any latex, so that people with latex allergies can use it.
    – Paul H
    Feb 9 at 6:52
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Yes - mixing sealants will either make no difference, or both will interfere and neither will work.

Start by checking the SDS (aka the MSDS)

Stans: https://www.notubes.com/pub/media/wysiwyg/GIS-004_R3_Stans_Tire_Sealant_SDS_GHS.pdf

Finish Line: http://www.finishlineusa.com/files/Tubeless%20Tire%20Sealant_EU%20SDS_UK%20English_6%20November%202017.pdf

Both are based on Propylene Glycol with Latex embedded as the solid. So there's similarity in their basic makeup - its not like one is oil and the other is water based. However I still would not mix them; Similar in this case means you don't need to dispose of the new tyres.

  1. I would unmount both tyres, pour out the existing sealant and dispose safely.
  2. Then wipe them out with a cloth rag or paper towels. Also wipe down the rims.
  3. Leave to sit open over night to let anything remaining evaporate.
  4. Then reassemble your tyres onto the rim and add you preferred sealant brand as per the instructions.

And consider doing this yourself - no need to pay a bike shop for a simple tyre swap.

Based on that, you may choose to try a couple more months on the original sealant, and go through this process after ~5 months because by then it would need a topup anyway.

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    When you've got the tyres off the rims anyway, you could also rinse them before wiping down. This should remove more than just wiping. I doubt it's really necessary with similar chemistry sealants though.
    – Chris H
    Feb 8 at 12:56
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    @MaplePanda your "both latex-based" is the opposite case to Criggie's and my "different chemistry", so we're all saying similar things: very different sealants - worry lots about what will happen/take precautions; similar sealants - don't worry much at all
    – Chris H
    Feb 9 at 8:26
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    @PaulH The best luck I've had with sealants was.... a tube.
    – Criggie
    Feb 9 at 9:11
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    @PaulH The best luck I've had with sealants was.... a puncture proof tire. Feb 9 at 9:42
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    @ChrisH Reading comprehension...not my forte today it seems.
    – MaplePanda
    Feb 9 at 15:48

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