Each type has their own pros, cons and rules to follow.
Use After The Puncture Has Occured
These can be bought from motor shops like Halfords for as little as £5, the small
size cans allow them to be stored under the seat etc until they are needed.
2 common makes are Tyreweld and Fix-A-Flat, both very similar to each other.
As soon as you realise you have a puncture you should stop the car and jack up the wheel if possible. Read the can and it will tell you the amount required although it's hard to determine how much you have used. The tyre should then be pumped up to the correct pressure before you continue driving.
The smart can come with its own solution which stores nicely in the footwell block.
The drawback is the price compared to all the other solutions.
You get a valve remover, bottle of tyre sealant with a straw..
...and a compressor to reinflate the tyre.
Shieldwell & Slime
There are a few other products out there that can be added to the tyre to repair punctures
as they happen of they can be added to repair a recently caused puncture. Products like
Shieldwell and Slime are ok in the smart to repair punctures but they should not be
preinstalled as they have limited speed and/or distance on the repairs.
Unlike Tyreweld and Fix-a-flat, these products aren't as easy to fit yet are still classed as a temporary repair. You can still only do a maximum of 60mph and depending on the product you may be limited to how far you can travel once the product is used. If you don't know you have had a puncture repaired because the product was preinstalled you will not know that you shouldn't exceed 60mph.
Use Before The Puncture Has Occured
These products are injected into the tyre and will seal any punctures as they happen.
Because they are pre-fitted to the car there is no need to carry the product around.
It also means that you won't be trying to do it late at night on the side of a road.
After a bit of research, the only product that falls into this catagory is Ultraseal.
There are ultraseal franchises everywhere that will fit it for you or you can buy a kit youself.
One wheel at a time should be jacked up and the valve removed, read the instructions and determine how much you should put in. Screw the container to the stem and add the correct amount. Disconnect the container and replace the valve, inflate the tyre to the correct pressure. Repeat with the other wheels.
Ultraseal is safe to use with the tire pressure monitoring system found on American smarts.
Ultraseal also make combat formula ultraseal for the army, an army HUMMV tyre survived a shot through the sidewall with a 7.62 round. The round went in 1 tyre wall and out the other, both holes self healed immediately and the tyre lost almost no pressure.
You! obviously, imagine not having to worry about punctures.
Ultraseal has everything covered for less than the cost of a new tyre, for this price you are protecting all 4 of your tyres. It is a permanent repair so it's fit and forget.
If you want Ultraseal fitting to your car, go to Google and type in Ultraseal.
You will be given a list of all the franchised fitters, you just have to find your local fitter.