OT - Using a Tire Mobility Kit (Hyundai)

[NHAero]

Our Hyundai Ioniq PHEV has no spare tire and instead comes with a tire mobility kit, which is a container of sealant and a 12V compressor. The instructions are clear, but...

Can it be used before the tire is completely flat?

We were driving home from Montreal yesterday and I was checking tire pressure because we'd had a flat fixed at home a couple of weeks ago. On the highway the tire was losing 1 psi every 6 miles or so (I'd started it at 43 psi once I figured it was a slow leak, to see if we could make it home.) We were lucky - a tire shop in West Lebanon was open on Sunday and fixed it in a short time. Amazing good fortune, and found out the previous repair was fine - we had incurred a second unrelated puncture. I've never had a flat on a car, and now two in three weeks on the same tire!

So - Could I have used the sealant kit at, say 30 psi, or would I have to had let all the air out of the tire first (the video from Hyundai online shows a flat tire to start with). With a slow leak, would the best strategy be to NOT let the air out, and to use the compressor every hour of so to add 10 psi, and forego the sealant?

[muz]

Is the sealant in a pressurized bottle, like the Vittoria PitStop? If so, it should be OK to add while the tire is pressurized.

[AngryScientist]

depends on the kit.

if the sealant pack you have is pressurized you may be able to add it through the valve core to the tire directly without de-pressurizing. if the sealant is not pressurized, chances are you need to deflate the tire completely and add sealant after removing the valve core.

i've driven gobs of miles in my day and have bunches of flats over the years.

my BMW came with no spare, and i promptly bought one and threw it in the trunk. no way i want to be without a spare, ever. i'm often enough far enough off the beaten path and doing ridiculous things that a spare tire is a must-have for me.

[pdmtong]

pressured sealant through the valve core works.

put some sealant in, then apply air compressor. see where sealant is blowing out. rotate tire to 6:00pm. now add more sealant. now inflate. now slow roll around parking lot. once spurting stops, go for a slow drive to rotate sealant.
change out tire when more convenient.

[oldpotatoe]

Is the bottle of sealant and compressor because of limited space in the EV? Seems a strange setup..re...like bike tubeless, if the cut/slice/hole is too big...tow truck for car..for a flat tire..

[NHAero]

Yes, no room even for a compact spare and jack.
I still haven't determined if the tire needs to be flat to get the sealant in, or if I could have hooked it up when the tire had 30psi in it still.

Is the bottle of sealant and compressor because of limited space in the EV? Seems a strange setup..re...like bike tubeless, if the cut/slice/hole is too big...tow truck for car..for a flat tire..

[buddybikes]

Do you carry regular bike floor pump? Good for upper aerobic exercise..

[oldpotatoe]

Yes, no room even for a compact spare and jack.
I still haven't determined if the tire needs to be flat to get the sealant in, or if I could have hooked it up when the tire had 30psi in it still.

I've used sealant for a stubborn tire that lost about 10 psi per week...when it was low...checked pressure..about 15psi(32 psi 'normal')..squirted the sealant in..checked pressure..went up about 5 psi...then use compressor to get to 32psi.

I think if you put the sealant in at 30 psi..it 'may' get to the pressure of the tire before enough sealant gets in there..you can always reduce the pressure, then sealant, then check and add psi..

[MattTuck]

Not sure about the tire, but glad west Lebanon served you well. There are few options 60 miles in either direction from there on 89.

[sitzmark]

Yes, no room even for a compact spare and jack.
I still haven't determined if the tire needs to be flat to get the sealant in, or if I could have hooked it up when the tire had 30psi in it still.

You can hook up with 30psi, but there are some caveats to consider...

- The compressor blows air through the gravity-fed sealant bottle valve. As long as the compressor is connected, but turned off, you should be able to screw the bottle's hose onto the tire valve without engaging the sealant as you work to get the connector fully seated. You'll lose some air during this process depending on how quickly you can engage and tighten the connector. https://youtu.be/8Gc6ezBBqaY

- Portable inflators are notoriously weak and slow. They'll get you to 30-40psi but it will take 5-10 minutes (or more depending on the compressor). The compressor will be trying to overcome the pressure coming out of the tire in order to push more air in. Note: the screw-on connector is going to open the tire valve core and for a brief period of time there is going to be back flow of air toward the sealant canister and ultimately into the compressor chamber (unless the sealant valve is a check valve). For precaution, you'd need the sealant canister inverted (valve up) to help prevent the back flow from carrying sealant into the compressor. Once the system pressure is equilibrated you could orient the sealant bottle valve down and lock it into the compressor mount. (see vid)

- Ultimate caveat... if your target inflation pressure is anywhere near 30-35psi, the compressor is not going to push a significant amount of sealant into the tire because you're only topping off with 15% or so of the volume of air it would take to inflate the tire from flat. Will that be enough sealant to coat the inner surface of the tire and find the puncture??? Crapshoot. The more air you need to push in - the more sealant you'll push with it.

[NHAero]

All super helpful, thanks very much.

I think I would start with just using the compressor to top up the tire, no sealant.

You can hook up with 30psi, but there are some caveats to consider...

- The compressor blows air through the gravity-fed sealant bottle valve. As long as the compressor is connected, but turned off, you should be able to screw the bottle's hose onto the tire valve without engaging the sealant as you work to get the connector fully seated. You'll lose some air during this process depending on how quickly you can engage and tighten the connector. https://youtu.be/8Gc6ezBBqaY

- Portable inflators are notoriously weak and slow. They'll get you to 30-40psi but it will take 5-10 minutes (or more depending on the compressor). The compressor will be trying to overcome the pressure coming out of the tire in order to push more air in. Note: the screw-on connector is going to open the tire valve core and for a brief period of time there is going to be back flow of air toward the sealant canister and ultimately into the compressor chamber (unless the sealant valve is a check valve). For precaution, you'd need the sealant canister inverted (valve up) to help prevent the back flow from carrying sealant into the compressor. Once the system pressure is equilibrated you could orient the sealant bottle valve down and lock it into the compressor mount. (see vid)

- Ultimate caveat... if your target inflation pressure is anywhere near 30-35psi, the compressor is not going to push a significant amount of sealant into the tire because you're only topping off with 15% or so of the volume of air it would take to inflate the tire from flat. Will that be enough sealant to coat the inner surface of the tire and find the puncture??? Crapshoot. The more air you need to push in - the more sealant you'll push with it.