Tyre/tube info and help please.

General cycling advice ( NOT technical ! )
Post Reply
Mattievrs
Posts: 50
Joined: 17 Jan 2017, 1:31pm
Location: Leicester

Tyre/tube info and help please.

Post by Mattievrs »

Tyre and tube info required please!
Recently got a gravel bike and I’m stumped a bit.

It use 700 x 38c tyres. I’m after some inner tubes but fancy the slime ones. They only seem to do them in schrader valves and I’ve got presta. Is there another size I can buy like 27.5 x 1.5 for instance? After any info on what would fit nicely if possible.

Also, with co2 canisters, a 20g one will put 30psi into a MTB tube. If I use 2, I’m guessing it’ll only inflate the tube to the psi the canister is pressured to?

Thanks in advance.

Matt
From Leicester
Road and mtb are my thing. Aswell as cars,women,fire,meat and beer.
mattsccm
Posts: 5101
Joined: 28 Nov 2009, 9:44pm

Re: Tyre/tube info and help please.

Post by mattsccm »

No and no really.
You need the correct size tube really. They can be stetched but it's not great. Slime tubes are not brilliant anyway. They can work but if they don't they are a real mess and very hard to patch.
A normal CO2 catridge will inflate a gravel size tyre to enough.
audaxjk
Posts: 155
Joined: 2 Mar 2020, 4:45pm

Re: Tyre/tube info and help please.

Post by audaxjk »

Have you considered using a bottle of slime sealant for your existing inner tubes? If you remove the presta valve core you can pop some in?
Mattievrs
Posts: 50
Joined: 17 Jan 2017, 1:31pm
Location: Leicester

Re: Tyre/tube info and help please.

Post by Mattievrs »

mattsccm wrote: 27 Apr 2021, 5:46pm No and no really.
You need the correct size tube really. They can be stetched but it's not great. Slime tubes are not brilliant anyway. They can work but if they don't they are a real mess and very hard to patch.
A normal CO2 catridge will inflate a gravel size tyre to enough.
Thanks for your reply, appreciated. Looks like I’ll stick to the proper size tubes then for piece of mind, maybe have a look at some better puncture protected tyres or some inserts for the tyres.
From Leicester
Road and mtb are my thing. Aswell as cars,women,fire,meat and beer.
Mattievrs
Posts: 50
Joined: 17 Jan 2017, 1:31pm
Location: Leicester

Re: Tyre/tube info and help please.

Post by Mattievrs »

audaxjk wrote: 27 Apr 2021, 6:01pm Have you considered using a bottle of slime sealant for your existing inner tubes? If you remove the presta valve core you can pop some in?
Hmmm, no I hadn’t actually. I’ll look into it thanks. Again, thanks for the reply.
From Leicester
Road and mtb are my thing. Aswell as cars,women,fire,meat and beer.
audaxjk
Posts: 155
Joined: 2 Mar 2020, 4:45pm

Re: Tyre/tube info and help please.

Post by audaxjk »

Hi Matt,

I should add to my post that you’ll need to have inner tubes with removable valve cores. If you’re existing ones have them, then I’d suggest a bottle of sealant is the simplest way to go.
Jamesh
Posts: 2963
Joined: 2 Jan 2017, 5:56pm

Re: Tyre/tube info and help please.

Post by Jamesh »

Have you kevlar tyres if not I'd suggest investing in a pair as the Kevlar belt will be very hard for thorns or flints to penetrate.

Cheers James
Eyebrox
Posts: 581
Joined: 5 Aug 2015, 8:56pm
Location: Ayrshire

Re: Tyre/tube info and help please.

Post by Eyebrox »

https://www.bikeparts.co.uk/products/sl ... e-tube-x-1


Also available in schrader valve format.
rogerzilla
Posts: 2887
Joined: 9 Jun 2008, 8:06pm

Re: Tyre/tube info and help please.

Post by rogerzilla »

You can work out the pressure a CO2 canister will achieve fairly well. Calculate the volume of the tyre in cubic metres - for a 26 x 2 tyre, this is 0.559 x pi x (pi x 0.0254^2) = 0.00355 m3.

There are 16/44 = 0.36 moles of CO2 in the usual 16g canister. One mole is 0.024 m3 of gas at room temperature and pressure, so the gas in the canister expands to 0.36 x 0.024 = 0.00864 m3.

If all of this gas is forced into the tyre, the pressure will be 0.00864/0.00355 = 2.43 bar, or 36psi.

In practice you get less pressure than this because some of the gas is left in the canister at 36psi. You can correct for this by adding the volume of the canister, but it's negligible compared to the volume of the tyre.

I would recommend a 25g canister for MTB tyres or for touring tyres above 28mm width.
Mattievrs
Posts: 50
Joined: 17 Jan 2017, 1:31pm
Location: Leicester

Re: Tyre/tube info and help please.

Post by Mattievrs »

Eyebrox wrote: 27 Apr 2021, 9:21pm https://www.bikeparts.co.uk/products/sl ... e-tube-x-1


Also available in schrader valve format.
Thanks, I’m after 38mm with a presta.
From Leicester
Road and mtb are my thing. Aswell as cars,women,fire,meat and beer.
Mattievrs
Posts: 50
Joined: 17 Jan 2017, 1:31pm
Location: Leicester

Re: Tyre/tube info and help please.

Post by Mattievrs »

Just to update really.

I’ve found some Halfords alternative inner tubes that are self sealing with a presta valve that goes up to a 38mm tyre, so will give them a try at £5 a pop and see.
Also found some panaracer flat away Kevlar inserts for the tyres so have got 2 of those to try out as well.

Thanks all.
From Leicester
Road and mtb are my thing. Aswell as cars,women,fire,meat and beer.
Post Reply