Tubes - on the big side or the small side...

[jimmy156]

My wheels are 650b with 40mm gravel tyres on, Replacement tubes are a bit thin on the ground

I am choosing between the schwalbe SV21 which can go from a 38mm tyres right up to 62mm mtb tyres (so will be pretty hefty) These weigh 205g

or

The Schwalbe SV12, which are marketed as 26" tubes, but the website states it will fit 584 up to 44mm (so on the small side.) These weigh 140g

Am I going to notice much difference between the two? I recently replaced a tube with a SV21 i bought ages ago, and it was defiantly heftier then whatever was in their from new.

[gazza285]

I would use the lighter tubes myself.

I have 18-25c tubes on my ‘cross bike, with 33c tyres, and one of my 29ers has 26” tubes in, because I had a load spare…

[frisbee]

Bigger tubes are more of a faff to squeeze into the tyre and avoid pinching them when fitting the tyre.

Some thinner ones can end up with narrower sections where the valve is when inflated. Which can be noticeable when riding especially on a trainer.