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I'm needing to buy some tubes this week and would normally get conti's, but as I'm skint after getting a bike unexpectedly I'm considering halfords own brand schraders if they are any good
Don't really have anything scientific, but I use them in both 26" and 29" flavours, and have no issues. So I'd say go for it.
Essentially, as long as they hold the air in, and aren't so heavy that you notice a difference in handling, then why pay more than you have to...?
They are heavy, but with that you get more robust tubes, use them for commuting wheels and they do the job, not the cheapest when you factor in the prices of bulk deals you get around the place.