Hi everyone, I ride a honda Transalp 650. It has a very slim front tyre,(90/90-21). It looses about 2 to 3 pounds of pressure per week. I have tried 2 new heavy duty tubes with the same result. The back tyre is much larger, and only needs toping up about once a month. Is this normal, or do I / have I, a slow leak. Can anyone recomend the the best make tube. Thanks everyone for taking the time to read this post. Chris.