Rim width V tyre width, and effect on seat tube clearance

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  • Rim width V tyre width, and effect on seat tube clearance
  • Premier Icon spooky_b329
    Subscriber

    I’ve a new bike and the rims are 19.5mm internal width, and the tyres are 2.35/60mm.

    I’m definitely at the narrowest rim suitable for these tyres, and I’m running them fairly soft as the bike is rigid. I’m also running tubeless so there is a small worry that I will be able to roll/burp them off the wheel. Finally, the seat tube clearance is fairly tight, around 6mm.

    It looks like the recommendation is that the rim sweet spot should 30-70% of the width of tyre, which would be 27-30mm. This will make a squarer tyre and be more stable at lower pressure, and going wider by 10mm would make the tyre about 4mm wider.

    However, I’ve not seen anything that suggests how much (if at all) the tyre height (and therefore seat tube clearance) would reduce. The tyre will square off but will the overall diameter change much?

    Wheels are a couple of years old but mint condition as the bike was never ridden, so I suppose the choice is sell now and buy wider rims, or save some pennies and stick with them.

    Thoughts anyone?

    MrTricky
    Member

    5mm clearance at chainstays would be fine so I’d be happy with what you describe for the seat tube.

    Wider rims will make the distance from tyre to seat tube larger as the outer diameter of the tyre is spread making it less bulb shaped and squarer.

    Premier Icon spooky_b329
    Subscriber

    Thanks Tricky. I found a review that said the tyre height reduced 4mm when they went from 35mm to 23mm, so 20 to 27 would reduce height by 3mm so pretty small numbers. I think I’ll stick with the current rims for a month or two before making a decision.

    Premier Icon BigJohn
    Subscriber

    The tyre height is determined by the circumference of the tyre. This doesn’t change, regardless of rim width.

    MrTricky
    Member

    It does change, plenty of evidence online and physical evidence in my garage.

    damascus
    Member

    We all ran mavic 717 rims  {17mm} with 2.2 26er tyres for years with no problems. The wide rim thing is just the new modern trend. The rims will be fine.

    Personally, I’d sell them to a gravel bike owner and buy something like a stans arch or flow.

    Premier Icon spooky_b329
    Subscriber

    That was my thinking Damascus, or swap them to MY gravel bike, and sell the old gravel bike wheels 🙂

    But whatever I do it’s going to cost a fair bit, and I’d also like a new dropper so might bide my time for a bit!

    Premier Icon BigJohn
    Subscriber

    Think again, Tricky.

    tjagain
    Member

    damascus – you can use lower pressures without tyres rolling off the rim and squirming with wider rims

    Big John – I agree with you on circumference – wider rims will make no difference – all you are going is moving the beads apart unless you put such wide rims on that you totally distort the shape of the tyre and they you would get wrinkled sidewalls

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