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tyre clearance calculation

stefanostefano Posts: 254
edited July 2018 in Workshop
Hi I move to a new place and the new training route includes some paved road and a bit of gravel. So I need to upgrade from 700*23 to 700*30 or 32 with mudguards.

I checked the clearance on the bike, with 23 tyres is 14mm. The clearance difference from 23 to 32 should be 9mm. Still I have 5mm for the mudguards.

Does it make sense? any advice?



  • me-109me-109 Posts: 1,728
    Sideways across tyre or radially? Front or rear? Chainstay or seatstay?
  • cyclecliniccycleclinic Posts: 6,865
    no tyre height varies between tyre brands and is dependent on the tyre. different 23mm tyres have a different bead to bead distances and the same goes for different 30mm tyres. Also the rim internal width is important too.

    An example is a 28mm conti GP4000sII on an 19mm internal width rim its 32mm wide and at least 30mm tall. An IRC 28mm formula pro RBCC tubeless tyres though is 28mm wide and 24mm tall. So you have to know what tyre your getting before and rim internal width before knowing what size it will be. -wheel building and other stuff.
  • crankycrankcrankycrank Posts: 1,830
    This site gives you actual tire width and height specs for most tyres available for comparison to what you have now. Of course they won't be exactly the same if you're not running the same rims used by the site but just measure your tyres and compare with their specs for the same tyre and adjust for the others accordingly.
  • stefanostefano Posts: 254
    Very good website I will definitely use it to chose tyres. I will build new wheels with m
    Mavic Open Pro which has 15mm internal width. Though it is recommended for up to 28 tyres many people have used 30 or 32 tyres.
  • imposter2.0imposter2.0 Posts: 11,965
    You haven't said what bike you have, but generally speaking a bike which is specced with 23c tyres from the factory is highly unlikely to be able to accept 32c..
  • stefanostefano Posts: 254
    Hi, It is a late 70s Koga Miyata steel frame with mudguard eyelets. The clearance with 23 tyres between the real brake and tyre is 14mm and for the front it is 18mm. Also, the frame is wide enough to take any tyres up o 38mm.

    Thus the tighter limitation is the 14mm height of rear tyre!

    There are horizontal dropout on the rear and there is a screw and a small washer that positions the rear wheel axle at about 5mm forward of the edge of the dropouts. Can I remove this screw and pull backwards to the end of the rear dropouts the wheel axle?

    By moving the rear wheel axle to the furthest back position may give me some more clearance. It has friction gears. I am not sure if this affects the rear derailleur shifting?
  • stefanostefano Posts: 254
    Here is photo of the bolt-stop on the rear dropout similar to one in my frame. Can I remove this and pull the axle to the back end of the dropout so as to gain some more tyre clearance? ... id=1&pid=1
  • Nick PayneNick Payne Posts: 288
    I checked the clearance on the bike, with 23 tyres is 14mm. The clearance difference from 23 to 32 should be 9mm. Still I have 5mm for the mudguards.
    That won't be enough clearance for mudguards - the mudguard itself will take up several mm, so you will essentially have zero clearance between mudguard and tyre. I reckon you need a minimum of ~6mm/¼" clearance between mudguard and tyre - if a stone or some other piece of road debris gets caught up between the tyre and mudguard, you don't want everything to come to an abrupt screaming halt.
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