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I bought a cheap road bike, reviews say that the frame is durable/good (tick), the group set is Shimano Claris (tick), rim brakes are TEKTRO Caliper Dual Pivot road brakes (tick), tyres 700 x 25c OK, but the wheel's rim outer diameter is 20mm which would be 13 or 15 mm inner width and are too narrow for my liking.

I want to change it with Shimano WH-RS100 Road Bike wheels, its advertised as a Shimano series: TIAGRA 4700, which are 700c and have a 17mm inner width.

In the new bike, I've tested the front wheel from my existing commuter bike which has Continental Ride Tour 32-622 and the same Shimano wheels as the one I wish to buy above and it fits perfectly on my new road bike.

I want to put wider tyres than 32mm, so I tested a front wheel with Schwalbe Marathon 700x35c, from another wheel set also 700c, but this don't fit the new road bike. The tyres are touching the top middle of the caliper bracket.

There is approx. 32 mm gap between the rim and the top of the caliper bracket.

I suppose the wider the tyres the higher the tyre profile from the wheel rim to the outside diameter of the tyre, in Car Tyre terms it's called the Aspect Ratio.

So if I want to buy tyres that would clear the caliper brakes, what should I look for when purchasing tyres online? I've noticed that there are two measurements on the Schwalbe Marathons, one says 37-622 and the other 35x700c. Will this measurements help me decide what tyres would fit my new bike?

Should I consider wheels that are slightly smaller in diameter that would allow wider tyres? I've looks at some tables on wheel/tyre sizes and I don't think this option is possible.

Thanks in advance. enter image description here enter image description here enter image description here enter image description here

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    35C with road caliper rim brakes is usually impossible. They are not meant for such large tyres. Many will struggle also with 32C and older ones even with 28C. 35C are really tyres for disc brake bikes.
    – Vladimir F Героям слава
    Commented Dec 1 at 13:10
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    @VladimirFГероямслава some still remember ancient technology known as "cantilever brakes" that was invented to solve this particular problem
    – ojs
    Commented Dec 1 at 17:49
  • OK I understand that disc brakes are taking over but the quote "A product for people with a sophisticated cycling culture" must ring the bell, mind you my new bike is no Colnago ;-))
    – MindDBike
    Commented Dec 2 at 6:01
  • @MindDBike Does not ring a bell at all. Where is it from? I do remember canti's, of course, but from cyclocross bikes, not road bikes. They might be a solution here, although they are a bit fiddly.
    – Vladimir F Героям слава
    Commented Dec 2 at 12:41
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    @MindDBike it sounds like the bearings need grease and adjustment, maybe new balls and at worst new cones. It's not a difficult repair but if you need an excuse for replacing the whole wheels it could be one.
    – ojs
    Commented Dec 3 at 8:10

2 Answers 2

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The schwalbe tyres have a significant amount of tread and a thick puncture protection layer that makes them much taller than a typical road tyre.

Nominally a 25mm road tyre is 25mm tall on the rim. This is just the casing size though and the tread pattern and layers will add from there. The sizing isn't as complex as car tyres with the aspect ratio.

Ideally, you should have (say) a 4mm minimum gap either side of the tyre where it sits in the frame or fork. The same is true of the top although often this gap is minimised for various reasons. This allows space for foriegn objects to pass through and variations in the shape of the tyre and wheel.

I would suggest you use proper road tyres, not Marathon commuter/tour tyres, if you are trying to fit 32mm, or use any tyre in 28mm width or below, if you must have Marathon or equivalent (eg Conti TourRide).

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A big difference between car and bike tyres is that bike tyres fit a range of rims. So the height and width of the tyre varies with the rim width used.

For sensible combinations of rim and tyre it doesn't change the height by a huge amount, but that's why the aspect ratio isn't specified. A few tyres do try to give both height and width dimensions, but that's for a particular rim the manufacturer chose to measure with.

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