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I am a large guy, nearly 2 metres (78 inches) tall and weigh about 160kg (350 pounds). I am aware that bikes are not really made with me in mind and that my best bet is to have new wheels custom built with 36 or 40 spokes etc but that is currently not affordable.

As it stands now my rims seem to be holding up however my current MTB tyres are 29x2.25 and can only take a maximum of 90kg or so they say and the back ones sidewall is splitting. I looked at the Schwalbe algrounder 29x2.35 and this is rated to carry up to 136kg per tyre and can be inflated up to 3.7 bar.

My question is really if I buy these tyres can I just slap them on? IE, go from a 2.25 to a 2.35 without changing rims or anything else? My current tyres are tubed knobbly MTB tyres. I use my bike to commute to and from work only every day so riding on road. Sometimes a little gravel through a park but that's rare. For what it's worth I have lost 20kg (44 pounds) already so the weight is coming off..... Slowly but surely.

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Yes, most likely you should be able to go from 2.25 to 2.35 with no issues IF the frame/fork can accommodate wider tires. You need some clearance at rest since the tire deforms now and then when riding.

This corresponds going from a width of 57mm to a width of 60mm. According to Scwhalbe(link at bottom) your rims internal width should be 19mm or greater. If this is not the case the tires (both old and new) would not be recommended(safety reasons) even though they might fit.

I am assuming your old tubes will fit the very slightly increased tire size, but you could check this if you want to be very thorough.

I would probably check the ETRTO dimensions on the old and new tires just to make sure the new tires fit. I am guessing the old ones are 622x57 and the new ones should then be 622x60.

If the new tires accept the pressure of your old tires, I would stay close to that pressure initially as rims are not indestructible either. If the low-end of the recommended pressure is higher than what you used to run(without issues) then start at the low end of the range and see/feel how it looks.

Good luck!

https://www.schwalbe.com/files/schwalbe/userupload/Images/FAQ/reifen_felgen_2020/2022/reifen-felgenkombination-etrto-22-en.jpg

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Nothing else to change, provided there's enough clearance (space between the tire and the frame/accessories - tire deformation is mostly at the interface tire/road, so I wouldn't worry about that). Tires measurements are a complex science, and the actual width also depends on the inside rim width, but the reference rim width is not mentioned (to take an example, I have on a bike 37mm tires, measured at 34mm, and on another bike 40mm tires measured at 42mm). Also, I would not be surprised that knobs are not included in the measurement, so going from 57 MTB to 60 "gravel" won't be an issue.

For wheels and tires, my recommendation would be to check with stores that are selling cargo bikes, as these bikes can have a max admissible weight up to 250kg (or take inspiration from the spec sheets of cargo bikes), although it looks like it's hard to find 29" wheels on this segment.

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  • You can also look at tyres used on tandems, as they have to handle the weight of 2 riders. There are mountain tandems which should have such wide tyres
    – Chris H
    Commented Sep 30, 2023 at 14:31

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