Ajax Bay
Guru
- Location
- East Devon
The thickness of a 28-35 tube used in a(n actual) 38mm wide tyre will be ~8% thinner than if in a 35mm tyre.
The benefit of using a size down is that the tube fits easier into the tyre during mounting, and for that reason I'd prefer it to the in-spec size.
As to pressures, that depends on load: 60psi for a 38mm wide tyre seems right for the rear if the rider+bike mass is 110kg. 50psi for the front would be plenty. @Sittingduck would be a 'bouncing up and down' duck with 75 in except on the smoothest of tarmac.
The benefit of using a size down is that the tube fits easier into the tyre during mounting, and for that reason I'd prefer it to the in-spec size.
As to pressures, that depends on load: 60psi for a 38mm wide tyre seems right for the rear if the rider+bike mass is 110kg. 50psi for the front would be plenty. @Sittingduck would be a 'bouncing up and down' duck with 75 in except on the smoothest of tarmac.
