Hi, I was wondering what is the max tyre size you can fit to this frame? The Decathlon website says 36mm. But I don't buy that. I've just roughly measured the clearence at the back wheel stays to be about 50mm. I have a gravel ride coming up and would like to fit 40mm tyres but as this is beyond what Decathlon say is permissable I would like to hear from someone with first hand experience. Thanks.