In Trials Fusion, do the upgrades made to a bike (body and/or wheels) affect performance at all, or are all the upgrades just purely cosmetic? There is the ability to buy new wheels and bodies, but it's not clear if those are just for looks or not.
Bike customisation does not affect performance in Trials Fusion:
1) There is no indication of improved statistics in the customisation menu. Normally when you get the opportunity to upgrade something in a video game (whether it's a bike, a car, a gun, or something else entirely), you will be presented with a number or a bar of some sort indicating whether it will make a positive or negative effect. In Trials Fusion, there is no such indication. And I don't think Red Lynx would implement 'hidden' upgrades.
2) In Trials Evolution, bike upgrades had no impact on performance. Each bike had its own performance ratings (visible on the bike selection screen), and installing new parts did not change those ratings in any way.
3) If bike upgrades did affect performance, it would result in imbalance. One of the most important aspects of playing Trials is picking the right bike for the level you're playing, and deciding which statistic will be the most important (eg speed vs acceleration vs manoeuvrability etc). If upgrades did affect performance, it would play havoc with the bike selection process (especially since statistics aren't displayed), and would result in players having unfair 'hidden' advantages in leaderboards and multiplayer matches.
In summary: I believe that if bike upgrades did affect performance, this would have been made evident by the developers, either by displaying performance statisitics, or by mentioning it in a menu or manual.
Yes, the upgrades do affect performance. I own the game and I've done upgrades to the bikes. They do affect performance.
Okay, looks like I made a slight mistake. Thought they did affect performance, but I guess I was just losing my mind. I am really sorry for the confusion. They don't affect performance.