Hmm, Chelsea is really gonna be interesting char' to watch as it seems. I personally can't tell much what formalities and standings were stated, bcs I read manga in English. But to me it seems Xeno has just met her on the summit, where all prodigies/well-known and distinguished scientists gathered bcs of petrified swallows. But Senku was the one, who noticed that swallows were petrified living creatures, he was the first, not her. This Senku's discovery was why Chelsea was invited to the summit, and she was invited bcs she's brilliant geographer who knows the whole world (places on Earth and what is happening there). But that dosn't mean she knows science in a Senku's way, she's just amazingly smart and highly apt in survival and orientation.... ofc, with it goes the knowing of cultures and countries. But still, she's a geographer (not engineer or such), that's why I don't think she would be able to make a rocket or motorbike herself to be able to outsmart Senku and Xeno in this field, not really, she's just talented in her own field very much in comparison with others (talented from her very young days, but in geography only)..... Senku hardly survived, when he woke up at first, but that's not surprising, he didn't travel the world like Chelsea as a child, he was an inventor, working primarily on pc, gathering infomations on one spot (and doing experiments in lab, outside) I think Xeno was just implying a different way of gathering informations, when talking to Senku. Chelsea gathers them as an explorer, on foot all around the world herself. Senku from his pc and surrounding (Taiju, Yuzuriha back then noticed the swallows first, but only Senku could research it so thoroughly to say - petrified swallows were living creatures). So rather the amazed face of Xeno (and his formalities to Chelsea) may be his general talking to fellow smart ppl, who are stars of their field. Xeno isn't so formal with Senku, bcs they were friends, knew each other for quite some time already. At least that is what I think for now. I don't see her as a rival to Senku or Xeno.
Wow, that is such a specific question, I don't understand cars much, but I can mention some notes I made through my "research"
The first wheel in the downhill vehicle was just from wood, the vehicle had no engine tho, it was practically a sledge with wheels XD The second one, wahah, it was the Steam Gorilla, which couldn't work uphill too at first, it used wooden wheels with "tyres" made of bamboo wicker. Those were unsurprisingly made by Kaseki. They had a problem with uneven roads. so they needed it to be springy or at least soften the bumping. The last invention was a pseudo-tread for a tank, Senku actually didn't say from what they were made, but it was in the final drawing - it looked as a very large wheel with an added layer of wood, inside was probably still the bamboo wicker as the filling, but this tank was meant to be disposed of - these tyres actually did broke down in war with Tsukasa and later they still used bamboo wicker only. I never found, from what were tyres made of afterwards, but there has to be some upgrade, I suppose the tank was transformed into a mobile lab on a way. This lab can float and travel on land, both, so there must be some missing step. But I couldn't find it anywhere, so frustrating XD Well, I was at least reminded while doing this "research" that the first plastic, bakelite, was actually made as a part of cellphone, so it was a very long time ago. But bakelite isn't usable in tyres...aa~h, I don't understand how can it be so hard to find one panel ahah.