Originally Posted by
antlockyer
I'm not entirely convinced this info is correct. I just came back from a high grip race. I tried S35/S35 and Ulti XM in practice and both felt similar (medium high but not grip rolling grip). On the third day i ran C35/C35 and it was great XM all round had tons of steering and no rear grip and S35/S35 felt just like C but a bit easier in the hugh grip. If I ever need a ton of steering I'll try Ulti again.
Aside from the complexities of accurately testing across brands (rim size, sidewall height, additive timing, car width, front end scrub, etc) please note that this information is mostly based on testing in the US on CRC grey and black carpet, with a sprinkling of input from elsewhere. I am guessing you were at Masters of Foam this past weekend, which I believe is on ETS carpet(?) I have only raced on ETS carpet once, but comparisons between tires felt very similar to what I have noted in my summary.
Also, please note that at the end of the JFT statement in the wiki, there is this:
For general setup, the JFT foam seem to generate more bite than the BSR, therefore the car tends to be a little more aggressive.
The same could be said for JFT compared to Ulti. JFT foam even of the similar family to BSR/Ulti/whatever appears to generate a bit more grip at a comparative shore. So a C35 in JFT will feel like it has more grip than a Blue or an XM, for example. Very different feel from an S35, though.
I don't believe the foam is actually identical (maybe BSR to Ulti is), but the goal is to be able to compare across brands and JFT C is most similar to Ulti X or BSR Blue/Green (or Yokomo S if you really want to go down a rat hole.) You are more than welcome to disagree with my assessment, but please don't be offended if I disagree with yours.