Becker on clay:
He made SF at RG in 1987 (lost to Wilander in straight sets), 1989 (lost to Edberg, in five sets) and 1991 (lost to Agassi in four sets).
Also made QF in 1986 (lost to Pernfors IIRC).
He was runner-up multiple times in big clay tournaments:
In Monte Carlo 1989, he got to the final (without losing a single set, defeating several good clay courters) and lost to Alberto Mancini in four close sets 5-7 6-2 6-7 5-7.
In Monte Carlo 1991, he defeated four very good claycourters (Sanchez, Volkov, Chesnokov and Prpic) and got the final again where he lost to great Sergi Bruguera in (again) four very close sets 7-5 4-6 6-7 6-7.
In Monte Carlo 1995 once again he got to the final (defeating Bjorkman, Corretja, Krajicek and Ivanisevic) and in the final he lost to Thomas Muster in five sets (was leading two sets to love, and had two match points) 6-4 7-5 1-6 6-7 0-6.
That match was the closest he got to a clay title.
In Rome he got to the SF in 1985 where he lost to Noah, and he was runner-up in 1994 where (after defeating Novacek, Sanchez, Pioline, Stich and Ivanisevic) he lost in straight sets to Sampras.
In Hamburg, he got to SF in 1988 where he lost to Leconte 6-3 6-7 6-7, again made SF the following year, in 1989, defeating several good clay courters but losing to Horst Skoff 6-7 2-6.
In 1990 also in Hamburg he got to the final (defeating Cane, Cherkasov, Arias and Leconte) but was clearly defeated in the final by stylish Spaniard Juan Aguilera by 1-6 0-6 6-7.
In 1992 Hamburg, he got to the SF again, but was destroyed by Stich 1-6 1-6.
He also made some other clay court final, like Gstaad in 1998, where he defeated Batl, Pioline, Mantilla and Rios, but lost in the final against Corretja by 6-7 5-7 3-6.
(even at the end of his career, he was still able to defeat Pioline, Mantilla and Rios back to back to back, on clay, without losing a single set).
He was very good on clay, at least as good as Edberg, Sampras, Stich, Ivanisevic or McEnroe (all of them won several clay court tournaments), but Becker was just unlucky not to win a single clay court title during his entire career.