Not positive, but I wouldn't try the LRP Sphere. 1/8 buggies really tax the speed control, and just about always use higher voltage battery packs to get the power these beasts need. The TC is limited to a 2s lipo I believe, the 1/8 guys are generally in the 4-6s range. The higher voltage is needed to get the current down to a manageable level. Even with the higher voltage speedos this still seems to be a weak point from what I have seen. Donít think a traditional 1/10 scale speedo like the LRP stands much of a chance.
Perhaps check the 1/8 conversion thread for more info, but Tekin, Castle Creations, and Losi/Xcelorin have dedicated 1/8 scale speedos.