Hi Folks, If I understand well, the design of the upper wishbone brackets (on the rear subframe) evolved due to weakness where they are welded to the subframe. It seems that it is not uncommon for subframe to crack in this area. I have an early M2.7, with the start of crack so will reinforce this while the engine is out. Would someone with a later car mind posting a picture of the upper wishbone brackets (front and rear) of a later car to see what design upgrade was implemented? (I believe it was just a larger fillet radius). Below are the brackets that I am speaking of. Thanks! Image Unavailable, Please Login Image Unavailable, Please Login
Someone posted this before because i thought the challenge cars were all done before the raced or shortly after. Theywere gusseted fro what i remember. Maybe Tim or Fbb have that info
I checked a couple of pics from our recent engine out, and ours is a '97. The two pics below are the best images I could find of the area you're looking for. It looks like the mounting bracket extends quite a bit lower down the subframe tube than the early cars. Image Unavailable, Please Login Image Unavailable, Please Login
Have one sitting here Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Andrew, Here are front and rear views of my right rear upper wishbone brackets... Image Unavailable, Please Login Image Unavailable, Please Login My 1995 F355 Challenge S/N is 100330, built in September 1994. The front bracket has the larger fillet. The rear bracket might have been reinforced a bit in the past... Image Unavailable, Please Login My car has ~19,000 miles on its 2200 lb/in F and 900 lb/in R Challenge springs. Barry
Just weighed it With crossmembers and the motor mount bushings way more then I thought, 100.8 pounds I got to stop messing with big girls when 100 pounds feels like 45 LOL
Thanks for weighing it Tim! Grant, you read my mind Probably not 50lbs but definitely some room for improvement.
ItsI a really clunky old design that's very weak Aluminum, chromoly even a hybrid with different geometry would be fun to try
Thanks Barry for the confirmation of what the challenge cars have as well. Nice to know it is the same solution!
You're welcome, Andrew. Another weak point on the 1995 cars are the front shock mounts. The metal is very thin there and prone to cracking with the 2200 lb/in front Challenge springs. The 1996 cars have bolstered mounts and the Challenge Manual for that showed parts for strengthening the area. My car never had the modification when it raced. I had it done a few years ago...
Barry, thanks again for he heads up on weak point in the front! Will check it out. As far as reccomendeded reinforcement, I think doing just as Ferrari did on the later subframes would be the reccomendation (but maybe there was a technical bulletin?) It is not really a difficult problem to solve, I am sure any type of gusset/fillet would basically work. I will reinforce mine just as the later cars have it, with the big fillet.