My new Challenge Wheels w/ Hill Titanium Bolts

Ghardt,

Good choice on the Silver Color! I like the white as well being an original color to the F355 Challenge but, Silver gives the street F355 a better more current look. Those bolts are just an added bonus!

Does anyone know if the 360CS Titanium wheel bolts will work on the F355 using the 355CH wheels? If not why and what are the specs for those bolts?

Ciao,

SRR

 

so 3mm difference or around 2 threads? Will that really matter?

 

I am not a mechanical engineer by any stretch of the imagination. According to all the published data from Ferrari, the research of Hill Engineering, and the many folks here who've competitively run the 355CH wheels on a 348, I am inclined to believe "yes, it does matter".

In my opinion, there are a lot of areas where 'close enough' is perfectly acceptable on these cars. Wheel bolts, I don't think is one of those areas.

 

If your wheel is not set on the hub evenly on a 348 or 355, it is very hard to detect at low speeds. After a period of time or at high speed and high temps these wheels can start to upset. Experienced mechanics have told me its just the wheel bearings, but in fact it's the wheel starting to come off the hub.
You have to make sure those wheel bolts are "dead on" or else! What I have done is wrap my hands around the wheel and pull it back and forth. If there is play then I remove the wheel and reset, but you HAVE to have the right wheel bolts!

 

Unfortunately for me, I am an engineer and hence I have a hard time accepting answers that don't have some sort of logical foundation, so decided to work it out for fun (yeah, sad). For a 14x1.5 metric bolt which is the stock Ferrari wheel bolt, the thread engagement is 10.8mm to where the bolt will fail before the threads pull out (based on formulas here: http://www.engineersedge.com/thread_strength/thread_minimum_length_engagement.htm). Given a 9mm brake hat thickness, you'd need 19.8mm of projection from the rim, which is 1.2-1.3mm more than what the stock bolts provide on a challenge rim (based on Bruce's link above). So, you could say the stock bolts are not long enough.

However, I don't think you should be operating anywhere near the tensile strength of the wheel bolts, so I do not see a big issue as 1.3mm will be a little less than one full thread with the 1.5mm thread pitch. I do see why Ferrari (or any manufacturer) would recommend the longer bolts as if you were to overtorque or damage the threads, you could pull the threads before the bolt actually broke and therefore a failed bolt would be less obvious. Given all that, there is a slightly higher risk with the shorter bolts. I would not trust a shop to tighten the bolts unless I knew they were careful and used a calibrated torque wrench, but if I were doing it personally I wouldn't be worried.

 

The regular 52mm bolts thread in 5 1/4 turns onto the hub. The longer 55mm bolts thread in 7 1/3 turns into the hub which I believe is the same amount the 52mm bolts thread into the original oem wheels. Me thinks.....better to be safe than sorry. I love those bolts and would dearly love to use them on my second set of challenge wheels that am going to refinish in satin black but $1000 ooooouch.

 

So what’s the conclusion? Will 52mm suffice? I ask because Ferrari makes only 52mm in titanium I believe. I prefer Ferrari bolts over after-market titanium mainly due to finish color.