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Discussion Starter #1
So I recently bought spacers from sector111. I'm sure they've done testing, and that they are safe in the applications that they have tested, however, I'm trying to decide if they really work for my wheels, and my application.

I've got SSR C-Type wheels. I run Hoosier A6 205/245 on 16/17 rims for autox. I have been running BWR 0.190" spacers (=4.8mm on each side). This winter I decided to learn to do alignments, built a string alignment system based on a thread here, and bought a camber tool. I maxed my camber, checking that it was relatively even side to side, and corrected about 4.5mm total front toe-in to 0mm total toe.

After one race, I discovered that my front left (only) had generated rub against the lower part of the frame rearward of the hub. The course had a pin cone with a strong turn to the left into an acceleration zone, so I surmised that when that wheel was mostly unweighted as I powered out of that very tight turn, it rubbed. Obviously, most of the time it won't rub as evidenced by a lack of rub on the other side, but I really really don't want to wear a weak spot in the frame so I re-added the 4mm of front toe-in, and the rub went away the next race, but the car felt a bit tail happy.

My mechanic has convinced me that the hubs on the elise are one of the weaker parts of the system, and frowns on my current spacers, but I think I only need just a little more space to put the alignment back. So I figured that f I doubled the Sector 111 3mm spacer I could move to 6mm and add a minimal 1.2mm per side, and try the zero toe again. (doubling up the thinner BWR spacers would have been slightly larger at 6.35mm) Also I'm pretty sure my sector 111 bullet studs have enough threads for another 1mm of spacer, but not so sure about 1.5mm more.

Sounded good, but then when i got the spacers from S111, I realized they were a lot smaller diameter than BWR, which means the contact area on the wheel is quite different, and much more concentrated at the edge circled below... When the car is turning, and there are lots of sideways forces on the wheel (1.4+ latteral G's) the bottom edge of the spacer will be compressed, and the area absorbing that pressure appears to have both gotten smaller (via the smaller, supported circumfrence where the wheel flat surface is smaller closer to the center of the wheel) and is being subjected to a greater mechanical advantage. (via the smaller diameter, and therefore greater leverage of the wheel crushng it against the brake rotor)

So does anyone who IS an engineer have a clue if what I see is at all relevant, and if the forces required for crushing alumimum plates is even in the same order of magnitude as the range of forces that would be generated by cornering in autocross.

Also another thing I see is that the wheel was designed for full contact with a flat surface, and it won't be getting that anymore, so I also worry about the wheel holding up properly... One assumes they eliminated most of the unnecessary metal for competition wheels such as C-types, and so If I stop using some of the metal they did leave, am risking wheel cracking problems?
 

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Discussion Starter #2
Any thoughts? Would appreciate some help here... Also considering whether or not I really have enough thread to increase the spacer...

I measured the bullet studs, and they seem to have 29-30 mm of thread, and the wheel holds the lugnut about 10mm away from the rotor, plus there's about 2mm threadless on the front of the lugnut, for a total of about 12mm unused thread. The lug nut itself has 16.5mm of threading, so the total with no spacer is 28.5mm... 1.5 - 0.5 extra thread. Torquing the nut probably collapses some of the space I am measuring, and stretches the bolt a bit, so maybe 1-2mm extra thread. Add a 4.8mm (current bwr) spacer, and there would be 3-4 mm out of 16.5mm of thread on the lugnut unengaged.

How much unengaged thread is too much? How much does the bolt actually stretch anyway at 78ft/lbs?
 

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FSPARV, This is a bit after the fact, but for the benefit of everyone.... The rule of thumb is that you want to have at least the the length of engagement that is equal to the diameter of the bolt. On an M12 you 12mm divided by 1.5mm per turn threads. Thus you would like 8 turns.

Our spacers are the size they are for a reason: They are fully supported the entire circumference of the wheel hub. Remember the forces you see are not just cornering loads but bump loads which can be higher. If it compresses, you can fatigue your lug bolts/studs. It is more expensive for us to make the spacers the way we do, but it is the right way.
 

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I use a set of BWR spacers on my LSS wheels, no issues. The LSS
wheels sit inside the fender too much and reduce grip.
If you have RAC monolites, then spacers are not required. The offsets (or whatever the terminology) allow the wheel to fit a 245/45/17 R888 tire perfectly without the rub.

-Robert
 
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