LotusTalk - The Lotus Cars Community - View Single Post - BMW Wheel Bolts = Perfect Fit! And they are Black!
View Single Post
post #99 of (permalink) Old 02-21-2006, 05:21 PM Thread Starter
Stan
-
 
Join Date: Jun 2004
Posts: 6,941
Quote:
Originally Posted by MitchT
Stan, I do check every time I do a session, the point is , and I understand that alloy expands and contracts, the factory lotus bolts stayed tourqued to spec and I do not know why. Fastliz and I run our cars together alot, I check my wheels after each session, one or two loose lugs, (ssr/bmw bolts) Fastliz car, lls wheels factory bolts his do not get loose. I do not know why. I origanally thought I was not making them tight enough, but I checked with two other wrenches.
Wheel bolts holding alloy wheels on don't actually back out or unwind or whatever. That which they are compressing, yields. Squishes out. Like if you shook someones hand only it was made of jello. Therefore the tension on that bolt, the stretch, is lost. You regain it back by retorquing. So if a bolt needs to be retorqued, it is not that the bolt unwound itself. If a bolt is not properly tensioned / torqued then things are not safe/stable and the bolt will experience premature fatigue failure at some point. I retorque bolts all the time on wheels that have been changed. Change a wheel back to your street stuff after an event? Well then retorque once or twice when you get home or the next day and you'll often find some that need it. By all means use what you prefer.

Suppose you retorque before a run on the track. You are out there for 20 minutes and the brakes and others things get hot. The wheel gets hot, mostly in the hub area. The alloy wheel expands a bit. But the wheel bolt holds steady. The tension on the bolt remains fine. That tension is the thing you want...the torque is just an indirect way of measuring it. Now when you pull in after a cool down lap and park, the whole deal cools off. It's common to lose some tension at the wheel fasteners due to the wheel itself compressive yielding (squishing). When the wheels cool off they get smaller. Get the situation? If you check right after you come in, most likely all will be fine. Check an hour later before your next run and they may not be. So you run around the bolt circle with your handy torque wrench..click-set to the desired figure. The whole car is done in maybe 2 minutes.

If you want the strongest, most reliable approach, convert to studs of adequate length and thread engagement for the use. Which are also not Lotus approved.

Also note that you might be seeing a difference between the wheels themselves. SSRs are not really forged they are semisolid forged. Sorta in between most cast and most forged in strength/toughness. The LSS wheels are true, real forged wheels and are stronger than they'd be were they semi solid forged. Forgings also tend to keep more of their strength when they are hot compared to lesser wheels. Soo what you may have seen is that the forged wheels are stronger, at least in the hub area. Forged wheels are formed by more or less squishing the aluminum into particular shapes under immense pressure from the forge. The forged material is denser than cast alloy. And it conducts heat through itself better too. It's more squish resistant, more likely to hold the torque.

EDIT: I looked for some strength comparisons for different wheels but found little useful information. I did find some mfr claims that the material in forged wheels is often about twice as strong as that in cast wheels.

Last edited by Stan; 02-22-2006 at 06:16 AM.
Stan is offline  
 
 
For the best viewing experience please update your browser to Google Chrome