Question for stoptech BBK users........
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AudiWorld Senior Member
Joined: Apr 2003
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Question for stoptech BBK users........
Did you guys check your lugs for proper length? After installation I noticed that due to the thickness of stoptech's rotor hat, there was less bolt thread-contact w/ the hub (~4 full turns).
I thoroughly cleaned the lug threads and reinstalled. This picture shows the amount of engagement a BBS lug (~29mm shank) has with the hub sitting on top of stoptech's rotor hat.
<img src="http://i9.photobucket.com/albums/a63/rasta4/CIMG0011.jpg">
I decided to swap out for the above pictured 38mm lug, so as to ensure more bolt/hub contact. Now I get ~8.5 full turns of the lug, which is plenty. IIRC, I read on tirerack.com that you should ideally have at least 6-7 full turns of the lug bolt.
I thoroughly cleaned the lug threads and reinstalled. This picture shows the amount of engagement a BBS lug (~29mm shank) has with the hub sitting on top of stoptech's rotor hat.
<img src="http://i9.photobucket.com/albums/a63/rasta4/CIMG0011.jpg">
I decided to swap out for the above pictured 38mm lug, so as to ensure more bolt/hub contact. Now I get ~8.5 full turns of the lug, which is plenty. IIRC, I read on tirerack.com that you should ideally have at least 6-7 full turns of the lug bolt.
AudiWorld Expert
Joined: Jun 2000
Posts: 29,356
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Flush with the face will not provide full engagment with the threads...
Examining the leading end of the bolt reveals a partial starting thread.
In order for there to be "full engagement", a full thread crossection must exist for there to be full engagement. This will result in a 1-2 thread protrusion past the face of the hub.
In many industries, 1-2 threads beyond, is standard, to ensure full engagement of threads.
How can you correctly determine if your lug-bolts are the "correct" length, without looking at the other side of the hub, and seeing exactly how many threads protrude beyond the hub?
How many threads are in the hub? 6? 7? 8?
Tire Rack says 7.5 turns...<ul><li><a href="http://www.tirerack.com/wheels/tech/techpage.jsp?techid=107">http://www.tirerack.com/wheels/tech/techpage.jsp?techid=107</a</li></ul>
In order for there to be "full engagement", a full thread crossection must exist for there to be full engagement. This will result in a 1-2 thread protrusion past the face of the hub.
In many industries, 1-2 threads beyond, is standard, to ensure full engagement of threads.
How can you correctly determine if your lug-bolts are the "correct" length, without looking at the other side of the hub, and seeing exactly how many threads protrude beyond the hub?
How many threads are in the hub? 6? 7? 8?
Tire Rack says 7.5 turns...<ul><li><a href="http://www.tirerack.com/wheels/tech/techpage.jsp?techid=107">http://www.tirerack.com/wheels/tech/techpage.jsp?techid=107</a</li></ul>
AudiWorld Super User
Joined: Oct 2005
Posts: 6,127
Likes: 3
2nd,.. Machine design theory rule is that properly formed and clean, lubricated threads, ....
minimum engagement is equal to the nominal diameter of the fastener shank, and will provide more than enough strength in the threads to withstand the stress of a fastener tightened to the stretch point of the steel bolt. However, the cast iron threads in the hub have different strength, so it's not a direct 1 to 1 relationship. Any threads protruding past the thickness of the hub are useless and can't contribute any additional load capacity of the joined parts, and will cause damage to the threads in the hub due to dirt and corrosion when the faster is removed. If the lug bolts extend past the thickness of the hub flange, the bolts should be shortened to be flush with the hub flange inside surface when tightened properly to spec torque. The thread pitch is 1.5 mm, so measure the depth of the hub flange hole, or flange thickness, then divide that measurement in mm by 1.5, to find the number of turns of the lug bolt. For example, 16 mm / 1.5 mm thread pitch = ~ 10 2/3 turns of the lug bolt into the hub flange.
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