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Discussion Starter #1
Let me preface anything in this thread with the idea that in my opinion I think TTY bolts are stupid unless you're looking to shave weight.

IMO car manufacturers are using these bolts two-fold. For one is to shave weight, but also to screw the consumer out of more of their money. What I'd like to do is comprise whatever suspension parts or in general any bolt used on our cars that isn't grade 5/8 steel non-TTY bring them all into one thread with their thread pitch and length. With that information, anyone can replace the bolt with peace of mind the bolt won't fail.

Not sure how many of you know this, but each bolt that is steel is supposed to be torqued to a specific minimum number based on size of the bolt, grade, lubricated or not, etc. You guys can find that online.

Has anyone already figured out the thread pitch of certain suspension parts bolts (eg. control arms, sub-frames, brackets, etc...)?
I'll be working on some stuff this weekend and start adding stuff to this thread.
 

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Discussion Starter #2
So I measured the bolts and its exactly what I had thought. They are not truly standard metric sizes. The thread pitches are common for the diameter of bolt used. It's been pretty difficult to find replacements in non TTY.

The following are the sizes I gathered:

Front subframe bolt = M16 x 1.75mm x 75mm (shouldered hex head)
Front subframe bolt washers = 50mm OD x 16mm ID x 2.5mm thick
Rear Subframe Bracket = M20 x 2.0mm x 80mm (shouldered hex head), M12 x 1.5mm x 20mm (shouldered hex head)
Steering Rack = M16 x 1.75mm x 70mm (shouldered hex head)
Swarbar Bolts = M20 x 2.0mm x 85mm (shouldered hex head)

Anyone owners from Europe know any sites that have a wide variety of odd sizes for metric bolts?
 

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@chronos,
I understand your fustration but TTY bolts actually have higher and consistent clamping force. We have learned the hard way with a couple engines that lifted the heads with ARP studs. Even the main studs have a 60 ft/lb spec however the factory TTY bolts load past 60. In other words when installed to 21 ft/lb then 90 degrees a tq wrench set at 60 will not move the bolt. If I remember correctly it took 75 ft/lb to move it. Same with the head. It was over 90 and the studs call for 60-65 ft/lb. On suspension it might not make much of a difference because of steel parts but on the engines (being aluminum) I would stick with OEM unless you drill and tap oversized.


"Torque-to-yield (TTY) fasteners are a completely different style of fastener that have come into vogue with 21st Century engines. These fasteners are commonly torqued into place using a torque-angle method, but that’s where the similarities end. TTY fasteners are designed to stretch to a certain yield point and not exceed this clamp load limit. This tends to stabilize the load for a head gasket, as an example, when the engine is both cold and then as it warms up – especially it the engine is all aluminum where material growth is a concern."

"Torquing a fastener to yield results in a high preloading of the fastener which, depending on the load frequency and amplitude, can significantly increase the fatigue life of the fastener. When the applied load doesn't surpass the clamping force of the fastener, the strain of the fastener will be lower than when the preloading is smaller than the applied load. It is therefore beneficial in high-frequency high-load situations with a higher risk of fatigue related failure, like a bolted down cylinder head, to use torque to yield bolts.
Advantage: Compared to normally tightened hardware, a smaller sized TTY bolt/screw may be used while still maintaining the same clamping force.
Disadvantage: A drawback with TTY hardware is that it normally has to be replaced when loosened, for example when the cylinder head is removed"
 

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For many suspension pieces, a TTY bolt is very beneficial. When properly applied, the bolt acts as a spring, and applies a constant pressure to what you're securing. In other words, things wont loosen, or are less likely to in the long term.

What that translates into, is better reliability (Not to mention safety). It's not a money play to sell more nuts and bolts, or a way for manufactures to make service more expensive. Nor is it a weight saving decision. It's a smart engineering decision IMO.
 

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BTW for suspension work, I'm not afraid to reuse a TTY bolt once maybe twice depending on location. I often will torque it about 10-15% more for no other reason as in my head that sounds nice.... I drive a Focus, I live on the edge. :p

If I did that repeatedly I'm sure the bolt would stretch and snap. Or if I torque to normal spec it wouldn't apply enough fastening torque to overcome backing out.
 

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How do you know when you're working with a TTY bolt vs. a traditional bolt?
 

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How do you know when you're working with a TTY bolt vs. a traditional bolt?
a smooth cut down shank. Basically a smooth section from the thread to the bolt head. But the section is often slightly smaller and a very specific size based on the tty value.

You can find other bolts with a smooth section. But they are the same size as the threaded section.
 

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Discussion Starter #9
As much as its an engineering decision for it, years prior to TTY bolts they used traditional style without suspension issues of any kind. Maybe there's a more in depth understanding in suspension nowadays given the designs of chassis' now that I don't know. If you torque a traditional bolt to the correct spec and add thread locker, it should do the job better than a TTY bolt.
 

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Ah and don’t forget accouting! They could see a material cost increase say $.05 per thousand bolts for one over the other. Or increased manufacturing time to apply a thread locke

That being said, what was done in the past doesnt mean its the most optimal. It would seem the entire industry moved to this direction and not just Ford.
 
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