TTY Bolt Alternative
 

I'm getting ready to do a full fluid change, and need to drop the stiffening plate. I don't want to pay 5 per bolt to replace the TTY bolts on the plate (yeah, I know, its the principal....). So why couldn't I just use standard 10mX55mm bolts high grade 10.9's, with new washers and nuts and just tighten the shit out of them (spec is 41lb + 90deg) and/or use some threadlocker on them to keep them from backing out.

Discuss...

I would say as long as the bolts are to the perspective torque setting of the stiffening plate I don't see a reason you couldn't use regular hardened grad 10.9 bolts. The key is the torque setting for the type of bolt used, stiffening plate bolts are TTY and only torqued once for structural integrity of the plate/front end. As long as the torque setting is kept I would think theoretically the integrity of it should be fine.

Good idea actually!

I bought bolts and nuts from McMaster Carr. I even welded the nuts so it would be easier to remove the plate (no need to unmount the wheel and reach with a wrench the other side). Makes removal and install a lot faster.

Welding the nuts is not a good idea. The threads on both the bolts AND nuts are subjected to deformation on a TTY fastener set. You will need to replace those nuts each time the stiffener plate is removed.

You missed the part when he say he bought (I assume replaced with regular, not TTY type) them from McMaster Carr.

I would not replace these with anything but the fastener specified by BMW. A different grade bolt will not deform the same as the OE bolt, what would the correct torque be for the new fastener?:dunno:

For the torque, I use what is listed for that size/grade of bolt. Many charts float around on inet. I don't really think a TTY is mandatory for that part, but I may be wrong. Sometimes TTY are used to deal with vibration, movement instead of lock washers or lock nuts.

Edit: ...and yes, I used non-strech bolts and new nuts (high grade)

My concern in changing bolt grades is the fact that BMW has put millions of miles and $s into developing the E53 chassis. Those bolts attach suspension components and the stiffener plate to the front chassis horns. During development/crash testing/DOT-TUV certification BMW may have seen the need for fasteners that shear/snap when stressed during a frontal impact or contact with substancial road debris to protect passengers and control deformation flow away from critical components and central occupant structure. I don't know this for sure, but would be willing to bet the farm that there are structural engineers at BMW that do. BMW doesn't use a Magic 8 Ball loaded with bolt grades when they engineer/develop a vehicle.

I did some more research last night. There seems to be a lot of misinformation and conflicting information about TTY bolts in general.


They seem to be clustered around.

1. is there such a thing as a tty bolt. As in, are they a unique bolt or
2. are they just normal bolts installed a certain way?

if #2 is correct, then there must be a very specific torque the OEM is trying to achieve and its possible they know the exact shear point of those bolts

#1 - if you try and buy a 'TTY' bolt, you simply wont find one for sale.

3. regular bolts can be installed with TTY LB's and procedures as the same effect would occur 'assuming the shear torque of the bolt is the same or higher'

4. you can use regular bolts if you take steps to ensure that a) they are as strong (which M10/10,9 bolts should be) and b) you ensure that the torque value doesn't change over time (use threadlocker)

The strange thing is that the 41lb + 90deg is a mathematical equation that should yield another torque value, less accurately (depending on the length of your wrench, and how accurately you measure 90deg).

I don't know, its all very confusing. People say toss'em, people say use'em, people say sub them with normal 10,9's.....


I'll give it a shot and report back...

Tiag is 100% correct. during a frontal offset impact, (as well as many other types of impact) the passenger cage must withstand the structural damage by deflecting the kinetic energy produced by crush.. this is achieved by absorbing the energy by the components surrounding the passenger cage and somewhat controlled manner, when certain parts of the body deform (thus, absorb the energy) in a specific fashion (thus deflecting the vector of force) that the rescuers see a mangled pile of metal, and live people emerging from it... take a look at the inner parts of the fender, where they attach to the unibody - you will see that the metal is fashioned with some "dimples", or "creases", that will fold in case of impact...

I am not saying that the other bolts will drastically change the results of a crush, but I am not the one willing to test the theory...

I had posted a few years ago a crush test results from a test of chinese made knock-off of a german Opel (ithink it was Chery Amulet) - the results of the test were devastating, the dummies were mangled to the point that they had to be pulled out piece by piece, while the original german car was fine with the TUV tests (or whatever the test authority in EC is)... of course the chinese knock-off was priced in the vicinity of $8-12 K brand new, while the original was much more expensive...