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Old 11-01-2012, 04:21 PM   #1458
PratoN
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What I Drive: 2012 Kona Blue Ti Hatchback, DCT

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Quote:
Originally Posted by Zillon View Post
While there is some play to allow for larger diameter bolts, how big we could go is something that I'm not quite certain of. If we were to step up to a M10 bolt, how much stronger would that be?
A lot.

M10 (10.9, even at 1.5 pitch) would be good up to 44 ft lbs (3028.2 kg tension - not including the load from the strut) with a maximum torque of 58ft-lbs (4271 kg).

Note: A grade 10.9 M8 with 0.5 pitch at 36ft-lb (I still have no idea what pitch thread this car uses, but it's probably M8x1) would result in 3125.9 kg of tension on that bolt

Quote:
Originally Posted by Zillon View Post
Along the same lines, I've been mulling over two different plans, one a little more drastic than the other. The first involves replacing the existing bolts with larger-diameter bolts, and drilling out and re-tapping the strut mounts for a larger bolt. The other involves drilling out the strut mounts, inserting a larger diameter bolt through the bottom of the strut mount, and securing it with a washer and locknut from the top of the strut tower. These are two options that I'm not quite willing to pursue yet, as I'd like to see how seriously Ford considers the data collected from us.
I'd probably recommend a grade 10.9 M10x1.25 - but can't recommend torque values until I know the loads these struts are putting on the bolt (maybe 200kg is a good guess based on the weight of the car...?)

After looking at these numbers, I'm almost positive these bolts are stretching.

Again, the site I'm using:
http://www.futek.com/boltcalc.aspx?mode=metric
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