Uprated Toe Link Failure

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Thebatman
Posts: 31
Joined: Fri May 30, 2014 9:54 pm

Uprated Toe Link Failure

Post by Thebatman » Thu Jul 03, 2014 7:42 am

Hi All

Whilst I appreciate that this is not regarding Lotus per se I thought I would cross post from VX220.org. A number of guys over there have suffered Toelink Failure and there was an interesting write up from a guy called John who spent the time analysing his situation.

http://www.vx220.org.uk/forums/topic/13 ... k-failure/

RichS2
Posts: 11
Joined: Wed Jun 18, 2014 9:31 pm
Location: Cumbria
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Re: Uprated Toe Link Failure

Post by RichS2 » Sat Jul 19, 2014 9:34 pm

The 8.8 Capscrews that failed are a cheap imported crap also if they have been zinc plated and not de-embrittled there is a good chance the heads will snap off, Capscrews should really be Grade 12.9 and preferably made by Unbrako. I supply the Ford works rally team with fasteners and all they will use is Unbrako if anyone is concerned about bolts snapping drop me a line and ill supply you with some proper spec branded fasteners and a very reasonable rate

pete757
Posts: 3519
Joined: Wed Sep 27, 2006 1:50 pm
Location: Perth OZ

Re: Uprated Toe Link Failure

Post by pete757 » Thu Aug 28, 2014 8:48 pm

FYI and as an alternative, IIRC, the Nitron toe link kit uses a specific titanium bolt...

That strategy seems sensible... I had their kit fitted to my S2 Elise and S2 Exige.

There is also an interesting thread on 'Ausi Elises' about another make of toe link failure during a normal drive on the street...

Scary stuff really.

AndyD
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Re: Uprated Toe Link Failure

Post by AndyD » Fri Aug 29, 2014 4:25 am

RichS2 wrote:The 8.8 Capscrews that failed are a cheap imported crap also if they have been zinc plated and not de-embrittled there is a good chance the heads will snap off, Capscrews should really be Grade 12.9 and preferably made by Unbrako. I supply the Ford works rally team with fasteners and all they will use is Unbrako if anyone is concerned about bolts snapping drop me a line and ill supply you with some proper spec branded fasteners and a very reasonable rate
I'm very interested to know about the 12.9 cap screw used in a toe link ( shear) application.
There are many discussions on the point that 12.9 bolts are more brittle than 10.9 and so must never be used in suspension applications. However maybe more important is the fact that you need to torque a 12.9 bolt higher to achieve the same clamping load so if you follow the manual its not good enough and then the nut comes loose. Probably then also a function of what nut your using, a nyloc or some better quality method. After all its the clamping load that is making the joint.

What I have seen is that its usually the nut that comes loose and then the screw is moving around and then it breaks. The hole is actually a bit larger than the 10mm bolt shank.

Then there are bolts that use too long a thread section so most of the force is concentrated in the thread not a shank and failure of the bolt occurs then.

I run the risk using 12.9 cap heads with a shank all the way through the upright and a little longer with a thick washer combined with K nuts that I torque up to 85Nm - checked every track day. I did however put some 12.9 cap heads in a strong vice and hit them with a sledgehammer and found they bent .. I then tried 10.9 and they bent much easier and then 8.8 that just folded over .. so there is also the question of what bends first, the bolt or the subframe ...

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