22 replies to this topic

[Zoobeef]

8.8 - 45Nm

10.9 - 68Nm

 

Noticed the new ones from Lotus are 12.9 so what torque do i do those to? I saw an old post from Arno saying you could go up to 84Nm but risk stripping the thread out the upright as we dont know the steel type used.

 

And everyone for gods (doesnt exist but ill use the term) sake run a tap through the threads, make sure the mating faces are clean and dont use copper slip.

[stu8v]

89 dry, 66 lubed

[Zoobeef]

The hub threads strong enough to take 89Nm?

[D-DAWG83]

89 dry, 66 lubed

Im guessing you mean with copper slip or similar. Do these require thread lock at all?

[oblomov]

89 dry, 66 lubed

That's interesting, where did you get the lubed figure?  I know theoretically you can lubricate threads if you know the correct reduced torque to use to compensate, but that seemed to me to open the can of worms that is the difference in the lubrication qualities of different products?  Something you really would need to get right on critical components.

 

Didn't Scuffers say somewhere that he does it though he knows you're not supposed to?

[Scuffers]

 

89 dry, 66 lubed

That's interesting, where did you get the lubed figure?  I know theoretically you can lubricate threads if you know the correct reduced torque to use to compensate, but that seemed to me to open the can of worms that is the difference in the lubrication qualities of different products?  Something you really would need to get right on critical components.

 

Didn't Scuffers say somewhere that he does it though he knows you're not supposed to?

 

kind of.

 

with steel uprights, I use 12.9's and work to a minimum of 55Lbft  (the spec for 12.9 is some 62lbft)

 

the important bit is the threads/shims/surfaces need to be spotlessly clean and dry, DO NOT lube the threads, use copaslip, or any other product.

 

Once you have them torqued up, by all means then coat in copaslip or the like.

problem with HT bolts is that if you fail to torque them enough, you won't have enough 'stretch' in the bolt to maintain the clamp load, and all the different grades of HT bolt have different loads.

 

ie. if you do them up to the 8,8 spec torque (~33lbft), a 12.9 will simply work loose.

 

the threads in the upright are plenty strong enough assuming they are clean and not already chewed up.

[Nev]

I've been using 12.9 bolts for a few years now (with no issues) and try to do them up pretty damn tight, however the cramped space under the rear arches makes it pretty tough to get the leverage, can't remember if I got as much as 60 ft/lb, probably a bit less knowing my weedy wrists.

 

One thing noone seems to mention is that once salt & grime and rust gets between the spacers I suspect the tension on the bolts increases. This might possibly even be why some bolts fail. It was this thought (and their easier sourcing) that made me swap to 12.9 bolts a few years back.

Edited by Nev, 18 November 2015 - 03:28 PM.

[Zoobeef]

Cheers everyone.

 

Will be fitting the new bolts to my car while its down at work between Bedford on the 28th and Brands on the 12th. The last set have been on a year so thought they were due a change.

 

 

Currently fitting a set of my other VX as they came with it but they are 10.9s so i knew that figure.

 

Its alot easier to torque them when the hubs sat in a vice Nev haha!

[stu8v]

[color=rgb(51,51,51);font-family:Arial, Helvetica, sans-serif;]Lubrication reduces the friction during tightening, decreases bolt failure during installation and increases bolt life.[/color]

 

[color=rgb(51,51,51);font-family:Arial, Helvetica, sans-serif;]Variation in friction coefficients affect the amount of preload achieved at a specific torque. [/color]

 

My guess is there are failures due to over-torque of the std bolts.

 

[Scuffers]

[color=rgb(51,51,51);font-family:Arial, Helvetica, sans-serif;]Lubrication reduces the friction during tightening, decreases bolt failure during installation and increases bolt life.[/color]

 

[color=rgb(51,51,51);font-family:Arial, Helvetica, sans-serif;]Variation in friction coefficients affect the amount of preload achieved at a specific torque. [/color]

 

My guess is there are failures due to over-torque of the std bolts.

 

Lubrication also causes issues with the bolts staying put (in the context of these bolts).

 

Most failures I have seen are down to them working loose and then shearing.

 

Without going mad, it would be very hard to have one fail from over-torque if it did not fail when installed.

[D-DAWG83]

Got to be honest, and say when i was spinning the hubs round to replace the bearings, that when i refitted mine, i just did them up tight, and they have been fine, and iv got no idea when they were last replaced. They were very tight initially to release, but the state they are in, that could be the weather, as well as the torque.

[Scuffers]

When Elise Trophy started, after ~3 rounds, these started breaking on peoples cars.

 

Trying to educate people into replacing them and that they were a service item was hard, and by service, not every 10,000 miles!

 

For cars I race, I tend to look at them every time I have the wheels off, and if in any doubt, replace them, they cost pennies, and the though of having them break is not good.

 

Touch wood - I have never had one let go on me yet... does not bear thinking about when your doing this:

 

[D-DAWG83]

How do you check them Scuffers? Do you measure them to see if they have stretched, or just give them a visual? Iv got a full set ready to go on, so got some reassurance when the car goes back on the road

[Scuffers]

How do you check them Scuffers? Do you measure them to see if they have stretched, or just give them a visual? Iv got a full set ready to go on, so got some reassurance when the car goes back on the road

 

put a spanner on them and check they are still tight.

 

they always work lose before failing..

[FLD]

Is a threadlock a good idea or not?

[oblomov]

Is a threadlock a good idea or not?

Apparently yes it does but the basic rule is on critical assemblies is follow the manufacturers instructions and use it if recommended.

These links are interesting.

http://benmlee.com/4...ads/threads.htm

 

http://www.boltscien...es/vibloose.htm  

[D-DAWG83]

Will be coming out soon enough as part of a suspension refresh. Car has been off the road since end of October, and i was part of the group buy for a complete set. Im guessing they stretch, work loose, then fail when things start morning around because they are not done up properly.

[Scuffers]

Is a threadlock a good idea or not?

not a good idea.

 

if you torque them up they will not come loose.

 

if you thread lock them, and they subsequently start to stretch, they will still appear tight when you check them because of the thread lock, when in fact, they are starting to come loose.

 

also, you have the problem of it lubricating the threads and messing up the torque settings.

[D-DAWG83]

So dry is the way forward?

[oblomov]

 

Is a threadlock a good idea or not?

not a good idea.

 

if you torque them up they will not come loose.

 

if you thread lock them, and they subsequently start to stretch, they will still appear tight when you check them because of the thread lock, when in fact, they are starting to come loose.

 

also, you have the problem of it lubricating the threads and messing up the torque settings.

 

Also if you threadlock them and they snap with no head protruding you have to send the whole hub assembly to CERN in order to have the stud remainder dematerialised in order to get it out.