Torquing wishbones on Caterham S3

[AlC]

Hi again

 

I know I only just posted another message regarding front suspension - but I thought it best to separate questions. Hope no-one minds.

 

I have two manuals for my car (one because I have a K series engine, one because I have a metric chassis). The K series manual tells me not to torque the wishbone bolts until the car is on the ground. The metric chassis manual tells me to hold the wishbones horizontal and torque them with the car still on stands. I spoke to Caterham and they told me it was advisable to wait till the car was on the ground as that way I am torquing everything up with the bushes in their resting position - doing anything else would be causing unnecessary wear. Makes perfect sense.

 

But I've now figured that once I have the damper unit fixed to the chassis at the top (my other posting), there is no space to get a socket (and hence a torque wrench) on either the nut or bolt holding the rear of the wishbone. So, my question is, can it be torqued later, and if so, how?

 

I'm half imagining I will have the same issue with the lower wishbone later - but have not yet spotted the blocker on that one.

 

Many thanks

 

Al

[Adrian Williams]

I always tghten them when on the ground, I use a torque wrench for the lower wishbone but not for the upper.

 

If it helps to have the wishbones fixed to build the front suspension just undo them again before the car goes onto the ground and then re-do them once it's settled.

[AlC]

Thanks Adrian.

 

Notice you don't use a torque wrench on the upper. Being new to this game I don't have much of a feel for how tight xNm actually is. So a thought I had, but forgot to mention before. Would welcome comments on whether I'm barking....

 

I'm figuring I currently have the upper wishbone correctly torqued. If I carefully mark both the nut and the bolt, then just before putting the car on the ground I can back off the nut a controlled couple of turns releasing the pressure on the bush. My theory is that then once the car is on the ground, and the everything in it's neutral state, I can put those couple of turns back on the nut, which should leave it back at the correct torque. Any thoughts? Seems to work for me, but then I'm an electronics engineer, not a mechanical engineer!

 

Cheers all

 

Al

[Adrian Williams]

You could do Al or having torqued them correctly in the first instance you could 'feel' how tight they feel with the spanners before un-doing them and re-tightening.

 

Either way you want them tight enough so that the bush doesn't rotate and not so tight that you strip the thread on the bolt.

[Rattie]

I just torqued them at the right angle, i.e. pretty much horizontal. If you torque them in full droop, yeah it's going to add wear, but a few degrees offset isn't going to add greatly to the rate of wear.

 

I can heartily recommend getting sets of metric and imperial crows feet. They came in useful for so many of the hard to reach fasteners. Crows foot wrenches

 

I can't confirm it now, but you might even be able to torque using those once the damper is in place.

 

Martyn

^{_{R300GRR SV trapped in Dartford until IVA on 12th March!!!}}

[6speedmanual]

Crowsfoot spanners can be used on a torque wrench but an correction calc has to be applied:

 

torque wrench extension calculation

 

(note the extension has to be co-linear with the line of the spanner for this calc to work. If you want to go in to access the fixing at some weird angle, eg with the crowfoot sticking out sideways the calc will be different)

 

Peter

 

BRAWNGP green SUPERLIGHT

FCITW 2009 😬

[Rattie]

If you use them at 90 degrees then no adjust ment has to be made 😬 Guess what I do...

 

Martyn

^{_{R300GRR SV trapped in Dartford until IVA on 12th March!!!}}

[Mick Day]

If you don't have the engine/gearbox in situ then it's a lot easier to torque up front suspension. However get someone of the same weight (circa 120kg's) to stand on the front chassis tubes whilst you do it.