GH Sigma Control Arms....

[skit]

Hi all,

Merry Christmas....

Well I have read through all the threads on using GH sigma LCA's and I have seen several comments saying that the taper inside the ae86 steering knuckle is different to the ball joint taper on the sigma LCA. It is claimed that the mismatch will flog out the inside of the steering knuckle....

Can someone please elaborate on this rumour of the taper mismatch? Is it even true?

If the taper angle of the sigma ball joint is greater than the toyota knuckle, then it may be possible to machine out the nuckle taper to suit. If visa versa then ok its a ligitimate problem.

Please - no comments on why would I want to go to GH LCA's. My car is basically used for track days only. I currently have xt130 LCA's, 15mm bolt on spacers, with 15x7 +12 rims. Also have camber tops & typically run 2.8 - 3.5 deg neg camber.

I run 25mm bolt on spacers on the back & want the GH LCA's to punch out the front track further, not worried if I have to flare the guards. I do not want to use thicker front spacers or wider/more neg offset rims to gain track.

Looking forward to some feedback. If no-one can answer then I'll get some from the wreckers myself to test fit.

Otherwise I will cut & shut my old std 86 LCA's to suit (Yes I am aware the authorities do not approve of this).

Cheers

[Konakid]

There is a type of sigma LCA which bolts straight in but you will need RA40 celica tie rod tubes and tie rod ends so that you have enough toe adjustment.

What are your reasons for not wanting to run wider and lower offset rims to increase track? This is the best way to gain extra track as it doesn't make the steering heavier due to keeping the scrub radius 'closer' to factory. The steering will feel much more accurate due to not having skinny wheels far apart, instead using rim width to gain the extra track outboard that you want (using a lower offset) and more inboard also due to wider rim.

[skit]

Thanks konakid.

Regarding scrub radius - so long as I maintain the same camber angle when switching to GH lca's I thought the scrub radius would remain unchanged. If i instead kept my xt130 arms and went to more neg offset rims then that would increase scrub radius.

I googled and found a pic which is how I understood things....

[attachment=20223:Align_Scrub.gif]

Is this wrong?

As far as why I don't want to change rims - well this costs more money & takes time to find the right rims. At this time of year neither is readily available(!). I quite like my rims at the moment, and the GH control arm conversion is fairly simple and cheap to do. If I don't like it - its easy to go back, just elbow grease.

<div class='quotetop'>QUOTE (KonaKid @ Dec 26 2007, 01:36 AM) </div>

[Konakid]

Yes, your right, the scrub radius does stay the same with the longer arms.

My point was that by going wider rims as well as a lower offset, you can get the edge of the rim to sit out further (increasing track) by using a lower offset but by using say an 8inch rim you can gain track inwards towards the strut due to the width therefore reducing the scrub radius and negating the need for the spacers (which increase scrub radius obviously)

That said, the longer arms are a cheap and easy way of scoring some extra track and i say go for it but its not the best solution. If you dont like it you can just change back as you said but it should still feel pretty good to drive with and will help with the turn in no doubt.

[Jonny Rochester]

I havn't stuffed around with Sigma arms too much. I use standard KE30/XT130/AE86 arms, cut in the middle, and weld to the length I want. Its probably easier and I don't think its dangerous if you can weld.

[Gilly]

you guys in TAS get away with a lot more than we can though Johnny!! a cut and shut arm in QLD would get you like 25 years prison

SA has regency
QLD has DOT
NSW, quite frankly i don't know what they have but i know they are strict

I was in Tas recently and saw maybe 2-3 police cars the whole time, and they were parked, and the officers were drinking coffee's talking to pedestrians and stuff :lol: they didn't look busy

[Hen is a total nutcase]

Correct, Sigma balljoint taper doesn't perfectly match AE86 steering arm taper.

Plenty of people bolt them together and I haven't heard of any issues resulting. However I don't like it much. The steering arm sits a long way up the balljoint taper. You can get the taper in the steering arms reamed to suit the Sigma balljoint taper, but finding the shop to do that may be tricky.

Hen

[skit]

Thanks guys.

Hen - thanks for confirmation. If that is so, it should be easy to use a reamer to match the tapers. Even though the diameter is small, the depth is short so it should be manageable. I am trying to get a set of gh arms for sale atm.

Gilly - we have RTA in NSW and yep, their favourite past times are ass-raping & defecting. I don't know if it matters what state we are in these days....probably all have the same attitude towards modified cars. Can we blame them with so many dickheads out there?

Side tracking a bit, I have been pulled over twice for "random" breath tests in my 86 (gutted inside, repainted, drivers seat only etc) and the coppers were quite enthusiastic about it. I think a mature attitude goes a long way, and as we get a bit older they seem to treat you with a little more respect. Of course that goes out the window if they actually catch you doing something wrong!

Sorry back on topic. Think we have clarified the issue of the tapers. I will post up to show how I go with reaming the knuckles.