Can You Have Too Much Castor?

[BHDave]

Simple question;

Is there such a thing as too much castor? If you can get up into the 11-13 range is it worth it? Can you run significantly less camber as a result or is it pretty negligible once you get past a certain point? Does too much castor bugger up the inside wheel geometry significantly after a certain point when it's turned?

No drive shaft angle issues, no scrubbing on the front of the guard issues. I have none of them.

I have installed a set of GTR adjustable upper arms in a gtst and it has shifted the top outer mount back a good 15-20mm. So bulk castor when combined with the 8 degrees i had to begin with.

cheers

Dave

edit: I can't spell

Edited August 20, 2007 by BHDave

[tacker]

again i stand to be corrected but your upper control arm governs your camber not castor. Surely with 13 degrees castor you would struggle to turn it i think

[B0oStEr]

I've never seen a maximum castor recommendation but 13 degrees does seem excessive.

I don't think there is supposed to be any difference in off set between gtr and gtst upper arms.

Are you sure they are installed the right way around?

[BHDave]

again i stand to be corrected but your upper control arm governs your camber not castor. Surely with 13 degrees castor you would struggle to turn it i think

I have these upper arms. Note that the position of the mounts is parallel as opposed to staggered with the out side forward on a stock arm. If you rotate one end the castor is either increased by a ridiculous amount over stock or reduced by a small amount depending on which way you fit it (noting that the inner and outer mount lengths are different so there are only 2 ways it can go in). left straight i'd say it gains atleast 2 degrees, haven't got it aligned yet to confirm the angle. But i can increase the castor further by rotating the outer end. Installed pic Hopefully this link works.

By winding them in and out it effects camber, so it does both, though i'm interested in castor at this stage.

Booster, definately installed right. I don't know if the stock gtr and gtst upper arms are different as i have never looked at a stock gtr upper arm beside a gtst one. During install i had the stock arm sitting on the ground next to the aftermarket one and as noted above it was either lose castor or gain castor. I went for gain because i've always understood more is better, but how much more?

[Abo Bob]

I have tried various caster settings from 4.5 degrees to 13. At 13 I had rubbing issues and settled on 8 or 9 I think. For the street I find this perfect. When it was at 13 I found it annoying to drive as it takes more effort to go off centre and strongly wants to return to centre when you are going around a bend. That said, turn in was brilliant.

Speaking to John at UAS about the slot car, he said he went up as high as 13 but settled on 11.

[BHDave]

Excellent. Thats good to know as the z has a similar front end to the 32

[Beer Baron]

to be honest too much caster means you end up sacrificing camber. in the begining I loved caster and yeah it's great but it's not substitue for neg camber. in the GTR with 255 fronts I can't get more than about 8 degrees neg caster as the front of the tyre is just about touching the guard liner. Also it limits how much camber you can run as of course the arms are pulling against each other to some degree. I would say get as much caster as you can until it begins to limit the static camber you have. if you want some track work I reckon you want the camber up around 3+ of neg.

[salad]

I did the same thing when I got those arms, the problem with mine was, as they're staggered arms, I put them in the wrong way and it gave heaps of castor and bugger all camber. When I had the arms maxed out (short as possible), the wheel aligning machine read about 16deg castor and about 1.5deg camber, so really sacrificed static camber.

I'm fairly sure that GTR and GTS-t arms are the same though, maybe one's a bit shorter than the other from stock, but I'm fairly sure the offset of the arms is the same for both. My adjustable GTR arms seemed to be pretty damn similar to my stock GTS-t ones anyway.

Edited August 21, 2007 by salad

[djr81]

There are two completely different circumstances where castor will & will not help you.

1. You are one of those drift type people. In which case loads of castor is good. It gives you strong self aligning torque (for when you let go of the wheel) & more -ve camber at large amounts of lock. All of which is good.

2. You have a track car, or atleast want to do hillclimbs/club days etc. In this case caster is much less important & certainly not at the expense of camber. Simply put more castor gives you more camber when you turn the wheel. However if the car if handling well you wont use much more than about a quarter of a turn of steering lock. The amount of extra -ve camber castor generates at these angles is negligible - particularly is you have an R32 which only has anout 3 degrees castor to begin with.

[BHDave]

2. You have a track car, or atleast want to do hillclimbs/club days etc. In this case caster is much less important & certainly not at the expense of camber. Simply put more castor gives you more camber when you turn the wheel. However if the car if handling well you wont use much more than about a quarter of a turn of steering lock. The amount of extra -ve camber castor generates at these angles is negligible - particularly is you have an R32 which only has anout 3 degrees castor to begin with.

This is the answer to the second question i hadn't gotten around to asking yet Obviously the caster is going to have minimal effect at small steering angles, at which point the camber has to be there to work the tyres properly. I would assume increasing both camber and caster would see the dynamic camber way too high on slow tight corners too.

Thanks for the input everyone.

Quick question for salad; When you put the arms back in the right way what did your camber increase to?

Edited August 21, 2007 by BHDave

[Beer Baron]

when I had those arms in the GTR (installed the correct way) I could only get arond 2 and a half degrees neg as I had so much castor. with my new noltec arms I can get about 3 and a half.

[dangerous_daveo]

I would just like to say Dave, I believe that your question is not stupid, and very valid.

So I guess the question now is, whats the equlibrium point? What is the best match of castor to static camber? (as a general rule of thumb)

[driftmeister]

I just did my alignment today and my caster reading is 5.4 deg for both sides. Camber is 2.1 deg front & rear. Currenly all my arm are adjustable pillow ball type for both camber & caster all round. The handling is so far acceptable but i wish to have a setting for canyon or back road type of driving with slight understeer since i still haven't learn the art of drifting.

Appreciate some feedback...Cheers!

[T04GTR]

yes you can it makes the car very unstable mid corner. basicly just a prick to drive fast. i pulled mine back to 7 degrees. (was 8.5-9) much better now

[T04GTR]

ps.. v8 supercars and alot of other built race cars only run around 4.5-5degrees.

[Abo Bob]

They run a lot of camber though don't they? What do you run on the utes Dave - camber and caster?

[BHDave]

Just a quick update and more insights into what happens to the front end geometry of a skyline when you change things around.

So i swapped the arms around this morning so that they are staggered forward again. I also double checked and yep, the outer on the arms sits 5mm further forward than stock so i will have lost caster.

But i did gain camber, somehwere in the order of -.5-1 degree by eye

And here's the funny part, as it rotated the upright so much the height of the car dropped by about 10mm due to strut alignment changes i guess. I had to wind the coilovers back up. bonus 10mm extra travel before i hit the bump stops

Edited August 24, 2007 by BHDave

[driftmeister]

yes you can it makes the car very unstable mid corner. basicly just a prick to drive fast. i pulled mine back to 7 degrees. (was 8.5-9) much better now

Do you reckon i should adjust my caster to 7 deg since i find the steering is kinda light on high speed corner. Mine is now at 5.34 deg with 2.1 camber.