While I was shopping for camber bolts for my Mustang, I noticed that they also offer caster bolts which allow for an additional .5 degrees of caster. Does anyone know how much of a difference this would make? How much would it would effect "actual camber" in a corner?
I nearly doubled the caster on my ZX2SR. I was able to run less camber and keep the tire temps in range. I made the car nicer to drive. I never did measure the camber when turned. .5 degrees is hardly worth it.
BMW uses much caster. That may make you happy, or not.
When you add more caster, you gain more camber as you turn the wheel. .5 doesn't sound like much, but can be huge if you have a camber limited car.
Agree with SWG, part of the BMW feel is extra caster. To a point it can give that "on rails" feeling to steering. The flip side is it can seem slow, and dialing the caster back toward zero can give a more immediate feel, at the expense of twitchiness. Dial the car in according to its intended use.
Sure makes a huge difference with an EP3 Civic McPherson set up. 0 caster stock, with no real adjustability. After the lca is even during compression the camber negativity declines - becomes more positive. So, up to 7? or so is a big help. I have about 4 degrees from JDM lcas and caster plates. What a difference. More can be had from extra washers pushing the sub frame forward and spherical offset bushings.
I would like to try the poly offset bushings as opposed to solid. Are they crap or will they hold up?
Caster effects how much camber gain you get from turning the wheel. Also steering resistance/how hard it will want to return to center.
Getting carried away with castor can also unload the inside rear...might not be the hot set up with a mustang if taken too far.
Another .5 is far from getting carried away however.
Also steering resistance/how hard it will want to return to center.
Just to connect the dots, this has a lot to do with people talking about 'communicative' steering and how the wheel 'builds resistance' as you turn harder etc.
I think more caster angle (in moderation of course) is one of the main things that separates cars that were designed to be sporty from cars that have to be forced to feel sporty. If that makes any sense.
1.2° made a significant difference for me.
On my B13 Sentra I ordered up some offset caster bushings from Whiteline designed for some other car in Australia that uses the same platform. Nissan Pulsar SSS? Can't remember. I saw them in a scanned magazine article, it looked like it would fit my B13. Said they added caster.
They ended up increasing the caster only 1.2°, which didn't sound like much, but BOY what a noticeable difference. Mind you, the B13 only had something like 2° to begin with, but the car was ~significantly~ different, and felt much more refined.
I did a writeup about the bushings on sr20forum.com. Couple years later, somebody else started raving about them, too, later on.
Small change, but big gain, apparently.
In reply to Vigo:
I believe buildup under hard cornering is more related to scrub radius. Scrub radius is where your grip related feedback comes from and is also (unfortunately) where torque steer in a FWD car comes from. You would of course run more caster to counteract twitchiness from lots of scrub radius.
Suspension design is one big 3D multivariable balancing act.
As has been said... Caster angle has a lot to do with the camber it creates during turning. Way back in the day, big American cars often had negative caster because they didn't have power steering.
Positive caster has a direct effect on camber during turning. Its not just a "more is better" thing, its a matter of how much grip, how much recovery, and how much camber is needed.
How much you "need" depends upon what the car's for. A FWD commuter with power steering doesn't need any additional amount (and any that's added may not be noticed due to the PS insulating it from the driver). OTOH, if you have a mid-engine sports car with little weight on the front tires and manual steering, you'll need all you can get. I designed in 8 degrees castor for Midlana and it could use more (on the to-do list).
It also helps to load the inside wheel.
Good for some, not so for others.
It is helpful to think about what adding rake to the steering of a bike does - the more you have the better and more stable it will track in a straight line and the more effort it will require to initiate a turn. It will snap back to straight when you let go.
Trying to ride no-hands with zero vs a lot of caster explains the difference pretty well.
On our 2nd gen rx7, adding .5 deg camber and 4 degrees of caster resulted in 3 seconds quicker lap times at summit point shenandoah.
iceracer wrote: It also helps to load the inside wheel. Good for some, not so for others.
Yeah - too much can cause the inside wheel to scrub on high speed, banked turns like the Lightbulb at NJMP or Outer Loop at the Glen. So, while the car feels rock solid it can be hurting lap times and cording tires you wouldn't normally be focusing attention on during a pit stop.
negative caster
zero caster
positive caster
in my mgb i dialed in 7-8 positive - stable but a little on the high effort side for a light front engine. ac 911s also had 8 positive
The shopping cart is still positive caster - the steering axis LEADS the wheel centerline.
Negative caster doesn't work because the wheels will try to flip around to positive caster. Just like a caster wheel does. Just like how your car is WAY twitchy when you are driving quickly in reverse. Down an alley. In the dark. While being chased by aliens.
My Volvo 122 was twitchy at speed; the whole front suspension is shimmed to provide the caster angle. I re-shimmed to add positive caster, and it really made it more stable. It seems to turn- in better, too, something which I'd never thought was related to caster but the adding of camber (since I run nearly 0 static camber) on turns makes sense. Running 165SR 15 tires more camber is always a good thing. If I had to guess how much caster it's running now I'd say about 0.5 degrees. Before it was actually -0.5 degrees (basically I moved the spacers from the front suspension mount to the rear mount). BIG difference!
SkinnyG wrote: The shopping cart is still positive caster - the steering axis LEADS the wheel centerline. Negative caster doesn't work because the wheels will try to flip around to positive caster. Just like a caster wheel does. Just like how your car is WAY twitchy when you are driving quickly in reverse. Down an alley. In the dark. While being chased by aliens.
I think the shopping cart has about zero caster in the image. It does have a lot of mechanical trail though. Where the steering axis is relative to the wheel center does not impact caster. It does change the trail though.
Back in the day, before I really knew what caster was, I added longer leaf spring shackles to the front of my old CJ-5. Boy was that a mistake. I couldn't figure out for life of me why it drove down the road feeling like it was on ice in the middle of the of summer. This being in the days before the internet I turned to the substantial pile of 4X4 periodicals to research the problem and implement a solution: wedges between the spring and axle which put it back into spec.
I believe buildup under hard cornering is more related to scrub radius. Scrub radius is where your grip related feedback comes from and is also (unfortunately) where torque steer in a FWD car comes from. You would of course run more caster to counteract twitchiness from lots of scrub radius.
I agree scrub radius can play into it but i dont think there are very many stock cars that have much in the way of scrub radius with stock wheels/tires. It has a longer list of negative side-effects than positive caster does.
Im open to being proven wrong on that point, though.
You'll need to log in to post.
