rickya

When is rear dynamic toe a good thing on a RWD car and could it be considered helpful like Rear wheel steer, if setup correctly? I am currently making plans for trackday suspension on my recently acquired Honda S2000 AP1. Why I ask is that the Honda engineers intentionally built in rear dynamic toe to make the car oversteer and be fun on track. (dynamic toe out when rear suspension is unloaded). They took this a bit too far and in subsequent years toned this down with less rear dynamic toe by changing rear suspension design and anti roll bar sizes.

As we know this can be immediately fixed on any of the earlier cars with a redesigned rear toe arms that act as an anti bumpsteer kit. But if I am going to reduce how much dynamic rear toe can occur by e. g. more static rear toe in, a softer rear ARB, stiffer 10kg coilovers all round, more caster, more neg camber, staggered wider wheels on back, more offset, stickier tyres - then would some now reduced dynamic rear toe (with standard rear toe arms), be a good thing to help rotate the car on e. g. a tight circuit. Could it be considered a help in a smaller dose like RWS or is any unplanned bumpsteer a bad thing?

thomsbrain

This probably isn't very helpful, but it really is just down to your personal preference for how you want the car to handle. As you mention, some modifications will increase dynamic toe on the stock arms and some will decrease it, based on whether the modification results in more or less suspension movement. Adding grippier tires or negative camber, or softening the rear ARB will increase the effect of dynamic toe because they'll result in more suspension compression during cornering. But stiffer springs will reduce it.

On road course tracks, I prefer as little rear dynamic toe as possible because the actual steering angles you need are so small at high speeds. The effect of any dynamic toe on the car's balance is amplified at higher speeds, particularly when lifting off or braking. But dynamic toe might still be helpful in auto-x to help rotate an otherwise understeer-y setup in tight situations.

ZDan

IMHO, it's never a good idea at all. Just leads to non-linear and weird handling, makes it more difficult to toss the car around without losing rhythm and time.
It wasn't a good idea on the 2nd gen RX-7, wasn't a good idea on the Z32 300ZX, wasn't a good idea on the original NSX, wasn't a good idea on the 2nd-gen MR2, and it wasn't a good idea on the AP1.
It's a lesson the Japanese never seemed to want to learn!

s2000Junky

I dont think there is a way to eliminate it entirely without having no suspension travel, but you can set it up to be as minimal as possible and toe IN rather then OUT which will actually help hold a more stable line in a steady state corner. Having a suspension that wants to toe OUT under compression is a sure way to end up ass over end when your pushing hard. That's my personal feeling based off of my big track experience and preference of course. Its already a short wheel base car thats sensitive at speed. It doesn't need rear steering help. If you want more rotation ability, id focus on this through tire stagger and suspension tuning, not wheel alignment.

ZDan

AP1 already does toe IN with compression, that's the problem! Any throttle modulation (lift) while cornering hard and the outside rear goes from more toe-in to less toe-in, giving more oversteer. This is a big reason the uninitiated find themselves in the weeds with AP1s in particular. Even for expert drivers like myself (nyuk nyuk) it is an annoyance at best. 240Z and FD I can go into and out of drifts smoothly and effortlessly without losing time, whereas in the AP1 it costs me some. It's just not as linear-handling and hence less tossable.

The idea that dialing in some toe-in with compression travel to "provide more stabilizing toe-in" during cornering has always been a misguided approach, and it's never worked right. It actually PUNISHES the people it's trying to protect! Newb gets skeered while cornering, lifts, and around she comes...

Zero toe change with bump is, for me, ideal. For the AP1 which unfortunately has a ton of toe-in with bump, I've found that running *minimal* static rear toe-in is gives the best, most responsive, linear, and stable handling.

rickya

Many thanks for comments and help so far. I think this is pretty much what i was thinking too but also wanted to see whether there is a viable alternative to the question. I was also wrongly trying to think that having some dynamic toe could be a good thing in terms of countering understeer. But this car really has no understeer issues and using dynamic toe for this purpose is an unpredictable hinderance and only loses time on track, from what opinions on here show. I just wonder why Honda engineers and others in the 90s thought this would be a good thing?!

s2000Junky

I agree, and its how I prefer to have my car set up as well. Problem is, there is still some toe change from full droop to full compression, even with my toe correction. It is what it is. My point was to address the issue of actually eliminating negative toe. I "think", if you had stock ap1 suspension at stock ride height, and dialed in that min Toe in spec we like, you would be getting actual negative toe under full droop, which would be bad news. Trick is to reduce the total travel (which lowering the car with aftermarket coilovers does anyway) get the toe arm geometry right with the bump steer kit, and then dial in the minimal static toe.

rickya

When you say "dial in minimum static toe", do you mean as close to zero. i. e. none or very little toe in?

ZDan

I run around 0.15 degrees to 0.20 degrees *total* rear toe in. This is less than the AP1 spec minimum of around 0.32 degrees total, and it's A LOT less than the AP1 spec max of 0.64 degrees total, which is totally out to lunch IMO and sucks bad, for everything (I tried it). I wouldn't be averse to trying 0.10 degrees total, or even zero.

s2000Junky

Yeah, I run 0.20 total also.