As mentioned in another thread I was thinking of ways to extend the suspension travel on my rallycross Miata. One idea involves extended tubular control arms to widen the track and increase travel. Any thoughts on the best way to do this? Or maybe other ways to increase the travel, either extreme or mild.
if you widen the track without switching to a wheel that would move the tire an equal distance back inside the fender, you will have clearance issues at stock travel. Widening the track by using extended control arms would give you a pretty limited increase in wheel travel, too, and you would have to stiffen your springs to get the same effective spring rate. Im not sure how much the factory halfshafts/cv's in back will let you go before they get unreliable, and I'm not sure how much more uptravel the factory fendes will allow.
I think one of the few ways to get more travel on a miata is going to involve making the car taller, which will probably adversely affect cog.
When widening the track I would cut the fenders and use flares.
Increase travel which way? The limitation for compression travel in the rear is the control arms hitting the subframes. At this point on stock diameter tires, you're pretty close to the ground. You can get to this point with well selected off-the-shelf parts.
In the front, it's usually the tires hitting something in the fenderwell.
Tall ride height isn't the end of the world, they can still work pretty well when tall.
My suggestion is to identify your target. Get some dimensions on your desired max droop and max bump wheel positions. Then see if there's something off-the-shelf that will do the job (ie, AFCO) or build your own. Find the shocks with the longest shaft travel you can and possibly build your own upper mounts to get the right balance of compression and droop travel. Depending on spring rate, you may need a secondary spring to take over when you hit the limits of the primary spring.
If you're looking to extend shock travel you could always make some extended top hats for the shocks. I had some for my CRX and they worked wonders.
I pondered this once and came up with using slightly taller and stiffer springs with stock or improved bumpstops to get a 1" lift and using 1-2" taller tires. I am pretty sure that keeps you within stock or stock type replacement shock travel and that extra 2" ride height would be phenomenal for the off road stuffs. Combine that with skidplates and that should be an incredibly fun offroad otter.
Ride height is secondary to having enough travel that you're not bouncing off of the stops at both ends :) You shoulda seen the look Will had on his face when we were changing the strut at Tulsa and he saw the oil soaked, mangled, shredded bumpstop, like maybe he was having second thoughts on which car he was driving!
One reason that I'm a fan of extending control arms (besides the rad dirt-buggy vibe) is that you know you won't run out of ball joint motion. When my car's front suspension is topped out, the ball joints are almost binding. This also makes it fun to try to put the car back together after a strut mount breaks and shoves the strut onto the wrong side of the inner fender. Suspension 3.0 is going to have to take this into consideration, probably with droop limiters.
One downside, besides the usual potential for mass breakage that goes with DIY suspension parts, is that you don't get much. Say the control arms are 18" long and you make them 2" longer. You've widened the track by four inches but realistically you have only gained maybe 1/2" of travel, all else being equal.
Now, if you could double the length, then you are doubling the travel available within the bounds of ball joint motion, but then you're making a subframe and buying a racing rack and pinion that's about a foot wide and all sorts of other things that are badass yet impractical.
EVS foam "soft" bumpstops that are tunable (by switching them out) will make a big difference in how a vehicle feels that is bottoming out shocks. Difficult on struts like miata, but jounce shocks, which are tiny shock absorbing bump stops, work great off road for soaking up big hits... in fact a lot of low travel off roady type vehicles are tuned to use jounce shocks almost like a progressive spring, when the wheel travel exceeds a certain amount it gets into the jounce shocks. Helps keep cog low.
rx7
f150?
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