Looks like 2.75" of positive scrub. That's about an inch more than OEM, but very similar to what I had with OEM spindles, spacers, and bigger tires.
Fuck turning wrenches, I wanna go wheeling; So I sold the taco.
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Looks like 2.75" of positive scrub. That's about an inch more than OEM, but very similar to what I had with OEM spindles, spacers, and bigger tires.
Not too bad. If you could get it under 1" it would save a ton of wear on your steering. Just go 40's and that number will go down a little lol
Not too bad. If you could get it under 1" it would save a ton of wear on your steering. Just go 40's and that number will go down a little lol
Even 40s wont get it that low, they take about 1/4 inch off. What I need is more king-pin angle, and/or less positive offset to get the scrub radius down. Unfortunately, the kingpin angle is about as high as recommended (8 is the max), and offset is a bearing/spacer packaging issue.
Why do you say 8° is the max? You can definitely go more than that. I would rather have less scrub radius than a lower KPI/SAI. Just increase the caster angle a little to make up for any negative effects of high KPI/SAI. The higher caster will help keep the camber change in the right direction when steering and body roll during corners.
Ref to "Race Car Vehicle Dynamics". They recommend<8 deg KPI for rear wheel drive, and live with the scrub that generates.
Given big/soft tires though the jacking effect of higher KPI will be absorbed in the sidewall. But messing with KPI requires changes to relative arm lengths, which has other issues (Instant Center will change).
I think the real answer is to make the spacer/bearing/hub stack a slim as possible to reduce the scrub, I'll never get it negative, which would be nice. But I should be able to get it closer to zero, but I have to make some careful measurements of the upper uniball vs the edge of the wheel.
kasnerd
Danny's Red Headed Step Child
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Curious "window shopper" question...
Would moving the UCA mount point on the spindle down by adding length to the UCA let you dial in the scrub angle and eliminate the spacer bs? This would mean a smaller spindle, less weight? camber might be a bitch though being so close.
Would moving the UCA mount point on the spindle down by adding length to the UCA let you dial in the scrub angle and eliminate the spacer bs? This would mean a smaller spindle, less weight? camber might be a bitch though being so close.
That <8° is probably for track cars that have very little wheel travel and body roll.
I don't think you'd ever want negative scrub, but getting close to 0" would be nice. I've heard you never want exactly zero since the wheel will have no resistance at all and constantly have a slight push/pull feeling depending on the road surface. Like 1/4" is ideal from what I've heard.
If you can get it less than 1" I think you'll have a much better handling vehicle and better steering performance at high and low speeds. Whether you achieve that by increasing the SAI or increasing the wheel backspacing, is up to you.
We are now back on the subject of IC. I'd put less focus on that number and focus more on things like camber curves (more negative at droop and bump the better to a degree), and scrub radius. Low RC can be combated by sway bars, but too high RC will cause jacking.
Yeah that is always an option. Just have to make sure the UCA is strong enough to handle the increased leverage of braking, and also making sure you have room on the frame side to go lower without compromising too much on geometry.
kasnerd
Danny's Red Headed Step Child
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GOALS!this looks pretty beefy. so impressive.
I wish I had the time, skill and money to build something like this.
That thing has a pretty low SAI angles and a decent amount of scrub radius. Also has full hydro steering rack.
Campbells car has more SAI and less scrub radius though.
kasnerd
Danny's Red Headed Step Child
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baller...
@Arcticelf there ya go. We expect drool worthy spindles and will accept nothing less. haha
@Arcticelf there ya go. We expect drool worthy spindles and will accept nothing less. haha
Yes, you're basically correct, and as @AssBurns points out the big issue is strength of components as you make the arms closer together vertically.
The other issue is the ratio of uca to lca arm length, the spindle bridges the two arcs created but the arms, if you notice on those cars the arms are almost equal length, and very long. Which makes thier horizontal displacement quite small relative to vertical travel.
I'm locked into a 15.5" LCA (oem+1.5") and a Tacoma frame. Which means my max uca is about 12". Longer LT, or a different frame geometry would make this way easier.
Comparing oem scrub to my new design, and the oem handling issues, I think I'm going to have to spend at least proving that it really can't be made any better before I start building.
My UCA is already mounting on the side of the frame, so I've got vertical room to play there.
kasnerd
Danny's Red Headed Step Child
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that was going to be a follow up question about relocating UCA mounts to be more in parallel with the LCA. Yea those arms on that buggy are long for days.
No JD LT? Especially if you gusset or box up the spindles should be able to take whatever you throw at it, as long as the bearings and seals hold up...
Which reminds me need to order ECGS bushing and get my spindles done asap for the new axles. Have new hubs that have been waiting for the right time. Damn this JD group buy... making me actually get some shit done.
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I'm doing hydro bumps off the UCA, it will definitely bend OEM spindles. And the angle off the uca adds caster as the suspension stuffs, which is fine for a road car, but sucks for performance driving. So I'm doing custom mounts and custom arms to get rid of that, and double shear horizontal uniballs upper and lower for a stronger setup.
The JD setup is cool, and probably the one I'd go with for a bolt-on, but I'm way too far into this for bolt on anything. It's rapidly approaching the point where a tube chassis would be a better idea.
kasnerd
Danny's Red Headed Step Child
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it'll be awesome to see how it comes out. The front frame leaves much to be desired on 2nd gen tacomas. I'm kickin around a cage setup. Stupid JD planted that weed a few weeks back and now it's growing on me.
also, you misspelled cha$$i$
Ha, yeah, that's the correct spelling.
I've already got the cage going, that'll tie it all together forward of the firewall, then the back will go together later.
@AssBurns it looks like 1.5" positive scrub is about the best I can get with all other packaging concerns taken into account. Any less than that that and the UCA isn't long enough to keep the IC inside the truck for the whole range of travel it's right on the edge of having the IC move outside the frame at full droop.
That also leaves me about 8" of vertical separation between the UCA and LCA frame side pivots, those UCA pivots are going to need gussets on the gussets.
That also leaves me about 8" of vertical separation between the UCA and LCA frame side pivots, those UCA pivots are going to need gussets on the gussets.
Well that's a huge improvement! Your steering will love you for that lol
Is there a reason to want to keep the IC inside the truck? I can't think of any negative effects of having it further out than the width of the truck Seems like a non-issue since so many cars run close to parallel arms which would put the IC almost an infinite distance away from the truck. A tight IC seems like it would cause drastic changes in geometry throughout cycle.
It mostly matters to keep the IC on the same side of the wheel the whole time. i.e. always outside or always inside. OEM Tacoma is inside, so I'm trying to maintain that.