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I used that kit with a coil cut out of what I remember was a 360# spring*. My car is about 300#'s lighter so I can't say how much my car was actually lowered,. Going by the spring constant I suppose it should be about 1/2".
And ... the kit did work, I measured essentially no bump steer. Be advised that you will experience some loss of steering ratio as the tie rod connection moves out from the innermost pivot. I got that ratio back with the addition of a Borgeson unit. I don't rightly know what that left me with but it seems about the same as before all these mods.
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*maybe I'm remembering my rear spring rate seems like the front springs are different number. I would have to leaf through a bunch of receipts to see what I started with. Let me say that I took a coil out of the small block stock spring whatever that is. Maybe a better number is the distance to the top of the wheel well arch which I just measured as 26", wheels and tires are about the same diameter as stock.
Found some before and after pictures, hope this helps
mine measured at 13.5 before i cut a coil and it dropped it but it wasnt enough, i had to take them out agaon and heat the cut coil to bend it. This dropped my car down to the 26" height i was looking for, I havent driven it much because the rear isnt lowered yet, while I was looking at the bolts from VB&P also and ran across this kit.
I use a bump steer kit in a car that's not even lowered. I think it dramatically improves the feel of the steering. I safety wired the bolts that retain the block to the steering arm. I also had to use a slightly shorter tie rod sleeve to get the toe right.
FWIW, bumpsteer stud setups facilitate finer-tuning of outer linkage heights without significantly altering effective tie-rod lengths, without increasing Ackerman, and without eliminating optional steering ratios at the knuckle.
FWIW, bumpsteer stud setups facilitate finer-tuning of outer linkage heights without significantly altering effective tie-rod lengths, without increasing Ackerman, and without eliminating optional steering ratios at the knuckle.
Unfortunately I figured that out after installing mine. Also, while I had just the chassis up I was unable to discover that there was any Ackerman at all, Perhaps I was looking at it wrong but if you have any background on Ackerman on these cars Charlie, I would be obliged.
Unfortunately I figured that out after installing mine. Also, while I had just the chassis up I was unable to discover that there was any Ackerman at all, Perhaps I was looking at it wrong but if you have any background on Ackerman on these cars Charlie, I would be obliged.
Tho I have yet to fully obtain sufficiently precise measurements of the C3's steering architecture with which to complete accurate Ackerman maths for our cars, I'll certainly attempt to contribute what I might to a general discussion...
1) Given that installing typical bumpsteer block kit moves both outer tie-rod links inboard by ~1.25", the theoretical Ackerman percentage (as calculated mechanically) is necessarily increased by a significant amount.
2) Theoretical Ackerman serves to eliminate tire scrub (and thus reduce steering effort) during stead-state turns. But, as cornering forces increase, so do the slip angles at which the tires are operating, skewing effective Ackerman (per thrust vectors) from the theoretical. In addition, slip angles will vary between the inner and outer tire as weight transfer increases, further skewing effective Ackerman. Thus, theoretical Ackerman is less and less relevant as a car is pressed harder and harder.
3) While higher Ackerman percentages may help improve low-speed handling in tight turns, and could well reduce the need to run toe-out for parking lot style AX courses, there appears to be merit to the argument that less, or even anti-Ackerman is desirable in higher speed bends.
4) Attempting to determine by maths a formula for calculating an optimum Ackerman percentage for a given application which accounts for the multitude of variables in play isn't likely to ever reach the top of my To Do List. That said, there are adjustable steering knuckles available in certain sectors of the racing industry. However, I'd wager that trial and error along with a trusty stopwatch would be the most practical method by which to judge a given Ackerman setting.
Anyway, I hope this sidebar on bumpsteer is worth $.02 to someone, if not the OP.
Tho I have yet to fully obtain sufficiently precise measurements of the C3's steering architecture with which to complete accurate Ackerman maths for our cars, I'll certainly attempt to contribute what I might to a general discussion... TSW
I think the basics on bump steer were covered with the discussion up to this point and hopefully the OP is good with it. When you mentioned Ackermann, I remembered being concerned about what the kit might have done to that geometry. Mostly it was, was fixing one thing bad for another? So I don't think I hijacked the thread so much as I brought in a related consideration. If anybody wants to take a look at what I blogged back when I first built the car, here's that
There are a couple of useful pictures and comments there that elaborate on your comments, SkunkWorks. I gave up on the blog because it was too much work for me, but at the time I remember using some string to map out the geometry. I was never able to determine if any Ackermann was built into the car but I concluded the kit wasn't hurting me. And what I concluded back then seems to agree with your comments. Knowing what I know today I probably would go with the alternatives to the VBP kit, but I have no compelling reason to change out what I did then. The car handles really well.
...what I concluded back then seems to agree with your comments. Knowing what I know today I probably would go with the alternatives to the VBP kit, but I have no compelling reason to change out what I did then. The car handles really well.
While it is indeed a piece of the greater puzzle that is vehicle dynamics, and one which deserves consideration by those genuinely pushing the envelope, IMHO there are plenty of other areas in the big picture that deserve a higher priority than does Ackerman. YMMV
i was placing an order for lowering bolts and stumbled across it and was wondering if it was worth buying.
Can't answer that question. There is one other consideration with the VBP kit. Unless they've changed something you will have to drill out your steering arm to fit the retaining bolts. That means losing the taper. I kept my originals and bought another pair when installing the kit.
Can't answer that question. There is one other consideration with the VBP kit. Unless they've changed something you will have to drill out your steering arm to fit the retaining bolts. That means losing the taper. I kept my originals and bought another pair when installing the kit.
I passed on this based on the comments from what was said here and the fact that I was hoping to do the DIY rack and pinion some day.
01-04-2017, 11:01 PM
