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JPhil 02-08-2009 08:41 PM

C3 Bump Steer Blocks Install Review
OK so I finally installed the VBP bumpsteer block kit last night. It was pretty straightforward, went pretty smooth.


I drilled out the OEM steering arms on my drill press. Bought a brand new 5/8" bit, set the speed to its lowest, 450 RPM, and used a lot of oil. Since it was enlarging a pre-existing hole, I did not worry about it staying true. I supported the arms on a couple 2x4s and just held them with my hand. They each snagged a couple times, but I still got a smooth bore. I radiused the top lip with a stone in my die grinder.

The holes in the arms and the holes in the blocks were off by about .015"+/-. This I attribute more to Chevy than to VBP. I thought about filing the arms to oval the holes, but decided I would have a better, truer fit if I filed the bolt threads instead. So I wrapped a piece of heavy cardboard (heavier than a beer carton) around each bolt, chucked it up in the drillpress and held a file against it to file down the threads on the top (bolt head end) 5/8" to make a narrower 'shank' for an offset fit through the arms. I did not take the threads all the way off, by file-and-fit, I removed a few thousandths from each bolt until they would fit through the arms and thread into the blocks.

All well so far. But after I had it all reassembled to the point of attaching the tie-rod ends, I found the tie-rod stud nut did not have enough clearance from the steering arm to go on. Five minutes with a rotary bit in the die grinder on the side of the steering arm and it went on. This was on the driver side only, passenger side was OK. A box end or socket will not fit on the nut now, open end wrench only. That's OK, those don't need a real heavy torqueing. But the VBP block must be a tiny bit thicker than the OEM steering arm, because my cotter pins would not fit. One more thread down and they would have, but I ended up having to use a skinnier cotter pin.

It took me about 6 hours, but I work slowly with lots of time outs.


Well, since my last alignment I have replaced the rear t-arms, rebuilt the differential, replaced the front 460# springs with shorter 550#s, and put these blocks in using only a tape measure to the frame to set the toe-in. So each wheel is running in a different plane, the only thing they have in common is they all rotate in generally the same direction. But each one is going toward a different destination. However in my couple-mile drive around the neighborhood this morning, there is definately a different feel to the steering wheel, one that feels like the geometry of the steering assembly has changed. The car is dangerously out of alignment now, I will have to be very careful driving it to the hotrod shop to do it.

So far, there is no appreciable loss in the turning radius (I have to make a sharp turn to get in the garage and I was a bit worried about that).
All I can say is, I will update this after I get it aligned. (But dang, bad weather is supposed to arrive tonight--When will I be able to get it on the rack?)

Stay tuned,

UPDATE: March 8, 09

Finally I was able to get into the shop yesterday for alignment.....
I've never done this before, but they just showed me how to run the equipment & said "Have at it!" Took me about 6 hours. Whoof. But next time it won't take me half as long!

The car was pretty out in all possible ways (see above). I'm surprised it handled as well as it did before, so a true 'before & after' comparison for these bumpsteer blocks is probably not realistic.
I strongly suggest that if you are considering this modification, do a good 4-wheel alignment first, before you proceed with it. (I've had a chronic problem with it pulling to the left upon hard braking--I had been blaming it on a brake system problem but decided to wait and sure enough, this alignment cured it. Woo hoo!)

OK, "Driving Impressions":

Wow it's like it's on rails!
The feeling of a steering geometry change is not there now, that must have been because my front toe was so far out (or rather, 'in') that Greg started laughing when he guided me onto the rack (I could hear & feel my front tires scrubbing & screeching on the drive to the shop!). The steering feels perfectly normal now. If anything it's a bit lighter but I attribute that to setting a little bit wider (open) toe on both front & rear than factory specs. It tracks beautifully, but it's 'lighter' and more sensitive.

And I have no bumpsteer at all, at least in straight-line driving. I drove down the county road where one or the other set of wheels is always in the chuck holes with my hands off the steering wheel. I took the railroad tracks at 35 MPH with my hands off the wheel. I have not yet taken it out for exercise, but the few corners I took were smooth & true, although they were not very bumpy.

As I pulled into the garage, I could feel I was against the steering stops (or at least maxed out on the linkage) where I did not used to be, so yes there is a slight decrease in turning radius. But I don't think it will make any difference except if you parallel park a lot or deal with tight parking spaces.

All in all I'm happy as can be. As I get used to it & exercise the car more, I will probably make some adjustments to the alignment. But I have so much more confidence in it's handling now, and not the least of it is it's ability to stay true over shitty road surfaces.

(If anybody is interested, I downloaded my alignment specs into 'my photos'. I did it with about 150 lbs of concrete blocks in the driver seat, so it's interesting to see the difference that made in the specs with & without. I know it's not exactly spot on, but damn, I think I got things pretty good for my first time! It's a hayl of a lot better than it has ever been before)

I'll update this again when I get more time in the saddle with it.


Twin_Turbo 02-09-2009 05:05 PM

Nice writeup. Xander will have to get some for his car, being lowered that much the bump is much more pronounced than stock even.

Also, there are steering arms available with 1 hole (later ones, all cars are power steering) this saves you the trouble of having to knock that plug out and secondly, you can drill out the taper hole first and then bolt the block on to precisely center punch for the 2nd one.

The problem with the cotter pins is something I have encountered with adjustable tie rod ends. I still need to buy that 1,5 foot taper reamer to ream out the holes for the stud to go through far enough for the cotter pin.

mrvette 02-10-2009 03:24 AM

This whole topic of bump stear is memorable with Norval going after the problem in the C3's....his solution with the stock cross link was to move the inner points, and lengthen the tie rods.....I forget about the inner mounts being higher or lower, but that would depend on ride height...NO??

anyway, I have super LONG rods what with the rack install....and Pete79L82 if I recall the handle me to raise the inner mounts on the rack ends, and so corrected a good bit of bump stear....

I call it that, because a hit a freeking COW decades I bumped a stear....what can I say....


turtlevette 02-10-2009 04:24 AM

I've never had any problems with bump steer. The only time it gets hairy is when i hit the curbing on the apex of a turn.

That block setup just adds another thing that will get loose and wreck you.

I try not to add any shit to the system unless it is absolutely needed.

Scotty had a saying about that. Too many gadgets stuffs up the plumbing or something like that.

JPhil 02-10-2009 02:26 PM

Turtle, I agree about too much crap--especially trendy crap. But I definately had a bumpsteer problem which showed itself most strongly on potholed curving highway entrance ramps. After a few good buttpuckers, I decided I needed to do something but I'm not going to get all Norval about it.
As I said, we'll see.

White76 02-11-2009 12:26 PM


Originally Posted by turtlevette (Post 35504)
That block setup just adds another thing that will get loose and wreck you.

I try not to add any shit to the system unless it is absolutely needed.

Scotty had a saying about that. Too many gadgets stuffs up the plumbing or something like that.

I agree on not adding gadgets, but I haven't had any problem with them loosening up and I can't really see it happening either. The two 5/8" bolts are installed at 180 ft-lbs with red lock tight.

JPhil 03-09-2009 03:26 AM

I added an update to the first post to keep it all together

redvetracr 03-09-2009 04:14 AM

If anyone is contemplating installing these along with a Rod end (heim joint) instead of a tie rod end I have a new set that was never reamed.....

Wesch 03-12-2009 08:56 PM


I might be interested.
Any pics and price idea ?

Thanks. GŁnther

To the thread initiator: The way I understand your text, you can't really be sure if the bumpstear bracket made the feel change or if it was the alignment that was already out initially.

I am not sure if bumpstear can be felt during normal driving.
It's more for hard cornering or when the front suspension is completely relieved due lift off or so ?

I might not understand it correctly, so you might correct me here.

Rgds. GŁnther

JPhil 03-12-2009 09:30 PM


Originally Posted by Wesch (Post 38429)

To the thread initiator: The way I understand your text, you can't really be sure if the bumpstear bracket made the feel change or if it was the alignment that was already out initially.

That is correct.
I still have not had a chance to exercise the car, it got cold again on the way home that day and there's still some snow on the ground again (& sand). I have no heater & have become a pussy in my old age, so I just haven't got out to test it on corners yet.
BUT it feels more secure, has less steering wheel jerk over uneven surfaces than it ever had before, even when I had a good alignment on the closer to stock suspension.

The bumpsteer was more pronounced when cornering, when the weight shifted, but whenever I had quick major movement of the A-arms, I could tell it was there.

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