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Discussion Starter · #3 ·
Nice!

Glad to hear you're enjoying the bar.

Do you have the part numbers for the front rack bar and mounts? Any trouble mounting/removing/getting scratches?
 
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Discussion Starter · #5 ·
The rims are German BBS 3 piece designed for the Vette. As such, the offset is different than that of our cars. I simply used a 2.00 inch spacer/adapter to adapt the different bolt patterns and get the offset back where it had to be. The rest is, as they say, too easy. As long as you keep the offset close to the same as original, you are not changing the load / forces on the whole geometry (provided the weight of the rim + tire + spacer stays the same as original).
In my case, it doesn't quite work out, as those big meats do way a bit more than the stock rubber. There is still plenty of space in the rear to go wider...but really, why?

The problem with the wide rubber is that you have a larger contact patch, ergo, higher rolling resistance. The larger contact patch effectively reduces the load on the tire contact area (ie- hypothetically: 10 sq inches original is now 20 sq. inches. If the weight on the rear end is not altered, then I have twice the area, therefore, half the lbs/sq inch load). This means that although the tire can theoretically have more grip, it also can be "underloaded", which promotes overstear in the rear, due to it sliding more readily. It's quite complex to explain, but it has been tested many times in racing cars. I know, as I used to drive rally cars and was a test driver for a european car manufacturer.

Roadmuncher- I don't quite know what you mean. My front bar is the stock one. I don't think that I will change it. The back is the Hotchkiss bar.

Matt
 
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Discussion Starter · #6 ·
Sorry Matt. I was wondering about the bar holding up the canoe. Looks like a great idea. I love my roof window, but have always longed for a full-roof-length rack. Looks like your idea may be the answer. Is it an off the shelf unit?

Loved your points on the wider tire dilemma. I think I now understand why my wagon wants to pull into ruts with the 255's. I've experienced that running the psi around 34 makes the problem liveable, 32 makes it disappear completely but I am concerned about the effect of a high speed cruise with only 32 lbs in the tires - should I be? I used to run the 225/75-15's at 36 cold and had no pulling at all.

Thanks,
John
 
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Discussion Starter · #7 ·
John,

the rear Yakima bar attaches to the roof rack rails- it's a Railrider for the Buick/Caprice wagon.
the front is the standard roof rack for the Caprice SEDAN. I had to slit the rubber seal (at the joint line) about 4 inches, so that the clamps can grab properly. I've coated the clamps and get no scratching at all.

the upside to my roof rack- I don't need front or back tie down staps, I am only using the cross straps on the Mako saddles (f) and hulley rollers (r). Even with a 20ft kayak (fully loaded with camping gear, therefore around 120/130 lbs), I get NO movement at all. Couldn't be more stable, even at speeds. :D So I not only have the rear cargo space, but use the boat for tents, sleeping bags/pads and a lot of the othe "light stuff". that way, I can take even more junk on my camping trips...


As for the tire problem- it is termed "nibble" and can be reduced by playing with the pressure. Unfortunately, you may not get the best grip with less nibble. So, for the ultimate grip, you'll have to make do with nibble. It is more pronounced in front, but will also affect the rear end. the 275/40's I'm running look cool but are, in reality, too wide for such a light boat (psi footprint loading). When I was driving Formula type cars, the wide tires really produced lot's of grip; however, it was easy to light up the rear end and get them to spin. Same in corners- you could get them to slide relatively easily by promoting a weight transfer bias to the front (ie- under braking). Then the rears would let go a bit (slide) and presto- instant oversteering.

Matt
 
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