Technical Is this supposed to be like this?

Typically the issue is the wheel used doesn't have a large enough hoop to fit the big buick drum. The ones that the drum is tucked in nicely have made a better wheel choice. And yes, scrub becomes an issue at some point.

 

Excessive scrub radius has a negative affect on proper Ackerman angle and can cause handling issues when cornering, especially at speed. It will also cause increased tire wear.

 

Yep
Minimum affect on normal driving
I don’t road race

 

You guys ever actually driven a car that violates your "scrub rule"? I have and it will drive circles around most of you. I don't run spacers, but my knockoff wheel adapters help push the wheels out past the "scrub" axis. It turns well, steers well, been faster than most of you will go, it is stable and fun to drive. Just sayin'

ATTACH=full]6784902[/ATTACH]
Right on, Billie. 15x4 AR Salt Flats, no spacers, 90K ROAD MILES, strip time, no problems, steers and rides just fine, thanks!

 

I have no idea what the scrub radius is. Haha! I guess I have some studying to do…

 

Google

 

I've seen this done on several cars, I particularly think it looks a little weird but you can't argue with the brake cooling.

 

I honestly didn’t notice anything while there taking the pics. Only afterwards looking through my photos did I notice the drum sticking out past the wheel.

 

If you take the pic too fast you might wear out your camera

 

That is what happens when you run Buick drums and 35 wires and have to have a spacer to keep the wire off the drum





With the right steel wheels not a lot of Buick drum shows URL=https://hosting.photobucket.com/c5e...fac1262c6.jpg?width=960&height=720&fit=bounds][/URL]

 

If Doc asked me to draw a picture of what I thought about it.

 

Looks to me like disc brakes with an aftermarket fake drum cover.


https://www.obrientruckers.com/disc-brake-covers.html

 

Zero scrub is not generally where we want to be. It can cause the steering links to flip-flop between positive and negative loads due to road irregularities, which can make for a "twitchy" feel. For road going vehicles, a little negative scrub will help with straight line stability and keep a little bit of consistent load on the steering system. Maximum scub should generally be kept under an inch and a half. The scrub radius on the car in the original post wouldn't even fall within the tire patch. Looks like way too much to me.

 

There are lots of guys in our hobby/p***ion that either don’t know or don’t care about ‘proper’ engineering concepts. Whether it’s scrub radius, scrub line, ackerman, or whatever. Most have no clue (especially the ‘car guys’ that buy, not build), and then there are others that are obviously more concerned with looks than engineering. Fair enough. We all make sacrifices to get the look we are after. I ‘cheat’ all the time to achieve a ‘look’ that I like. AND, I would bet almost everyone on the HAMB and elsewhere that build hot rods, has fudged a little. How many times do we read on here; ‘mine is like that and it’s worked fine for years’?
Now, when I’m looking at hot rods at shows, I always look at these things and a few others (like steering joint angles, cowl steering, caster and camber, and, and, and…), but I’m a judgey *****.
.

 

Yes, I have.

I changed the front wheels from 14x7's with 205/70r14 tyres to 14x8's with 245/60r14 tyres. (OT Aussie ute)
The backspace on the wheels was the same, so it added around an inch of scrub radius per side.
Looked great... but handled like a dog on a polished floor. It wanted to tramline and follow all the road irregularities.
Off they came and on went the old wheels and tyres. Made for a much happier me.

You may not be having as bad an experience due to your narrower front tyres, but trust me, it does have an effect.

 

Given the choice between a negative scrub radius and a positive scrub radius, I'll take the positive radius (to a limit) hands down. A negative scrub radius can make a car twitchy at speed, and that would be the last thing I would want to experience at a high speed.

There are several proper engineering "rules" that have been established as a proper foundation for steering and suspension for a very long time. These long standing "rules" have become the industry standard for creating the best handling, steering, safety, and tire wear, design combinations because they have been proven to be the best combination of long term function available.

That said, the auto manufacturers and hot rod people have simply ignored, or down played the importance of several of those "rules" because they have interfered with the ease of manufacturing, or have come into conflict with some desired appearance perimeters.
It needs to be said that violating, or adjusting some of the rules slightly, probably does not make the vehicle unsafe. In some cases, those changes to the rules can have a positive effect on how well some things function under certain conditions.

The scrub radius and the Ackerman theory are two "rules" that have often been violated completely, or have been seriously modified. Both of them cover how the front tires track during the time the steering wheel is turned and the vehicle goes around a curve. That is the only time these two rules are in effect and both usually have very little long term negative effect, other then a shorter time frame for tire tread life.

The scrub line rule is another "rule" often ignored by hot rod people. That refers to ground clearance under the vehicle in the event of a total tire failure. The scrub line means that it is bad news if any part of the vehicle undercarriage touches the ground before the wheel hits the ground if a tire fails. The reason for that is because any solid part under the car that touches the ground before the wheel hits the pavement can cause the vehicle to skid on that part and the vehicle could go out of control. The scrub line is simply a straight line from any wheel (not the tire) to any other tire, anything that would be below that line fails the scrub line test. The hot rod argument here is "when was the last time you had a complete tire failure?" The actual question should be "what might be keeping the wheel off the ground if I have a tire fail?" If you have a flat @ 60 mph, that could be a serious safety concern.

 

Either a little positive or a little negative is fine.
Zero is no good.
And too much of either can catch you very much by surprise at speed.

 

That's right.

 

What does "supposed to" really mean? When people imagine skinny wire wheels on Buick drums, they fit better in their head, but if you want wire wheels and Buick drums that's how they look together. If anyone wants a finned drum look with wire wheels, I really recommend the Finned '40 Ford drums from Boling Bros, they look great with wire wheels. With a buick drum, the entire wire wheel hub has to sit outside of it, and wire wheels just don't have very much room for backspacing.

 

In some cases I have to believe that showing off all of your polished Buick drum is more important than how well the car handles overall.
I'd have to think that many guys just flat do not understand that a wheel like a 35 wire does not fit newer hubs and drums that are not designed for them or are not a carry over design.

On my boat tail that has Chevy running gear I swapped to Huck brakes on the front to use the 18 inch Chevy wires and will have to have spacers made for the back to fit them to the 55 Chevy 3100 rear axle. This is a two seat boat tail roadster with a late 20's Chevy grill that is probably commercial. The whole idea is to have people think old race car when they look at it.