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Wheel offsets and spacer plates |
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Patrick 
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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 Posted: 28 June 2011 at 11:57am |
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Damien, I'm NOT chastising you (honest), but that wasn't the best comment to post after all the hassle that Johnny was forced to endure at the hands of "professionals". Yes, Johnny has had plenty of problems with his rear suspension, but it was well documented here that it was due to negligence by two alignment shops. The first one, Dale's, didn't tighten the tie rod lock nut, and the second, Tru-Line, didn't even notice before doing their alignment that the rear ball joints were just flopping around as the mounting nuts/bolts had never been tightened! We've all seen The video that Johnny posted. There was NO excuse for a "reputable" shop missing that (and then compounding the issue by refusing to acknowledge and/or correct their screw-up). Johnny's suspension problems had NOTHING to do with the use of wheel spacers. Yes, there's obviously still some bitterness felt by many of us over that whole unfortunate experience.
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 28 June 2011 at 1:00pm |
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Okay, back to the original topic... I'm glad to see there has been some good discussion generated over the question of using spacer plates. I'm still trying to get my head around the issue of stress on the bearings due to the distance of the wheel from the hub. The argument seems to be that it's the extra distance from the hub due to the spacer plate that creates this extra stress, as opposed to what I was suggesting that the extra stress was due to the distance from the outside edge of the wheel/tire (the end of the "lever") from the pivot point of the lower control arm. Here's another diagram. Both wheels are mounted to the hub (no spacer plates). The wheel on the left has extreme negative offset, the wheel on the right has extreme positive offset. I suspect there is a whole lot more stress on the wheel bearings on the left wheel as the leverage from the outside edge of the wheel/tire to the pivot point is MUCH greater than the leverage created by the wheel pictured on the right. If I'm understanding you guys correctly, you're going to tell me there is no difference between these two examples in regards to stress on the wheel bearings. Is that correct?
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Dawg
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Joined: 15 August 2009 Location: Canada Status: Offline Points: 988 |
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Posted: 28 June 2011 at 1:01pm |
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It's just my opinion guys. I was there, trying to help diagnose the problem to help out a friend. I think I'm entitled to an opinion. Any more to say on this? Please PM me. As for the spacer issue on your car Patrick, the car you intend on using for autocross, I'm giving you the best advice I know how to give. Use it as you see fit. Cheers, Dawg
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You dream it up....I'll make it
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Dawg
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Joined: 15 August 2009 Location: Canada Status: Offline Points: 988 |
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Posted: 28 June 2011 at 1:22pm |
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I've obviously hit a nerve here. Sorry Johnny.
It's apparent that there is nothing holding anyone back from spacers then. Patty, you first....:) The Dawg |
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You dream it up....I'll make it
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 28 June 2011 at 2:19pm |
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There's always a certain amount of risk involved when you modify a car from it's original specs. Patrick ended up riding on his bump stops last time he did it so it's probably a wise choice to be a bit more cautious this time.
I've given the problem a bit more thought and there's a few things I think I should mention. In my original example I was looking at the vertical forces only, so hopefully that makes a bit more sense if it didn't already. I also maybe simplified it a bit too much. What I described originally is that the centre of mass of the wheel is further outward which causes more torque on the bearing. Let's try to simplify the system a bit by looking at it two dimensionally and only looking at the vertical forces. The system can be represented by 4 rods connected like this:  In order for the bearing to be stressed (for there to be a torque at the bearing), there must be a vertical force applied to where the long middle rod connects to the what would be the hub (at Pivot B). Where does the force come from? It seems like it'd be primarily from the car bouncing along the road. I'd argue that the forces applied to the outside edge of the wheel mostly end up causing torque at pivot C rather than at the bearing and that the manufacture of the wheel takes this into consideration and makes the wheel able to withstand this. |
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88 Formula 5 speed
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 28 June 2011 at 8:15pm |
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Citing your example Patty, yes, both bearings would be stressed equally. The force of torque would be going straight in to the hub. Now, a positive offset plus spacer causes this stress to travel through a mechanical advantage, applying more torque when it reaches the bearing. If I'm not mistaken, this torque typically applies to the top of the bearing, if that aids you in inspecting the bearings after.
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Never shift into reverse without a back-up plan.
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Car-2-Lo
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Joined: 14 February 2007 Location: Canada Status: Offline Points: 1266 |
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Posted: 28 June 2011 at 10:03pm |
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It's not holding me back and also Hugh's V8 TURBO, I always agreed with you all about having lots of stress on the bearings, what's the big deal, if they go, get new ones, but not the cheap ones  (I edited this, Johnny Boy, in the interest of everybody loving everybody else - Tristan) |
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Johnny-B-Good
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 28 June 2011 at 10:22pm |
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My opinion for what it's worth here is that I don't like "mods" editing member's posts. If it was my post that was edited I'd be plenty ticked.
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Patrick
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Posted: 28 June 2011 at 10:29pm |
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Back on topic, again...
I guess what I'm going to have to do is to build a model of my diagram and see for myself if the forces are equal no matter what the offset of the wheels (or the length of the levers) are.
Sorry Colby, I don't understand the diagram.
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 28 June 2011 at 10:33pm |
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I cannot deny being a touch confused by it myself. I'm sure it does make sense, it just needs an explanation, that's all. Anyways, we should make a small-scale experiment of it, would be interesting to see (Measuring the force will be hard, mind you). As for the edited post, consider it a matter of keeping the peace. Only time I've done it, and I don't intend to make a habit of it. |
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Never shift into reverse without a back-up plan.
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 28 June 2011 at 10:49pm |
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They're pivots, but that doesn't mean there is actually movement there, it just means torque is applied about those points. There is probably a better word for it. That's just my attempt to describe the system in a somewhat crude and simplified way using a bunch of rods (think of looking at a slice of the rim). |
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88 Formula 5 speed
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Patrick
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Posted: 28 June 2011 at 11:08pm |
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Here's my above diagram altered to show it as two levers. The red squigley things are springs. The blue things are legs for the pivot. I cannot believe that the force required to compress the springs X number of inches would be the same for both setups.
Same thing, but with less positive offset on the right hand lever.
Whether we're measuring the force required to compress the springs a prescribed distance, or measuring the compression of the springs as the result of an applied force, I can't see how there would be any way they'd be the same for both setups. No way. The same force (weight of car on road, moving or not) would compress the springs more in the left hand setup. In other words, the more the negative offset, the more force/stress there'd be on the wheel bearings. Colby, Tristan... explain the error in my thinking!
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Car-2-Lo
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Joined: 14 February 2007 Location: Canada Status: Offline Points: 1266 |
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Posted: 28 June 2011 at 11:35pm |
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Great place to get spacers HERE
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Johnny-B-Good
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 28 June 2011 at 11:40pm |
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My diagram confused you and now your diagram is confusing me... lol.
 Why do you care about the effect on the springs? Yes, the force required to compress the springs a certain amount would be different in each of those examples. |
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88 Formula 5 speed
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 28 June 2011 at 11:47pm |
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Colby, see what I've added to my last post.
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Colby
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Posted: 29 June 2011 at 12:18am |
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I'm just confused now since I'm not quite sure what you're thinking. How about we talk about this at the autocross? I'd like to explain my thought process from the start again and doing it in person would let you interrupt me if I'm not making sense. |
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88 Formula 5 speed
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 29 June 2011 at 12:32am |
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Sure, that would be fine.
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 29 June 2011 at 12:34am |
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Johnny, those spacers are worth more than my car! I need to check out the cheap Made in China eBay junk first.
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Car-2-Lo
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Joined: 14 February 2007 Location: Canada Status: Offline Points: 1266 |
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Posted: 29 June 2011 at 8:38am |
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That's okay, I'll bring flowers for Dawg at next meeting, I love you 
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 29 June 2011 at 10:08am |
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LOL! Quote. Of. The. Year. 
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Never shift into reverse without a back-up plan.
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Dawg wrote:
What are these multiple pivots?
