a-arm rubbing issues - solution came in the mail today
Oct 12, 2005 | 04:32 AM
#22
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Joined: May 2002
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From: Binghamton, NY
Not to sidetrack from the spacers thing... but I have a couple of questions about the initial a-arm issue.
You said you were concerned when you aired down... that doesn't really change things, does it... as the buldge form airing down is at the bottom, where all the pressure/weight is, right?
Also... the first pic looks troublesome... the second pic looks fine. Back when I had my stock a-arms and 32/11.5-15s, I could juuuuust barely squeeze 1 finger between the a-arm and the tire. I ran/wheeled those tires for almost 50k miles with no problems. When the suspension travels, the a-arm moves with the tire, so the distance between the tire and the a-arm should never change, right?
Am I missing something here?
You said you were concerned when you aired down... that doesn't really change things, does it... as the buldge form airing down is at the bottom, where all the pressure/weight is, right?
Also... the first pic looks troublesome... the second pic looks fine. Back when I had my stock a-arms and 32/11.5-15s, I could juuuuust barely squeeze 1 finger between the a-arm and the tire. I ran/wheeled those tires for almost 50k miles with no problems. When the suspension travels, the a-arm moves with the tire, so the distance between the tire and the a-arm should never change, right?
Am I missing something here?
Oct 12, 2005 | 09:32 AM
#23
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From: Ann Arbor, MI
punkbek - Sorry I don't have the spacers, sold them a long time ago
jackson - I started thinking about that recently as well. From what I gathered talking to a few tire engineers, the conclusion is that when you do air down, you are actually safer. Reason being is that when you air down, the bulge will be more at the bottom, and the top section width will barely increase by 1 mm if that. This is because the inflation pressure is not great enough to keep the cords stretched and round, and normally the top half of the tire is in more tension than the bottom, so the lesser tension at the bottom of the tire will allow it to bulge out more so you start getting material compression at the bottom. And the top half doesn't bulge out more because the cords are still in higher tension.
As for the a-arm issue, in our case, the a-arm actually moves inward when you droop the tire, this I noticed when they were installing my 285's. At full droop the tire was rubbing against the a-arm, but once we set the vehicle down it didn't touch (but was VERY close). I'm still trying to understand completely why, I started thinking about the upper and lower a-arm acting as a 4-link with the vehicle but then it shouldn't go inward if it moves in any direction from horizontal.
Either way, that's what I noticed about the a-arm. I'll look into it more.
btw first pic and second pic are the same side. Just from different angles.
jackson - I started thinking about that recently as well. From what I gathered talking to a few tire engineers, the conclusion is that when you do air down, you are actually safer. Reason being is that when you air down, the bulge will be more at the bottom, and the top section width will barely increase by 1 mm if that. This is because the inflation pressure is not great enough to keep the cords stretched and round, and normally the top half of the tire is in more tension than the bottom, so the lesser tension at the bottom of the tire will allow it to bulge out more so you start getting material compression at the bottom. And the top half doesn't bulge out more because the cords are still in higher tension.
As for the a-arm issue, in our case, the a-arm actually moves inward when you droop the tire, this I noticed when they were installing my 285's. At full droop the tire was rubbing against the a-arm, but once we set the vehicle down it didn't touch (but was VERY close). I'm still trying to understand completely why, I started thinking about the upper and lower a-arm acting as a 4-link with the vehicle but then it shouldn't go inward if it moves in any direction from horizontal.
Either way, that's what I noticed about the a-arm. I'll look into it more.
btw first pic and second pic are the same side. Just from different angles.
Oct 15, 2005 | 01:19 PM
#24
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Joined: Nov 2003
Posts: 2,315
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Originally Posted by jacksonpt
When the suspension travels, the a-arm moves with the tire, so the distance between the tire and the a-arm should never change, right?
Am I missing something here?
Am I missing something here?
With the stock balljoint, the upper a-Arm moves closer to the tire the further it droops, because of where the pivot point is located, unlike the Uniball design that stays virtually the same distance from the tire all the time.
Oct 16, 2005 | 10:18 AM
#25
Originally Posted by AznSky
punkbek - Sorry I don't have the spacers, sold them a long time ago
jackson - I started thinking about that recently as well. From what I gathered talking to a few tire engineers, the conclusion is that when you do air down, you are actually safer. Reason being is that when you air down, the bulge will be more at the bottom, and the top section width will barely increase by 1 mm if that. This is because the inflation pressure is not great enough to keep the cords stretched and round, and normally the top half of the tire is in more tension than the bottom, so the lesser tension at the bottom of the tire will allow it to bulge out more so you start getting material compression at the bottom. And the top half doesn't bulge out more because the cords are still in higher tension.
As for the a-arm issue, in our case, the a-arm actually moves inward when you droop the tire, this I noticed when they were installing my 285's. At full droop the tire was rubbing against the a-arm, but once we set the vehicle down it didn't touch (but was VERY close). I'm still trying to understand completely why, I started thinking about the upper and lower a-arm acting as a 4-link with the vehicle but then it shouldn't go inward if it moves in any direction from horizontal.
Either way, that's what I noticed about the a-arm. I'll look into it more.
btw first pic and second pic are the same side. Just from different angles.
jackson - I started thinking about that recently as well. From what I gathered talking to a few tire engineers, the conclusion is that when you do air down, you are actually safer. Reason being is that when you air down, the bulge will be more at the bottom, and the top section width will barely increase by 1 mm if that. This is because the inflation pressure is not great enough to keep the cords stretched and round, and normally the top half of the tire is in more tension than the bottom, so the lesser tension at the bottom of the tire will allow it to bulge out more so you start getting material compression at the bottom. And the top half doesn't bulge out more because the cords are still in higher tension.
As for the a-arm issue, in our case, the a-arm actually moves inward when you droop the tire, this I noticed when they were installing my 285's. At full droop the tire was rubbing against the a-arm, but once we set the vehicle down it didn't touch (but was VERY close). I'm still trying to understand completely why, I started thinking about the upper and lower a-arm acting as a 4-link with the vehicle but then it shouldn't go inward if it moves in any direction from horizontal.
Either way, that's what I noticed about the a-arm. I'll look into it more.
btw first pic and second pic are the same side. Just from different angles.
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