Ok, what wheel-tire?

[linuxgod]

@sickspeed and @kreiten,

I have to agree with @kreiten on this. Diagrams from rimsntires.com:

Assuming the same +60 offset, the larger 9" rim with means you increase the backspacing by 1/2". In that case the same tire size on different width rims does have an increased likelihood of rubbing against the UCA, LCA, frame, etc.

Now, if you adjust the offset by -13mm to +47mm on the 9" rim so that the total backspacing doesn't change, then I agree with @sickspeed

 

[sickspeed]

@sickspeed and @kreiten,

I have to agree with @kreiten on this. Diagrams from rimsntires.com:

Assuming the same +60 offset, the larger 9" rim with means you increase the backspacing by 1/2". In that case the same tire size on different width rims does have an increased likelihood of rubbing against the UCA, LCA, frame, etc.

View attachment 1384922

Now, if you adjust the offset by -13mm to +47mm on the 9" rim so that the total backspacing doesn't change, then I agree with @sickspeed

View attachment 1384923

You must be assuming then that you're rubbing your actual wheel, not the tire, on the frame or UCAs. In the diagrams though, it shows that the width of the tire doesn't change (e.g., 285mm) and neither does the location of the center of the tire (it is always centered at the plane of the offset/backspacing). The diagram changes the offset, not just the width of the wheel. That's why i said all other things being equal, wheel width alone doesn't effect rubbing, certainly tire rubbing.

So again, unless your actual wheel is what is rubbing, the width of the wheel does not effect whether your tires will rub. Again, this also assumes that your tires are wider than your wheels, which is typically the case when discussing rubbing. Changing the offset, tire sizes, diameter, etc definitely will effect rubbing but the width of the wheel itself, does not, unless the wheel has the potential to rub parts located near the inside of the rim or the internal diameter of the tire, so not fenders, liners, etc.

 

[MScruiser]

Changing the wheel width certainly does affect the width of the tire, and consequently the likelihood of increased or decreased rubbing on components.

 

[kreiten]

You must be assuming then that you're rubbing your actual wheel, not the tire, on the frame or UCAs. In the diagrams though, it shows that the width of the tire doesn't change (e.g., 285mm) and neither does the location of the center of the tire (it is always centered at the plane of the offset/backspacing). The diagram changes the offset, not just the width of the wheel. That's why i said all other things being equal, wheel width alone doesn't effect rubbing, certainly tire rubbing.

So again, unless your actual wheel is what is rubbing, the width of the wheel does not effect whether your tires will rub. Again, this also assumes that your tires are wider than your wheels, which is typically the case when discussing rubbing. Changing the offset, tire sizes, diameter, etc definitely will effect rubbing but the width of the wheel itself, does not, unless the wheel has the potential to rub parts located near the inside of the rim or the internal diameter of the tire, so not fenders, liners, etc.

Let's slow down here a little bit, couple things going on... We are kinda both right, you're talking about the width of the wheel not affecting frame and UCA rubbing all other things being equal, i.e. backspacing, bingo! I agree with ya on that 100% Now for the couple of things that we don't agree on or maybe I just have not elaborated my point very well. Let's try this again. First things first, if you put a 285 tire on an 8 inch wheel and a 9 inch wheel the one on the 9 inch wheel will be wider, so there's that. And my second point on rubbing that if you create the same backspacing on the 8 inch wheel and 9 inch wheel (so to not rub on the frame and UCA) that extra inch then pushes out. that extra inch pushing out will push your tire into your inner fender linings the minute you turn your tires. Head down to Discount tire and have them slap on a 18x9 inch wheel with the tires you already have and then turn the tires, it's gonna rub!

 

[sickspeed]

Let's slow down here a little bit, couple things going on... We are kinda both right, you're talking about the width of the wheel not affecting frame and UCA rubbing all other things being equal, i.e. backspacing, bingo! I agree with ya on that 100% Now for the couple of things that we don't agree on or maybe I just have not elaborated my point very well. Let's try this again. First things first, if you put a 285 tire on an 8 inch wheel and a 9 inch wheel the one on the 9 inch wheel will be wider, so there's that. And my second point on rubbing that if you create the same backspacing on the 8 inch wheel and 9 inch wheel (so to not rub on the frame and UCA) that extra inch then pushes out. that extra inch pushing out will push your tire into your inner fender linings the minute you turn your tires. Head down to Discount tire and have them slap on a 18x9 inch wheel with the tires you already have and then turn the tires, it's gonna rub!

1) Why, or I suppose where, would a 285-70-18 tire be wider on a 9" wide wheel than it would be on a 8" wheel? A tire is only as big as it is and would simply be narrower where it contacts the wheel when mounted on a narrower wheel.
2) I believe you're describing changing the offset to maintain backspacing whereas my comparison is, for instance, identical wheels offered in 2 different widths. You seem to be addressing the fact that most wheels offered in different widths tend to also have corresponding different offsets to maintain backspacing intended to avoid interfering with or rubbing brakes, suspension, body, etc. If all other dimensions being equal, the difference between an 8" wide wheel with et25 and an 8" wide wheel with et50 is that the outside vertical plane of the one with et25 sits roughly an inch further out, closer to the fender plane. Similarly, the outside vertical plane of a 9" wheel with et50 vs a 8" wide wheel with et50 is that the outside vertical plane sits a half inch further out, closer to the fender. Keep in mind that the offset simply changes where the wheel is centered on the hub so changing the offset moves that point whereas changing the width of the wheel by an inch, for example, extends the wheel a half inch further out AND further back, hence why many wheels adjust the offset to maintain backspacing and clearance. So for back space clearance to be maintained on a wider wheel, you'd vary the offset with the width. The rear/inside vertical plane of a 8" wide wheel with an offset of et50 will sit in the same plane as the rear vertical plane of a 9" wide wheel with an offset of et38. Think of it as centering a donut on a stick in the wheel well. The wheel width just changes where the vertical planes at the rim edge sit whereas the offset changes where the vertical plane passing through the center of the tire tread sits, which also changes where the planes at the edges of the rim sit.

I should point out that this is not my opinion, its based on having to do relatively precise measures to fill the wheel well of certain german sportscars, with much tighter clearances than our trucks have. If I were a bit more internet savvy, i might be able to graphically demonstrate it better but I think what you're envisioning or describing is really based on experience fitting tires under these trucks on wheels that typically vary more than just the width OR offset. That is, wheels offered in wider variations often have different offsets than the same wheel offered in a narrower variation, hence, not all other things are equal. In any event, this is really just a cautionary exercise to point out that when fitting wheels and tires, wheel offset is just as important if not more important than wheel width in addition to the actual tire sizes. There is always a lot of discussion on this topic when it comes up and people often fail to share wheel offsets. Sometimes its because wheel manufacturers don't always hand out the offset numbers because they treat it as intellectual property or otherwise guarded info.

Hopefully that is a bit more clear. Otherwise, sorry for rambling ; )

 

[kreiten]

1) Why, or I suppose where, would a 285-70-18 tire be wider on a 9" wide wheel than it would be on a 8" wheel? A tire is only as big as it is and would simply be narrower where it contacts the wheel when mounted on a narrower wheel.
2) I believe you're describing changing the offset to maintain backspacing whereas my comparison is, for instance, identical wheels offered in 2 different widths. You seem to be addressing the fact that most wheels offered in different widths tend to also have corresponding different offsets to maintain backspacing intended to avoid interfering with or rubbing brakes, suspension, body, etc. If all other dimensions being equal, the difference between an 8" wide wheel with et25 and an 8" wide wheel with et50 is that the outside vertical plane of the one with et25 sits roughly an inch further out, closer to the fender plane. Similarly, the outside vertical plane of a 9" wheel with et50 vs a 8" wide wheel with et50 is that the outside vertical plane sits a half inch further out, closer to the fender. Keep in mind that the offset simply changes where the wheel is centered on the hub so changing the offset moves that point whereas changing the width of the wheel by an inch, for example, extends the wheel a half inch further out AND further back, hence why many wheels adjust the offset to maintain backspacing and clearance. So for back space clearance to be maintained on a wider wheel, you'd vary the offset with the width. The rear/inside vertical plane of a 8" wide wheel with an offset of et50 will sit in the same plane as the rear vertical plane of a 9" wide wheel with an offset of et38. Think of it as centering a donut on a stick in the wheel well. The wheel width just changes where the vertical planes at the rim edge sit whereas the offset changes where the vertical plane passing through the center of the tire tread sits, which also changes where the planes at the edges of the rim sit.

I should point out that this is not my opinion, its based on having to do relatively precise measures to fill the wheel well of certain german sportscars, with much tighter clearances than our trucks have. If I were a bit more internet savvy, i might be able to graphically demonstrate it better but I think what you're envisioning or describing is really based on experience fitting tires under these trucks on wheels that typically vary more than just the width OR offset. That is, wheels offered in wider variations often have different offsets than the same wheel offered in a narrower variation, hence, not all other things are equal. In any event, this is really just a cautionary exercise to point out that when fitting wheels and tires, wheel offset is just as important if not more important than wheel width in addition to the actual tire sizes. There is always a lot of discussion on this topic when it comes up and people often fail to share wheel offsets. Sometimes its because wheel manufacturers don't always hand out the offset numbers because they treat it as intellectual property or otherwise guarded info.

Hopefully that is a bit more clear. Otherwise, sorry for rambling ; )

Funny thing is we are pretty much agreeing on most of this " In any event, this is really just a cautionary exercise to point out that when fitting wheels and tires, wheel offset is just as important if not more important than wheel width in addition to the actual tire sizes." This has been my point all along, both wheel width and offset affect whether or not you will rub. I was more focusing on wheel width because what offset you can run is somewhat predetermined by the backspacing required. In your example of running an 8 inch wheel with 50mm offset and then running the 9 inch wheel with a 38mm offset to create the same backspacing you still have an additional 13.6mm of wheel sticking out past where the edge of the 8 inch wheel would end. That half an inch could and would cause the same tire as on the 8 inch wheel to now rub the fender. Your point is well taken that most of the wider wheels also have more offset, causing the rubbing issues to be worse. i.e. Most of the 9 inch wheels I have seen for the 200 come in 20 or 25mm offset, causing them to rub more than if you maintained the factory backspacing of the RW wheels by running a 37 or 38mm backspacing. I'm worn out man, we on the same page now?

 

[sickspeed]

Funny thing is we are pretty much agreeing on most of this " In any event, this is really just a cautionary exercise to point out that when fitting wheels and tires, wheel offset is just as important if not more important than wheel width in addition to the actual tire sizes." This has been my point all along, both wheel width and offset affect whether or not you will rub. I was more focusing on wheel width because what offset you can run is somewhat predetermined by the backspacing required. In your example of running an 8 inch wheel with 50mm offset and then running the 9 inch wheel with a 38mm offset to create the same backspacing you still have an additional 13.6mm of wheel sticking out past where the edge of the 8 inch wheel would end. That half an inch could and would cause the same tire as on the 8 inch wheel to now rub the fender. Your point is well taken that most of the wider wheels also have more offset, causing the rubbing issues to be worse. i.e. Most of the 9 inch wheels I have seen for the 200 come in 20 or 25mm offset, causing them to rub more than if you maintained the factory backspacing of the RW wheels by running a 37 or 38mm backspacing. I'm worn out man, we on the same page now?

Yep, the tire will rub if you change the offset... : )

 

[kreiten]

Yep, the tire will rub if you change the offset... : )

hah, well played