bnaritomi

I understand that the offset for the OEM wheel is 55. But does anybody know what the required maximum or minimum offset is? I’m looking to buy a set of wheels but am not sure what offset is required to clear the calipers.

If it matters, I am looking at a wheel size of 18x8 or 18x8.5.

sleepinxlionhart

yeah, I'm kind of in the same boat too. I found these that I think look pretty good,
http://store.excelerateperformance.c.../i-171197.aspx

but I'm also unsure of the offset..

bnaritomi

Sleepin... nice wheel. My guess is that with a 48 offset, the wheel would fit. The offset for the OEM wheel is 55 so it's pretty close and I think one of the Acurazine members has wheels with an offset of 45. All the wheels that I am interested in have an offset of 40 or 35. I think the Ronjons have an offset of 41 but I have found a couple of fitment tools on wheel websites that say wheels with an offset of 40 will fit. Talk about confusing!!

Roy Cya

Gentlemen,

keep in mind that the offset is always going to change due to wheel size (17" vs. 20"), as well as type. A wheel with a lot of lip and a concave center will always have a different offset than a wheel that is flush all the way around, ie RonJons... My 19" Ace Stradas have an offset of 38 and they are right where they need to be. Others have 35 and 40-42. In the 20" you'll probably see 35-<40, assuming all these wheels are 1-piece. This would all be different once again with 2- or 3-piece wheels due to custom nature...

Good luck,

robarsan

I bought a set of wheels/tires from the tire rack at the beginning of the year. I gave all the pertinent information about the year model etc. for the RL, and they had two or three sets of wheels they said would fit. I bought a set and when I went to install the first wheel, it hit the caliper. I ended up sending the wheels/tires package back for a refund.
They insisted at first that the offset for the wheel (45 I think) would fit the RL. Luckily, I took some pictures of the wheel hitting the caliper and emailed them. They have since removed that set of wheels as an option for the 2G RL.
Just a cautionary note.

bnaritomi

Thanks for the info guys but this is exactly why my head is spinning. I can't comprehend why a wheel with a 45 offset would hit the caliper but Roys set of Ace's with an offset of 38 fits. Ugh...

Robarson - can you provide details on the wheel that you purchased & returned? Did you buy a different set? If so, what are the specs for that wheel?

robarsan

This was the package I purchased (tires included):

Wheels: 17x7 Borbet Type CA Silver Painted
Tires: 225/55R17 Blizzak WS-60

The wheel weren't anything fancy, I just wanted to have a set to mount the snow tires on. If or when I do get a set of wheels, I am going to have them physically mount one on the front to ensure it clears the calipers. Getting burnt once was enough.

robarsan

I stand corrected on the offset for the 17" Borbet type CA. It was 38mm, and not 45.

Roy Cya

The issue here is that my wheels are 19s and Robarsan's were 17s. In that size the OEM offset is 55, which is quite a bit more than 38, again on a 17" wheel. It all has to do with the diameter of the wheel, but also type of wheel... You might have to rely on online companies like TireRack, DiscountTire and others, or find a local shop that is willing to work with you.

Good luck!

Chas2

I have been thinking about this question and come up with my two cents.


I think that offset is only part of the equation. Offset is the distance, in millimeters, from the centerline of the wheel width to the mounting surface.

Positive offset, in the case of our Acuras, means that the mounting surface is moved toward the outside of the wheel, which means that the inside edge of the wheel/tire is closer to the the suspension, more tucked under the fenders than, for example, a zero offset. The less offset you have, the more the wheel/tire combo sticks out toward the outside of the fender. The inside edge of the wheel/tire combo is farther away from the suspension components.

I think there are at least two other parts to the equation.

1) The shape of the backside of the spokes of the wheel, from the center mounting surface to the wheel rim itself. Take a look at post #20 in thread about new RJ wheel designs for the 4G TL. One aspect of this drawing shows the mounting surface, and the additional space provided by the shape of the backside of the spokes. For example, if the wheel in the diagram has a +55 mm offset at the mounting surface, you can see there is far more clearance than +55 mm behind the spokes, and that is the space the brake calipers fit into. If there is not enough spacing behind the spokes, the brake calipers will hit the back of the spokes.

You can imagine that wheels that have a lip, might have more spoke clearance issues than those wheels without a lip. One way to allow more space behind the spokes might be to decrease the offset.

2) The other part of the equation is wheel width. The +55 mm offset for OEM wheels is based on an 8 inch width. I have 19x8.5 in wheels. This means that if the +55 mm offset were maintained, the inside edge of the wheel/tire combo would be 1/4 inch closer to the suspension components, and might cause rubbing, which would not be good. 1/4 inch is approximately 6.4 mm, so to move the inside edge of the wheel/tire combo out 1/4 inch to prevent rubbing, the offset is 48 mm or 7 mm difference, which is pretty close to the theoretical ideal of 6.4 mm. My wheels have no lip.

The Ace Stradas are 19x8.5 also. Ace have chosen a 38 mm offset. These wheels also have a very attractive polished lip. I am guessing that changing the offset about 10.6 mm from ideal allows that lip to be more easily designed in. The trade off is that the outside edge of the wheel/tire combo is closer to the inside edge of the fenders, and the inside edge is farther away from the suspension components, but that does not appear to be an issue with the RL, at least in terms of fitment.

If you read through the TL thread, cited above, RJ notes that he has designed the wheels to be 8.5 inches wide in 18, 19 and 20, and that projected offset is about 40, with no lip, so that he can clear big brake calipers. The implication is that a lip would mean possible caliper clearance issues.

We have also read elsewhere that 19x8 MDX wheels, with a +45 mm offset rub on the RL brake calipers. So again, offset is not everything. I think the design of the wheel spokes, particularly the back of the spokes, creates the necessary space for the brake calipers. Also width plays a part in offset measurements to maintain a specified distance from the inside edge of the tire/wheel combo and suspension components to prevent contact.

So that is my long winded on the topic, based on deduction.

Comments welcome!

slawek65

Chas2,how are You man. This is my BBS RE wheels,19x8.5 and 18x8.5 same wheel with same offset. 18x8.5 have waaaay more caliper clearance then 19x8.5 wheel.Why???????

Chas2

No clue. It is all just theory on my part based. I could not really find anything that explains brake caliper clearance.

How are you doing!

So how are the 18's? They are certainly lighter than the 19's and you have much more choice in rubber!

bnaritomi

OMG... so basically, go to your local wheel shop, have them throw your RL up on the lift and install or try to install your wheel of choice to see if the wheel fits or not. Ugh...

Thanks for all of your input guys.

Chas2

I think you should first ask the manufacturer if they will fit. If you can, do it by email so you have it in writing, in the event you have issues when you go to your local wheel shop.

Also raise the issue with the wheel shop before you go, and if you do it by internet sale, I would write/contact them directly about what happens if it does not fit.

By the way, remember to get TPMS installed, which is another variable to pay attention to. Most wheels these days are compatible with the Honda/Acura TPMS, but I think some are not, and the Tire Rack or other reputable vendors can set you up with another solution that is not integrated into the valve assembly.

It may seem daunting, but it is really not that bad, and you have folks on this forum that can help review your decision process.

My tome was just theoretical as to why things may not fit even when the offset appears to be compatible. As usual, I make it more complicated than necessary!