Lets try this again.


I have a 05 DB9. I want custom wheels. BC Forged RZ21's. Does no one on this forum have a DB9 with custom wheels that they would share their offsets. Vantage offsets don't help. I did make a whole thread on this, but no one but Vantage owners responded. Unfortunately, the DBS w/ 21's is not a help either. Looking to put 20's on it, likely going 245's and 285's. The DBS wheels are a 54 offset and 11 wide rear with 295's. They stick out a bit and on PH, they say don't due to possible fouling at the limit. So, I am going 10.5's, but to get them tucked in a bit more than the DBS I am thinking the 285's and a 52-53 offset. But, would really like for help if possible.


Thanks,

 

I think you have it. The DBS wheels on my DB9 are flush at the rear, and with the sidewall actually protrude about 3mm. At the front the wheels could use about 10mm to be flush and a true match with the rears.
Using this I would take 4mm off the DBS offset at the rear and add maybe 8mm at the front.
Knowing that you can add spacers up to 11mm with aftermarket lug nuts will allow you to fine tune if necessary.
How about some 3pc wheels? The hoops can be ordered in pretty small increments..

 

Great thanks,


You are confirming my numbers and suspicion of the DBS wheels sticking out a tad bit much for me. 3-4mm sounds about right. Amazing that much makes a difference.


I keep tweaking the settings for offsets to see if I can get the 295's under the back, but keeps putting me inwards a tad, and outwards the same or a bit more than the DBS. So 285's I feel are likely tops to make the wheels flush.


I was suggested 255's up front, but Seeing the speedo changes the 245.35 are so close to stock sizing that I am going to stick with that, and just push the 9in wheel outwards. From what I have always read 15mm are the correct spacers for fronts, so offset wise that should be about a 42 or so, which is the same custom specs for a Vantage Front

 

I'm not at home for another day, but I'd be happy to check the inside clearance in the rear. Of course this would be with the suspension at full droop, (in the air).

Taking 1/2" out of the rear wheel width will not help the fit of the 295s, maybe there is some clearance back there so you can stay with 11"s?

I see no sign of clearance issues in the rear, but I have not tracked the car yet...

Wondering about the function in the ABS/traction control/yaw rate sensors that compares the front and rear wheel speeds based on rolling radius? I have not looked at how this system works, but the DBS sizes are close, 777/771revs/mi and the DB9 sizes are even closer at 787/782 revs/mi.

So, what is the tolerance for difference between front and rear sizes before the computer decides a wheel is spinning/skidding?

 

See if you can see how much clearance there is behind the wheel ON THE Ground. I think the A-member up top is the issue with possible fouling at the extremes only. Daily driving I dont think anyone has complained, however its the outside sticking 3mm out too much.

245/35 and 285/30 I think is about perfect matching, but gotta look at the speeds on a site to see. They are the downsize match for factory at 19in wheels I am pretty sure.

Offsets of 9in front at +42 seems about just right, same as what Vantage owners use.

Offsets for rear at 10.5in wheel seems to run the same as the DBS at +54 on the 285/30's for the best fit. IF you go 295/30 it pushes the wheel in .10in and outwards .71in. My route with 285's does .02 inwards and .64 outwards which should look about perfect.

The tire listing I put in my other thread measures all that offsets, but it measures it by Tire size not wheel size. 10.5 is about perfect for 285's.

Still working things, gotta see if factory aluminum centers measure all the same, if so, then have to make some decisions. Found a few pics google search of DB9s with DBS wheels and they look good, but maybe could be inwards just a bit. Hell, 3mm is pretty small, so really not sure what to think.

IF you could post some pics of the rears, how much they stick out from front view, rear view, and from the top. What you would want to see if you were having to make decisions 9k miles away and wont see the car for another year.

 

I have been thinking about some small spacers for the front, but the look is not jarring to me..I would say 90% of people would not notice the offsets.
Don't have many photos, will have to take some after the snow passes tomorrow

 

Those actually look really nice.

I am putting my order in for,

9in ----245/35/20 +42 fronts going with Continental Extremecontact Sport tires
10.5in-285/30/20 +52 rears going with Continental Extremecontact Sport tires

I kept looking at rear offsets and the DBS 11 in 295's are .71in outward more than factory 275's. I wanted something slightly less outwards than the DBS, but just couldnt make it work without going inwards more than the DBS ones do already. So had to stick with 285's and 10.5in wheel. They come out .61in so its only a .10th of an in less, but should make the difference.

We will see what the factory verifies.

 

DBS vs stock is 1.1" more outwards, not 0.71". So your 10.5/52 will be 0.17" more inwards than the DBS wheels.

 

IF you can help me out with your calculations please.

On the wheel offset calculator, inputting factory 275.35.19 and +62-63 offsets and inputting the DBS +54 offset and 295.30.20 size, the calculator puts the DBS outwards .71in more than factory wheels.

Where am I going wrong or if you have a better calculator tool please let me know.

 

Wheel face projection is unrelated to tire width. 11 vs 9.5 results in 1.5/2 increase in outward (and inward) face projection. This is modified by the difference in offset of 8.5 mm, which moves the wheel faces outward by that amount. Add to the 3/4" from the increased wheel width and you get 1.1"

 

Here, finally are some shots taken with a plumb bob and a vernier.

The front shows that the outside of the fender to the face of the rim is 9mm.

The rear shows that the outside of the fender is set back from the rim a mm or so. The plumb line hits the rubber before the rim.

not sure why these all come out sideways...

 

Thanks so much for the info.

The DBS infö is not only helpful to me, but to many who ask those questions from time to time.


Here is what I went with and why-----

Final:
Fronts- 245/35/20 with a 9in wheel offset +42
Rears- 285/30/20 with a 10in wheel offset +46

What I wanted was a 10.5 in wheel at +52 which would have been slightly smaller than the DBS fitment.

But.... the RZ21 BC Forged style wheel they cannot make above a +46 offset due to design. I didnt not want to go to a straight spoke type wheel similar to the V8V standard wheels, and really wanted the HRE P101's but wont spring for 11k in total. So we worked numbers and with the 285's and the 10in we can bring it out to +46 on the rear and still be 2-4mm shy of the DBS fitment. I have the exact measurement, but not handy. I will have similar pictures taken when they get installed. This will still put 285 worth of rubber down which can be done with factory wheels, just mine will move outward some, instead of filling everything out. Hope that make some sense.

This will be the first set of RZ21's BC has done like this, but they wanted to open their business to DB9 owners also, so they said they would make them. Their fitment for Vantages is no issue, just they never had a DB9 get wheels. They do have caliper measurements so that was taken into the mathematics.

 

Thanks for the offset numbers. That helps tremendously.