Ok, what is the stock wheel offset on the EVO? 35mm? Also when going with wider rims, eg: 17x8.5 or 17x9 ... how does offset change? or does it change at all?
The way I think about it, is that the offset stays the same, so that the rim grows by equal lengths on both sides of the hubs and this in turn prevent premature bearing wear. Or is my thinking wrong and offset is actually a ratio with respect to wheel width and it grows as the rim's width increases?

 

I believe stock offset is +38mm, and my 9" rims are +35mm. I'd be curious to know the math as well. In the meantime, here are some wheel offset calculators:

http://www.1010tires.com/WheelOffsetCalculator.asp
http://gs.tolan-hoechst.com/tirecalc.htm

 

Speedo from the link you provided, it pretty much agrees with my initial thought. If the offset stays the same with a wider rim, the rim grows by equal amounts on each side. I'm still curious about wheel bearing wear and what the offset should be set at to avoid accelerated bearing damage. Don't want the scrub radius to get outta control

 

Bump! come on I'm sure one of you vendors can chime in ... Neal@tirerack? Subydude? Z1auto? Evasive EVO? Gruppe-s?

 

there have not been issues of premature wheel bearing failures on these cars that I have seen yet...and there are guys running 9's and 9.5's with mid to low 20 offsets in some cases

 

stock wheels are 17x8JJ +38

the offset is the distance from the plane of mounting (wheel on to hub) to the actual centre plane of the wheel. the amount the wheel protrudes 'inwards' would be:

[(wheel width x 25.4)/2] + (offset) = 139.6mm

'outwards' would then be:

[(wheel width x 25.4)/2] - (offset) = 63.6mm

This also works if your offset is -ve.

I will look at the section diagram of the wheel hub (think i have it somewhere) and get back to you on the bearings. Basically, I think the point is there there are other forces acting on the wheel bearing that shifting the vertical reaction force by a few mm's aren't going to hurt.

Having said that, i wouldn't advise running +20 mainly cos it will rub and i think the bearing life might be affected if you go crazy and run -ve offset or something like that.

 

x838nwy that is exactly the kind of info I am looking for. So as long as the offset is a few mm off it won't affect the bearings much but how much is acceptable? The actual center plane for the wheel should be in the same spot regardless of the wheel width. So ideally we would want wheels with 38mm offset regardless of the width ....

Which brings me to my next question, anyone know of any wheels out there with 17x8.5 or 17x9 with 38mm offsets?

 

Again, its been shown many times by many people that the wider widths and lower offsets are not affecting anything bearing related. There are people here who have run for 2 + years with these setups, and not had issues. The lower offsets not only look better, but dramatically assist in turn in response.

The issue you get into the sheer lack of wheels that are wider than stock and have a stock offset - 95% of them won't clear the brakes due to the spoke design. The only one I know off of the top of my head is the Black Racing Pro N1 in 17x9 +38.

There is a thread here someplace about wheels that are confirmed fitments....it dates back 2 + years and is very comprehensive

 

can't seem to find that the wheel hub internals look like. Anyway, you're right about the offset - it would be ideal to keep the same figure.

Prodrive GC-010G comes in 17x8.5 +39 and 17x9.0 +36 and the GC-07C comes in 17x8.5 +39 - how annoying is that?

I still have those numbers saved cos when I was looking for wheels i tried to keep the offset also. Somehow the only wheels that are +38 are 8" wide...

 

Enkei makes the RPF1 in 17x9.5 and 18.9.5 +38. However, I'm not sure if there are caliper fitment issues.

 

yes they come in that size, but it's not what Prodrive recommends, so my guess is they don't fit.

For a GC010G for example, recommended fitment is 17 or 18x8.5 +34
For the GC07C has no recommended fitment fro Prodrive but I know the 17x8.5 +32 fits, the +39 version does not according to the info I got when looking at them for a customer about a year ago

Bottom line is with this car, due to the brakes, it's not just offset and width, it's the pad height and the design of the spokes. All these factors play into each other in determining what will fit and what won't. If you search the boards, people have used just about every wheel in every conceivable size/offset and width at this point in the cars lifecycle, it just takes some time to search the threads and comments

 

true, Z1 performance. I probably didn't make it clear - i don't think the change in offset will cause wheel bearings to fail prematurely. I was looking at it more along the lines of suspension geometry and contact patch location and all that. It's probably best not to faff about with that stuff, but again, I don't think anything dramatic will happen if you chage your offset by 5mm or so.

I finally went for the volks which are +30, mainly cos they fill the width nicely. I think the main point is that shifting the centre line by a few mm's isn't going to hurt anything. The bottom line, as you pointed out, is clearance. Go too much either way and you'll rub the fenders or hit the struts. Go with some designs and you won't clear the calipers.

While the recommendations from the manufacturers are useful, some wheels will also fit that are not of the recommended specs (obviously). For a while I ran CE28N's 17x8.0 +38. I borrowed it for a while and they fitted fine...

Having said that Enkei recommends +30 for the RPF1's 17x8.5 but 18x8.5 +38 for the NT03 (note not 17) so probably caliper issue for both?

 

I know what you are saying...but like I said, look at what the guys who road race alot are running and you'll see - the car loves camber and it loves wide tires. To achieve that, guys are running 9's ad 9.5 inch wheels with offsets that range from the mid 30s to the mid 20's (granted in the 20's you are looking at body mods, but that's an aside). In other words, this is an easy car when it comes to wheels...there is literally a ton you can run, which is great

RPF1 happens to have lots of caliper clearance - you can run both an 8.5 +30 and an 8.5 +40, and both clear without spacers

 

This is great info, thanks everyone ... yes I did look through the confirmed wheel fitment guide thread but as usual there was too much junk (Read: wheels that were of sizes and offsets I was not remotely interested in). Yes I was aware that clearing the brake calipers seem to be the biggest issue with wheel fitment for the EVO but I would rather hear from you guys, who seems to be privy to this knowledge.
So from what I understand the EVO gives a lot of room for error in offset( upto 10mm)?

 

the short answer is yes, but it's all down to spoke design more often than not. Even though the offset might look ok, it is not a guarantee it will clear the spokes.

If there are specific wheels you are interested in, feel free to let me know and I can do my best to confirm fitments