Mk3 Wheel Spacer Information
I've been getting a lot of wheel fitment questions recently and thought that creating this thread might be helpful given my experience. Like the lighting thread, I will try to put as much info here in the first post and if you have more that you would like me to add to it then send me a pm and I will go edit it in for easier information retrieval. Also, this is not a thread for arguing. If you don't want to space your wheels then don't; this thread is for people who want to and are looking for information.
My car came OEM with the Handling Package 18's with OEM PS3 tires. These are 18x8" ET55, 235/40 R18. All of the numbers I've calculated for spacer and wheel fitment have used this as the starting platform because I know what does and does not work on it without throwing in camber arms or (when available) camber plates. The fitment calculator that I use is located here. The wheel diagram itself is relatively useless, but the numbers listed on the bottom will tell you everything you need to know before making a decision.
First off, the maximum offset that I have achieved before wheel rub is ET35 by using 20mm adapters. The only way I was able to articulate my suspension to get the rub was by doing gradually increased speeds at full lock into my driveway, which has a relatively steep incline. This is with the OEM struts and Eibach Pro-Kit springs (.75" drop). Even though I firmly believe that I could safely run that offset without putting myself in the situation to cause rub, I want to make sure people are aware because you never know when you could be turning a corner quickly and not see a pothole. Know where your limitation is and then determine your work-around.
So that means that anything up to and including a 15mm spacer is safe and will work without rub, right? Well, not really. The front hub would need to be pulled off in order to remove the studs and replace them in order to have enough length for any spacer over 8mm in thickness. Removing the hub will also require new bearings to be pressed in. For my car and schedule it wasn't remotely feasible, but maybe for you and yours it is. The largest wheel spacer that you can safely fit on OEM studs that is currently readily available is 5mm. I can say that I have run larger on the OEM studs, but I have my own torque wrenches and made sure that I set up a good safety net of torque checks and re-torques. I'm not advising that you go larger than 5mm for safety sake without properly investing your time and money.
Should you be so inclined, the front fenders have room to be rolled. With rolled fenders you *should* be able to safely adapt 20mm up front. I currently have a 15mm set of adapters up front that are sourced from a C30, but I do not recommend going this route. Another member gave me the information and I double-checked the part specifications and went for it, but I was not able to mount my wheels without doing some 'modifications'. Even if his wheels mounted up fine, I can not openly recommend purchasing them. What it boils down to is that my OEM studs were too long, and the recesses in my wheels were not large enough to accommodate the nuts that mounted the adapters to the hub. There is a reason they are not listed for our Focus.
So that means that anything up to and including a 15mm spacer is safe and will work in the rear, right? Yep. If you go anything larger than a 15mm in the rear, you will need the more expensive hub adapters instead of regular spacers because you won't be able to get the longer stud into the hub without pulling the hub. I actually have 20mm DRM adapters in the rear right now and they work great. The only possible issue you might have regarding 20mm in the rear is that you may not be able to fully dial out the negative camber induced by lowering your car as there isn't a lot of room for the top of the tire to swing out.
It also needs to be mentioned that not all tires are alike-even if they are listed as the same size. The first number in a tires size is it's width, but that can come from any area when measured from sidewall-to-sidewall. The PS3's are very wide at the rim protector but actually taper back in to meet a narrower tread. If you went to replace them with different tires that had a 235mm tread width with no rim protector, it would greatly affect what spacers you could run. If your spacers were already installed could lead to having a very long, slow drive home... just food for thought.
Stupid knowledge for those that may be curious- ET comes from the German word Einpresstiefe (insertion depth). It is synonymous with the word offset. This number dictates the mounting surface of the wheel to its center line. A positive offset has the mounting surface closer to the outer edge, zero offset would be direct center line of the wheel, and negative offset would have the mounting surface closer to the brakes (i.e.-deep dish wheels). ET55 on a 8" wheel is NOT the same as ET55 on a 8.5" wheel. Tire Rack for more info.
I'd rep you for your brilliance. But, alas, FF only allows 1 rep per every 1500 given. [facepalm]
So, in lieu of this, I will buy you a beer at FF '13 and give you a hug. [thumb]
Duane=wheel spacing Godfather. [thumb] i'll rep you when I get home.
It's all good, thanks guys [:)]
I'll have more Mk3 fitment information when I add coils and my special offset wheels arrive [ninja]
Here are some pics of unprofessional quality. Left side is ET55 (OEM), Right side is ET35. 8" wide wheels-
When it comes to tire sizing, you can play with the numbers to get a wheel/tire fitment that you like. In the example of my OEM 235/40R18 tires-
235- Widest measurement of the tire, from one side to the other. Note that this is not the tread width.
40- Aspect ratio of the sidewall as a percentage of the tire width measurement
R18- 18" tire for 18" wheel
If that is my OEM sizing and I want a narrower tire, I simply lessen the first number. As an example, the tires going on my summer wheels are going to be 215's instead of 235's. Keep in mind that tire manufacturers are all different, so a 215 from one company could actually be wider or narrower than another. Those that are into stretch and poke are all very familiar with this.
When considering a width change, you have to consider changing the aspect ratio as well if you are wanting to keep your speedometer/odometer correct. Using my summer tires as an example, I am keeping the same aspect ratio of 40. Because it is now figured off of a smaller number, my sidewall is now smaller as well. 8mm, to be precise. That means that not only is my wheel and entire car closer to the ground by 8mm, I actually also have 8mm more wheel gap. Because it is smaller, the circumference of the entire tire is actually around 50.3mm less. This means that as my wheel turns, if I marked a line perpendicular to the tire and road, that when the tire line became perpendicular to the road again I will have gone 50.3mm less than the OEM. You can see how this adds up to create a gap between how far/fast your odometer/speedometer thinks its going versus what is actually happening in real life.
If I went with a larger aspect ratio, say 215/45R18, I will actually have gone in the other direction in comparison to OEM. I will have raised the car and decreased wheel gap by 2.75 mm. The circumference will actually be larger than the OEM tires by 17.2mm. Now my car is actually going farther than it thinks it is going. If you use the wheel/tire calculator in the first post, you'll see how changing these numbers correlates in regards to shape, size, and wheel/tire fitment.
In any direction, the tire that you choose is really only limited to what is produced, what you can afford, your wheel size, and what you can fit in your fenders (with or without body work).
I know this really isn't the purpose of your post... but why did you go with such a narrow summer tire? The stretched look?
There is a certain fitment that I am trying to get, but it doesn't really fall under the category of 'stretched'. I'm still going to be using an 8" wheel, so the actual fitment is going to look similar to the PS3's.
For a stretched look, you really have to be running an 8.5"+ wheel if you are using 18"s. The narrowest tire that you're going to find on that size is a 205, and they are few and far between. I did contemplate some 205/40R18 Neo-Gen's, but ultimately determined that they would be too small for the fitment that I want.
Any update on you spacers? :)
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