Rear Wheels on the Front

[hanknum]

Hi All,

I've only had my Roadster about a month now and I'm all ready thinking about "personalizing" it...I can never leave "well enough" alone.

So in the interest of reducing the understeer and the lack of OEM sized rubber, I have been thinking about new/different wheels. As has been noted in previous threads, the PCD on the Roadster is not very common. I have been considering putting the rears (17x7.5) in the front and running 205/40 tires which would have the exact same overall diameter (23.5") as the OEM 175/55-16. Without any spacers, this setup would extend out about 6mm further from the car than stock. From what I've calculated, others have put on aftermarket wheels that extended out 15mm w/o any problems. But, again w/o spacers, the inner edge would extend toward the car 32mm. I've read that another, had a different aftermarket wheel that extended inward 27mm again w/o any issues. So, has anyone tried the rears on the front? Any thoughts?

As for the rears...I have found a 17x8 wheel that is very similar to the OEM wheels. It is a straight eight spoke design (no twist), 65.1 CB, 5x110 PCD, and 30mm offset. I think a 245/40 would work just about perfect...the overall diameter would be 24.7 as compared to the stock of 24.9.

Any and all input appreciated.

Thanks,

Henry

 

[X.l.r.8]

My rear wheels skims the plastic arch liner and has worn a small hole. Despite looking like it has loads of clearance it didn’t take much to wear the plastic away. But damn they look sexy.

 

[gregd]

Do you have a 1.5 or 2.x? The 1.5's are pretty fussy about tire size. The 2.x a bit less so since they have a "tire learning" mode, but it's not perfect. If the tire sizes are too far out from what the car expects, you won't have Traction Control, which could be bad.

 

[hanknum]

My rear wheels skims the plastic arch liner and has worn a small hole. Despite looking like it has loads of clearance it didn’t take much to wear the plastic away. But damn they look sexy.

What wheels are you running? What size wheel & offset? What size tire? Got any pictures? Thanks.

Do you have a 1.5 or 2.x? The 1.5's are pretty fussy about tire size. The 2.x a bit less so since they have a "tire learning" mode, but it's not perfect. If the tire sizes are too far out from what the car expects, you won't have Traction Control, which could be bad.

I have a 1.5 (pretty sure)...#187 with shift lever. As I mentioned, the overall diameters are just about spot on with the OE sizes. The widths don't matter. The computer just cares about the number of revolutions compared to one another. Thanks.

 

[slcasner]

As I mentioned, the overall diameters are just about spot on with the OE sizes. The widths don't matter. The computer just cares about the number of revolutions compared to one another.

The number of revolutions depends upon the effective radius of the wheel+tire combination, which is the distance from the center of the axle to the ground. A larger wheel with shorter sidewall may compress less than a smaller wheel and taller sidewall. So you can't go just by the static diameter of the tire.

 

[hanknum]

The number of revolutions depends upon the effective radius of the wheel+tire combination, which is the distance from the center of the axle to the ground. A larger wheel with shorter sidewall may compress less than a smaller wheel and taller sidewall. So you can't go just by the static diameter of the tire.

Good point. But, keep in mind that different manufacturers that make the same size tire (ie. 245/40-17) will vary in the actual dimension. The same size tire from one manufacturer to another can vary as much as 0.25" for the diameter. Then, again with the different manufacturers, the amount that a tire "compresses" can vary due to the construction of the tire. Some manufactures will provide a rolling radius for each tire size that would be the most accurate. The sizes on the tires are somewhat "nominal". So with all these variables, in my opinion, the best place to start would be static diameter.

The computer "should" be able to account for such variables, as well as for the wear of the tires...a worn tire can be as much as a 1/2" or more smaller diameter than a new tire.

LMK what you think...

 

[hanknum]

My rear wheels skims the plastic arch liner and has worn a small hole. Despite looking like it has loads of clearance it didn’t take much to wear the plastic away. But damn they look sexy.

Sorry, reread this post...so, you are running rears up there .

Did it require a spacer...looks like it might. If so, how thick?

What size tire are you running front and back?

 

[X.l.r.8]

I just meant going wider and bigger in the rears is super close to clearence issues. I don’t actually remember what size they are. It’s in a post here somewhere.

 

[X.l.r.8]

• Wheel Brand: Enkei
• Wheel Style: EV5
• Front: 17x7,0 ET 38 (P/N: 446-770-5238HB)
• Rear: 18x7,5 ET 38 (P/N: 446-875-5238HB)
• Weight (Front): ~21 lbs
• Weight (Rear): ~22 lbs
• Bolt Pattern: 5x110 / 5x105
• Hub Bore: 72.6 mm
• Front Tires: 195/45-17 XL
• Rear Tires: 225/40-18 XL
• Tire Brand: Yokohama
• Tire Style: S.Drive XL
• Spacers: 15 MM (Front/Rear)

 

[X.l.r.8]

However the increased rolling circ, will probably not work on a 1.5

 

[hanknum]

I just meant going wider and bigger in the rears is super close to clearence issues. I don’t actually remember what size they are. It’s in a post here somewhere.

Oh, so you aren't running rear wheels in the front, but rather, the Enkei aftermarket setup...is that correct?

Are you rubbing on the inside or outside of the tire.

Your Enkei rears are the same width and offset as stock...the only real difference is the 15mm spacer and different tire to a small extent. Per Tirerack, the overall dia is only 0.2" larger. The main thing is, with the spacer, the whole wheel is pushed outward by that 15mm...so, I'd assume you are rubbing on the outer side of the tire?

• Wheel Brand: Enkei
• Wheel Style: EV5
• Front: 17x7,0 ET 38 (P/N: 446-770-5238HB)
• Rear: 18x7,5 ET 38 (P/N: 446-875-5238HB)
• Weight (Front): ~21 lbs
• Weight (Rear): ~22 lbs
• Bolt Pattern: 5x110 / 5x105
• Hub Bore: 72.6 mm
• Front Tires: 195/45-17 XL
• Rear Tires: 225/40-18 XL
• Tire Brand: Yokohama
• Tire Style: S.Drive XL
• Spacers: 15 MM (Front/Rear)

Thanks, did you buy this setup from Ari?

However the increased rolling circ, will probably not work on a 1.5

Not sure what you mean by "rolling circ". Can you explain?

 

[X.l.r.8]

The rears are skimming on the outside. But the spacers are needed to clear the fronts. I wanted to reduce the front spacers first because I had a rally car that have a narower track on the rear and on the road it was terrible.
Yes it is Ari’s setup, and to be honest the Intrax shocks may well tighten the rear end up enough to help. I don’t think the stock non adjustable give enough control on the rear end on anything past smooth roads. The roads in Toronto are anything but, I just replaced my 2nd front tire from pothole damage.
Back to the plot, the spacers are there to clear the brakes so if you can clear that you should be golden. I’ll take a pic in a sec to show. I’m heading out in a bit

 

[X.l.r.8]

 

[hanknum]

View attachment 377408

Yikes!

Is that just from the tire contact? Thought you said "has worn a small hole"...

 

[X.l.r.8]

Yup, but that was also the strut I blew hitting the moose, so I did a lot of miles with that side blown. Hence why I’m warning about going to wide on the rear.

 

[hanknum]

Now I'm really confused....

You blew out your right rear strut after hitting a large animal? But, you continued to drive without any damping at that corner. This would cause excessive oscillation and greater travel of the wheel. Don't you think this damage was more from the blown strut than the wheel/tire combo? And, actually, your tire is the same width as OEM, just pushed out a little. What about the other side...is there damage/rubbing on the other rear?

Any issues or rubbing on the fronts?

 

[X.l.r.8]

fronts are fine, rear right is the only contact point. At the time I had little option being a few thousand miles away from home. Once the weather warms up I’ll be putting the new shocks on and see if that helps. As mentioned in the tire thread, the rears can come in slightly but the fronts had to be spacered to clear so the rears got matching spacers. I may throw the spacers on my lathe to bring everything to a closer tolerance but for now the damage is done and some thermo mounded plastic will easily fix the damage.

 

[hanknum]

Sorry, one last question...

I thought the wheels that Ari had bought were a 5 spoke design...what wheel is that in the picture?

 

[X.l.r.8]

winter wheelset. They don’t rub.