20 inch Racmonolite aftermarket wheels - Page 14

M3Racer · 28th January 2006, 04:23

Shep/Chuck:

From the measuring and research that you guys have done, do you think we will have any clearance issues at all with plus-sized (275/305) tires on these wheels?

I'm thinking of going with H&R lowering springs around the same time and I don't know if I should be looking to achieve more negative camber somehow at the same time or not...?

Also, does anyone know if the speedo is based on rotation or some other method? With plus size tires, we'll be off from the stock overall diameters by as much as nearly 4%. Is there someway to fix or compensate the speedo (and odometer) error that would come with the different tire heights?

jfenley · 28th January 2006, 04:37

Good points. I am also doing H&R springs. Any potential issues?

Quote:

Originally Posted by M3Racer

Shep/Chuck:

From the measuring and research that you guys have done, do you think we will have any clearance issues at all with plus-sized (275/305) tires on these wheels?

I'm thinking of going with H&R lowering springs around the same time and I don't know if I should be looking to achieve more negative camber somehow at the same time or not...?

Also, does anyone know if the speedo is based on rotation or some other method? With plus size tires, we'll be off from the stock overall diameters by as much as nearly 4%. Is there someway to fix or compensate the speedo (and odometer) error that would come with the different tire heights?

ChuckD · 28th January 2006, 09:03

Quote:

Originally Posted by M3Racer

Shep/Chuck:

From the measuring and research that you guys have done, do you think we will have any clearance issues at all with plus-sized (275/305) tires on these wheels?

I'm thinking of going with H&R lowering springs around the same time and I don't know if I should be looking to achieve more negative camber somehow at the same time or not...?

Also, does anyone know if the speedo is based on rotation or some other method? With plus size tires, we'll be off from the stock overall diameters by as much as nearly 4%. Is there someway to fix or compensate the speedo (and odometer) error that would come with the different tire heights?

Guys.. the complete answer to this question will have to wait until Shep returns from the track this weekend. For the most part I am the administrative arm for this project.

I can comment that RAC builds aggressive fitments that not only look appealing, but function as well. For instance the M3 fitments are as aggressive as can be spec'd yet still allow considerable height adjustment.

There are many parameters with that can have an influence on fitment. Tire size, tire brand, ride height, spring choice, and alignment parameters are some to name a few. That said.. normally our specs allow quite a large range of adjustment.

Below is my car on RG4s.. the offsets were nailed perfectly!

With aftermarket tires.. sometimes you make a sacrafice depending on how their diameters compare to stock. The speedometer can be off although not much. This is the price you pay for increased grip, traction, and aesthetics.

The beauty of the M5 RG41 specs as I understand them is you will be able to run the stock rubber on the wheels if you like. All while widening the track of the vehicle which can enhance the car's dynamics tremendously.

M3Racer · 28th January 2006, 16:58

Chuck/Shep...

Just to clarify for people b/c some of your comments mention using the stock rubber...We will be able to use stock WIDTH rubber. Stock are 19s, these are 20s. Shep had made a comment about something to the effect of "you could always throw the stock tires on them".

I just wanted to clarfiy for those who may be reading more casually...

metalman · 28th January 2006, 17:52

M3 Racer, you in on the wheels?

M3Racer · 28th January 2006, 18:02

Quote:

Originally Posted by metalman

M3 Racer, you in on the wheels?

Yeah, I faxed in yesterday.

ChuckD · 28th January 2006, 19:37

Ok.. so I have had some responses for participants screen names. This is not the complete list yet as some people have not had a chance to reply yet. I will edit this post as as they do. This can be considered the "official participant list". In no particular order..

JFENLEY
David.L
RONRACE
Terrence
M3Racer
Metalman

shep01 · 29th January 2006, 17:22

Quote:

Originally Posted by M3Racer

Shep/Chuck:

From the measuring and research that you guys have done, do you think we will have any clearance issues at all with plus-sized (275/305) tires on these wheels?

I'm thinking of going with H&R lowering springs around the same time and I don't know if I should be looking to achieve more negative camber somehow at the same time or not...?

Also, does anyone know if the speedo is based on rotation or some other method? With plus size tires, we'll be off from the stock overall diameters by as much as nearly 4%. Is there someway to fix or compensate the speedo (and odometer) error that would come with the different tire heights?

There should be absolutely no rubbing issues with the 275/315 plus sizing; even with lowering springs. I did some research into 20" choices and there are some very interesting possibilities out there. Look around the tirerack site and search the various manufacturers. There is a 255/30/20 that matches up well to the 295/25/20; there is obviously the 275/30/20 that pairs well to the 305/20/20; there is also a very intersting choice from pirelli in theirThe Pirelli P Zero System, albiet a tad taller, offers a very interesting choice that would get my attention - a 245/35/20 and a 285/30/20. This is a next lever tire and frankly, for street performance, this one has a strong reputation. Ths is also easily accomodated by these wheel sizes and may represent an excellent middle ground in oarticular where you drive wet weather a lot or for the summer ( i always prefer a tad thinner front tire in the summer - it reduces hydro-planing a lot) .

The speedo is electronically interpolated from rotation, so, yes, regarding diameters - the tire will effect the speedo to some degree depending on the diameters. It is ordinarily not all that consequential. I have lived with it for years on all my M3's. No easy fix for this.