track wheels...17x9 +45..GTFO

[Ludachris]

I believe that when Mitch Rusu worked with Team Dynamics to come up with the optimum wheel fitment for the 1g for a 17x9 they took a few things into consideration. I'll see if I can get Mitch in here to explain.

 

[Bryan 93]

I think the change in offset does make sense once you start going to a taller tire. The taller tire means the point where the steering axis meets the ground moves further out from the car. So in order to keep the same scrub radius you would need to move the tire center line out, decreasing the offset would accomplish this. Might be on the right track with this.

 

[snowborder714]

The reason +27 was chosen for the TD group buy is that it allowed for a wide choice of tires (up to 275, I believe) while not having to use spacers. If you run the widest tire possible on that wheel, it will keep the factory suspension/handling properties as close to possible. The key is to get the tire as close to the knuckle as possible.

In regards to running a 17x9 wheel with a stock offset, it will not work on a 2g in the rear. That will hit the knuckle. To run that wide of a wheel/tire combo, you would need roughly a +38 offset. This would put you very close to the rear knuckle, depending on the sectional width of the specific tire you chose.

I'm not sure how the 1g's work with wheel clearance.

 

[Bryan 93]

Can you expand on these "factory suspension/handling properties"? The width of the tire has no effect on scrub radius, its all about center of contact patch, so I don't think it's that. The track width I don't think is it either as a smaller offset increases the track width pretty substantially from stock. I would think the kingpin should be the same regardless wheel offset, same goes for center of gravity and roll center. I'm curious what changes, specifically.

The reason +27 was chosen for the TD group buy is that it allowed for a wide choice of tires (up to 275, I believe) while not having to use spacers. If you run the widest tire possible on that wheel, it will still keep the factory suspension/handling properties. The key is to get the tire as close to the knuckle as possible. If you run a 255 tire on that wheel, for example, you will not keep the same suspension/handling properties.

In regards to running a 17x9 wheel with a stock offset, it will not work on a 2g in the rear. That will hit the knuckle. To run that wide of a wheel/tire combo, you would need roughly a +38 offset. This would put you very close to the rear knuckle, depending on the sectional width of the specific tire you chose.

I'm not sure how the 1g's work with wheel clearance.

 

[snowborder714]

Note the edit above (compared to what you quoted).

I don't have specifics on what was taken into account when they chose this offset, so I can't address the "suspension/handling properties" question properly.

 

[Phil1320]

If anyone is interested, I can mount the TD wheel to the front and rear of my 1G AWD and snap some pics and post them up. They do not have tires mounted.

 

[snowborder714]

That should help some people at least looking at that offset who can then calculate inboard tire clearance as long as you measure wheel clearance to anything that might get in the way.

 

[Bryan 93]

Thanks for the offer, I am more interested in the theory. I think I have a good idea what will physically fit on a 1g AWD. I am more interested in the effects on the handling characteristics. What I don't want to do is shoehorn something in and screw up the handling.

If anyone is interested, I can mount the TD wheel to the front and rear of my 1G AWD and snap some pics and post them up. They do not have tires mounted.

 

[Ludachris]

Thanks for the offer, I am more interested in the theory. I think I have a good idea what will physically fit on a 1g AWD. I am more interested in the effects on the handling characteristics. What I don't want to do is shoehorn something in and screw up the handling.

I don't know that you're going to screw up the handling - as if the stock handling is great. If anything, adding to the scrub radius will likely just make the steering heavier (in the unlikely event you don't change the stock camber and caster), which will likely only be a negative for daily driving.

Going with a wider wheel/tire on the 1g will result in compromises no matter what. Clearance, geometry, contact patch - you can't have it all. The quest for grip can get tricky in these cars. As noted on <a href="http://www.miata.net/garage/offset.htm">this page</a> (read #2), the added contact patch and stability from moving the track outward outweigh the potential negatives of the additional positive scrub radius.

 

[Phil1320]

Thanks for the offer, I am more interested in the theory. I think I have a good idea what will physically fit on a 1g AWD. I am more interested in the effects on the handling characteristics. What I don't want to do is shoehorn something in and screw up the handling.

No sweat. I think unless Mitch himself makes it up here, all the info that's available is in these couple of threads. As far as screwing up the handling, please research Greg Collier right here on dsmtuners. I'm willing to bet Noone up here has driven a 1G DSM around a road course at his speeds. He also was in competition, and winning against cars you wouldn't think a DSM had a chance against.

 

[Bryan 93]

I guess screw up the handling is a bad way to put it. I literally haven't driven my DSM for over 10 years, been waiting for me in the garage. Blame my job, house, wife, dog, and kid for that. When I did drive it I remember the tramlining being really bad, and the bump steer not all that great either. I am now building this car up, it is basically completely for street use, probably won't see much track time. The roads where I live are not good at all, blame that on the 150" of snow we get yearly. So I really want to make sure I get the suspension right, and the wheels and tires are a big part of it.