11 replies to this topic

[racer466]

New to the class, currently building a 99 for SM.  Do I need to buy spacers to get the wheels out to the fender lips, or is there an offset that will do just fine? Looking at TR1 wheels.

 

Thanks

 

 

[Jim Drago]

New to the class, currently building a 99 for SM.  Do I need to buy spacers to get the wheels out to the fender lips, or is there an offset that will do just fine? Looking at TR1 wheels.

 

Thanks

Use the 25 mm offset wheels from Tire rack and you will not need anything

[Steve Scheifler]

Use the 25 mm offset wheels from Tire rack and you will not need anything

Maybe lug nuts.

[Tom Sager]

Maybe lug nuts.

and a tire for each wheel works best. 

[Steve Scheifler]

Oh, right, but those are $$$ so I hear we will be restricted to one sticker set plus one spare per season. Which means a budget increase for a few but that can’t be helped.

[Sphinx]

I know everyone was excited about the 25mm when they were allowed a few years ago.  At this point, is there a difference from a performance perspective or just driver preference v. 30mm?

[Ron Alan]

I know everyone was excited about the 25mm when they were allowed a few years ago.  At this point, is there a difference from a performance perspective or just driver preference v. 30mm?

Allowed? What are you smoking?   Maximum track width has always been achieved safely with 25mm wheels since the beginning! Early on these wheels weren't readily available in this size...but now the most common. And when the NA rear track width(maximum) was changed to match the NB...5mm spacers could be used with your 25mm wheels! Now besides this option you can run NB rear uprights on your NA car in which case your 25mm wheels are still perfect! 

 

Run what you have Sphinx(30's if thats the case)it wont make a difference

[Sphinx]

Allowed? What are you smoking?   Maximum track width has always been achieved safely with 25mm wheels since the beginning! Early on these wheels weren't readily available in this size...but now the most common. And when the NA rear track width(maximum) was changed to match the NB...5mm spacers could be used with your 25mm wheels! Now besides this option you can run NB rear uprights on your NA car in which case your 25mm wheels are still perfect! 

 

Run what you have Sphinx(30's if thats the case)it wont make a difference

 

 

I left that California stuff behind!   I've got both sizes and have used 25 for the last many years - was mostly curious whether there was any consensus.

[Steve Scheifler]

I know everyone was excited about the 25mm when they were allowed a few years ago. At this point, is there a difference from a performance perspective or just driver preference v. 30mm?

Greatly simplified, you want a wider track if you can get it, but of course it isn’t so simple and at some point there are trade offs. Unfortunately I don’t have accurate models of our cars or tracks we run but just for grins I wanted to see just how small an impact a 10mm track increase has on something I can sim with a high end simulator demo.

So this is total apples to oranges but on a Porsche Cup car running the Silverstone GP course, adding 10mm track front and rear dropped lap times from 2:34.51 to 2:34.44. Reducing track by the same amount below the original had a slightly larger negative impact yielding 2:34.59.

So how much is too much all else being the same? Well, I couldn’t find that because there’s a big difference between making the basic chassis/platform wider and simply moving the wheel further out from the suspension upright/spindle as we are doing.

While not even remotely close to our scenario it’s probably safe to think that the differences are not orders of magnitude, so the benefits are at best very small. But so is the qualifying gap between cars in a strong SM field.

[Brandon]

I know everyone was excited about the 25mm when they were allowed a few years ago.  At this point, is there a difference from a performance perspective or just driver preference v. 30mm?

 

I've had it presented to me as both a personal preference and plausibly frontal area increase concerns.

 

Prior to the Penske shocks, our cars were oversprung and underdamped meaning the marginally softer each corner could be made (upwards of 13mm from +38 to +25 wheels), it was a net positive (if that was your goal) with an offsetting negative of increasing your frontal area at the tires. If you learn how to drive the car on +38 wheels you don't lose that potential top speed impact. I know of one racer here in the NE who is always fast on +38 wheels so he's figured things out.

 

I've also heard scuttlebutt from another team running an STL Miata, in their application, having more tire in the airstream does impact top speed so they've not gone to an offset that causes a 15x10 (I think) wheel/tire to protrude much beyond their front airdam.

 

My personal decision was to go with Jongbloed +30 all around and have sold off all my K1s and Team Dynamics Pro Race 2s.

[BlueJay73]

So, if I have Jongbloed 30 offset wheels, can I run a spacer? 5mm front and rear?

[Sphinx]

So, if I have Jongbloed 30 offset wheels, can I run a spacer? 5mm front and rear?

 

Yes.