Budget is as budget does

I’ve been busy with work and haven’t had much time for driving. I’m still planning on posting some more off-season training exercises. But for today, I want to give you some insight into my racing ethos.

Race as fast as you can afford

This is my attempt to make a statement as witty as:

Take a late apex as early as possible

I love my high performance driving hobby, and race weekends are a big part of that. But I don’t love it enough to break my bank. That’s one reason I have a Toyota Yaris racecar. It was cheap to build, burns only 4 gallons per hour at full race speed, and still let’s me get the better of most Miatas.

I recently purchased a set of Maxxis VR1 in 205/55/16 for my Z3. These were on sale for $60 with free shipping direct from Maxxis. The tires in the bargain bin were 4-5 years old using their “S1” compound. I don’t know exactly how these differ from their newer “S2” compound (other than being $100 cheaper), but I found them to be very good on track. I think they performed about the same as the typical endurance 200TW from 4-5 years ago (Star Spec, 615, NT05, RS3, RE11, etc).

I have a couple races planned in the near future: Sonoma in March and Thunderhill in May. Who knows, maybe Buttonwillow in Fall? Tires are expensive, even when racing on a budget. My go-to tire is the Hankook RS4 in 225/45/15. As most people know, they strike a great balance between performance and longevity. The current price on these is $600 per set at Tire Rack (that price includes free shipping). As race tires go, that’s not very expensive since RS4s tend to last a long time. However, for $600 I could by 10 VR1s on sale. And being the miser that I am, that was too good of a bargain to pass up.

So I purchased 12 of them, which arrived on a pallet. There are two problems here.

  1. I don’t own any 16″ rims with a 4×100 bolt pattern
  2. 205/55/16 has a 25″ diameter and 225/45/15 has a 23″ diameter

However, did I mention that they were $60 with free shipping? Sometimes you have to make compromises. I found some Mini wheels in 16×6.5 on Craigslist for $120 for the set. At $30 each, I didn’t even bargain. The total bill for 4 wheels, tires, and mounting was just over $400. Replacing a set of RS4s would have cost me $700. That $300 difference bought me another set of tires and the cash to mount them.

So what about this 25″ vs 23″ diameter? That’s going to change the shift points a little. 2nd gear will now be good for 65 mph and since the car doesn’t go faster than 95 mph at Sonoma or Thunderhill, we aren’t going to need 4th gear. The 8.7% difference in diameter will also affect braking, but the Yaris has always had plenty of brakes, so I’m not worried about it.

The springs are stiff enough that I don’t think the tires will rub, but the suspension has height adjustment, so I can raise the vehicle if necessary. You can see the fitment in the picture below. It’s looks okay.

YSAR reader Kyle asks what the expected performance difference is. Let’s see what Optimum Lap says. A tractive force diagram shows you how much power you’re getting to the ground at various speeds. This is dependent not only on the engine, but also the gearing, final drive, and wheel size. As you can see in the diagram below, the gears are spaced pretty far apart. So the switch from 2nd to 3rd gear results in a massive loss of tractive force. The 25″ tires allow you to drive various parts of the track in 2nd gear where you would normally be at the bottom of 3rd gear. It also allows you to stay in 3rd gear instead of switching into 4th.

The elapsed distance graph shows that the 25″ Yaris (orange) has a slight advantage in the slower corners and high speed sections, as expected. The net result of all of this is that the 23″ Yaris beats the 25″ Yaris by 0.22 seconds.

In reality, I’m not sure what the difference will be. I’m normally reluctant to shift into 2nd because I stay in it such a short time. So I prefer to drive around at the bottom of 3rd gear than make a switch. Having a useable 2nd might mean I actually use the gear. But shifting takes time and concentration, so there’s no guaranty that I’ll actually be faster. This is one of those things I need to experiment with on a test day.

Thanks Kyle for reminding me to finish the post.

One thought on “Budget is as budget does

  1. Given who you are I’d think you’d estimate the decrease in acceleration as a hypothesis and then verify it at the next test day. ;)

    Like

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