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MAX Update No. 76: Wheels Are Turning


Now that MAX is getting streamlined, we can handle taller gearing, but we’ve pretty well gone through the inexpensive options for the differential gears, and we already have an overdrive transmission, so what’s to do? Easy — we go to larger diameter wheels and tires.

Larger than the 13” wheels that came with the Corrode Warrior (the ancient Toyota wagon that contributed so many of the driveline parts) or the 14” “snowflake” wheels (equally ancient) saved from a foundry scrap bin. It’s time for 15” wheels.

The problem is, as wheels get bigger they tend to get heavier, and suitable fifteen inchers aren’t cluttering up the scrap bins. Fortunately we still have some budget left, so I decided we’d invest $400, and if we had to, up to $500 on a set of wheels.

Wow, that’s five percent of the whole budget, but wheels are important, and as we’re closing in on our 100 mpg line-in-the-sand, these are the details we need to address. So I put out the word: I was looking for the best 15” wheels I could find, to fit MAX and MAX’s budget.

Man, I scoured the internet, and found the aptly named, which sells wheels too and plenty of them.  The customer service guy picked up on my concept of “best” quite quickly, and didn’t seem to think my goals were weird at all (in fact he found it an entertaining break from the norm); I wanted lightweight, narrow wheels, that wouldn’t look so modern or flashy that they’d throw off MAX’s classic racer look, and if possible I wanted dual stud patterns so I could try some high mileage tire tests on more conventional cars too (my Miata in particular). Oh yes, and they had to cost less that $125 apiece, $100 preferred.

He knew just the wheels: Drag DR-9, 15 x 6.5 diameter x width, 13.2 pounds apiece, dual stud patterns, available in a MAX-like white with a red stripe, and $100 each from Discount Tire.

So we arranged for a set of wheels and a set of Goodyear Assurance Fuel Max tires to meet up at the Discount Tire Store near me (America’s Tire Store in Eugene, Oregon—same outfit but called America’s Tire Store in these parts, probably for trademark reasons) and I fetched them on my way home from the Puyallup Mother Earth News Fair, and I’ve got to tell you three things about the experience:

1) These wheels look gorgeous on MAX. Drag Wheels is the name of the manufacturer, by the way, they’re not wheels for drag racing. Folks familiar with MAX before-and-after tell me how great it looks with the new wheels. I picked these wheels for their mileage attributes, but the good looks is a nice bonus.

2) Eugene is the greenest town this side of Madison Wisconsin, and the folks at the Eugene branch of America’s Tire Store loved MAX, were eager to help, let me work on MAX right there in their lot*, and just generally treated me great. I put their contact info on a link ‘cause it’s my way of saying Thank You.

3) I don’t have fresh mileage data for you yet, but with these new wheels and tires, MAX is really hitting its stride. The increased diameter has bumped its top speed (5th gear at 3000 RPM) from 72-1/2 mph to 76 mph. Closed course and professional driver blah blah blah and it’s faster than I want to go, but what’s important is, these wheels drop MAX’s RPM by 5% all across the board; for example, cruising at 60, the engine is spinning at 2375 instead of its previous 2500, and I expect that’ll make a difference at the fuel pump.

*I made these fenders to fit this wheel and tire combo, but it's pretty dang snug and the rear fenders have to come off before the rear wheels come off. It's pretty easy (I designed it to be easy) but it's still a bit disconcerting to see a customer taking his car apart in your parking lot

Photos by Jack McCornack 

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john m_3
7/23/2011 4:59:41 PM

how many mpg are you getting now. i never hear the progressive mileage gains from these improvements. fess up, how many mpg are you getting now after the larger tires have been installed?

abbey bend
7/8/2011 2:18:52 PM

Propane injection increases the Cetane rating of the fuel. This in turn allows the injector timing to be further advanced, producing more power at a given RPM. With your engine choice, it is unlikely you would actually have any boost in power and even less likely you notice an increase in fuel economy. Propane is good for modern computer controled diesel engines, but largely worthless for non-computer engines. So save the money when it comes to propane!

jack mccornack
7/5/2011 2:34:39 PM

Oh yes, Jeff, I'm quite willing to spend over ten grand on the R&D aspects, and indeed have. For example, if you build your own MAX (or I build another one), we'll only need one body for it, right? I've read mixed results from propane injection. It does indeed seem to reduce diesel fuel consumption, but I don't know if it actually saves any money, resources or emissions, since I'm having some difficulty finding out how much propane is being used...does it actually increase efficiency, or is it just trading one fuel for another? The two stud patterns are 4 x 4.5" (early Toyota etc) and 4 x 100mm (Miata etc).

jeff dean
7/3/2011 10:44:22 AM

Jack, what are the two bolt patterns for the new rims. This is going to allow you to change the differential in Max, for more gear ratio options. Maybe you could swap in a 2.56:1 differential out of a Chevy Monza/Vega.

7/3/2011 2:34:40 AM

It may not be the look your going for but what about smooth/moon hubcaps and wheel skirts? I have heard people have seen improvements in fuel economy with such additions.

jeff dean
7/1/2011 10:40:52 PM

Max looks great with the new wheels. I hope the 5% decrease in rpm helps with mileage. Are you willing to spend more than $10,000 for Max, such as research that wouldn't need to be spent to create another Max? I have read that propane injection into diesel engines can substantially increase efficiency. It would take some research and experimenting to get it to work, but that might put you over your budget.