Centramatic front brake clearance

 

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Centramatic Wheel Balancers

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James Langan

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Mount and Balance, Maxxis Bighorn LT285/70R17D

Almost enough debris inside to weigh!

It was obvious these Bighorns had been stored outside as there was varying amounts of desert grit inside the tires. A thorough cleaning with compressed air prepared them for a trip to the tire shop.

Inside of the bead, this sand was difficult to blow out.

The Bighorns were not going on my nicest set of wheels, but my local Les Schwab Tires still used their nice, new rim-clamp machine to insure damage free mounting.

Rim Clamp tire machine.

New high-pressure valve stems were purchased for the TRD Rock Warrior wheels.

My experiences with Maxxis tires, all LT255/85R16D prior to buying this set of used 285s, have been positive. The Bighorns are a little loud, a softer, nicely gripping tire, and I’m usually impressed with how little weight they require to balance.

Having the correct, small center cone for the balance machine is important.

Hunter Road Force GSP9700 tire balancer.

These 285/70R17s did not disappoint, the Hunter GSP9700 balance machine indicated the tires needed little weight to balance, even with their uneven wear.

Tire #1. Amazingly little weight for a dynamic balance of a 33" mud tire. The final balance required 1 ounce on each side.

Balance Data

On my shop scale these 17-inch Bighorns weighed 55–57 pounds depending on how much rubber remained, and 80 pounds mounted on the very light forged aluminum 17″ TRD Rock Warrior wheels. Although I’ll often use a static, single-plane balance for truck tires, these Bighorns were dynamically balanced.

  1. 1.00/1.00
  2. 2.50/2.00
  3. 2.00/4.75 (The most cupped, unevenly worn tire.)
  4. 3.50/1.50

The lack of wheel weight required to balance these 33-inch mud tires was amazing. Tire #3 needed 6.75 ounces, still very respectable for a new tire, and simply impressive for one that has notable uneven wear.

Copyright © 2012 James Langan

Tire Wear Analysis: Maxxis Bighorn LT285/70R17D

Rear Maxxis Bighorn with 15/32" of tread remaining.

Careful inspection of the tread confirmed what I’d thought upon initial scrutiny: It’s obvious which pair of tires had been on the rear axle of the turbo-diesel Cummins and which had been on the front. The rears were evenly worn but had about 2/32″ less tread than the fronts, an obvious result of the substantial diesel torque, loading, and type of use they received.

17/32" in the center of a front tire.

The additional tread in the centers of the fronts was nice, however the outer edges were unevenly worn due to poor front-end alignment, driving style, or both.

Front Tire Feathering.

Rounded Outer Lugs, Front Tire, Maxxis Bighorn 285/70R17D.

Below you can see there is 10/32″ of remaining aftermarket siping in the center lugs.

10/32" of remaining siping cut into the center lugs.

Copyright © 2012 James Langan

Cooper S/T MAXX LT275/70R18E Preview (Traction Tire Part 2)

The Cooper S/T MAXX 

After deciding the LT275/70R18 was my perfect 33-inch tire for an 18-inch wheel, and seeing there is a nice selection of tires in this size, a tread had to be chosen. This was relatively easy as I’m familiar with most of the popular light-truck traction tires. I’m a fan of Cooper Tires and their subsidiaries, and the new S/T MAXX design was already on my to try list, offering the type of any-terrain tire I prefer—not too biased toward on or off-highway. Cooper calls this a 50/50 tire (on/off pavement) and I’d say they are very close to hitting that mark.

LT275/70R18E Cooper S/T MAXX

After some online shopping, my local Discount Tire matched a price from TireCrawler, a mere $242 each delivered. (This was a few months ago; tire prices change, usually increasing.) Discount ordered the tires and a few days later I hauled my 18-inch wheels to their shop for mounting and balancing. Cooper says the LT275/70R18E MAXXs are 33.35 x 11.2 inches and my scale said they weigh 60.5-pounds each. Combined with the relatively heavy, 30-pound, 18-inch cast aluminum SR5 Tundra rims, each tire/wheel combo weighed 91-pounds!

Stout Construction

Once you get your hands on one, there will be no doubt the S/T MAXX is a super stout tire. The scale tells part of the story, though not all load-range E or 3-ply sidewall tires are created equal (see Wheels, Tires, and Sidewalls). Grab an unmounted ArmorTek3® sidewall and give it a good jerk back and forth, they’re stiff, similar the Toyo MT, and more substantial than the 3-ply sidewalls on the very common BFG All-Terrain. The MAXX sidewalls are much stiffer than the older and lighter-duty Cooper S/T, which offers flexible sidewalls and very little sidewall tread. Similar name, and I like both treads depending on the intended application, but they are very different tires. Try not to confuse the S/T MAXX with the S/T, or the Cooper STT… maybe Cooper needs some new letters?

The S/T MAXX has beefy sidewall lugs/tread.

The S/T MAXX is an impressive looking tire. The sidewall lugs are attractive and thick, more impressive in person than in the photos I’d seen, and possibly the most aggressive sidewalls I’ve seen on a tire in this class (not a mud-terrain). The tread is a hybrid 4–5 rib design with a bit less void than the older 4-rib S/T, the center circumferential groove is noticeably missing. There is a moderate amount of siping and the cut & chip resistant compound is studdable. Cooper describes the MAXX as a “commercial grade traction tire”, an accurate description.

S/T MAXX 4-5 rib hybrid tread design.

Mount & Balance 

Mounting a 275/70R18 S/T MAXX on Tundra 18 inch SR5 aluminum wheel.

Mounting the first tire and giving it a spin on the balancer showed it wanted 3.25-oz. inside and 4.75-oz. outside for a dynamic balance. Eight ounces is not much weight for a 91-pound spinning mass, but I generally like to add less weight to my wheels when possible.

While dynamic balancing is the technically the best as it balances in two planes, I’ve had many positive experiences using the single plane static balance method for heavy RV tires (an old term). Static spin balancing counters vertical imbalance (hop) of a tire & wheel, and I don’t run very wide tires where dynamic balancing can be more important. Generally, I see how the first couple tires in a set balance and if they can be dynamically balanced with moderate weight, that’s what we do. If they are going to ask for substantial weight using the dynamic method, I choose static.

Modern balancing machines are very good.

Sometimes this difference can be very dramatic. A few months ago a heavy, high-quality tire wanted about 9 ounces for a dynamic balance, but only 1.5 ounces for a static balance. Guess which one I chose? The S/T MAXXs were single pane balanced and the road force (RF) was also measured—which was very low—another indication of quality. For more thoughts on tire balancing you can read Static Balance Details.

Static Balance Numbers

#1) 4.75-oz. RF .002″.

After seeing this low road force number the kid doing the balancing commented “Wow, that’s like a Michelin.”

#2) 4.25-oz. RF .008″

#3) 5.50-oz. RF .007″

#4) 1.50-oz. RF .009″

Cooper Tires’ website lists the tread depth for every S/T MAXX currently made as 18.5/32″, which it probably is. But it would be pretty easy to call this 19/32″ as measuring down to one-sixty-fourth can be a challenge. The original tread depth is important, more is better for most truck tires, though the long-term wear rate is also important. Combine deep tread with a low rate of wear and you have a long-lasting tire.

LT275/70R18E COOPER S/T MAXX tread depth.

Because my original 17-inch Tundra TRD wheels use tapered lug nuts, which are uncommon for modern Toyota trucks, I needed new shank-style nuts for the 18-inch wheels. Searching online I found a source for the Gorilla brand lug nuts and locks, a complete set was delivered for about $110. I’ve been using an impact-gun on Gorilla wheel locks on my 4Runner for years, and they have held up to my intense use. I wish they would fit on the OE 17-inch TRD Tundra wheels.

Shank style Gorilla locking lug nuts needed for SR5 wheels.

Driving Impressions

To be continued…

Copyright © 2012 James Langan


LT255/85R16 Tire Delivery Part 2

With a bed and trailer full of tires & wheels I was off to see my tire guys for dismounting, mounting, and balancing so I could get my 4WDs off jack stands and rolling again. A few days later I loaded the bed of the Tundra with the Bighorns and Cooper S/T treads, as well as one old Multi-Mile Wild Country TXR so Brian would have a proper 255/85 spare.

Years ago the TXR was a big seller for the western tire chain Les Schwab. I really liked the void ratio of the TXR—not an A/T nor an M/T—and I purchased a few sets over several years. However, they were not the most rugged tire and tended to cause a steering wheel wobble. The last rig I ran the TXR on was my 2005 Wrangler, which was not as tolerant of their idiosyncrasies, so I moved on to better tires…and have yet to stop.

A load of LT255/85R16D tires, a Multi Mile TXR in the foreground.

I had a few goals for this little trip; deliver the tires, meet my new friend Brian, enjoy a country drive, and conduct a mileage test. After fueling at my local filling station and resetting the trip meter, it was time to roll with a goal of keeping my speed at 65 mph or less.

Through the cities and into the fertile Sierra Valley I drove. It cost, but one of the features I enjoy on the new Tundra is the satellite radio. There are a few stations I like, but I seem to listen to Outlaw Country often, Steve Earle came on singin’ Hillbilly Highway.

Copyright © 2012 James Langan

Static Balance Details

Got Wheel Weight?

A reader asked a few good questions, see below.

Q. Via this balancing method, did you reduce the amount of weight required? 

A. In general, static balancing methods reduce the weight needed to balance a tire/wheel combination, and this is true for both bubble balancing and machine static balancing. Static balancing only balances a tire and wheel in one plane, vertically. More weight is needed for a dynamic balance, partially because dynamic balancing also helps correct lateral imbalance.

The amount of weight needed to balance a tire using this bubble balancer appeared similar to a machine static balance. Maybe slightly more weight and less precise.

Q. Have you tried rotating the tire on the rim to minimize added weight?

A. While using this bubble balancer there was no need to rotate the tires on the wheels, the weight needed to balance was not excessive once I was competent. Obviously it’s not easy for a man working with hand tools to breakdown a tire and rotate it on a wheel. However, many times in the past while having tires machine mounted & balanced I’ve had the tires rotated on the wheel. This was done is response to a tire/wheel combination that required more weight than I thought should be used.

How much is too much? That depends on the wheel (size, aluminum vs. steel) and the size, weight, and tread of the tire. I’m generally very particular and don’t want to feel any tire imbalance from a warmed-up tire. For my trucks, all of which currently run 33-inch tires, I’m typically happy if less than six ounces are needed for a static balance. Generally a few more are needed for a dynamic spin balance. When a new tire starts needing more than 8-9 ounces (dynamic) I like to rotate the tire on the wheel 180-degrees, hoping less weight will be required. This doesn’t always work, and sometimes the tire must be returned to its original position. The weight mentioned above are personal maximums, less weight is better. Regardless of the weight needed, more important is the quality and repeatability of the balance.

Q. Have you tried balancing the rim by itself? 

A. I’ve checked the balance of wheels without tires, though I’ve never actually needed balance a wheel without a tire mounted. Checking the balance of a wheel has invariably showed that either the tire or the balance machine was the source of a problem, but of course wheels can be damaged. I’ve been using light, factory aluminum wheels and moderate sized tires for many years, and been lucky my heavily used wheels remain true.

Copyright © 2011 James Langan