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March 2012 Techline: Your Tech Questions

Jeep Truck
Willie Worthy | Writer
Posted March 1, 2012

Wrong Cam, Snow Tires, and More!

Snow Tired
I have a ’10 Toyota Tundra Double Cab 4x4. I need a tire that is great in snow and will get me where I need to go when going up and down steep hills in snow. But, I want a tire for towing and occasional off-road use. Can you help me find the right tire for my ride?
Chris Newsman
Roxboro, NC

Don’t we all wish we could find that perfect tire. Yes, we have also been searching for it for years now and it just does not exist. However, there are a large number of tires that do come close. For a tire to work exceptionally well in snow and ice it takes a special rubber compound that is compliant in cold weather. The problem here is that in warm weather that particular rubber compound does not hold up well at all to cuts and slices that rocks produce and it wears quite rapidly. For a tire to work well in snow the tread must be fairly tight with lots of small sharp biting edges. These small edges have a tendency to tear and chunk off on gravel roads and sharp rocks. The tread must be able to grab and hold onto the snow for one revolution as snow to snow offers the best traction. However, if the snow stays in the tire too long, it turns to ice, and ice to snow has little traction.

For mud the tire must be able to grab a big chunk of the stuff where it can push against the other mud and then clean itself on the next revolution so a new bite can be taken. If it is not able to clean itself, the mud becomes packed within the tread and then the tire just wants to slide across the top of the mud.

Now for towing, you’ll want a tire with fairly stiff sidewalls to add stability under load. But a stiff sidewall doesn’t lend itself well to flexing and contouring to the terrain and has a tendency to ride a bit rougher. Generally speaking, the further the tread extends down the sidewall the stiffer the tire. But load range and sidewall construction are also very important.

Keep in mind the more aggressive the tread is, the louder the noise the tire will make driving down the highway. Part of the noise comes from the way the tire makes contact with the pavement and part of it is caused by air flowing over the tread and being compressed between the tire and the pavement.

As to the wear factor, like I said in the opening lines, winter tires do not like high speeds and hot weather. A tighter tread pattern will wear more evenly across the face than a tire with large open voids. The more open the tread the more it has a tendency to cup with uneven wear. But then again, keep in mind that uneven tire wear is often not a problem with the tire but with suspension and steering geometry not being correct.

As a starting point I would say look at a tire like a Cooper Discoverer STT (www.coopertire.com) or a Mickey Thompson Baja MTZ (www.mickeythompsontires.com) (Editor’s note: BFG All-Terrain, Goodyear DuraTrac and Goodyear MT/R also work well). I am not saying that these are the tires to buy, but just the tires that should give you a general idea of a good all-around tire. You can then decide if you want to go to a more or less aggressive tire design.

Oh, and one last thing, like any product, you get what you pay for. I have found that a low cost tire will provide marginal performance both in wear, strength, and traction.

Wrong Cam Man
I have a ’92 Ford F-250 with a 351W and shorty headers, K&N intake, MSD box, throttle-body spacer, and a Jet chip. I added a Comp Cam part number 35-239-3 with 218/226 duration and .493/.512 lift and my MAP sensor doesn’t like it. The cam has low vacuum at idle so it surges from 700 to 1,500 rpm, plus it has no power. I understand that the MAP sensor likes 22 inches of vacuum at idle but it’s getting 18 inches so it does funny things like hiccup.

Can you please help or do I have to change the cam?
Cliff Grexton
Summerland, British Columbia

The tech guys at Comp Cams tell me that this cam was not designed to be used with your EFI and after studying the specifications I agree. In other words you really need to change it out. I am wondering why you picked this camshaft or did someone talk you into it?

I am a real believer in contacting the cam manufacturer of choice and talking to one of the tech guys about what you expect a cam to do for you. You want to be sure to give them all the specs on your vehicle, including vehicle weight, transmission type, gear ratio, tire size, and other engine modifications. The aftermarket cam manufacturers want you to be happy with your choice and will not sell you something that will not meet your expectations. Usually the companies have a toll free number for the technical department listed on the Website.

Wimpy Willys
I have a ’52 Willys pickup with oversize wheels and tires that the Willys’ wimpy frontend cannot handle. The wheels wobble something nasty and the steering dampener keeps wearing out. I heard it was possible to swap the Willys frontend with one from a Scout; do you have any information on this?
Gabe McGann
Puako, HI

The words “oversized tires” can mean anything from one size larger than the 7.00x16 tires that it originally came with to let’s say 33-inch tires. The Willys frontend is not that wimpy, just most likely pretty much worn out. It can be fixed with properly adjusted and perhaps new wheel bearings, as well as steering knuckle trunion bearings. Then there are the steering components to take a look at, as being nearly 60 years old, they probably need some work.

Yes, a Scout II Dana 44 frontend could be used as a replacement. It is only about 1-inch wider, which would not cause a problem. Better brakes would be an advantage if you found one with disc brakes, but keep in mind a matching master cylinder change would be necessary. However, my guess is that because of more differential offset to the right side there may be a problem mounting the Willys leaf springs to it. The Jeep frame is narrower. You could remount the springs to the outside of the frame but this is quite a bit of work and requires fabrication and welding.

The Scout steering is entirely different so that also means more changes including a steering box swap if you want to do the job right. Advance Adapters (www.advanceadapters.com) has a universal kit that will work. Front axle caster on a Scout is 0 degrees while your Jeep is probably in the 3- to 5-degree range. This most likely will not be a problem but do keep an eye on pinion angle if you change the caster angle with shims. When using a Scout front axle you generally have to cut the steering knuckle welds loose from the axletube, rotate them the appropriate degree and re-weld them. It’s not a difficult job but it does require precision.

The most important thing of all is to match the gear ratios. Your truck most likely came with 5.38 gears; however, there were several optional gear sets such as 6.17 or 4.88. Scouts came with 4.09, 4.27, 3.31, or 3.73 axle gears depending on year, model, and options. So a gear change would be necessary.

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