Toe In / Toe Out question

1985 - Present, Questions, discussions, regarding anything related to the Humvee. (NO AUCTION or EBAY)

Moderator: Kurt Lesser

Post Reply
RockHillWill
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 265
Joined: Sun Aug 20, 2017 9:13 am
Location: Rock Hill SC

Toe In / Toe Out question

Post by RockHillWill » Sun Feb 18, 2018 4:32 am

Getting ready to have the Baha tires and 24 bolt wheels balanced prior to setting the front end. I am reasonably familiar with caster, camber and toe in/out, but am not certain about the toe in settings as described in the TM's. The toe in / out settings are different for: curb weight vs normal operating weight. I have been busy getting everything mounted and installed on this M1026 to arrive at the weight that I will be operating it at, prior to making these adjustments. I am assuming that this is the 'normal operating weight'. I also have an interest in operating with as small a toe in / out number as possible to minimize tire wear. I will not be doing much 'offroading', as wife and I both are interested in day or weekend trips to MV shows, etc. Advice?? Thanks!


User avatar
lkgindy
G-Lieutenant Colonel
G-Lieutenant Colonel
Posts: 1038
Joined: Mon Oct 24, 2005 4:27 pm
Location: Indianapolis, Indiana

Re: Toe In / Toe Out question

Post by lkgindy » Sun Feb 18, 2018 6:57 am

I have always set my front at 1/8” toe in and rear at 1/8” toe out. This has worked great for me in the 20 plus years that I have owned these trucks.

Larry
1987 M-998 Project
1995 Hummer HT

User avatar
Ted Gates
G-Major General
G-Major General
Posts: 2667
Joined: Sun Dec 15, 2002 12:13 pm
Location: Eaton Rapids, MI

Re: Toe In / Toe Out question

Post by Ted Gates » Sun Feb 18, 2018 7:02 am

Start on flat asphalt/concrete. I use a very long aluminum angle iron and hold against front tires horizontally at center of hub height. The other end should be parallel to tub rocker when straight. Do both sides. Take care that adjusting one tire will effect the other. When close, drive forward several car lengths and back up. Do not turn steering wheel. Readjust and repeat proceedure until you have what you want. Don't forget to tighten clamps on tie rod tubes. Also, best to have new ball joints, tie rod ends, idler and pitman before doing this.
I've done many many hmmwvs this way with good results.

User avatar
lkgindy
G-Lieutenant Colonel
G-Lieutenant Colonel
Posts: 1038
Joined: Mon Oct 24, 2005 4:27 pm
Location: Indianapolis, Indiana

Re: Toe In / Toe Out question

Post by lkgindy » Sun Feb 18, 2018 1:12 pm

I have never had my trucks aligned at a alignment shop. I use the “string method” very similar to what Ted described with the aluminum angle.

Larry
1987 M-998 Project
1995 Hummer HT

RockHillWill
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 265
Joined: Sun Aug 20, 2017 9:13 am
Location: Rock Hill SC

Re: Toe In / Toe Out question

Post by RockHillWill » Sun Feb 18, 2018 3:38 pm

Thanks, guys. I actually have had 40 years setting front ends with the race cars and have used about any of those methods. I quit using the string and straight edge methods after finding bent wheels and erratic sidewalls from heat and storage. Got in the habit of jacking up one wheel at a time and using a scribe on a fixed holder to scribe a line around the circumference of each tire, then rolled the car two full tire circumferences to weed out the inherent play in bearing and tie rods, etc., and measured between the scribed lines. I rolled the car two tire circumferences after each adjustment for the same reason in addition to account for the differences in tire hysteresis and durometer values. I eventually learned to lock down the steering column as well to prevent the difference in caster values from inadvertently steering the car while rolling.Towards the end of that career I was using ball bearing radius plates and dial indicators.

The purpose of using a toe-in / toe out setting is to account for the gyroscopic effects on taking up the accumulation of play in the steering system components and it has been my experience that when using a larger number you can experience harmonic variables at certain speeds. I may be over thinking this whole thing considering these trucks don't look like they go much faster than 60-65 MPH.

Perhaps I should apologize for poor questioning. What I was actually asking was with the truck fully loaded for driving, would I use the settings specified for 'curb weight' at 1/4" OR 'normal operating weight' at 1/16"? To me, the difference in 1/4" and 1/16" is significant, and I was not able to figure out which number to use and why!

johncarrol
G-Staff Sergeant
G-Staff Sergeant
Posts: 51
Joined: Sat Feb 24, 2018 4:44 am
Location: S. Central PA

Re: Toe In / Toe Out question

Post by johncarrol » Sun Feb 25, 2018 11:45 am

The TM specs. confused me as well. I believe AMG/the military intended HMMWVs will be mostly operated loaded during their lifespan, vs most civilian light trucks that are operated unloaded mostly and do not have quite the load capacity that changes camber and toe-in like in a HMMWV. A HMMWV loaded can be checked using the "normal operating weight spec. while one that is unloaded can be checked using the "curb weight" spec. which should change to the "normal operating" spec. when loaded which will wear the tires evenly. I've owned my M1123 about 7 months and put 9,000 miles on it as a daily driver, and am not only concerned with tire wear, but stability as well. This is what I did: First, I installed 4 new front 954 lb. coil springs all the way around, which improved the ride and dropped the height 1 inch to decrease the cv joint angles. Then I used a 12 inch long level and added/removed shims to correct the camber to zero at all four wheels. Then I used a tape measure to check my front toe-in which was set at a desirable 1/16 inch. Then I used the TM string method to adjust my rear toe-in/toe-out to zero which is where every straight axle vehicle is at. Checking front toe-in is an easy one person job with a tape measure because the edges of the tread blocks on the military tires are centered on the tread. 99% of the time the only load I drive around with are me, my wife, and daughter which will not change the alignment enough to worry about. Lastly, I trued and siped the military tires to give me a smooth ride on pavement and supreme traction on snow and ice. Yes I said ice. It is a pleasure to drive.

Action
G-Lieutenant General
G-Lieutenant General
Posts: 5181
Joined: Mon Feb 06, 2006 3:19 pm
Location: East Tennessee
Contact:

Re: Toe In / Toe Out question

Post by Action » Sun Feb 25, 2018 2:45 pm

I had Tire Discounters align mine. I told them I wanted it not for unloaded. My front tires are perfectly vertical. The rears lean out slightly. A motorpool guy down here told me that, when driving at speed, the tops come in slightly.
This is just some useless info. :|

Jason

RockHillWill
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 265
Joined: Sun Aug 20, 2017 9:13 am
Location: Rock Hill SC

Re: Toe In / Toe Out question

Post by RockHillWill » Mon Feb 26, 2018 4:08 am

I made some mention of this is my 'build' post. I also decided to use the operating weight recommendations after loading all that I expected to normally carry with me and put a 50# bag of parts and/or spares in each seat while the settings were arrived at to make an attempt at passenger weight. The front axle is considered 'rear steer' as the steering arms are to the rear of the axle, and the rear axle is considered 'front steer' as the steering arms are to the front of the wheels. The reason that the front is toed in and the rear is toed out is because as the wheels increase in RPM, the rotating weight creates an inward linear load on the steering mechanism, taking up accumulated clearances and tolerances. This brings the wheels to a more parallel position that minimizes tire wear and the tendency to wander.

johncarrol
G-Staff Sergeant
G-Staff Sergeant
Posts: 51
Joined: Sat Feb 24, 2018 4:44 am
Location: S. Central PA

Re: Toe In / Toe Out question

Post by johncarrol » Thu Mar 01, 2018 2:15 pm

I agree with everything you are saying, but is it possible that it pertains to ordinary street driven cars, light trucks, and racecars that you are familiar with, but not necessarily HMMWVs? My theory is: and please, anyone, correct me with proof if I am wrong. The TM states with radial tires: Front Toe-in setting[0 to 1/8] and Rear Toe-out setting[0 to 1/8]. So if a HMMWV is travelling down the road, whether it is empty or loaded to the max, and the front/rear toe-in/toe/out is zero on all four wheels, then it is within specs. and there should be minimum tire wear. AMG built them and the military purchased them not to be used to drive around in as a pleasure vehicle that only occasionally carries any substantial weight. That is why they use such heavy springs, especially on the rear. I don't think adding any extra weight accounting for passengers and gear will be enough to make any difference that will change the settings, or even driving down the road at a reasonable speed with all the forces acting on it. I was always led to believe, most street driven vehicles are given 1/16 toe-in to keep the front end from wandering on irregular road conditions. As far as rear toe-out goes in my personal experience with my HMMWV, before setting it to zero, I drove over a patch of packed snow covered road at approx. 40mph with just my right tires, the rear of my HMMWV would steer left. Driving over a patch of packed snow covered road with just my left tires, I could feel the rear steer right. I checked and corrected my rear toe-out to zero and it solved that problem. I also noticed a problem with towing a boat on a trailer, that my rear would tend to wonder one way or the other when braking with the rear toed out. I really enjoy this discussion and hope to learn a lot from your post and other people's input.

RockHillWill
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 265
Joined: Sun Aug 20, 2017 9:13 am
Location: Rock Hill SC

Re: Toe In / Toe Out question

Post by RockHillWill » Fri Mar 02, 2018 4:15 am

If in fact, it is good for street cars, race cars, light trucks, what piece of information makes it not important for the Humvee. I am making an assumption that even for the most intense use, the Humvee spends its most mileage off the rough terrain that you mention, and I do not understand the willingness to live with mediocrity. Why would the Government go to the trouble of adding the specifications to the TM's if the manufacturer and designer did not feel that it was important. I have not taken the time to study in detail the steering geometry of the Humvee, but I know from experience that the effect of 'bump steer' has a more negative affect on higher suspension travels, making driving a miserable situation on rough terrain.

Bump steer is the self-steering of the suspension due to any vertical movement of the control arms independent of input from the steering wheel. With different lengths of the upper and lower control arms and tie rods, self steering is induced. The larger the degree of initial toe-in / toe out will compound this self steering input. While caster gain and camber gain effect tire wear more that steering input at Humvee operating speeds, high degrees of bump steer not only make steering uncomfortable, the strong and rapid movement of the steering wheel has been known to break thumbs and even wrists. The simple suspension settings that I recently underwent to correct specifications made a HUGE difference to me in the way that it now drives.

I learned the hard way about bump steer early in my car career. I designed and built a sports car/chassis taking three years to complete. It had tires and wheels from an Indy 500 race car. On my first road test, I tried to take a medium speed corner using trail braking and ended up three rows deep in a local corn field. I spent the next few years investigating details about suspension characteristics.


Post Reply

Return to “Humvee Technical Knowledge Base -”

Who is online

Users browsing this forum: piodik and 68 guests