Make a note of the spacer length needed at the length of the new mount. Now pull the wheel, fender and all to the rear until the axle hits the back of the slots. The difference between the two points, usually about 1.75-inches is the total amount of adjustment you'll need when fabricating the new mounts if you want the tire to always remain centered in the fender. You'll seldom use that full range of adjustment, but it pays to prepare for it.
We’re almost finished with most of the drudge work on mockups and the fun stuff is about to begin and a good place to start is to get the rear wheel, sprocket, rotor and fender mounted.
Before we do that however we have to talk a little more about frame designs because after all the years of writing articles about frame dimensions some people still do not understand how manufacturers manage to make room for a wheel and drive system in narrow frames and why some frames are basically ‘unbuildable’ from the standpoint of practicality. This is especially true of swingarm frames that have had cheap ill-conceived hardtail kits installed.
If you take a good close look at the lower frame rails on an old stock Harley rigid frame, you’ll notice that the drive side rail has what we call a ‘double joggle’ that provides clearance for the final drive chain. Without that extra 1/2” of room provided by the joggle the chain would chew up the tubing. Note that there are two joggles. The frame jogs out 1/2” just after leaving the rear transmission mount crossmember but then it jogs back inward 1/2” before it straightens out and meets the left-hand axle plate.
A portion of an old original factory blueprint clearly illustrates this double joggle in the view of the lower rails as seen from below in the attached scan.
The red arrow highlights the area where the lower frame rail jogs to provide chain clearance. The critical thing about using a double joggle is that it permits the entire frame to be perfectly symmetrical left to right on each side of the true longitudinal centerline. With this frame geometry if you center your wheel between the axle plates it’ll also be perfectly centered on the backbone and the lower frame rails.
For an aftermarket frame manufacturer these joggles are expensive to tool up for so to save $5 per frame many build their products with only one jog on the left side. This creates a frame that’s asymmetrical. It’s a half-inch wider at the axle plates on the left side of the true frame centerline so that if you center your wheel between the plates it’ll be offset to the left from the centerline of the backbone and steering stem. There really isn’t a problem with this relatively minor offset but it causes a lot of people endless aggravation when trying to line up their rear tire with the bikes steering neck and backbone. This type of frame is very common and once you recognize it, you’ll be able to better line up your drive train rather than worrying why the tire ends up being slightly offset.
Another method used by some to save a few manufacturing bucks, including some who claim to be making authentic reproductions of old stock frames, is to basically build an asymmetrical frame having one jog on the left rear rail but then skew the backbone and steering neck so it lines up with the centerline of the rear axle plates and not the true centerline of the frame. This type of frame is very hard to spot unless you know what you’re looking for. Again, there really isn’t a huge problem with this minor 1/2” discrepancy but it’s still aggravating having to work around other people's cost cutting measures. This type of frame actually has two longitudinal centerlines. One for the lower rails and another one offset 1/2” to the left when viewed from the rear, for the backbone, steering neck and rear wishbones. The seat post slants to the left by about 1.25-degrees from the lower crossmember to its intersection with the backbone.
At least on these types of frames the axle plates are in the same plane as the steering neck so centering the wheel at least looks attractive. The problem however usually occurs when you try to align the primary and secondary drives, which are located relative to the lower rails with the rear wheel sprocket that will be aligned with the offset centerline of the upper rails. You’ll spend a lot of time with various spacers before everything gets to where it works.
A third type of frame is a design built by numerous custom builders that remains completely symmetrical but both upper and lower rails are simply made 1/2” wider than stock which virtually nobody ever even notices.
Anyway, this is just part of chopper education 101and armed with this information you’ll be better prepared to troubleshoot any misalignment problems you might encounter when you’re centering your rear wheel.
If you’ve followed along the preceding sections of this build series, you’re already aware that you need 9.25-inches clear as measured inside between the rear axle plates to fit the typical rear wheel assembly used on most Harley based chopper projects. You also need a minimum of 9” clear measured inside between both the upper and lower frame rails to have enough clearance for the chain. You can get by with 8.875 but things will be extremely tight, maybe even unworkable depending on up your specific hub and tire size.
At this stage of the build, you’re still basically in mockup mode so you really don’t need a brand-new wheel and tire if you can’t afford it. Just buy anything used that’s a 130 or140/90-16 and runs true. Now’s a good time to read up on truing wheels and learning how to do it if you really want to build bikes.
Try to find a used tire that’s at least the same brand and model as the one you’ll finally mount on the bike as tire diameters and widths can vary significantly from one maker to the next. Your fender will be mounted around whatever tire you use during the mockup.
For our project we’re using an old disc wheel mounted with an even more well-used 140 tire, but it’ll get us through this stage of the work.
To start you’ll need the wheel tire combo, an axle, an assortment of spacers, (or a lot of 3/4” washers) a sprocket, a brake disc and some axle adjusters. If you’re building up a rig using a drum brake, you’ll of course need the drum, and it has the sprocket already installed.
Adjusters can be either generic or frame specific depending upon what type of frame you’re working with. The adjusting screws themselves can be either 3/8-16 (course) or 3/8-24 (fine) thread so check the threads on the lugs welded to your frame before ordering.
Here’s a shot of just a few adjuster sets.
The set in the center is for a Softail. Note the cheesy chrome nut covers.
Axles can also be generic or frame specific so if you know the make and model of your frame you can easily order an axle assembly that includes the correct wheel spacers but if you’re working on an aftermarket frame, you’ll need to order a more or less generic axle assembly suited to the distance measured between your axle plates.
Here’s a picture of a generic ‘chopper’ axle set that we’ll be using.
I buy all of my axle assemblies from Paughco since they have the largest assortment, I’ve run across for both stock replacements and custom applications.
There is no guarantee that the spacers you’ll get will actually fit your specific application since wheel hubs vary in width so be prepared to either have some custom cut, or if you’re lucky, they end up being a ‘standard’ width and can be bought over the counter.
It really pays to have a helper around when you reach this stage of work as you’ll occasionally need three hands and it’s no fun to drink beer by yourself.
There are two schools of thought about how to align the rear wheel/sprocket with the transmission sprocket and eventually the motor sprocket. We’ll cover each method but I’m pretty sure you’ll develop a technique that works for your particular situation as nothing is chiseled in stone when it comes to bike building.
Of course, everything hinges around having the transmission installed first and the tranny sprocket correctly mounted.
The first school holds that you mount the rear wheel along with the sprocket but minus any spacers and center it in the frame by running a string line from the steering neck, along the line of the backbone, and stretched over the tire to a point that you’re sure is the exact middle of the tread.
The second school maintains that you start at the motor and get the crank sprocket properly aligned with the clutch basket sprocket (or belt pulleys) and then use a long straightedge to get the wheel sprocket aligned by using spacers or even offsetting the wheel slightly if necessary. Unfortunately, this only works if you’ve already got the motor and clutch installed and is probably best suited to final assembly.
Getting exact precise measurements and alignments isn’t important at this stage of doing the mockups so long as you’re within an eighth or better of spot-on. In fact, during the initial stages of the process, being within a quarter inch is really pretty good as we’ll fine tune things as we go forward. Right now, just going through the process so you understand what the objective is can be as important as performing the final assembly.
Clean out the interior of the wheel hub by pushing a segment of clean rag through the bore using a dowel rod. Even new wheels can contain a significant amount of dirt and debris. Test fit the axle in the wheel. It should go through with only firm hand pressure. If it doesn’t, then put a light coat of white lithium grease on the bearing bores and try again. If it still resists, try lightly tapping the end with a rubber mallet. If it still won’t go through you’ve got a problem that I’ve never encountered before and either the axle is too large or the bearing bores to small and both things are extremely rare.
Fortunately, you’ll seldom have a problem, so we’ll go ahead and install the wheel for the first trial fit in the frame.
The first thing I did while the bike was still sitting on the table was to double check the transmission alignment with the rear axle plates. I knew for sure that the frame was square, true and plumb every which from Sunday when I first checked its alignments early on in the project.
I put my straightedge on the tranny sprocket extended back to the axle plate as seen below.
I found a little over 1/8-inch discrepancy, so I loosened the tranny mounting bolts and shifted the unit slightly until I had perfect alignment with the frame. Had I not checked the frame for alignment early on, when it came around to wheel installation, I would have thought the frame was ‘off’ and tried to suck in the gap when I tightened the axle bolt down thereby making it almost impossible to align the tranny and wheel sprockets.
Once you’re ready to install the wheel it helps to have two cycle jacks, one big enough to hold the frame steady and a smaller one to put under the wheel as it’ll be mounted and dis-mounted several times during the work ahead.
Alternatively, just put the frame on some wood cribbing to get the center of the axle slots about 13-inches off the shop floor. You can then use wood shims, if necessary, to roll the wheel into, and out of, the plate slots. This works well if you’re working singlehandedly.
Since I’m working by myself, I just put the bike on a small furniture dolly since I’ll be rolling it around. I put down some wood shims for the wheel to roll on and raise it up enough, so the axle slots and bearings were at the same height.
Install the adjusters in their lugs but don’t screw them in very far. Hoist the wheel up between the axle plates and then insert the axle without any spacers. Loosely affix the axle nut.
Push the wheel all the way forward and put a door stop or a shim of some kind under the wheel to hold it in place. Slide it left or right as needed to get the tire centered in the frame by ‘eyeball’.
Loop a string around the steering neck and extend it back along the backbone and over the top of the tire. Move the tire as needed until its centerline and the stringline are in a perfect straight line from the neck back.
The string looks a little off in this snapshot, but I was holding the camera slightly left of center. In actuality the alignment is perfect.
As a double check measure the distance from the edge of the tire to the upper wishbones on each side.
Once you’re satisfied that the wheel is centered take a straightedge and lay it along the face of the tranny sprocket and rear wheel sprocket.
As a quick triple check using a narrow straightedge held vertically you can measure from the wheel centerline to the centerline of the wheel sprocket. If everything is within factory specifications, you’ll get a distance of 3.5625-inches, which we did.
We have perfect alignment using a .245” (standard) dished sprocket so now I can measure for the axle spacers.
If your frame has the correct dimensions to begin with and has the tranny aligned properly you won’t have any problems getting things to line up correctly and have plenty of room for chain clearance.
You’ll sometimes hear on discussion boards that the axle only fits the hub if it’s installed from the left side of the bike, but this is just a myth. The axle can be installed from either the right or left side of the frame but traditionally it’s installed from the left so removal doesn’t interfere with the exhaust pipes.
To measure for the spacers, I just use a small machinist sliding rule that I slip in through the axle slot and then measure the distance between the inside face of the plate and the bearing. On this bike with this particular hub, I needed 1.25” spacers on each side.
Fenders Mounts
Fenders come a huge variety of shapes and styles that range from simple flat ‘trailer’ fenders to handmade ribbed, beaded and contoured styles. Along with the fuel tank the fender contributes significantly to the visual image of a specific bike. The ‘Tins’ largely makes or break a build.
A nice fancy rolled and beaded fender would look totally out of place on our project bike which is an old-school budget build just as a flat fender on a custom show bike would be completely out of place. It’s going to be up to you, the builder, to select a fender that compliments and brings together all of the elements of your project into a cohesive whole that ‘looks right’. This means that you’ll probably go through more than one fender during mockups before finally picking one that’s ‘just right’.
The specific type of mounting system you'll use depends upon what shape fender you select as well as what type of frame you're working with and whether or not that frame already has some mount points welded in place.
The original factory mounting system consisted of a bracket welded to the rear transmission mounting stanchions as shown below.
And depending upon the year, simple clamps for the upper mounts shown in the next picture.
Or a combination of the clamps and a bracket bolted to the lower rear oil tank fastener holes seen next.
The bracket is shown below.
Most aftermarket frames will be fitted with provisions for these 'stock' mounting options if you can use them with your particular fender.
When you get into completely custom-built frames or, heavens forbid, one of the horribly engineered weld-on hardtail kits you'll end up having to fab mounts from scratch.
Before going further however a few things need to be mentioned. The first is that you never want to have it become necessary to try and put a wrench up under a fender to remove a fastener. I can't count the number of times I've worked on bikes where we had to remove the rear wheel just to remove the fender.
Secondly, nothing should protrude down past the interior surface of a fender except perhaps a welded-in button head fastener.
Tires 'grow' in diameter under speed, so you want to keep at least 3/4" clear between any protuberance and the outer surface of the tire.
Thirdly, you'll often be dealing with 'rounded' surfaces but 'flat' ended lugs or bungs so, when necessary, use 'spherical', 'conical' or 'tapered' washers in conjunction with your bolts as these are designed to accommodate misalignments. These are commonly available at all industrial supply outlets.
Lastly, crib up the frame if necessary to get it situated into the stance you expect it to have when it's on the road. Since the whole frame pivots around the rear axle your fender (and sissy bar) might not look the same if the mounts are welded in place while the frame is sitting flat. Also, the frame should be level from left to right so that you can use a level on the fender to insure its mounted level with the frame transversely.
Mount Fabrication
Sometimes you can use old stock mounts, even from Softails, and modify or alter them to suit your situation. Other times you'll have to buy tabs, lugs or bungs from Bung King or the slick little mounts from TC Brothers.
The snapshot below illustrates just a small segment of the products available from Bung King that come in handy when building mounts and sissy bars. The mount in the upper right of the photo is from TC Brothers. They offer several different versions for specific applications. I usually buy them in pairs and use them for both upper and lower mounts on custom frames.
It also pays to do research before you start on the fender mounts and I mean in-depth internet searches for chopper fender mounting ideas. The more options you can see the better because it'll enable you to come up with the most elegant way to handle your specific needs.
Someday down the road somebody else will own your bike and when they tear it down for a rebuild, they should not be horrified at how you built it. Don't take shortcuts no matter how tempting it is. Many people dash through a project. They just slap it together to get it on the road and then think they'll go back and do it right in their spare time, but that time never comes. Do it right the first time.
Our project is a budget bike, so we'll be using a 'flat' six-inch fender that fits the radius of our 140 tire pretty good. It really could stand to be re-radiused but that's a completely separate article that we'll do later.
Not all flat fenders are equal so it pays to buy at a swap meet where you can see the item in person. Some flats are indeed very flat and have a small radius curve leading into the skirt. Others have a slight crown to the tops and a nice large radius into the skirt and are much more attractive. What I dug out of the stash is somewhere in the middle with good corners, a short skirt and a very slight crown so it's not too ugly.
Here's a section I cut off an identical fender a number of years ago. I always save these cutoffs from fenders to use as templates when I'm making fender braces.
To space the fender off the tire during mockups a lot of people use sections of 3/4" diameter garden hose taped over the tire. I prefer to use the large kitchen sponges that I'll wet and then let dry, conforming to the contours of the tire. They get surprising hard when they're thoroughly dry and make good spacers when taped in place.
I didn't have time for sponge drying so I bought some hose.
One is standard radiator hose, and the other is a reinforced acrylic, both having 3/4" inside diameter, with close to an inch O.D. The acrylic is much stiffer, so I chose to use that.
When mounting flat fenders, I've found it helps if you use two segments of hose side by side since it prevents the fender from flopping back and forth sideways.
I put strips of thick printer paper between the duct tape and the tire, so I don't have to clean off tape gunk later on. Just bend the hose to follow the contour of the tire and tape it down every few inches making sure you closely lined up with the center of the tire.
Put the fender over the hose and rotate it until it's positioned in an attitude that you're happy with. Use some long tie-wraps, string, wire or shock-cord to hold the axle fully forward in the slots.
You should have from a quarter to three quarters of an inch clearance between the fender and the wishbone crossmember on top and about the same down below at the stock mount point or the spot where you'll fab a new one.
Make a note of the spacer length needed at the length of the new mount. Now pull the wheel, fender and all to the rear until the axle hits the back of the slots. The difference between the two points, usually about 1.75-inches is the total amount of adjustment you'll need when fabricating the new mounts if you want the tire to always remain centered in the fender. You'll seldom use that full range of adjustment, but it pays to prepare for it.
Now you can visualize how you can use or modify the prefabricated mounts sold by others to make something of your own just by cutting the 'tail' shorter.
This position shown below is pretty close to what I want. Maybe rotated a couple of inches more to the left but it's close enough for now.
If you look closely at the picture, you'll see that the front end of the fender is already hitting my cribbing so it's time to cut off the extra length. Make a mark about an inch longer than you think you'll eventually need near the lower mount area and then chop the fender with a saber saw, saws-all or cut-off wheel.
This is a really good time to take a beer break and take some time shifting the fender around and taking a gander from several different viewing positions. When I'm really happy with the stance I'll mark the vertical centerline location on the fender up from the axle using a sheetrock square so I can easily reposition it again.
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