Page last modified: 08/24/08

By Peter Huppertz

Ever tried to mount a hard bag rack with a generic mounting set, since specific mounting braces for your bike were no longer available? Then you’ve probably found out that those "universal mounting sets" are indeed universal in that it’s virtually impossible to mount the rack to the bike in a remotely satisfying manner.

Usually it’s quite possible for the rack to move around in a way that bears no relationship to bike movement -- which is a
problem when stability at speeds over driveway speed is desired.  On top of that, it is usually damn nigh impossible to mount the rack anywhere snugly to the rest of the bike, leaving you with a scoot that may have the luggage capacity of a small town car – but is probably just as wide as said car to boot.

I could tire you with the train of thoughts that led to the solution that I eventually applied to my GSX1100EZ (that’s GS1100EZ for you Americans), but let’s suffice to say that at first it seemed too simple to be true, and yet it appeared to work. Not willing to keep it to myself, I decided to put pen to paper. So, here goes. 

Starting point:

• said GSX1100EZ (’82)
• a GiVi Wingrack
• 3 x GiVi Monokey 45 litres hard bags (lemme see… that’s about 10.2 dry US gallon each).
• A universal mounting set.

Initial results: more luggage capacity than a Suzuki Alto cage, and indeed just as wide. Over 100 mph stability: zilch.

The reason for all this is: the universal mounting set does bolt the rack to the bike using three mounting points, but none of the braces cover more than one hole in the rack, and one mounting point on the bike, leaving the rack free to turn along its vertical plane, unless you tighten the bolts really hard. Furthermore, the mounting braces of the universal rack are about as rigid as a live eel, so the whole plot gladly wobbles as the bike is perfectly stationary in the longitudinal plane. Of course, it doesn’t take long for a loaded rack to transfer said movement into the rear of the bike, which feels as if your rear is suddenly suffering from a bad case of Parkinson’s disease.

To attack the jittering movement, I just had to:

• use stiffer material, and
• attach it to the bike more solidly.

To stop the vertical hinging movement of the rack, I had to think of a ‘beam’ that held itself to the bike in at least two places, and grabbed onto the rack in two places as well.

So, here’s what an evening with an inspiring drink came up with (nooo… I wasn’t driving, officer!):

I found myself a strip of 8mm stainless steel, which I bolted to the bike on to points:

1.at the pillion footrest
2.at the rear of the sub-frame on which the buddy seat is mounted, at the point on which the indicator was mounted (which had to go anyway, since the rack came with its own indicators). 

To this strip I then bolted the rack which was to hold the hard bag.
Fig. 1 will give you the basic idea. The beauty of this is twofold:

When you bolt it to the footrest, it can only hinge in one way: the vertical plane of course. If you then find one other point to firmly bolt it down to, there is no way in which the strip can move anymore.

Using a strip of stainless steel, you are basically free to bend it to fit as closely to the bike as possible.

Of course, the practical implementation didn’t stop at "the basic idea" as depicted in Figure 1.
For starters, there were twin shocks to deal with. In my valiant effort to get the rack as close to the bike as possible, they proved to be in the way, so some bending had to be done to overcome this problem (see fig. 2). Now, stainless steel strip isn’t the easiest to bend, especially when it’s 8 mm thick, but with enough determination and the help of some tools available at a workshop it can be done. I happened to have access to a shipyard when doing the job… yes, some editors-in-chief have all the luck. This may also give you an idea of where I got the 8mm strips.

Secondly, the mounting points on the subframe are not where you can just bolt the strip straight to it, so you have to use a tube to overcome the distance between the strip and the sub-frame. For optimum rigidity, it’s best to weld these to the strip. I needed a 110 mm tube, but don’t trust me: take your own measurements (which goes for all parts that we use: even if you do have the same bike, I can’t imagine that your final solution would measure out exactly the same as mine. So: carefully take your own measurements as you go along.
Again, see fig. 2 to see what I mean.

In the case of my GSX1100, I had to take some of the plastic of the rear cover out with a grinder to be able to get the tubes through at all, so I wasn’t too sentimental on that point. Don’t try to break it out or anything: you will probably regret it. I didn’t take the chance, so I’m not definitive at that point, but with a grinder and some delicacy you can’t go wrong.

Once the strips were ready, I started to bolt them to the bike.
Rats. It was at that point that I discovered that 145 mm long bolts with an 8 mm thread (to mount the strip through the tube so the rear point at the sub-frame) are not reality available, even at a shipyard. But when you really set your mind to something, creativity usually knows no end. I found myself some 8mm thread by the foot, sawed off the correct length, found myself an 8 mm nut, which I screwed onto the thread and then welded things together, and lo and behold: a fourteen point something centimeter bolt!

When I had one strip bolted to the bike, I noted where to drill the holes to mount the rack to the strip, drilled the holes, bolted the rack to the strip, and voilà: one side ready. I then bolted the strip to the other side, took the other rack, fitted the top carrier onto it and put the plot together to see where to drill the holes in the other side. By now, you will have got the picture.

A few things to keep in mind:
Depending on the rack, you may have to machine the strip a little to make the rack fit snugly. You may need a grinder or something to do that.  You may even need a strip that takes a bend in the vertical plane… if you have a GiVi Wingrack you’re in luck, since then you can use a straight strip, but with a Krauser K2 rack it might not work with a straight strip. In that case, you’re in for more welding. 

To top things off (and to be careful with your sub-frame) when you’ve finished the situation as outlined in figs 1 and 2, you then add a support strip, which runs from your original strip, through the rack, to the bolts that hold the top of the shock. See fig. 3 to get the picture.

Strictly spoken this may be unnecessary, but it does take some of the weight of heavily loaded hard bags off the rearmost point of the sub-frame, and it provides a little extra rigidity. You won’t need to weld anything to make these, but you may have to get at the grinder to machine these support strips to fit them around the top of the shock.

Please bear in mind that these are only guidelines! From looking at the pictures and considering the objectives I had at the time, you should be able to come up with a solution that will apply to your specific bike and rack, but there is of course a chance that what works perfectly well for you only slightly resembles the geometry of what I describe here. When thinking, keep one principle in mind: whatever you come up with must be unable to hinge or move by design! not by the fact that you stop its 'natural' hinging movement by tightening the nuts with a 10 ft pole.

But before you do anything, think! Why, maybe you could come up with an even better idea!