Frame design & hubguards
Posted: December 18th, 2008 | Author: Jmy | Filed under: BMX, Design | Tags: BSD, Frame, Hubguard, Idiots, Mutiny, Profile | 2 Comments »Yesterday I got a question to my e-mail why I don’t draw the Simple frames with slightly bigger spacing between the dropouts to accommodate for hubguards. The standard is 110mm and making it bigger might make sense at first glance. Below, I’ll go into the details of why it’s a bad idea.
Personally, I had never even considered adding bigger spacing as a “feature” of a frame before, and after I spent a very short time thinking about it I came up with the following reasons why to stick to 110mm.
First off, a standard is a standard and it’s always better to stick to that (unless you plan to make everyone else change at the same time). Just look at all the problems, misunderstandings and confusion that has been caused by the BB sizes in BMX. US, Mid, Spanish (and maybe soon Spanish V2), Mexican, Euro and the latest on the board — German (KHE showed something ridiculously small at Interbike). Where will it end?
Do we need the same confusion when it comes to dropout spacing? I would think not.
Secondly, more spacing between the dropouts also means there is a risk that you will need to add spacers on your crank spindle as to not let the crank arms hit the chainstays. Maybe not the biggest problem, but there are already clearance issues on some frames out there, so it would not make sense to make matters worse. Also, adding spacers on the spindle weakens the crank arm/spindle interface by reducing the amount of material in contact. This might be a very miniscule loss of strength, but a loss nonetheless and that is undesireable.
Third… a guard that adds to the overall width of the hub will also offset your wheel in the rear triangle. This has to be compensated for by either making the frames wide enough (or stretch them open even more) to allow extra spacers on the drive side to center the wheel, or you have to “dish” the wheel by tightening/loosening spokes on either side of the wheel as required.
The fourth argument is that the people who do not want/don’t have to run a hubguard would have to make up for the extra spacing by adding spacers on the inside which does not make sense at all. You’d have an inferior contact surface, maybe throw the chain alignment out of whack and it would just look plain stupid, like the frame or hub didn’t fit properly — which would actually be true. Also, many people wouldn’t put any spacers in there and just tighten the axle nuts and that way put unnessecary stress on the frame. Then some would argue that spreading the rear end to fit a hubguard will also put stress into the frame — this is true, but there are good ways to avoid it. And this brings me to the fifth argument:
Get a properly designed hubguard instead! There are already a number of hubguards on the market that are actually designed in a way so that you do not have to spread your frame to fit them. BSD, Mutiny and Profile all have guards that are designed that way. BSD’s “Jersey Barrier” has a high grade aluminium core that is threaded and completely replaces the locknut hardware on the non drive side of the hub. The first version only fits Odyssey and similar hubs, but I assume more versions that will fit other hubs are coming. Version 2 of Mutiny’s “Hub Buddy” works in much the same way and you get a good instruction manual and all the bits you need to fit it onto several different hubs. Profile have got their own guard made specifically to fit their hub. It slides over the locknut and wedges up against the cone spacer on the hub. Very efficient.
So I guess my conclusion is that instead of frame manufacturers adapting their frames to fit inferior hubguards, the hubguard manufacturers should adapt their products to the already existing standards.
