bullfrog Posted August 31, 2004 Report Share Posted August 31, 2004 Thanks for that last response Dan. I have a little personal study going comparing vintage trialers with the modern ones. Over time I'll probably manage to come up with some modern bike weights (front and rear) using a digital bathroom scale to compare with some of the vintage weights I already have (actually, precious few of those have been obtained so far). I thought for a second I might get a bunch of data really easily, oh well . . . Bullfrog Keep the rubber side down! Quote Link to comment Share on other sites More sharing options...
ronm Posted September 1, 2004 Report Share Posted September 1, 2004 (edited) Actually, This is a copy of my notes from the comparison Dan mentioned: 2004 Bike Weights - Full fuel tanks. Measured at TTC by Ron and Charlie on Bathroom type scale. GasGas Pro 280 - Front 79.5 Rear 79.0 Total 158.5 Beta 270 Front 82.5 Rear 84.0 Total 166.5 The interesting thing is that the Beta has a weight bias toward the rear and the GasGas is evenly distributed. However, when riding, it takes noticeably more effort to raise the Beta's front wheel for obstacles, etc. I haven't taken time to analyze it, but it may have something to do with the vertical center of gravity. Anyway, they both work well. I guess more effort is not quite the way to describe it. Maybe it is that I need to pay more attention to the front end on big stuff. On rolling -rise and fall turns where the front end sometimes comes up when you don't want it to, the Beta sticks better. Edited September 1, 2004 by RonM Quote Link to comment Share on other sites More sharing options...
dbrown Posted September 1, 2004 Report Share Posted September 1, 2004 Ok Ron, now you have piqued my curiosity. I won't be back at TTC until later tonight, but tomorrow I will go weigh some of the bikes and see. I suspect that maybe the light feeling front end on the Gas Gas may have to do with the position of the pegs and maybe the relative position of the swing arm pivot point plays a part. I'll check that too, and also check the weight bias on the other bikes. My recollection from some of the vintage bikes is that the front end felt light on the Ossa MAR relative to the Bultaco or Montesa. But that is just a riding impression, I haven't weighed any of them. We have one vintage bike in the garage, Charlie's old TY250. It handles a lot like the Ossa, but that's not surprising since Mick Andrews had a big part in the development. Stay tuned, details to come! dan Quote Link to comment Share on other sites More sharing options...
bigfoot Posted September 1, 2004 Report Share Posted September 1, 2004 Dan It would be interesting if you measured each bike with the bars set at the same position and a rider mounted. Arms and legs straight each time should produce a similar standing position and distribution. Just a thought. Quote Link to comment Share on other sites More sharing options...
bullfrog Posted September 1, 2004 Report Share Posted September 1, 2004 Dan: Oh, Oh, Oh - now you are getting me excited about data! In most cases the rider weighs more than the machine, therefore the location of the rider on the machine is rather important to the overall handling characteristics. In addition, there are ergonomic factors which affect the rider's comfort and ability to move about on the bike. I have a "generic" diagram which "asks" for certain dimensions which allow direct comparison of one bike to another regarding some very important machine and ergonomic factors. Let me know if you'd like a copy. Ed Quote Link to comment Share on other sites More sharing options...
ronm Posted September 2, 2004 Report Share Posted September 2, 2004 Dan, It seems like we checked the peg position, swingarm pivot location, swing arm length, etc and did not find much difference. I think though that all other things being equal, the bike with a lower CG will have a heavier feel to the front wheel. This is because the front wheel has to move higher to get the same weight shift to the rear. Just like when you try to weigh a bike on bathroom scales without blocking up the other tire to the height of the scale. I haven't figured out an easy way to measure this directly. I did play around with a scale last winter. I measured front and rear weights on my '04 Beta and my '00 GasGas. I then raised the front wheel with a concrete block stood on end, and measured the rear wheel weight again. I never took time to work out a free body diagram on it, but from the data, it should be possible to determine the location of the centroid in 2 axes. I bet that the Beta ends up with the center of gravity lower. Since you have all brands there, you could check them all pretty quickly. I guess another method would be to lay the bike on its side on a scale. (block of wood to raise it up a bit and maybe a foot square piece of plywood between the bike and the block incase the cg turned out to be located in a hole). Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.