turbofurball Posted December 9, 2017 Report Share Posted December 9, 2017 Three weeks ago, while practicing on my newly minted TY, I managed to bottom out the forks. My first thought was that I've been eating too many mince pies, but then I figured it's time to sort the front end so off to the Majesty website I went ... One week later I tackled the same spot (moderate downhill with a 18" drop, then more downhill), and the difference is night and day! It felt like I was being gently lowered down the drop by little cherubs. Now, this was during a trial, and over all the bike felt far more ballanced with the Rock Shocks on the back and it did have a big positive effect on my confidence. Less stodgy, but harder to wheelie for some reason. I love the way the TY handles now, which is a relief since when I first got it I thought I might have made a terrible mistake. Turns out, it just needed money spent in the right places 9 Quote Link to comment Share on other sites More sharing options...
pmk Posted December 10, 2017 Report Share Posted December 10, 2017 This past week I was talking about rear shocks and the forks on my and my friends OSSA MARs. His bike, he wants to replace the rears, currently the modern Betors. He is in email conversations with NJB, decided Rock Shocks are a bit more than he cares to spend. I did suggest he have a look at the Majesty shocks and also fork springs. As for myself, my OSSA has vintage Curnutt shocks on it, freshly rebuilt. New to trials, but not suspension tuning, I am learning that although these vintage bikes when new had very noticable damping, they are not as lightly damped as modern bikes. Saying that, I am learning that even though I am not hopping the MAR around, it is overdamped in the rear. With that, I have swapped to a lighter rated fluid, and even have been drilling the pistons for added flow. Time will tell if I am headed in a good direction or need to buy new shocks. 1 Quote Link to comment Share on other sites More sharing options...
cangy1000 Posted December 10, 2017 Report Share Posted December 10, 2017 I got a pair of Magicals from the Majesty site. Think I had the original 37 year old springs in my Fantic 200. I found them quite bouncy compared to the old ones, a bit disconcerting at first but soon got used to them. Unlike the OP I find it much easier to pick the front up. I have modern rear shocks but nowt fancy. Definitely time and money well spent. I have light fork oil and soggy rear shocks, seams to suit me for now. Quote Link to comment Share on other sites More sharing options...
turbofurball Posted December 10, 2017 Author Report Share Posted December 10, 2017 (edited) Yeah, my TY doesn't feel springy, just plush ... maybe if I went to thinner oil (on 10w at the mo) or added more preload I'd see more bouncy-ness for wheelies ... it suits me like it is though The Rock Shocks are very nice, I only went for them as I wanted to be able to rebuild them and maybe change their length in the future (I went for 370mm, which is a bit taller than most people like on TYs) Edited December 10, 2017 by turbofurball Quote Link to comment Share on other sites More sharing options...
pmk Posted December 11, 2017 Report Share Posted December 11, 2017 Not sure what is stock length on a TY. On the OSSA MAR, if remembering correctly, the Curnutts are 10 mm longer than stock. Curnutts are 350 mm and not shortened, but could be easily. Too much experience working on suspension for mx and woods bikes and none on trials bikes is adding to the learning curve. Eventually, I will find the setup. If you do plan to possibly make a fluid change to alter damping, be cautious since true viscosity is very random when stated as a weight. I will add a link to Peters V chart, that list many fluids by cetistokes, which is an easy and better way to make changes. http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid Quote Link to comment Share on other sites More sharing options...
turbofurball Posted December 11, 2017 Author Report Share Posted December 11, 2017 The springs were the same length as standard, but offered a lot more resistance to getting the end caps on, so I guess the originals were just completely toast. I'm not planning on changing it now, as it's lovely! 1 Quote Link to comment Share on other sites More sharing options...
dadof2 Posted December 11, 2017 Report Share Posted December 11, 2017 "Saying that, I am learning that even though I am not hopping the MAR around, it is overdamped in the rear. With that, I have swapped to a lighter rated fluid, and even have been drilling the pistons for added flow." The original MAR was primarily developed for riding slippery stream beds as that is what many of the sections were then. With the lower grip of tyres at that time too little damping would cause the back end to kick sideways and slide off boulders. The stiff damping was right for the time and the tyres but certainly will feel much less bouncy than modern suspension. Also travel was limited without the benefits of rising rate linkage so stiff damping helped prevent bottoming out. Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 11, 2017 Report Share Posted December 11, 2017 (edited) 1 hour ago, dadof2 said: The original MAR was primarily developed for riding slippery stream beds as that is what many of the sections were then. With the lower grip of tyres at that time too little damping would cause the back end to kick sideways and slide off boulders. The stiff damping was right for the time and the tyres but certainly will feel much less bouncy than modern suspension. Think your analysis is about 99% out !! (@pmk, incorrect) Edited December 11, 2017 by b40rt Quote Link to comment Share on other sites More sharing options...
pmk Posted December 11, 2017 Report Share Posted December 11, 2017 1 hour ago, b40rt said: Think your analysis is about 99% out !! Honestly, is 99% out mean it is accurate or incorrect. My guess is that yes, back then, all the brands were kind of designed to be a bit more damped. Riding the same bikes, in more modern sections, granted nothing crazy, seems less damping may be a bit better. Not so little to bounce around on the rear wheel, but just a bit more lively. The oem Betor forks came around easily and do feel much better with a fluid change from Mobil 1 ATF to Maxima 5 wt fork fluid. This was a drop in viscosity to about 16 cst from around 33. The rear shocks as I first built them up, I also used Mobil 1 ATF as back in the 70’s per the Curnutt rebuild instructions, they wanted type F ATF. I have since tested the original pistons at 5 wt Maxima fork fluid, and stayed with that, but have been enlarging the drilled ports in the piston. I enjoy working on suspension of all types. Ironically, not having even a simple rebound adjuster makes me appreciate having them on modern stuff. 1 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted December 12, 2017 Report Share Posted December 12, 2017 pmk, I figure you are enjoying the process of developing your Curnutt shocks to the point of getting them working well for trials use. It is quite interesting to hear your voyage of discovery. As far as shock lengths go, the Betors that came with my OSSA are 350mm long and TY250 twinshocks originally came with 325mm shocks. Most people nowadays ride TY250s with something between 340mm and 360mm and my OSSA steers nicely with both 350mm and 360mm shocks. The reason why trials shocks in the 1970s had shorter travel and heavier damping than trials shocks do in 2017 is because the development work that has produced the amazing trials shocks we can buy now, hadn't happened yet. 2 Quote Link to comment Share on other sites More sharing options...
pmk Posted December 13, 2017 Report Share Posted December 13, 2017 (edited) FeetUpFun, my OSSA came to me with oem shocks. I gave the oem shocks to my riding budding so we could try to build 2 good ones from 4 less good shocks. Show bike so fluid in them was less of an issue. Somehow I thought when I measured the Curnutts came in at 10mm longer but who knows. Ironically, comparing modern vs old, yes, new stuff is more advanced, but travel wise, these Curnutts have 4.7" of shaft travel so this gives the MAR just under 5" of travel. Not quite modern but more than the 3.5" ish they did come with. Hope tomorrow I can make my last mod for a bit. With like it will be pretty good, and the event Saturday could be proof of the pudding as they say. Edited December 13, 2017 by pmk 3 Quote Link to comment Share on other sites More sharing options...
pmk Posted December 13, 2017 Report Share Posted December 13, 2017 b40rt, curious, regarding setting up the suspension on these vintage machines, is your thought they should retain heavier damping, or should tne damping be lightened? Maybe not so little damping to fully mimic a modern trials machine, but maybe it should. From some easy simple rides at tne house, the lightened damping so far in the forks and shocks seems an improvement, just concerned that there is an edge of too lighly damped I prefer not to cross. FWIW, using the sometimes referred to push down test, the MAR at the moment has the forks reacting slightly faster than the rear shocks, when applying pressure onto the footpegs. Quote Link to comment Share on other sites More sharing options...
turbofurball Posted December 13, 2017 Author Report Share Posted December 13, 2017 If it works for you, then it's better. I like moderate damping, and both the TY and Cota are squishy rather than bouncy (the Cota has old Marazocchi shocks IIRC, stock fork springs, and it all works very well). 1 Quote Link to comment Share on other sites More sharing options...
b40rt Posted February 15, 2018 Report Share Posted February 15, 2018 On 13/12/2017 at 3:11 PM, pmk said: b40rt, curious, regarding setting up the suspension on these vintage machines, is your thought they should retain heavier damping, or should tne damping be lightened? Maybe not so little damping to fully mimic a modern trials machine, but maybe it should. From some easy simple rides at tne house, the lightened damping so far in the forks and shocks seems an improvement, just concerned that there is an edge of too lighly damped I prefer not to cross. FWIW, using the sometimes referred to push down test, the MAR at the moment has the forks reacting slightly faster than the rear shocks, when applying pressure onto the footpegs. Just noticed this just now @pmk. IMO, a well handling t/s or pre65 will have lighter damping and lighter springs than back in the day. This combined with tyre carcasses that are far more flexible make them easier to ride and improve grip dramatically. 4 Quote Link to comment Share on other sites More sharing options...
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