I don't know about you guys but I never really paid a lot of attention to suspension, just something to keep the exhausts dragging on the ground. A few years ago I rebuilt my Ducati Darmah suspension with parts off one on the Ducati sites. Works Shocks to suit my weight and riding style....and Works dual springs. I did it all and found the results less than stellar, if anything I found the front too harsh. Might explain why its been pushed to the back of the shed. Three years ago built up the BMW R90 race bike and fitted a set of Ikons to the rear that I had from the Thruxton I briefly owned. The front got fitted with emulators and linear spring to suit my weigh riding style etc. I set up the sag at 30mm at the rear and I think about the same at the front. WTF is Sag I hear you say? Its the difference between a bike off the stand with no rider and one with a rider. At this point just following what I gleaned off the net. Recently I purchased this book. I got it off Amazon but you can get it cheaper off Fishpond http://www.fishpond.co.nz/Books/Race.../9780760331408 Its not a book you sit down and read so much and I take a while to absorb stuff so its read, look at bike...read a bit more. Well anyway, I measured the Ducati sag.... 35mm at rear with no pre load ( the spring adjuster) and almost nothing at the front. This means that when riding it can compress on a bump but if there is a dip or hole it cannot extend. With damper rod forks ( what most pre 1990 bikes have) the oil in the forks moves from one chamber to another via holes. The holes are fixed but the rate the forks move is variable so not much control over damping. What Mr Ractech developed was a device with a spring loaded shim stack. The holes in the damper rod were drilled out and the emulater took its place. So instead of a fixed hole trying to regulate flow the emulator opens up on pressure demand, the spring tension can be adjusted. Rebound is done by the original set up but can be adjusted by adding or removing fork oil and or changing the oil from 10 to 15 This also uses the air in the top of the fork as secondary damping. Well that's how I understand it. So todays exercise is to go out to the shed and measure you sag. Bike off stand-measure to a point on the bike, tail light, handlebar end. Then with rider on Report back with findings.
It wasn't until I forked out the money for rear Ohlins and spent some time getting them how I wanted that I realised how shit the Ducati suspension really was,next bike I think I will do the front first
They did the best with what they had at the time. I had some of these marzocchi stradas, like most Italian stuff they look nice. Oversprung and underdamped. Good to see that BFTP still has 2 or 3 members left.
I promise I'll do my suspension test tonight Herr Voltmeister.
Getting Toby at Auckland Motorcycle Services rebuild my forks has made a huge difference to the bike.
My suspension is perfect. No need to test it.
With preload only shocks, the more you wind the spring up, the less damping there is. Not being a heavy weight, I always have my shocks on the lightest setting, this gives me more damping. On the airhead this is spot on for sag too. When I rode bikes with 300mm travel front and rear, I'd start off with factory settings, and being Japanese set up for girl size Japs, they would be pretty close for me, just a small fine tune for sag, and for those 16 way clicker things...ah, do they work? Stock was close enough. Oh, and for forks, I've tried fork oil a few times, and don't find it any different to ATF. So ATF in all my forks....and I use it in my rear shocks too.
I got a stainless front brake hose - it is firmer, but in the real world just the same. Went for a ride on some back roads - I'm not big on brakes, I tend to set corners up well in advance, but was able to use a lot more lever pressure to haul things down...not that I couldn't before, but there is an improvement. Put some oil in the Stornello forks, the manual says Shell Tellus 33, knowing how the bike was back in the day I thought that was a bit light so got some ISO 46 from work. Did some research and found that was a pre ISO rating and Tellus 33 is now Tellus 68, so it could be a bit light. ISO 33 is about SAE 10, 46 SAE 20 and 68 SAE 30. Anyway, looking at the ISO46 got me thinking...made my own quick centistoke rig (funnel and bleed screw) to check ATF to ISO46, and it looked pretty good. Googling later I found ATF is SAE 10 and ISO 46 SAE 20. Could be a bit heavy for the BMW, but thought I'd give it a try. I did a test on SH22 down to Te Uku, with some gravel roads in for real world testing. BMW recommend some light oils, SAE 5 to SAE 10, so ATF is the correct viscosity, works OK, but it does seem a bit soft to me. ISO 46 works pretty well, didn't seem too harsh, coped with gravel road corrugations perfectly, didn't patter on corners - seems to be just right.
i recently changed all the fluids on the TS, inclusive of forks, not sure what was in there before and the levels weren't quite right but changing it to ATF (after reading your post above) worked a treat , i noticed a huge improvement, also toying with the settings on the rear shocks found a medium setting in combination with slight decrease in Tyre pressure worked best as well, cheers
People these days seem to like high tyre pressures, but I've always liked mine on the low side. To me low pressures means more grip, high pressure always feels greasy to me.
