| #1  05-Jul-2004, 14:46 | ||||
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| New rear shock headache Hi All, I've got the chance to get a very reasonably priced Ohlins rear shock, but am up in the air a bit about whether to go for the old SS length or the IE length version.... If I understand right then the Showa IE shock is about 10mm longer but with the same mounts as the Showa SS shock. I assume Ohlins make the standard ride height in the middle of the shock's adjustment range (about 15mm end-to-end?) meaning the Ohlins IE shock on lowest setting would be about 3mm higher than a fit, standard Showa. I've always found the rear ride height to be too low on SSs, so I doubt I'll be wanting to go below standard, but I'd like to have the ability to go 3-18mm up from standard. The way I see it is that, as the shock is at 45 degrees not vertical like a 916, 15mm of adjustment is actually only equivalent to 8mm vertical adjustment. I'm absolutely positive that I've got some of the above wrong, so feel free to laugh at my massive ineptitude in all things suspension related...  Cheers, Ali ps: I will be doing the front end soon, but once you get into changing the springs, you may as well change to 996 forks, so you'll need a 996 wheel (or a mag), so you'll need a cyclecat yoke, so you'll need goodridge hoses, to connect to your brembo billet master cylinders, so you don't mess up the look of your cyclecat clip-ons, etc......... About £2k if I've got me sums right   |
| #2 05-Jul-2004, 16:20 | ||||
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| #6 02-Oct-2004, 16:26 | ||||
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| Cheers guys. Had a chat with Harris about this, as I'm really looking for something with a range of 335mm - 347mm. They reckoned it'd only be another £40 to modify the DU 235 to suit. Doesn't alter the fact that it still costs and arm and a bloody leg to start with...... Don't want shot of that Penske by any chance Kev??? Thought not.  Cheers, Ali |
| #7 02-Oct-2004, 17:54 | ||||
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| Quote:
I would say you are a bit wrong there Ali, the chances are your shock ratio is about 2:1 but the not in the way you have discribed. Assume 50mm of Stroke on the shock this will give 100mm of rear wheel travel if the ratio is 2:1 To get a rough idea of the ratio measue from the swingarm pivot to the rear wheel spindle and then from the swingarm pivot to where the shock fixes on the A-frame of the swing arm, this will give you a basic ratio, a small degree of rising rate is added as the shock moves through a arc, this means things aren't totaly linear so you end up with a rising rate curve could be in the region of 1.9 to 1 through to 2.0 to 1. Now if you increase the shock length by 5mm it will push the rear wheel futher from the seat by 5mm X the ratio.. try taking 5mm of preload off the rear spring, this will effectively make the damper rod sit futher into the shock body simulating a 5mm shorter shock, I bet a distance measured between the rear spindle and a point on the rear of the seat unit reduce by nearly 10mm, conversely increasing the shock length by 5mm will raise the bike by 5mm X the ratio so almost 10mm in the example. A Harris Magnum 2 with the cantilever rear end has a ratio of 1.7 to 1 And no you cant have my Hi/Low speed damping Penske it cost more than a Ohlins and unlike a 916 Ohlins it also has a rideheight adjuster. Kev |
| #8 02-Oct-2004, 21:03 | ||||
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| You are, of course, 100% correct. Can't quite believe how I missed that.... Many thanks for the lesson in simple trigonometry. The question now is, how much of an increase is too much? And would the money be better spent on having some kind of bodged spacer made up to extend the shock, while spending the rest on a mag/carbon front wheel? And I love the idea of hi/low speed damping on the penske shocks. Can't quite work out how it manages it, but I'm sure you'll be along with an answer shortly.  Cheers, Ali |
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