cornishflyer Posted December 5, 2017 Report Share Posted December 5, 2017 (edited) Hi all, I have purchased some new fork springs for my #158 Sherpa T 250 which are just over 500mm long and are so stiff when I install them that I can hardly compress the front end. My bike only came with one spring so I can't compare compression but the one old spring I have is about 450mm (50mm shorter) and comes up to the top of the tube when I remove the top cap. These new ones stick right out and it's a real struggle to the get the top caps on. The reseller tells me these springs are correct for this bike and something else must be wrong with the fork. So, I took the fork apart and it all look ok, perhaps I have incorrect length damper rods. The top tubes are 550mm and the damping rod assembly is 100mm My old Sherpa had very plush forks, and I tried another over the weekend that was also plush. This thing is rock hard with these springs in. Any help appreciated, especially the length of the springs I need. Thanks Edited December 5, 2017 by cornishflyer Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted December 5, 2017 Report Share Posted December 5, 2017 The M158, 182, 190 250's have shorter sets of forks than other sherpas and I would assume they need different shorter springs. I am not sure of the actual measurement but your supplier should have known that. My guess would be the springs protrude about 20-25mm out of the top triple clamp before assembly, which is a lot less then yours. Inmotion list Sherpa forks at 500mm so I reckon you have springs for the standard forks and the 450mm one in the bike was the correct length original. Cheers Greg 5 Quote Link to comment Share on other sites More sharing options...
mrb505 Posted December 5, 2017 Report Share Posted December 5, 2017 I think the 158 182 190 tubes are only about 10mm shorter but the rods are also 10mm shorter as well so they use the same length springs as the 350’s of that era or maybe even all Sherpas Id probably just cut those 500+ Pursang springs down to a suitable length All the sherpa springs I’ve measured are between 450 to 475mm long 1 Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted December 6, 2017 Report Share Posted December 6, 2017 (edited) It makes sense that they would do that I had a quick look in my shed and found two leftover springs one is 475mm long 59 coils and 3.9mm dia steel the second is 463mm long 50 coils and 3.4 dia -so a fair bit softer I can remember trying some Alpina springs back in the day so the longer one could be Alpina but I am not sure Edited December 6, 2017 by sherpa325 appearance 2 Quote Link to comment Share on other sites More sharing options...
old trials fanatic Posted December 7, 2017 Report Share Posted December 7, 2017 I always used Persang springs in my Sherpas with no problems. However they were all later i.e. 198 and onwards models. Then again i'm 17.5 stone and one thing you havent mentioned, well i dont think you have, is your weight ? 1 Quote Link to comment Share on other sites More sharing options...
cornishflyer Posted December 8, 2017 Author Report Share Posted December 8, 2017 I'm 82kg, what's that? Around 12 stone? The engine is out but I've factored that in (I reckon that's another 25kg tops) still it's WAY too stiff. I can barely compress it by jumping all my weight on the bars. I think I'll just shorten the springs to around 475 and adjust from there, like the idea of the grinder, I hadn't thought of that. The seller has assured me he's sold thousands of 500mm springs with no issues so I don't know what the difference is in my bike. Perhaps Aussie bikes where shorter, less gravity down here, I dunno. 3 Quote Link to comment Share on other sites More sharing options...
cornishflyer Posted December 8, 2017 Author Report Share Posted December 8, 2017 Oh and the selling that was in the bike was 150mm long, 59 coils, 3.7mm wire thickness. Different again. ? Quote Link to comment Share on other sites More sharing options...
old trials fanatic Posted December 8, 2017 Report Share Posted December 8, 2017 Not trying to teach my grandmother to suck eggs but have you tried compressing the legs out of the yokes and with the mudguard and wheel removed ? Just in case something is binding. Quote Link to comment Share on other sites More sharing options...
cornishflyer Posted December 9, 2017 Author Report Share Posted December 9, 2017 Hi OTF, yes I have, they run lovely and smooth with just the old spring in there, no binding at all. I've got some video I'll try to post so you can see what I mean. No probs about the eggs by the way, I'm all about the most obvious that I've probably missed. 1 Quote Link to comment Share on other sites More sharing options...
scifi Posted December 11, 2017 Report Share Posted December 11, 2017 We don't know why your bike only had one spring, but what you need is another 450mm spring to make a matched pair. Show your supplier the original spring, and ask him for another identical one, in exchange for the wrong one he gave you. . Quote Link to comment Share on other sites More sharing options...
cornishflyer Posted December 12, 2017 Author Report Share Posted December 12, 2017 5 hours ago, scifi said: We don't know why your bike only had one spring, but what you need is another 450mm spring to make a matched pair. Show your supplier the original spring, and ask him for another identical one, in exchange for the wrong one he gave you. . Yeah I tried that but he insists that 500mm springs are what I need in this bike, even though it was solid as a rock All good now though, I shortened the new springs to 475mm and it feels a lot better. I will wait till I get the engine in and then set the sag properly, possibly by taking a little more off. Thanks everyone for your help. 2 Quote Link to comment Share on other sites More sharing options...
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