Sektor RL DPC spring compatibility
I went for it. To explain my situation, I had a 110-140mm spring laying around since I sold my previous RL DPC (which I regretted almost immedietly), and I couldn’t find any 140mm models to buy. The maximum travel of my frame is 140mm, and I really don’t feel the need for any more on my trails either, hence the want to go for 140mm.
It all seemed to go fine, and it feels fine when riding from the little but I’ve done, but off the bike I noticed some odd things which I emailed Loco about but thought I might put on here as well (as I’m not a customer, atleast not yet, he shouldn’t feel any obligation to priorize my question after all).
“I’ve recently bought a 120-150mm Sektor RL DPC 2013 and popped a 110-140mm spring assembly in it. The stanchions have markings for 140 and 150 and the fork doesn’t appear to be sold in the 140 variety anymore that I could find, so I thought the spring assembly would be the only thing separating them. Was I wrong?
I ask because while the spring in question gave me 30% sag on my 110-140mm Sektor RL DPC 2012 (which I stupidly sold and soon regretted), it now gives me 20% sag (according to 140mm sag markings).
Also, when “resting”, assembled to the bike but with no other weight on it, the fork is at 150mm. If I put a little bit of weight on it and carefully let go it will stop at the beginning of the 140 markings however, until I lift the front wheel completely of the ground whereby it goes back to 150. I don’t know how relevant that is though.
So, what have I done exactly? Just made a 150mm fork with a slightly firmer spring than if it was the correct one, or can I expect any weird characteristics? Can I do anything else to definitely turn it into a 140mm fork? The last bit is quite important to me since that’s the maximum travel of my frame.”Posted 4 years ago
I took out the short spring to compare them. They are the same length all the way through, except the tube where the 10mm difference is. As far as I can see there’s nothing to stop the shorter spring to simply stretch out to the full 150mm, which I guess is exactly what’s happening. No idea how to solve it though. Is the short spring assembly simply not made to produce 140mm in this chassis?Posted 4 years ago
Isn’t actually the CSU that’s different rather than the lowers? If you have a look at the RS parts manual for 2012, the only one on their site, there are two CSUs listed: a 140mm one and a 150mm one. I’m not familiar with the dual spring assembly, but with the coil u-turn, there was a top-out spring on the rebound damper stack that actually cushioned top-out and the rebound side would have limited movement.
Presumably you can extend the dual spring further than 140mm by pulling it, so the rebound would still be the limiting factor on your fork and set at 150mm still. But you could maybe add some sort of spacer to limit travel on the rebound damper shaft, a 10mm one under the top-out spring?
That could be absolute cobblers, but if you have the fork apart, have a look and see if that makes sense.
Or you could see if you could pick up a 150mm coil U-turn spring and simply run it at 140mm with the damper leg as it is?Posted 4 years ago
Looking at the 2013 spare parts catalogue the uppers are the same – across both 140mm and 150mm DPC’s
The rebound damper shaft is different! Maybe that is the root cause of the problem?
If the rebound shaft is shorter on the 140mm ones your get the same effect – the spring may stretch out that extra 10mm?
Maybe a spacer under the top-out spring on the damper side to shorten the rebound stroke as a bodge to check?
Easy way to check – lowers off – pull the rebound shaft all the way down and measure the length of the exposed rod to bottom of stanchion and compare that to same measurement on the spring side.Posted 4 years ago
U-turn spring would definitely be a rather inexpensive and quick fix if all else fails, thanks for that suggestion.
What I don’t quite get is, how would the U-turn be able to limit itself to 140mm if my current spring can’t do it? What is the actual technical differences between a U-turn spring run at 140mm and my current spring? Why isn’t the rebound shaft causing issues with the former?Posted 4 years ago
What I don’t quite get is, how would the U-turn be able to limit itself to 140mm if my current spring can’t do it? What is the actual technical differences between a U-turn spring run at 140mm and my current spring? Why isn’t the rebound shaft causing issues with the former?
I’m not sure it would, I can’t remember, but people, I think, are suggesting the 150mm coil u-turn assembly run at 140mm rather than the 140mm one. I’ve got a 140mm one from a Pike sat in the cupboard somewhere, but the Pike one has a top-out/negative spring on the U-Turn assembly [edit, that’s not quite true, it sits separately at the bottom of the stanchion], whereas the Sektor one has a top-out spring on the rebound damper shaft. But anyway just fitting a 150mm coil u-turn would do it, just run it at 140mm.Posted 4 years ago
I was referring to running a 150mm u-turn at 140mm too, sorry if I was unclear. I don’t get how the travel adjustment works or how it’s different to running an actual 140mm spring when it comes to the rebound shaft causing issues (or not).
Sorry if I’m being terribly daft.Posted 4 years ago
The u-turn is effectively a screw – as you turn the knob the spring rotates, and the spring rod is fastened in place to the lowers. As the spring rotates it moves up and down the rod, effectively shortening or lengthening the rod. The spring itself doesn’t change length.
Does that make sense? So if the 150mm u-turn spring is wound down to 140mm, it effectively shortens the spring rod that is attached to the lowers.
When you do this you also start to move the rebound shaft up in its travel as its fixed to the lowers.
Hence why you can’t adjust the travel with the fork locked out as it stops the rebound shaft moving up inside the damper leg due to hydraulic lock.
Which takes me back to my original point – if the damper shaft is longer than the spring rod, you may end up stretching the spring out.Posted 4 years ago
Wasn’t sure what “all travel spacer” was referring to exactly, but yes that’s what I was thinking. I know spacing it has been mentioned, it’s just that I thought of it as a bodge more than anything else which I wanted to avoid if possible. I might even have the spacer laying around in the box then. Good stuff.
Thanks all and sorry again for my daftness – even the simplest of technical lingo has a tendency to get over my head. 🙂Posted 4 years ago
I think it’s worth a shot to see if it works – a simple 10mm spacer is easy to knock up or get hold of.
I’ve got an old 20mm rubber spacer from a pair of solo air forks that you can cut down to try it?
Drop me your address – e-mail in profile and i’ll send it off tomorrow if you want?
If it works then great, problem solved – and if it plays on your mind you could try and track down the proper damper shaft later.Posted 4 years ago
Okay, so it worked. The air travel spacers don’t, though – the hole is slightly too small (I think there’s probably enough material to widen it if you have the tools – a vice and a wide drill bit should do). I used four 2.5mm metal washers instead since that’s what I managed to find in the garage. I do get a slight clonking sound when I fully extend the forks, which I guess would be much less noticable if at all with one solid plastic spacer, but it really is a matter of a sound and not something I can actually feel so I’ll probably live with it until it’s time to service.
Here’s an image clearly showing where to place the spacer.
Thank you everyone for all the help.Posted 4 years ago
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