Spring side thread reducer for cap made for 35mm stanchion into 36mm stanchion?
I doubt if this exists. Is there some kind of self tapping shim that could work as a heavily loaded reducer...safely?
I've looked up catalogs on Ni coated Brass and SS standard size reducers. The step down that seems closest to what the larger fork stanchion inner diameter would be is a 32mm to 25mm, which is far too thick, if there is a stock reducer to the fork with the larger stanchion.
My hope is to adapt a Lyrik u-turn coil assembly into a fork with a larger stanchion, and larger female threads. The Lyrik u-turn assembly has a cap to thread into a 35mm stanchion. The fork I'd like to adapt it to is an X-Fusion Vengeance having 36mm stanchions.
The Lyrik u-turn cap slides into the larger Vengeance stanchion, stopped by the cap's flange. There is about a 1.5mm to 2mm of "slop" in thread reduction needed... if this is feasible.... and of course needs to be hold up to rare but occasional harsh bottom-out loads.
I thought I'd ask the expert frame builders and machinists here before returning the Vengeance fork, if they would take it back. Or selling it, now that it has been opened up and they won't take it back (with no marring or damage from tools). The u-turn assembly compression rod appears it can adapt to the larger Vengeance lower leg hole using a steel washer inside.
If asking, "Why not just use the 160mm Vengeance travel all the time?" I usually run my Lyrik at around 140mm for tight local trails and adjust the u-turn near this height frequently, sometimes up to 160mm for long or steep descents or during trips to ride in the rocky high mountains or deserts. I really like this u-turn feature for tuning handling on-the-fly. I wanted to try the X-Fusion Vengeance having only rave reviews for improved speed sensitive damping over the Lyrik and other forks, and the increased stiffness, and to match the factory designed higher quality damping of the X-Fusion coil shock I recently put on my bike.
If adapting the u-turn is not feasible, I'll buy an Avalanche damper cartridge, designed to bolt into the Lyrik. The Lyik's damping leaves much to be desired to match the X-Fusion Vector HLR coil shock's damping quality.
That's too tight a gap for it to work well. I can't picture the Lyric U-Turn assembly well enough to remember if you could feasibly ditch just the top cap and make a new bigger on or not but you need more room to work with than that to do a spacer like you're picturing.
If both the cap and stanchion are same thread pitch, perhaps experiment with some 0.75-1.0mm diameter wire, wrap it around the cap threads to bend the wire into a coil so as to form a custom pseudo heli-coil to take up the space. Unscrew the wire coil from the cap and then try to get it threaded into the stachion (this will be the really tricky part) and secured into the stanchion with loc-tite. Round profile of common wire will not work as well as square shape of real helicoil material but it might still work?
Thanks for the creative suggestion.
Originally Posted by GrayJay
Even if the thread pitch is the same, and visually it does appear to be, the gap between the cap's OD and stanchion thread's ID is probably too big and ride time fork bottoming loads too great to be safe with a heli-coil like insert.
I think the risks of thread damage and trashing both pieces, and the possible safety issue, is not going to work for me.
Thanks again to this forum for all the views, and the brave suggestions.
If you're just looking for travel adjust the Vengeance does have a 170-140 adjustable version now. You'd want the HLR DLA version.
X Fusion Shox - HLR DLA
why not just machine your own top cap? the u turn top cap is not all that complicated
I haven't given up yet.
Originally Posted by Metty
You got me looking at the u-turn top cap closer.... it is very simple.
I removed the cir-clip keeping the top cap on the coil's rotating top perch. And low and behold the main top cap cap came off. It's thicker in depth, but otherwise it's a simple cap with a hole in it.
The x-fusion coil top cap is wide and flat, and could be drilled for a hole to fit the rotating top perch. And with a few shims or washers, it should fit the rotating perch, secured by the same cir-clip, and bolt on the u-turn hand knob easily.
Or like you say, get a machinist to custom turn a wider top cap with a hole, having the original for a reference.
Humm.. it's beginning to appear feasible! Thanks!
Also, looking up in the Heli-Coil catalog, there may be one that actually fits to work as a thread reducer. No way to know without trying. I'll be looking into this option too.
No go for Heli-coil, too tight a thread difference between the two cap sizes.
I did rummage around and found washers to fill in the inside of the Vengeance top cap which I could drill to fit the u-turn's rotating upper perch, and metric bolts to extend the reach of the lower compression rod through the Vengeance leg.....Now I'm waiting to see if X-Fusion can supply a spare top cap, in case I fail in my efforts to adapt the drilled top cap with durability and functionality, and then want to reassemble it with the stock top cap and coil.
Last edited by derby; 06-20-2012 at 09:19 AM.
Well I did it, and have a u-turn Vengeance HLR
Thanks for the help and suggestions!
Well, I did it. I drilled out a hole in the X-Fusion Vengeance top cap, which I found to be 6 or 7mm thick, to clear the u-turn coil assembly's top end.
Other than drilling the hole in the top cap it was bolt in with existing u-turn parts and off the shelf hardware, including some drilled out faucet plumbing rubber washers to seal the bottom end to maintain the air pressure during compression, and bottom out ramp up adjustment with splash bath oil volume.
I'll be looking for aluminum washers or spacers and a metric threaded coupler to replace the steel washers and metric car exhaust stud and steel nut I used to mount the u-turn assembly.
The fork works great with a u-turn coil, except there's no travel marks on the stanchion to reference height easily. Maybe a Sharpie or dots of paint will stick to the anodized stanchion.
The measured Vengeance stanchion was 5mm top travel lower from the original coil's 170mm travel to 165mm with the u-turn from a 160mm Lyrik. And the minimum travel of the Vengeance with the Lyrik's u-turn is 130mm compared to the Lyrik's 115mm low limit. (The Vengeance a2c is 10mm longer than the Lyrik if measured with the same travel settings.)
The Vengeance with u-turn coil weighs the same as the Lyrik u-turn did, picking both up by hand. Maybe up to an ounce heavier at most.
I'll do a review of the Vengeance fork performance in the Shocks forum after some more ride time. After one good ride so far the damping is amazing and easy to tune to balance with the best coil shock damping I've experienced, the X-Fusion Vector HLR with DWL factory tune. And the Vengeance without being heavier is noticeably stiffer in flex and more precise in handling and feel of traction than the Lyrik.
Derby- The more I research my new bike needs the more I end up liking your ideas.
I think we should approach Avy or some decent machinist for a run of a few caps.
Are the U-turn springs still readily available? Seems RS has stopped producing the U-turn Lyrik. But I see that parts seem available on Ebay and other sources.
What did you do with the topout spring on this mod? The RS parts listings show a wavy spring system for topout.