Upgraded to a FS frame, downgraded performance.

[BarkMau]

When I found this ’03 Jekyll I thought it was time to upgrade to a FS frame. The conversion wasn’t that bad, wish I could say the same about the riding experience. Whenever the rear wheel hits a bump on the road, bounces off losing grip. If it happens when leaning, it tends to fishtail. The same system worked great in a HT frame http://endless-sphere.com/forums/viewtopic.php?f=6&t=43879and never showed the mentioned behavior. Wondering if it is related to the rear swing arm being asymmetric. Any ideas?

 

[full-throttle]

Increase rebound damping

MTB shocks are tuned to MTB wheels, not hubmotors. Go mid drive for best results.

 

[dogman dan]

Shock could be toast, and giving a no dampening pogo stick action too.

Definitely can't tune a hubmotor shock same as a pedal wheel.

I would say that poor suspension can definitely be worse than hardtail. But even tuned right, and with good shocks, it will not ride the same as hardtail. Like all engineering problems, you get two of three things you want, not all three.

That bike has frame geometry that I prefer least. I think the rocker style shock mounts help shitty shocks feel much better. Wouldn't be surprised if my piece of crap mongoose blackcomb actually has a better ride. Especially if that shock is blown.

 

[Ykick]

I have pretty much the same swingarm on my SuperV's and 'doesn't seem to flex much. I also have properly functioning Fox shocks and the rebound seems to keep things mostly under control.

Qualify your pivot bearings are not worn and tight - one of mine unscrewed itself which introduced some slop until I realized what was going on and tightened it back up.

 

[MadRhino]

Building FS, you need to do it worthwhile. Stiff frame adjusted to proper geometry, adequate weight distribution, and custom tuned suspension. If you can't do that, a hard tail will be a better ride.

For now, you can set your shock to minimal rebound and set the preload for your riding weight and min 30% sag. Shock tuning will improve the rebound control, but most shocks need a custom tuned damper valve to slow down rebound enough for the weight of a heavy hub. Riding fatter tires with lower air pressure will help too.

Fishtailing is a matter of swing arm and pivots stiffness, not much to do there unless it is only a matter of replacing worn out pivot bearings. Stiff swing arm construction is not found on so many bikes and symmetry has nothing to do with it. You need to build on a pro DH racing frame, or to improve yours by mod and welding.

 

[BarkMau]

Thanks for the input!
Time to figure things out. So far, not looking so good. It seems this shock does not have adjustable rebound.

 

[SHARKBITEATTACK]

Just an idea, maybe heavier weight oil would give you better damping?

 

[dogman dan]

Then that's the primary problem, in addition to possibly worn pivot. Is it a cheap pogo stick shock with a cover that makes it appear to be an air shock?

Best source I know for a shock that can fit old model frames is Chain Reaction Cycles in England. They ship fast to the USA. Other places just have shocks that are longer to fit more modern bikes.

 

[BarkMau]

Then that's the primary problem, in addition to possibly worn pivot. Is it a cheap pogo stick shock with a cover that makes it appear to be an air shock?

Best source I know for a shock that can fit old model frames is Chain Reaction Cycles in England. They ship fast to the USA. Other places just have shocks that are longer to fit more modern bikes.

Pivots look good to me, no play whatsoever. It is an actual air shock...holding pressure!

 

[dogman dan]

Start playing with how much air then I guess. Odd, no way to adjust the rebound though.

 

[MadRhino]

Air shocks are usually doing good with a hub motor, but you need one that has complete tuning options. Your old Float is outdated anyway. I have had some success with a Fox DHX 5 Air, Marzzo Rocco Air WC, and an X-Fusion. You may be lucky and find one at a good price on Pinkbike.

 

[BarkMau]

Thanx for the replies. It looks like my frame is not gonna do it, for that shock is proprietary. Oh well..

 

[Drunkskunk]

The Jekyll frame is great, but the shocks on those are 10 years out of date, and were never very good to begine with. Risse Racing makes a couple shocks that fit that frame. I don't know about there rebound control, though. Fox makes one, too.

And yeah, you problem sounds like a rebound issue. Your shock may work fine for human weights and speed, but add a bunch of unsprung weight at higher speed and the wheel is going to start bouncing without better rebound controll.

 

[BarkMau]

Air shocks are usually doing good with a hub motor, but you need one that has complete tuning options. Your old Float is outdated anyway. I have had some success with a Fox DHX 5 Air, Marzzo Rocco Air WC, and an X-Fusion. You may be lucky and find one at a good price on Pinkbike.

Do you think the Fox DHX 3.0 would work?

 

[cal3thousand]

Air shocks are usually doing good with a hub motor, but you need one that has complete tuning options. Your old Float is outdated anyway. I have had some success with a Fox DHX 5 Air, Marzzo Rocco Air WC, and an X-Fusion. You may be lucky and find one at a good price on Pinkbike.

Do you think the Fox DHX 3.0 would work?

That's the shock that came on my Norco VPS Six frame so I hope so :wink: But I'm under the suspicion that it might fall a little short. I haven't ridden the bike around yet, so I can't personally tell you yet.



To those with DH rig experience: What's the key measurement when trying to upgrade the shock. Eye to eye length?

 

[MadRhino]

...

To those with DH rig experience: What's the key measurement when trying to upgrade the shock. Eye to eye length?

Both eye-to-eye and displacement measurements are important. On an air shock the travel can be longer than the original, but an RC shock need to be a fit. Normally a shock description in inches will be (for eg.) 8.75 X 2.75 and must be replaced with a shock that has the same dimensions. This is even more important with progressive suspensions, for the difference of travel will affect progression curve and the tuning range will be limited. Never install a shock that has a shorter travel than the original.

 

[full-throttle]

Do you think the Fox DHX 3.0 would work?

No chance.
The shock on Jekyll '03 has one of eyelets in the middle of its body. All the shocks incl DHX have eyelets at the ends.

 

[bionicdan]

If you just liked the beefy look of the bike and still want speed (I see slick tyres so guess you do) I would just bolt a bar in place of the rear shock for now to save having to take all your gear off again.

Or It doesnt look too hard to make some sort of adapter to fit a more normal shock in place. It would need to be some sort of L shape legged device to cater for the longer shock eye to eye. Maybe some 10mm plate aluminium and some bolts.

I just fitted a van Rc fox coil shock with rebound and damping adjust and its so tunable for the mac motors weight. I ordered a 200x57 shock to replace my blown 190x50.

This raised my bike and sharpened the steering 3 fold giving me 6 inches of travel to match my 6 inch forks. Dont give up but you need to use your imagination a bit.

*people have made their own mounts to use normal shocks and one person has done as I would do and use two lock rings to insert a threaded coil over shock into the trunnion mount. But im dodgy ha ha

http://forums.mtbr.com/gt/schwinn-4-banger-straight-six-93415.html

You can buy trunnion plates with smaller threads for direct connection to a coil over shock but its meant for a gt lts and would need to get the dimensions of the width and diameter of the interfacing parts.

http://www.mountainbikecomponents.co.uk/items.asp?CategoryID=103&Name=GT+Lts+and+Sts+spares

 

[BarkMau]

Do you think the Fox DHX 3.0 would work?

No chance.
The shock on Jekyll '03 has one of eyelets in the middle of its body. All the shocks incl DHX have eyelets at the ends.

I meant, would the 3.0 be "tunable enough" for a rear DD hub? I am thinking my next build which is a FS long tail utility bike.

 

[BarkMau]

If you just liked the beefy look of the bike and still want speed (I see slick tyres so guess you do) I would just bolt a bar in place of the rear shock for now to save having to take all your gear off again.

Or It doesnt look too hard to make some sort of adapter to fit a more normal shock in place. It would need to be some sort of L shape legged device to cater for the longer shock eye to eye. Maybe some 10mm plate aluminium and some bolts.

I just fitted a van Rc fox coil shock with rebound and damping adjust and its so tunable for the mac motors weight. I ordered a 200x57 shock to replace my blown 190x50.

This raised my bike and sharpened the steering 3 fold giving me 6 inches of travel to match my 6 inch forks. Dont give up but you need to use your imagination a bit.

*people have made their own mounts to use normal shocks and one person has done as I would do and use two lock rings to insert a threaded coil over shock into the trunnion mount. But im dodgy ha ha

http://forums.mtbr.com/gt/schwinn-4-banger-straight-six-93415.html

You can buy trunnion plates with smaller threads for direct connection to a coil over shock but its meant for a gt lts and would need to get the dimensions of the width and diameter of the interfacing parts.

http://www.mountainbikecomponents.co.uk/items.asp?CategoryID=103&Name=GT+Lts+and+Sts+spares

I kinda lost interest on this one. Good bike, but can't rival the usefulness of a long tail and that's why I'm pursuing one...

 

[full-throttle]

I meant, would the 3.0 be "tunable enough" for a rear DD hub? I am thinking my next build which is a FS long tail utility bike.

I'd say no. It only has preload, LS rebound and boost valve pressure. Ideally you'd want LS and HS compression with a decent range. And even then it really depends on what you expect out of it.

 

[BarkMau]

Thanx!