E-bike / mountainbike suspension setup

[manitu]

I've often wondered if DownHill Bikes are really the best for a street EBike. The application seems so different. I'm running a hardtail now and it seems expansion strip bumps are the most violent loads encountered so far. (I've been able to avoid potholes). I like the idea of running motorcycle tires at low pressures as was discussed in the Deathrace thread however i would imagine the sidewall compliance would be too stiff.

Missed this one.

Downhil bikes for street riding: This is a bit outside my expertise , but I'll try to answer,
A tall, soft sprung , heavy bike with 8" of suspension does not seem ideal for street racing. however , when the speed gets higher , the slack head angle on Freeride and pre 2010 DH bikes really starts to shine. The newest fad in DH racing with less than 64degree Head angle and insanely low bottom bracket , I think are to extreme for decent road handling. I think a 6 inch freeride/all mountain bike with 66-67degree HA and a really high BB would be ideal. lower the fork by a inch and put in a shorter shock. Then you have bike wich is 2-4 pounds lighter , coupple inches lower CoG , and the same head angle as old DH bikes.

Just my thoughts on the subject. No hard sience in this post.

By the way , just added a setup guide for the Progressive Suspension's 5th element/Manitou Swinger shock to the links. The swinger was produced by Manitou under licence from Progressive suspension , so it's the same shock.
.manitu

[Ykick]

Thank you for the incredible resources! I shoulda mentioned this fork uses air valves on each leg and single rebound adjuster bottom RH leg. I narrowed it down to something called MX Pro AIR in 2004 and also 2005 manuals but the 2006 manual looks basically same.

I have some m/c fork seal experience so I understand how to proceed with simple services.

Fox videos are awesome and all your information is very helpful. If you hadn't mentioned English is not your native language, I wouldn't have guessed otherwise. You're an excellent student too!

Quite a pleasure, thanks again...

[manitu]

Oh , for kart track racing , a 4X bike might work well. It's basically 4" full sus bikes made for racing side by side on dirt tracks.
Low slung, fast bikes.

.manitu

[FMB42]

My favourite shock? Any custom tuned one with a proper high-speed shimstack.

Good stock shocks for off-road: Cane creek double barrel , 5th element/manitou swinger WITHOUT THE SPV!

I've had good luck with my 2006 Manitou air shock. This unit is still capable of accurately maintaining it's air pressure setting for weeks on end.

When it comes to forks , I'm a bit biased towards Marzocchi...

Ya, I had a pair of Marzocchi forks on a 1975 (and a 1/2) Bultaco 250 Pursang. This factory World Championship "replica" was one of the finest handling MX bikes that I ever owned. Marzocchi forks had a reputation for being "bullet-proof" even back then.

[torker]

I don't know how my rock shox Judy sl uturns stack up. I am sure they are entry level. They and the FSR Comp are the best equipment I have ever ridden. I can pretty much blast over anything on the street flatout now.

[manitu]

I promised to post this a couplr of days ago , but I've ben busy.
Unbeliveable how the workload goes trough the roof , when the puppies learn to walk!

Well , I promised you my procedure for adjusting suspension , and here it is.


Adjusting your suspension. First of all, sag and rebound should be adjusted before even hitting the trails.

Before starting , turn all compression dials to fully open (soft) and rebound about 1/3 in from fully open (fast) If your shock or fork has some sort of pedal platform damping as Fox' propedal , Manitou SPV or floodgate , turn it off. on manitou swinger use minimum spv pressure.

Sag should be about 20% for 80-100mm suspension , up to 35% for 180-200mm suspension.
With a off-road bike , you allways set sag while standing in your attack-position. For a road bike , you have to consider if you aproach the bumps you encounter in your rides sitting or standing. Use a zip-tie on your fork , and a o-ring on your air-shock. It's a bit more dificult with coil-shocks , you might just have to eyeball it. If you have a fox terralogic fork you have to stand in position up to half a minute , while the fork sinks into its sag.

Setting rebound: The easiest way to find a basic setting for rebound , is riding off a curb or a single step 2/3 of a foot to a foot high. Try to land as balanced as possible on both wheels. When you land , you should go down into the travel , then rebound ONCE, and stop. You should ideally rebound as fast as possible , without overshooting up and the down again. A gopro on slow-motion , or a friend with good eyes are invaluable when doing this.

Compression: Compression is a bit more difficult to set , as it highly depends on riding style and preferences ,wich controls you have on your shock , and the design of the suspension.
There is no easy test you can use to eyeball it , it's all about feel.

Fork: The goal on downhill bikes is to use as much suspension as possible without bottoming out on a certain track, but for general trail-riding , and for a e-bike doing higher speeds You could do with more compression to keep the wheel from getting airborne.

First , if you have low-speed compression , you use it to dial out brake-dive , and to get a stable feel when going over smooth, flowy terrain. I start fully open , and do a series of braking tests at about 10-15mph. I turn in the lo-speed dial two clicks between each brake test. until I dont feel a significant decrease of brake-dive. then I turn it out two clicks again and do another test. then I turn it one click in again. One of the three last positions usually feels best.

Find a square bump on a straight about 1/2 foot high. do a high speed run over it, starting with compression fully open. Between each run, you turn the compression (high speed if you have) two clicks in until you feel the force from the bump trough your handlebar starts to ramp up.

Now it's time to adjust the rear compression.

First , low speed compression , if you have. The idea here is to get a good balance with the front lo-speed compression. I just pump the bike up and down when riding slow (5mph) Sice you are done with the fork's lo-speed , and the rear lo-speed comp is fully open , the rear will be much softer than the front. adjust a couple of clicks in and try again. If the rear get firmer than the front , you back off a couple of clicks.


Then at last you find a nice berm , put a rock or a small log in the middle of the turn to make a half foot square bump. Then I go riding over it. If I feel the bump hard trough the handlebars or the saddle, reduce compression damping (high speed , if you have). If you feel a wheel skipping outwards in the turn , and changing my line , I use more compression damping (again , high speed if you have)on the wheel that skips.
It's important to find a nice wide berm , as it makes for a much easier recovery from skipping sideways over the bump.

A nice way to fine tune low-speed compression is to find a trail with wery flowy profile , where you go down into a mild compression. Here you will easily feel it ther is a imbalance between the front and the rear.
This is my basic procedure , but there are many more. I'll try to find some more and post up later.

.manitu

[amberwolf]

I was thinking about changing oil - do you know if I can start with ATF (auto transmission fluid) and see how that viscosity works? Do you know if ATF harms seals or anything?

I don't know what ATF might do to fork seals and stuff, but it's pretty corrosive to most plastics, epoxies, etc, that I have ever tried it on.

@manitu: this kind of info is very useful, and thanks for posting it!

I'm in the process of building a new cargo bike, and have had several ideas for rear suspension for it, including one of using an old Manitou Skareb (2005-ish?) fork as the rear shock and dampers, simply because I can air it up to increase the stiffness and decrease sag, when I have the bike loaded down vs empty. It's somewhere in this thread's beginning:
http://endless-sphere.com/forums/viewto ... 20&start=0
for the first ideas about that, though it has evolved since then. I don't yet know if the fork coudl even handle what I want to do with it, and I know it needs service (have found a few Manitou manuals online that I will eventually follow for doing this, if it is feasible).

If you happen to have any ideas on whether it might work (based more on the idea of using the fork semi-vertically over the rear dropouts, than horizontally, but with the basic frame design of the later pages), I'd be interested in them.

[fizzit]

Hey Manitu, I have a quick suspension question...

Is there any way to correct for going from a normal 2.75" travel fork to a triple-clamp 7" travel fork, or is it worthless to even try putting it on a bike?

[manitu]

@ykick: No you do absolutely not use ATF on a bike at all. You can use a 75w manual transmission oil in AIR CHAMBERS , but not as suspension oil..

@ amberwolf: Well , Idont know. The scareb is a light fork for XC racing. I think I would prefer a beefier fork.

You are putting the rear wheel on trailing arms. (chainstays) , and only using the forks as suspension/seatstay?
I would definatly not expose the fork in the rear to any sideloads.

But then again , this is far from my previous experience with suspension.


@ fizzit: No I wouldn't do that , the force on your headtube will increase significantly. Only way to correct would be going from 26 to 20 inch rim. (only in the front) And that would just correct for the head angle , the dual crown would still transfer more force to the headtube than a single crown.

.manitu

[amberwolf]

@ amberwolf: Well , Idont know. The scareb is a light fork for XC racing. I think I would prefer a beefier fork.

So would I, but this was basically free with the bike (which itself was apparently cobbled together badly from various other bike parts). The Trek frame it was on is now the front part of that new bike.

I'm sure there are other better ways to do this, too, but most of them cost a fair bit of money (like the Firestone 4001 series air-ride spring), and seem to only be available new (where my purpose is to recycle and reuse unwanted, broken or damaged things where possible).

You are putting the rear wheel on trailing arms. (chainstays) , and only using the forks as suspension/seatstay?
I would definatly not expose the fork in the rear to any sideloads.

Yes, tha'ts essentially it. I hadn't thought about sideloads but there should not be any AFAIK; that should all be taken by the arms/frame/pivot. The fork would just attach to the rear arms via pivot bearings clamped on the former dropouts, and the stem and/or crown would be clamped into whatever frame I end up with above and forward of that point.

But then again , this is far from my previous experience with suspension.

I kinda figured...I have never seen anyone else do this, probably for good reason, but possibly simply never thought of it.

[full-throttle]

Very impressive manitu!

There is one more thing. I would argue that is the most impotant aspect of rear suspension (especially when using hubmotors) - ignore it and your shock will eventually blow - oil volume.

DH shocks are designed for short (<10min) heats with long-ish breaks in-between, front-heavy weight distro and to be as light as possible. Just think of where all that energy dissipates when the compression damping is increased

[dogman]

That is one impressive thread I agree with.

Re the FSR, that's a crosscountry ride bike, which I think make the best street Ebikes. Not as much travel, but good for less pedal bob. The extreme shocks of DH bikes are not needed as much as a nice smooth ride across the cracks and smaller bumps common on the street. But it's still got the suspension you need when you discover a big fat speed bump, and happen to be going 35 mph.

For sure, Ebikes can wear the hell out of everything on a bike faster than designed for. Rear shocks, forks, rims. But nothing has lasted better for me than my current commuter. It's an old Giant DH bike. Tame by todays DH standards, but when you do need 5 inch travel on the rear wheel for a chuckhole you didn't see in time, it sure is nice. Even so, I'm on rear wheel number two and front fork two with about 5000 miles on the thing. The best thing about the bike is it's frame stiffness. The mongoose blackcombs have limp noodle frames by comparison. Even cheaper FS wallbikes are even worse.

[fizzit]

So triple crowns translate more force to the headtube than normal forks? I would think that it would be the other way around, so I am curious how that works. Does it mean that my headtube would be likely to snap, even for street riding?

[manitu]

About the FSR . The FSR Comp wich somebody mentioned earlier is a XC bike , yes. But FSR in itself is Specialized's name for the Horst Link , wich Horst Leitner patented in the early nineties. He was the first to design a bike suspension based on advanced brake and bump force calculations.
The FSR Demo 8 is defo not a XC Bike. I'll add some info on the different designs later.

Shock going hot.

Yeah , the shock heats up from hard riding , and harder compressions setting affects this too, but not to much , in my experience.
Only reasons I can come up with , is that when running harder compression settings , some of the force is distributed to tire, rim, and trough the saddle.

About the oil , yeah , more oil would be nice, to spread the heat , but you cannot just add more oil , you know. It will only lead to hydro-lock an loss of travel. You should ofcourse never use the shock with less oil than it is designed for. The trick of using different oil level is ONLY for those Marzocchi FORKS wich is designed for it. (and most motocross forks)

@ fizzit: Well , the total force transferred from the fork to the headtube is the same. But since a dual crown fork (or tripple clamped?) is much more rigid , and don't have the flex wich a single crown fork has between the fork legs and the steering tube (in the crown , that is) , the peak force will be higher. Just look down on the fork wile braking and you will see what I mean.

edit: Every frame has a max recomended axel to crown length. If you cant calculate the forces AND enshure yourself that the construction is suffient , NEVER exeed this. (by much , anyway)
.manitu

[fizzit]

Thanks for answering my dumb questions
So if I were to put too long of a fork on, I could be riding along and brake hard and due to the leverage, my head tube could snap off and I could die.

My bike is an old 1999 raleigh m7000, built from 7005 aluminum. It's pretty strong but I don't have a way to calculate the forces or anything like that, and I can't find any documentation on the maximum axle-crown length for it. If I adjusted the sag on the triple-crown fork so that it was 40% or so and the axle-crown was only increased by a couple of inches (right now it's at like 18" I think), would that be pushing it?

[manitu]

I dont think you would snap it from braking , but braking with a single crown fork , you clearly see the flex in the crown.
You most likely snap it on a hard landing or a square bump.

.manitu

[full-throttle]

Yeah , the shock heats up from hard riding , and harder compressions setting affects this too, but not to much , in my experience.

And how much experience have you had with running a 5+ kg hubmotor?

About the oil , yeah , more oil would be nice, to spread the heat , but you cannot just add more oil , you know. It will only lead to hydro-lock an loss of travel. You should ofcourse never use the shock with less oil than it is designed for. The trick of using different oil level is ONLY for those Marzocchi FORKS wich is designed for it. (and most motocross forks)

I didn't say oil level I said oil volume. Use a different shock full stop.

[manitu]

Yeah , the shock heats up from hard riding , and harder compressions setting affects this too, but not to much , in my experience.

And how much experience have you had with running a 5+ kg hubmotor?

About the oil , yeah , more oil would be nice, to spread the heat , but you cannot just add more oil , you know. It will only lead to hydro-lock an loss of travel. You should ofcourse never use the shock with less oil than it is designed for. The trick of using different oil level is ONLY for those Marzocchi FORKS wich is designed for it. (and most motocross forks)

I didn't say oil level I said oil volume. Use a different shock full stop.

No , No experience with hub motors, I got my experience on full suspension bikes and motorcycles. And yes you might be right , a proper Öhlins setup might be the way to go if you are really pushing it. Still , it does not heat up as much as calculated forces would imply. But yes it heats up.

Ahh. of course.. yes defenatly get a hi volume/ piggyback shock for off-road riding. Sorry , I misunderstood that one.

.manitu

[Ykick]

Manitu, thanks again for the great info - very helpful thread along with many of your other posts.

[geetarboy]

Just got back from my 1st test run w/ my "Rock Shox Tora 302" - OMG What a difference!!! It's AMAZING - I glide over potholes that used to give me a good jolt, The headshake I had disappeared so now I can ride 'no-hands' @ 35mph, It's 3 inches longer and heavier so it balances out my load better, and w/ the new "Avid BB7" disc brake - I can stop at least 3 times faster. IT'S LIKE A WHOLE NEW BIKE...

[hydro-one]

Thanks for the information on setting up suspension!! I am in the process of setting up the sus on my new "bullit" with 5th element , bombers, ht35. ill let you know how it works out!!


ps geeterboy, when you grow up you can graduate on to a real mans fork, but you are learning young grasshopper....

lol kidding man!!