E-bike / mountainbike suspension setup

[manitu]

When the question about proper suspension setup on electrifified MTB's came up in the stealth owners thread , I realized that there's not much info here about suspension. (wich i can find , anyway)

So I've decided to make my first contribution to the forum, A suspension setup thread.

First , the basics. The spring and the shock has two different jobs to do.
The spring's job is to carry the weight of you and the bike , + to push the wheel out again , after a hit.
The shock's job is to control the wheel movement when riding rough terrain.
The compression cartridge controls the force needed to control the compression of the shock/fork, and the rebound sets the speed wich it extends at.

You can never correct for a heavy hub-motor with a firmer spring , it will only give you less sag , and make the shock/fork top out.

Setting sag.
XC bikes use 20-25% sag while DH bikes use 30-35% sag . I Think these are good values for on-road and offroad e-bikes.
The sag is adjusted with you standing on the bike in attack position for a off-road bike , sitting for a road bike.
If you can't get the correct sag , you will need a firmer or softer spring. On air-shocks , adjust the main chamber pressure.

Setting rebound.
Rebound controls the speed wich the wheel extends at after a hit. It works against the spring , to slow down the wheel on its way down , to avoid the bike feeling like a pogo-stick. on DH/freeride bikes you set it as fast as possible , without overshooting. if you get top-outs , you have to little rebound damping.
The amount of rebound your shock/fork must have is dictated by the spring. While you may have to use a firmer spring than standard , rebound should be in the range of the adjustments.

Setting compression.
Compression damping have to cope with two tasks , wich isn't allways compatible. When you jump , it must stop the suspension from bottoming out violently.
I dont imagine too many e-bikers doing 6 feet jumps to flat , so I will no get too detailed here.
The other task is a bit more difficult. The compession damping must keep your wheels to the ground , while driving over bumps and potholes.
When you hit a bump , the unsprung weight will be accelrated upwards , and the compression damping must stop the wheel from leaving the ground.
Here we easily see the problem with hub-motors. The unsprung weight at the wheel can easily be 6 times as much with a hub motor, as it used to be.
Few shocks will cope with the extra weight without modification.

Modifications.

Oil.
MTB suspension usually use a suspension oil between 5wt and 10wt. You can get oil up to 25wt, and with most brands you can mix different oil weights to get the one you need. However , since most forks and all shocks use the same oil for rebound and compression damping , there are limits to how heavy oil you can use. (this is one reason why I love my marzocchi forks. Most Marz forks have the rebound in one leg , compression in the other) But as long as you don't have the rebound at the fastest setting , the first thing to do is to experiment with the oil.

Custom tune.
Lets face it, nothing beats a custom tune.
The guys at push factories (US) and tftuned (UK) can do magic with your suspension. (se links section)
they don't service all brands , so you might be out of luck. You might call them anyway , they will tell you wich shocks that will work for your application.
For forks , you have avalanche racing , wich makes dual and tripple shimmed cartridges wich fits inside a lot of forks.

Well , let the discussion begin! I'll update this post with the important bits as the thread develops. All links will be in post nr.2

One thing. English is not my first language , so please PM me if corrections is in order.

.manitu

[manitu]

LINKS

5th element/manitou swinger manuals http://www.progressivesuspension.com/literature5thelement.html
Avalanche Downhill racing http://www.avalanchedownhillracing.com/
Fox service videos http://www.foxracingshox.com/fox_tech_center/service_videos.htm
Fox user manuals http://www.foxracingshox.com/fox_tech_center/manuals.htm#bike
Fox thecnical website http://service.foxracingshox.com/consumers/FOXDisclaimerUserChoice.htm
Fox DHx and ROCO WC rebuild http://www.mediafire.com/?sharekey=7facf2b496331f13d2db6fb9a8902bda
Marzocchi service info http://www.windwave.co.uk/documents/techinfo/marzocchitechinfo.html
Marzocchi <2006 manuals http://my-sport.spb.ru/manual_1/index-16.htm
Marzocchi 2006 shop manuals http://www.wheresweyland.com/mountain_biking/110/2006_marzocchi_service_manuals/
Push Industries http://www.pushindustries.com
TF Tuned suspension http://www.tftunedshox.com/

[adrian_sm]

Awesome contribution. Thanks for taking the time to do this.

Okay now the question.

. The compession damping must keep your wheels to the ground , while driving over bumps and potholes.
When you hit a bump , the unsprung weight will be accelrated upwards , and the compression damping must stop the wheel from leaving the ground.
Here we easily see the problem with hub-motors. The unsprung weight at the wheel can easily be 6 times as much with a hub motor, as it used to be.
Few shocks will cope with the extra weight without modification.

So this is when the wheel is still rising, the shock is still compressing, but the ground is no longer rising as fast? Since if the ground is still accelerating up, the wheel will have no problem staying in contact. it is only if the ground is rising, but starting to flatten off. I think....

Because as soon as the shock starts extending again, that is rebound dampening, right?

[manitu]

question:.

. The compession damping must keep your wheels to the ground , while driving over bumps and potholes.
When you hit a bump , the unsprung weight will be accelrated upwards , and the compression damping must stop the wheel from leaving the ground.
Here we easily see the problem with hub-motors. The unsprung weight at the wheel can easily be 6 times as much with a hub motor, as it used to be.
Few shocks will cope with the extra weight without modification.

So this is when the wheel is still rising, the shock is still compressing, but the ground is no longer rising as fast? Since if the ground is still accelerating up, the wheel will have no problem staying in contact. it is only if the ground is rising, but starting to flatten off. I think....

Because as soon as the shock starts extending again, that is rebound dampening, right?

Yes , this is mostly correct. Since the wheel is 5-6 times heavier than it used to be , it carries much more momentum and it takes a much bigger force to prevent it from leaving the ground , and bottom out. If you have really soft compression , the wheel might not even follow the rising ground , but get thrown into the air by the first part of the bump.

.manitu

[Jethro56]

Manitu: Great post! Your command of the English language is impressive. 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.

[FMB42]

Great post manito.

One of the biggest problems with bicycle suspension systems is that the average rider out weights the bike by a large margin. This, coupled with the various rider positions, can make proper suspension tuning troublesome.

Another difficult factor facing hub motor ebike suspension systems is the un-sprung weight of the hub motor/wheel assembly. This hub motor/ un-sprung weight often runs at 10-15lbs. which makes up as much as 15-20% of the total bike weight (less rider). The result is that the hub motor/wheel un-sprung inertial mass can, at times, exceed the weight of the bike itself.

[kfong]

Great post, this is the problem I'm starting to realize with my BMC motor in the trails, way too much unsprung weight in the back. I will see if I can try tuning it better.

[Ykick]

Great thread, just what I've been dealing with - thank you!

I lucked into a nice SuperV outfitted with Marrzochi Bomber fork and Fox float shock. 'think it's adjusted pretty good for street but the forks exhibit some stiction. 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? Motorcycle fork oil okay?

Bomber forks

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The Fox shock is great but with my 225lbs I've got it pumped up to over 250psi. Being electric I really don't need the "float" setting so I'm wondering if I might be better off installing a quality coil over shock with hydro dampening/rebound adjustment? Your thoughts please?

Fox float shock

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This bike rides so nice - floats over roughest road. 12S2P most days, probably around 60lbs ready to roll...

Ykick commuter

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[geetarboy]

Thanks Manitu, I am in the process of upgrading to a disc brake up front. In order to do so I have to change the fork to one that accepts a caliper. Even with dual suspension, hitting a pothole at 35+ mph can be scary. My current fork - Rock Shox Indy C - has 60mm max travel, the new one - Rock Shox Tora 302 has 85-130mm. I am hoping this makes a big difference in the ride as well as being able to stop faster. I have never tried to adjust the settings on my suspension, it's gonna be an adventure.

[RWP]

Fabulous post! Thank you.

For those on the west coast:
CR1 Engineering Services -- http://www.cr1engineering.com/index.php

[manitu]

@ FMB: Yes , the increase in unsprung mass at the end where you you put the motor is the largest problem with hub motors IMO. But the Rider to bike weight ratio on the other hand , can be both a problem or an advantage. You can to a large degree change the suspension response after the terrain. Like moving back on the saddle when hitting a bump at high speed , to to counteract the weight of the hub accelrating upwards (if your motor is at the rear , that is) . On the other hand , If this happens in a fast turn , where you need all the traction the front wheel kan get ,it's another thing. You can still find the correct balance point wher none of the wheels loses traction , or both skips by the same amount , but the margins are much smaller.

@ ykick:
Marzocchi MX air or coil? do you know wich year it's from? generally , if it has a air valve on top of one leg , its a air spring , if it got valves on both , or on none , its a coil spring . the air on those is for spring preload / sag adjustment. This is most likely a ssv damper. it has an internal rebound adjuster , and you can tune the compression with different oil weight. the bottom out is adjusted with how much oil you fill it with. oil on the MIN mark= linear stroke , no bottom out damping. Oil at the MAX mark= progressive , heavy bottom out damping. Find out what year it is and I'll find the manual on pdf.


Wow! what year is that? Is it a Float RP or RP2 ? That must be the oldest float shock I've seen. I.ll need to check my books for that one , but The newer floats have a nitrogen filled core , wich is hard to service yourself. The thing you can and should do yourself is a air sleeve service.You should have a "Fox float air seal kit" in case something needs replacing.
Procedure:
First thing TAKE ALL AIR OUT OF THE SHOCK!!
You basically put the end of the shock , wich now points forward on the bike , in a soft jaw wise , with the frame bushings still in the shock. The bushings in the other end you'll have to remove. Put a rag trough the hole where the bushings were. This is to stop the air can (the black part)from flying off the shock , if there's air trapped in the negative chamber.
now , you can unscrew the aircan from the shock, turning it counter clockvise , when looking at the wise with the shock toward you. It can be pretty tight , but you should be able to unscrew it with your hands. Now , it might come off with a bang when you reach the end of the threads , most of the times it gently slides off. Now remove the rag , and clean the air sleeve and the piston assembly. Inspect the seals you can see. There's a lot of seals , so look carefully.
When everything looks OK , it's time to put it back together again.first lube all seals with fox float fluid (basically a overpriced 75w manual transmission oil).
Slide the air chamber carefully back on the shock , taking kare not to dirupt the seal in the bottom of the air chamber. push it on util the piston allmost goes in to the air chamber. put one or two ml with gear oil under the piston, push the air chamber over the piston , and add 5ml of gear oil on top of the piston. it takes a bit of effort to reach the threads ,but when you do , you are finished. Now: NEVER USE GEAR OIL IN FORKS OR SHOCK DAMPER INTERNALS!! ONLY IN AIR SPRING CHAMBERS! Dampers need proper motorcycle fork oil.

You have rebound damping , thats the small red wheel right in front of the swing-arm bushings. The blue lever is the "pro pedal" a kind of compression adjuster.
I'll add some stuff about adjusting them later tonight.

@ geetarboy. The tora is a strong fork , wit cro-mo upper legs , and magnesium lowers. if your old fork had 60mm susp , I would'nt use all 130mm on the Tora , Your head tube might not take the stress. 100 should be ok but dont take my word for it. The Tora can be had with two different dampers , the 318 has a cartridge called "Motion Control" wish works suprisingly well for a budget fork. The cheaper ones (lower numbers) have a "turnkey" cartridge , wich works OK , but the adjustments don't do much. The 302 could have both. Tip: the tora , recon and reba forks are basically the same design , but different materials and internals. Lots of interchangeable parts.

.manitu

[Ykick]

Thank you Manitu! 'sure didn't intend to work you this hard but so much great info and detail - I can't thank you enough!

I also found some PDF manuals and it looks like this fork is likely 2004 MX Pro AiR. It holds pressure great and feels pretty good just kinda sticks after sitting so I figure new oil? Your input about viscosity is most helpful.

The Fox is a FOAT RL. It may be quite old but still working good and holds air great too. Will definitely copy/paste your detailed rebuild instructions into a Marzocchi folder. Quite nice, thank you for sharing your expertise!

Would you make any suggestion about good but reasonably priced coil-over spring/shock for this bike or best just stick with Fox FLOAT RL? Feels really good so far but worried I might break it as a daily rider...

best

[manitu]

Post nr 2 updated with Fox and Marzocchi manuals.

@ykick: No problem . I'm sitting at home , watcing over my dog and her one week old pup. Not much else to do.
I could not positively identify your fork , would need a bit more data for that , like if there are any external adjusters and how many air valves placed where.
Some Marz forks are named "Air" even if they're coil sprung , because of the air preload. You got the motor in the rear wheel , I would just change the oil to standard, 7,5w on most Marz forks. If you had the motor in the front hub , I'd use 10w , or even 12,5w in the compression leg , standard in the rebound leg.
The Marzocchi forks are easy to service , once you have it open , you'll find the right manual in post 2, no doubt. Before you start , put some clean paper on your workbench. Then put every part you remove in order on the bench , one row for each leg. REMEMBER TO CHECK TORQUE SPECS , AND USE A TORQUE WRENCH WHEN ASSEMBLING , aluminum parts easily snaps if you are too heavy-handed.

If you look in post 2, there's a link to "Fox service videos". There , you'll find a great video/presentation of the Float air sleeve service.
Float RL? have not worked on tha model , but the Float shocks are generally decent shocks for road riding and moderate off-road use. Unless you're trying to set speedrecords onroad or riding hard offroad , I would just keep the float as long as you think it feels good. The only downside with it is the lack of compression adjustement. Push industries can do a custom tune , I think it's about 150$ with a full service including oil change and a nitrogen refill. You might not feel it's worth it. If you go road racing or hard off-road riding , its defo worth it.

I'll write a bit about comp & rebound adjusting procedures , but it will have to wait until tomorrow.

.manitu

[kfong]

Thanks for the info and look forward to the rest. I want to eventually upgrade to higher end shocks and reading about them gives me better insight on what to get next. What are some of your favorite shocks.

[manitu]

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

Good stock shocks for off-road: Cane creek double barrel , 5th element/manitou swinger WITHOUT THE SPV! , Fox dhx air is a good one for lighter riders. I've just tested the Fox rc4 , and it feels like a killer shock. I'll have to test that one more. I have'nt tested the Rockshox shocks much , not many bikes here use them, but newer rockshox forks are decent stuff. I've got a lyrik u-turn wich I love. good adjusters , high-speed compression shimstack and allmost as easy as a Marzocchi to service. So their shocks should be decent too. I know the first models of the monarch had problems with air-seals.

When it comes to forks , I'm a bit biased towards Marzocchi , as I guess people have noticed. They are a bit heavy , but even the cheapest models of their coil sprung off-road forks with no external adjusters can be tuned to a great degree , it just takes time.
Too soft compression ? heavier oil in the comp leg. To much rebound damping? lighter oil in the rebound leg. Wont use all travel , take out a few ml of oil. bottoms out ? add a bit more.
A reputation for being bomb-proof does'nt hurt either.
As stated above: Newer rockshox= good stuff.
I'm no fan of fox forks though.. Killer performance , but a PITA to service. Just look at the talas service video in "fox service videos" , post 2 . and thats just the regular service , not the full service.
if you're racing seriously and have a mechanic , they're the great.

.manitu

[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.