Front suspension upgrade

Drivetrain upgrades, engine upgrades, or any other mods to gain speed or acceleration.

Moderator: Modsquad

User avatar
Oyabun
Frequent Poster
Frequent Poster
Posts: 640
Joined: Sun Jun 28, 2015 4:24 pm
Year: `12,`15,`19
Color: black&black
Location: Europe

Re: Front suspension upgrade

Post by Oyabun »

Mario wrote:Oyabun you got my attention ;)

Found this info on a application list from YSS
They speak of "265 + spacer / 15W / 195 / 35C"

265 must be the diameter 26.5mm / spacer?
15W fork oil thickness (how much?)
195 (maybe ml ?)
35C (don't know)
265 is the PD diameter, 15W indeed fork oil to me used, 195 - is in theory the level from the fork tube to fill with oil !without PD valves installed!, 35C is the outer diameter of the fork sliders - C meaning conventional (no upside down) fork.
Mario wrote: You speak of enlarging holes (than there is now way back!!) is this also necessary for my Forza 300?
That's correct. Once installed, the damping rods are modified so no direct way to go back. But trust me. You would not want to go back for sure. In case you want to sell the bike without the fork valves - best way is to order two factory new damping rods ($9.38 each from bikebandit) and reinstall everything with those.
Mario wrote: Is there a picture/video tutorial how to do this mod? (I never worked on front and rear suspensions)
Frankly I'm not too good in creating tutorials, as I like to work on things and usually don't have anybody around to document so I have done it based on the installation instructions linked. You can search for general work on conventional forks - the whole installation is different by enlarging the compression holes on the damping rod and installing the PD valves between the damping rod and the spring.
I can definitely send you the email flow what we have exchanged with Tom while he was doing his upgrade to help a bit. The whole upgrade can be done in 4 hours tops (I can do it in less than an hour by now as I had the front apart a few times)
Mario wrote: I am also planning to buy the rear YSS Shock Absorbers (like the Öhlins more but way to expensive o_O ) , I think there must be some balance between the front and rear suspensions??
Good thing. I love the Ohlins also, but the YSS ones are really good too.
The main difference between the two is that the YSS Forza specific dampers are only adjustable on spring preload - while the Ohlins ones can be adjusted for rebound and compression damping also. I have never ridden a forza 300 - their rear shocks seem to be a bit better quality than the 20 cent PCX ones.

Speaking of balance - most of the guys around have modified only their rear suspension and can live with it. Some has added stiffer springs at the front - without touching the damping at all. Which is helping to avoid bottoming out for heavier riders, but definitely not helping traction as the already very weak damping will not be able to control the stronger spring. So in my opinion the front upgrade is absolutely worth it - but it is often neglected.
User avatar
Mario
Regular User
Regular User
Posts: 221
Joined: Sun Jul 19, 2015 2:13 pm
Year: 2015
Color: White
Location: The Netherlands

Re: Front suspension upgrade

Post by Mario »

Oyabun wrote:
265 is the PD diameter, 15W indeed fork oil to me used, 195 - is in theory the level from the fork tube to fill with oil !without PD valves installed!, 35C is the outer diameter of the fork sliders - C meaning conventional (no upside down) fork.
The 195 means that you have to fill the fork tube with 195mm oil or 195ml oil?
Oyabun wrote:
That's correct. Once installed, the damping rods are modified so no direct way to go back. But trust me. You would not want to go back for sure. In case you want to sell the bike without the fork valves - best way is to order two factory new damping rods ($9.38 each from bikebandit) and reinstall everything with those.
Trust me, iff it works and the harsh shocks that I get now on bumps are gone I never go back ;)
How big must I drill out the existing holes?
Oyabun wrote:
Frankly I'm not too good in creating tutorials, as I like to work on things and usually don't have anybody around to document so I have done it based on the installation instructions linked. You can search for general work on conventional forks - the whole installation is different by enlarging the compression holes on the damping rod and installing the PD valves between the damping rod and the spring.
I can definitely send you the email flow what we have exchanged with Tom while he was doing his upgrade to help a bit. The whole upgrade can be done in 4 hours tops (I can do it in less than an hour by now as I had the front apart a few times)
I love to receive the emails you got from Tom, my email address marioderoos@gmail.com

Btw, you have a PM from me.
May the Forza be with you!!
tomtomclub2005
Regular User
Regular User
Posts: 207
Joined: Mon Aug 17, 2015 5:56 am
Year: 2014
Color: white
Location: Brussels

Re: Front suspension upgrade

Post by tomtomclub2005 »

Dag Mario,

I'm pretty sure the install procedure is the same as per PCX. As for which size of valve to use, available sizes of YSS PD valves can be seen in the pic i have posted above, and to get guidance on minimum diameter please head to the racetech website Oyabun has posted in the first post, which is quite exhaustive. If you can find a compatible valve and install them, you won't regret it.

* Edit* I've just seen answers have been posted meanwhile*
Reaper
Regular User
Regular User
Posts: 110
Joined: Mon Jun 16, 2014 4:20 am
Location: Siberia

Re: Front suspension upgrade

Post by Reaper »

Hello there!

I have to drill out 4 holes to 8mm size, right ?
tomtomclub2005
Regular User
Regular User
Posts: 207
Joined: Mon Aug 17, 2015 5:56 am
Year: 2014
Color: white
Location: Brussels

Re: Front suspension upgrade

Post by tomtomclub2005 »

Yes 8 mm is fine. Don't go overboard. Clean and deburr like a maniac...

Edit: only the bottom ones neare , don't touch the ones near where the valve sit ( visible in my pics)
tomtomclub2005
Regular User
Regular User
Posts: 207
Joined: Mon Aug 17, 2015 5:56 am
Year: 2014
Color: white
Location: Brussels

Re: Front suspension upgrade

Post by tomtomclub2005 »

..near the small end not "neare" as i wrote...
Reaper
Regular User
Regular User
Posts: 110
Joined: Mon Jun 16, 2014 4:20 am
Location: Siberia

Re: Front suspension upgrade

Post by Reaper »

Thank you! Clear that, will do ! I promise to provide a report and review of this product.
tomtomclub2005
Regular User
Regular User
Posts: 207
Joined: Mon Aug 17, 2015 5:56 am
Year: 2014
Color: white
Location: Brussels

Re: Front suspension upgrade

Post by tomtomclub2005 »

Reaper,

Before you start here is a quick tip Oyabun gave me which i found useful: Start with the pcx on its stand and loosen a bit the two bottom allens on each fork leg. just half turn or a turn will do. Then proceed to dismantle wheel and fork. It will be a lot easier to take the allen bolt that holds the damping rod after, no vice needed. Same thing for final torquing of these bolts when remounting, you can do them last.
Best,
Reaper
Regular User
Regular User
Posts: 110
Joined: Mon Jun 16, 2014 4:20 am
Location: Siberia

Re: Front suspension upgrade

Post by Reaper »

Thank you! I took them off and opened them already exactly this way, i have bought daytona 20% stiffer springs with oe height ( not lowered ones), but they didnt fit. The are made for the first generation pcx125, they are 1inch shorter and a little less in diameter.
Now, with the yss pd valves, i may select to go with preloaded OE springs or to go with 20% stiffer daytona springs, because they are shorter exactly for the valves height. What way to go? :)
tomtomclub2005
Regular User
Regular User
Posts: 207
Joined: Mon Aug 17, 2015 5:56 am
Year: 2014
Color: white
Location: Brussels

Re: Front suspension upgrade

Post by tomtomclub2005 »

I was facing the same question as you. ( but not the smaller diameter of springs o_O )

Ideally Test both according to your weight (and roads), i have harder springs too ( not Daytona) bought through the german pcx forum. They are shorther but not by 1 inch , more 0.2/0.3 inch. The valves will add about 0.8 inch. I have not measured the spring rate of these harder coils, nor did i make the comparison with stock + Valves yet-
Oyabun is using stock and is happy, i keep wondering if i should'nt revert to stock to try and squeeze the last drop of comfort. I should add the roads are incredibly bad here, cobblestones, pot holes, speed bumps all over the place, sometimes 5 of them in 150 meters!
What is your weight with gear? Do you ride solo/duo? What shocks do you have at the rear?

Now the fun begins because you adjust a few things :)
PS: Also use a 15W oil.
mrgizmow
Forum Benefactor
Forum Benefactor
Posts: 19
Joined: Sun Jun 12, 2016 1:28 am
Year: 2015
Color: black
Location: Northern California

Re: Front suspension upgrade

Post by mrgizmow »

Finished up my emulator install two weeks ago while it was raining. The Sun has been out for the last two days and the temperature is above freezing. A test ride seemed in order. At 68, I place more value on comfort than performance. Given the PCX is a bit short on both and 3 inches of travel is not much to work with, fork valves seemed a reasonable gamble. This thread inspired me to give the emulator valve a try. The process is pretty straightforward and does not involve a lot of money. Like the other posters, I purchased YSS units from Brooks Barn for around $100 (Euro's). Each of my new valves also had to be adjusted down from 4 turns to two. As well, a taper had to be ground into the face of my damper tube so my valves would properly seat. Used a tapered stone in my drill press (see picture). Adjusted my oil level to 70 cm from top and for whatever reason this process caused me lots of frustration. My scooter only has 600 miles on it. Fork oil was reused and the slight amount lost during the process was replaced with automatic transmission fluid (ATF). My PCX experience is minimal, but when new it did not take more than a ride around the block to make it clear, you did not want your tongue to spend much time between your teeth. :roll: After a 15 mile test with the valves in place, I find myself happy with the outcome. Might be inclined to play a bit more with oil level/air space in the fork tubes, but more testing is needed. Though silly, the tongue/teeth metaphor gives meaning to the sharp response of the stock front suspension. I would venture a guess that any/every vertical edge of 3/4" or more gets your attention. With the variable response of the YSS valves, much of the 'sharpness' from such impacts is muted. A shallow hole now feels more like a gradual depression or dip. Don't get me wrong, you won't imagine you're on an $8,000 touring scooter. I am pretty confident though, you will be thinking it was money well spent.
[img][IMG]http://i267.photobucket.com/albums/ii303/mrgizmow/IMG_0826_zpsxnbnr9sg.jpg[/img]/img]
mrgizmow
Forum Benefactor
Forum Benefactor
Posts: 19
Joined: Sun Jun 12, 2016 1:28 am
Year: 2015
Color: black
Location: Northern California

Re: Front suspension upgrade

Post by mrgizmow »

Here is another picture for seating the valve onto the damper rod. [Image[/url]Image
grambo
New Member
New Member
Posts: 3
Joined: Sat Mar 04, 2017 1:24 pm
Year: 2013
Color: black/red

Re: Front suspension upgrade

Post by grambo »

LOVE your front end work. I ordered what I am hoping is a SET (2) of valves from "http://www.brooksbarn.co.uk/YSS-238MM-P ... 1KYPC.aspx)" but the email receipt said I ordered '1' so I'm not sure if that is ONE valve, or ONE set :) I sent them an email to ask
User avatar
k2apache6.0
Forum Benefactor
Forum Benefactor
Posts: 507
Joined: Thu Apr 21, 2016 9:03 am
Year: 2013
Color: Red
Location: Fort Lauderdale, FL

Re: Front suspension upgrade

Post by k2apache6.0 »

grambo wrote:LOVE your front end work. I ordered what I am hoping is a SET (2) of valves from "http://www.brooksbarn.co.uk/YSS-238MM-P ... 1KYPC.aspx)" but the email receipt said I ordered '1' so I'm not sure if that is ONE valve, or ONE set :) I sent them an email to ask
Relax, its one set (2 emulators) I found 2 turns in good for me at 190lbs, go by your weight and driving style and whether potholes roads are a frequent issue. For most riders 1 or 2 turns in is in the ballpark
Attachments
pcx trusty final.png
pcx trusty final.png (1.2 MiB) Viewed 9651 times
My PCX mod build here..
http://www.hondapcx.org/viewtopic.php?f=7&t=7113
ScottDR
Forum Benefactor
Forum Benefactor
Posts: 313
Joined: Tue Jun 14, 2016 9:37 pm
Year: 2013
Color: Black
Location: Kitchener, ON Canada

Re: Front suspension upgrade

Post by ScottDR »

Thread revival time!

So I have YSS PD valves on the way. Already bought YSS upgraded springs. Now I'm stuck between a rock and a hard place. OE springs and 15W oil and 2 turns on valves or upgraded springs 15W and 1.5 turns? I weigh about 85KG and on occasion ride 2 up. I'm aiming for comfort and less static and braking sag. I already installed the rear YSS XL preload adjustable only shocks and like the improvement.

I just want to do fronts once as I don't have a shop.

Thanks!
ImageImageImage
2013 Black PCX 150
Mods/accessories:
Honda tall windshield, Honda top box, NCY variator and face with 13gram rollers, LED headlamps & taillight with, Backoff indicator
Kawell rectangular lights-fork, mounted
Cheeky Seats seat cover (de-humped), YSS PDC and front spring upgrade 15W fork fluid, YSS rear spring/damper upgrade-preload adjustable only, lots of reflective tape and other accessories


Previously owned:
1969 Honda K50 mini trail (first bike, still runs great and in the family)
1975 Honda CB125
1978 Yamaha DT400 (bored 2 stroke insanity)
1986 Kawasaki Ninja 250r
User avatar
Oyabun
Frequent Poster
Frequent Poster
Posts: 640
Joined: Sun Jun 28, 2015 4:24 pm
Year: `12,`15,`19
Color: black&black
Location: Europe

Front suspension setup

Post by Oyabun »

Scott,
Good direction. If you'll get the yss fork springs in hand, please measure spring wire diameter, total length - and in case it is dual wound spring as the stock, the number of coils and length of the separately wound sections. A picture could help too. Based on that info, I can calculate spring rates for your new spring to be able to aid better with the setup.

In order get the suspension parts set, you have to understand how they are working.

Springs are storing energy, and supporting the bike and rider. The oem dual rate springs are weaker (about 4,5N/mm) for most of the travel, and get significantly stronger (about 7N/mm) for the last 15mm of the travel to avid hard bottoming (it will be still hard). There's also a second spring on your forks - an air spring. Depending on the fluid level in the fork, the last part of the stroke hardens up progressively as the air is compressed in the forks. Keep in mind, that increasing preload on the forks, will keep the same spring rates, but will start to use the sptonger part of the spring sooner.

Damping is to slow down the suspension and to keep it connected to the road - despite the irregularities and "springing" kickback nature of the spring. Any suspension has two ways of damping - compression and rebound. The emulators will take over damping only on the compression stroke of the forks - rebound will stay the same as stock. Which is a reasonable compromise - as while compression damping has wide range of changes, rebound is relatively simple as it only has to compensate for the force of the spring recoil.
As compression forces have wide variety, we usually differentiate them to low (it is low suspension speed, not related to vehicle speed) and high speed suspension action. Low speed compression damping like braking, cornering etc. is regulated with a small bleed hole on the emulator, while high speed (e.g. fast suspension action caused jolts and bumps on the road) is governed by the preloaded small spring letting the emulator's cap opening. The difficulty of damping is that one wants a digressive damping profile - relatively firm on small stuff, and soft(er) on big bumps.

Setting options on these forks are:
- setting spring preload of the main spring (it will not change spring rate of the spring, but set the sag to the right level)
- altering oil level for adding or removing air spring action at the end of the stroke
- adjusting slow speed compression and rebound damping by changing fork fluid viscosity (thinner is less damping thicker for more damping)
- manipulating the high speed compression by the small spring preload of the cartriges.

To try the above making sense, let's see suspension action difference between a weaker and harder fork spring.
weaker OE springs. Adding emulators equals to the same amount of preload to the fork springs. They'll have still relatively low spring rate so need quite a bit of low speed damping to support them in cornering or during braking. However you want to have a bit more than oem but still moderate rebound damping (weak springs don't need too much rebund) and fairly low amount of high speed compression damping to balance between subte suspension action and avoiding blowing through the full suspension travel too quick due the soft spring.
Stronger aftermarket spring: My aftermarket springs are shorter than OE, so they have minimal preload after the emulators installed. This means that without preload the initial action is softer, but by the end of the travel it reaches the same force as the weaker spring with preload. Due the higher spring rate it needs less support on the slow compression stroke (both on low speed and high speed Comp), however it needs more damping on the rebound stroke to compensate for the spring.

Setting suspension starts with setting sag.
- You want to have about 30% sag of total travel on the front and about 25% at the rear. Adding preload will raise, removing (if applicable) will lower the suspension in the stroke. In case in doubt, just google for setting motorcycle suspension sag (eg. Racetech has a great article on the topic).
- Next step is rebound. As per above you can only set rebound by the fork oil viscosity. For the OEM springs I'd use 15w (or even mixing 15w and 10w fork oil from the same product line in 1:1 to get to 12.5) for subtle action. For stronger aftermarket springs i'd use 15w or 17.5w (potentially 20w depending on your preference) to provide more rebound damping. Sadly using thicker fluid will raise low speed damping too, which would not needed with the stronger spring, but it is not a big issue - will lead to less dive during braking.
- Last is high speed damping. For OE springs I'd use 2 turns in on the emulators. As both thicker fluid and stronger springs are supporting the forks on compression stroke, I'd use max much less preload here than on OE springs - 1.5 (or better 1.2 turns) on the emulators for stronger springs.

Finally - a scooter has a weird balance and center of gravity - so adding luggage or a pillion (above or behind the rear axle) has almost no impact on front suspension setup.

It got a bit too long, but hope it helps.
User avatar
Oyabun
Frequent Poster
Frequent Poster
Posts: 640
Joined: Sun Jun 28, 2015 4:24 pm
Year: `12,`15,`19
Color: black&black
Location: Europe

Analysis of spring options

Post by Oyabun »

While our bikes have simple suspension and relatively short suspension travel, we don't have to suffer. Installing emulators, and later a stronger aftermarket spring helped a lot, but I'm still not satisfied. Sportbikes traditionally also have short suspension travel (despite their higher than PCX weight) in the range of 100-120 mm, but they are still much better.

After sorting my CB500x's suspension (making a one-off cartridge insert with increased travel and externally adjustable preload, compression and damping - I thought I'll give another run to the PCX boinkers.

I'm thinking about experimenting with weight matched linear wound springs. Such linear springs are used in aftermarket, as well as in race bikes, dirt bikes and anywhere where rider weight is known and better suspension action is needed. In theory they'll need minimal preload to set right sag, softer initial action (read compared to a spring which already has 20mm preload), firmer mid range and would be able avoid the big change in spring rate at the end of the travel.

Too good to be true eh? So why manufacturers don't use linear springs? All major manufacturers use dual rate springs to minimise production costs and sell the same bike to all sizes of riders. So they save a pretty penny, and they don't have to have stocks of 4-5 spring rates depending on rider weight.

You can see the analysis on the attached JPG. Colored lines are spring forces [N] vs. Suspension travel [cm]. Also displayed usable travel and "feel" represented by equally colored range arrows.
Spring rate.JPG
Blue line is stock spring: With approx 5mm preload (this is the stock amount dialed in by installing the fork cap) by reaching 10mm of travel a single spring accumulated 68N of force. So compressing it further, it requires additional 46N every 10mm until reaching approximately 80mm travel (80% on the PCXs 100mm total front travel) where it suddenly becomes stiffer - requiring 69N to compress it further by every 10mm.
While the stock spring is quite well designed for a standard Asian male of 65kg or 140 lbs, it is way underperforming for a heavier rider. Due the weight difference the forks will start their initial action too deep in the stroke, and all is left is often less than half of the total possible travel. Initial action is comfortable (due to low spring rate), but they are blowing through the rest of the short stroke too fast reaching the last 20mms with higher spring rate and eventually the bump stop. Such a high change in spring rate, not to mention reaching a hard stop at the end is highly noticeable to say at least.

Installing emulators on the OEM springs increases preload by ~20mm for a total of 25mm (Gray line). It will provide better sag, so the suspension works better in the stroke, but still blows through the mid section and get to the much stronger part very early. This mod almost completely eliminates the bottoming of the forks, but it has a significant trade-off of a pronouncedly different suspension feel between the first 60% and the final 40% of the travel. Also the same damping force what is dialed in for the first part will be completely out for the rest or vica versa.

Stronger than stock linear springs (orange line) which I plan to use - will have softer initial action, firmer mid section to keep the suspension more in the usable range, and a liner but slightly softer action at the end of the stroke - which can be compensated by filling a bit more fork oil to achieve more air spring action if needed.
User avatar
GeorgeSK
Forum Benefactor
Forum Benefactor
Posts: 986
Joined: Thu Jun 27, 2013 9:36 pm
Year: 13PCX,15Forza
Color: Both Red
Location: Danvers MA USA

Re: Front suspension upgrade

Post by GeorgeSK »

Your post(s) may be long, but they are the best explanation of how the front shocks do their deed that I have ever read. I'm not sure I will ever dive in to improve the fronts, but I am certainly bookmarking this post. Thank you very much for your time and expertise.
On my scoot, getting there is WAY more than half the fun!

Please paste this address into a new tab and add yourself to the map: https://www.google.com/maps/d/edit?mid=1NlP7xk7KMdJReQnm-iDhldFBdpQ&ll=4.995760578398276%2C0&z=2
but please, don't delete anybody, no matter how badly they deserve deleting :)
User avatar
Oyabun
Frequent Poster
Frequent Poster
Posts: 640
Joined: Sun Jun 28, 2015 4:24 pm
Year: `12,`15,`19
Color: black&black
Location: Europe

Re: Front suspension upgrade

Post by Oyabun »

Thank you George.

For some reason the picture I've made is not showing up for me in my the last post, so I'm reposting to see if it will work.

Admins, please if you can somehow get that post straight I'd be really thankful.

You can see the analysis on the attached JPG. Colored lines are spring forces [N] vs. Suspension travel [cm]. Also displayed usable travel and "feel" represented by equally colored range arrows.

Attachment:
Spring rate.JPG
Spring rate.JPG (40.92 KiB) Viewed 8978 times
Blue line is stock spring: With approx 5mm preload (this is the stock amount dialed in by installing the fork cap) by reaching 10mm of travel a single spring accumulated 68N of force. So compressing it further, it requires additional 46N every 10mm until reaching approximately 80mm travel (80% on the PCXs 100mm total front travel) where it suddenly becomes stiffer - requiring 69N to compress it further by every 10mm.
While the stock spring is quite well designed for a standard Asian male of 65kg or 140 lbs, it is way underperforming for a heavier rider. Due the weight difference the forks will start their initial action too deep in the stroke, and all is left is often less than half of the total possible travel. Initial action is comfortable (due to low spring rate), but they are blowing through the rest of the short stroke too fast reaching the last 20mms with higher spring rate and eventually the bump stop. Such a high change in spring rate, not to mention reaching a hard stop at the end is highly noticeable to say at least.

Installing emulators on the OEM springs increases preload by ~20mm for a total of 25mm (Gray line). It will provide better sag, so the suspension works better in the stroke, but still blows through the mid section and get to the much stronger part very early. This mod almost completely eliminates the bottoming of the forks, but it has a significant trade-off of a pronouncedly different suspension feel between the first 60% and the final 40% of the travel. Also the same damping force what is dialed in for the first part will be completely out for the rest or vica versa.

Stronger than stock linear springs (orange line) which I plan to use - will have softer initial action, firmer mid section to keep the suspension more in the usable range, and a linear but slightly softer action at the end of the stroke - which can be compensated by filling a bit more fork oil to achieve more air spring action if needed.
ScottDR
Forum Benefactor
Forum Benefactor
Posts: 313
Joined: Tue Jun 14, 2016 9:37 pm
Year: 2013
Color: Black
Location: Kitchener, ON Canada

Re: Front suspension upgrade

Post by ScottDR »

Oyabun, I can't thank you enough. My experience is with linear rate car springs and rebound only adjustable dampers. Used to visit road courses all over. But comfort an effective suspension is the goal on the PCX.

Anyway, dimensions are:

OAL 263MM
ID 15.35MM
OD 22.86MM
Wire thickness 3.57MM

Variable rate. Close coils are:
OAL 82MM and are spaced at 2.08MM average.

Wider spaced coils are OAL 183MM spaced at 7.03MM average.
ImageImageImage
2013 Black PCX 150
Mods/accessories:
Honda tall windshield, Honda top box, NCY variator and face with 13gram rollers, LED headlamps & taillight with, Backoff indicator
Kawell rectangular lights-fork, mounted
Cheeky Seats seat cover (de-humped), YSS PDC and front spring upgrade 15W fork fluid, YSS rear spring/damper upgrade-preload adjustable only, lots of reflective tape and other accessories


Previously owned:
1969 Honda K50 mini trail (first bike, still runs great and in the family)
1975 Honda CB125
1978 Yamaha DT400 (bored 2 stroke insanity)
1986 Kawasaki Ninja 250r
Post Reply