Front suspension upgrade

[ScottDR]

Here are pictures. The package was labeled '15 PCX. Sure hope that is correct! My PD valves arrived today and appear to be correct at 23.8MM.

[ScottDR]

More... Hard to edit on phone and keep track of each! And do I still open the larger holes to 8MM?

[tomtomclub2005]

Constant spring rates is what Race tech (inventors of emulators) are recommending once you install the valves. However that is for motorbikes with proper forks, can get away with it in a scooter with short forks and limited travel? I doubt it...
Where can we find made to measure springs in Europe for a reasonable price? I have long been wondering to change the springs on my YSS rear shocks which are really only comfortable with two up (L size) , otherwise too hard.

[Oyabun]

Thanks for the pictures. It seems to get interesting.

The spring on the pictures is significantly stronger than the original, and also has the crossover point at a different location.

Spring rate _YSS.JPG (41.98 KiB) Viewed 4797 times

The new line is drawn with brighter orange.

A quick rundown comparison with the OEM, all in mm
OEM YSS
initial spring rate 4,55 6,4 +32%
secondary spring rate 6,9 10,8 +56%!
Total length 290 263 -27mm
Crossover w/o preload 85 70
Max. force @100mm 523N 855N +63%
What the above means:
Yss seems to have done the basic math creating this spring. It has ~25-27mm less total length, so installing the PD valve does not put extra preload in the forks.
This spring will require significantly less preload, and initial suspension action should feel similar to the stock spring. 6mm preload of the will produce roughly the same sag numbers as the oem spring @25mm.
On the other hand, it changes to a much stronger spring rate fairly early even with less preload, so about 40% of usable travel will be firmer than stock, then 60% almost fairly strong.
In short, the good news is that your front forks will most probably never bottom out. On the other hand the new spring will make your ride rather sporty than comfortable.

It is also a bit difficult to create good damping for such significantly different spring rates.
As you cannot change valving on the stock damping rods (well, in theory you could close up the existing rebound hole and redrill a smaller one, but without a shop I would not go into that) the only way to change rebound damping is to use thicker oil. with such a high spring force I'd go for the 20w oil, and not more than 1.5 turns preload on the fork valve.
Use slightly less oil in the forks, to have less air spring effect. fork oil is metered by filling and bleeding the forks, collapse the fork completely without the spring, and filling it to a specific level from the top of the stanchion. I have the original values here in the site somewhere, but from memory I recall something around 173mm. I'd use slightly 5-7mm less than that.

As a last sanity check, could you please measure sag figures on your PCX before the modifications? Measuring the sag figure of your bike with your weight and your riding position, we'll be able to calculate the required preload for your new spring - so make it a fully prepared one time effort with the installation.

It helps a lot to have a helper who can hold the bike upright when you do measurements. When I have no helper, I do the measurements beside a wall or door, so I can horizontally support myself whithout changing from normal riding position or putting weight on the ground. I usually use a thin zip tie on one of the fork legs to act as a resettable reference point as it records maximum suspension travel. There's stiction in the forks, and suspension travel is short, so I suggest to use the ractech method of two way measurements.

Step 1: Extend the fork completely (put the bike on the centre stand and ask someone to psh down the back so that the forks are in the ir. pull down on the forks, to overcome the top out springs and stiction of the surfaces) and measure from the wiper (the dust seal atop the slider) to the bottom of the triple clamp. This measurement is L1.

Step 2: Take the bike off the stand, and put the rider on board in riding position. Get and assistant to balance the bike from the rear, then push down on the front end and let it extend very slowly. Where it stops, measure the distance between the wiper and the bottom of the triple clamp again. Do not bounce. This measurement is L2.

Step 3: With the rider in position, lift up on the front end and let it drop very slowly. Where it stops, measure again. Don't bounce. This measurement is L3. Once again, L2 and L3 are different due to stiction or drag in the seals and bushings, which is particularly high for telescopic front ends.

Step 4: Halfway between L2 and L3 is where the sag would be with no drag or stiction. Therefore L2 and L3 must be averaged and subtracted from L1 to calculate true spring sag: static spring sag = L1 - (L2 + L3) / 2).

This method of checking sag and taking stiction into account also allows you to check the drag of the linkage and seals. It follows that the greater the difference between the measurements (pushing down and pulling up), the worse the stiction.

[Oyabun]

Constant spring rates is what Race tech (inventors of emulators) are recommending once you install the valves. However that is for motorbikes with proper forks, can get away with it in a scooter with short forks and limited travel? I doubt it...
Where can we find made to measure springs in Europe for a reasonable price? I have long been wondering to change the springs on my YSS rear shocks which are really only comfortable with two up (L size) , otherwise too hard.

As I wrote before, IMHO suspension is not rocket science or black magic but a balancing act. If most of the suspension travel is not not used due to wrong spring rate selection it will not do it's thing. Sport bikes have similarly short suspensions but with the right setup they can be comfortable. Not super long suspension travel cruising comfortable, but still much better than our scooters despite their higher weight. On the other hand while proper spring rate springs would not cost any more at the factory level, but a proper set of shocks and some proper damping at the front would cost significantly more for every bike.

I'm also after a set of springs for the rear too. IMHO YSS have gone to the other end of the spectrum with too strong spring rates. I could not find any reasonably priced aftermarket springs so far.
I'm currently in the process of trying to work with a local spring manufacturer to build some one-off springs for me, and so far their pricing seems fairly reasonable - but these are bare springs with no surface protection so far. Will try to get them to look for some steel silicon stainless wire or find a powder coater to finish the springs.
Will keep you posted of the progress.

[tomtomclub2005]

Right- i was quoted by YSS Europe € 90,75 + shipping for a set of springs for rear shocks. I wanted 46-12-22-200 springs but they only have 10-15. It's almost the price of a new set of shocks!

If you make some, maybe we can organise a group buy?

[Oyabun]

Right- i was quoted by YSS Europe € 90,75 + shipping for a set of springs for rear shocks. I wanted 46-12-22-200 springs but they only have 10-15. It's almost the price of a new set of shocks!

If you make some, maybe we can organise a group buy?

Good idea, I'm sure it can be done. Will organise once I'll be confident in their quality of work.
I believe that a set of front and rear (2+2) springs could be managed under 100 EUR in case of a group buy.

[ScottDR]

Oyabun, again I thank you for your time. I'll do the measurements and post the results. But sounds like OE front springs may be more comfortable already! Disappointing. I may have to suck it up and try to sell the YSS springs and copy your original install and redrill to 8mm on the larger holes.

[Oyabun]

Scott, don't give up.
Harder springs especially on this short suspension travel very often more comfortable than weaker ones.
Weak springs are difficult to set the sag properly, and also blow through their stroke quickly and bottom out. this is the worst.
A harder spring with firm action feels much better and strangely softer many times.

[Givestrong]

That is a very interesting topic.

I totally agree with you Oyabun, i worked a lot on mountain bikes suspensions (Downhill and enduro), and for best performance, the fork needs to stay most of the time in the "high part" of the travel. With this setting, you have more "available travel", very useful when you have big impacts during braking or during very steep descent.
If the spring is too soft or too progressive, you are most of the time around the "crossover part" near the end of the travel, and you don't have enough travel to absorb the impacts.

It is not the same type of impacts on a scooter, but the idea is the same. If only i could have my bike settings on a pcx...

I got the new model of PCX V4 (2018) and the fork seems to be more harsh, i feel more the impacts than with my previous V3. I noticed than the travel is slightly inferior on the new (93mm vs 100mm)

I plan to modify my fork to have better performance, i found a complete kit for the 2018 model on a Thai site (Bikerbitz)
https://bikerzbits.com/honda-pcx-150-20 ... 1-017.html

[Oyabun]

I got the new model of PCX V4 (2018) and the fork seems to be more harsh, i feel more the impacts than with my previous V3. I noticed than the travel is slightly inferior on the new (93mm vs 100mm)

I plan to modify my fork to have better performance, i found a complete kit for the 2018 model on a Thai site (Bikerbitz)
https://bikerzbits.com/honda-pcx-150-20 ... 1-017.html

I don't know why the V4 has less front travel. In theory if it still uses the same 33mm stanchion diameter - swapping in a set of older damping rods could get you to 100mm travel.
My assumption is that the front suspension travel was limited because the rear link was moved, thus the rear of the bike rides lower and in order to balance the turn in- they have lowered the front too - but it is just speculation.

Regarding the kit.
If it is indeed the one shown on the picture then the spring is a much less radical than the YSS above. On the other hand I'd definitely check the new PCX's fork stanchions. Unfortunately I have no access to the new parts fisches yet to do so. At least the stanchions of older models I've seen so far had a circlip type of cap, not a thread-on cap - so either the picture is not correct, or part of the kit is not usable. 121EUR is definitely good price for springs, emulators and a cap if it is really usable.

In case you have the possibility to do some measurements on your new bike's components I would be very happy to see them here.

[tomtomclub2005]

It looks like it's exactly the same spring as shown above by ScottDR see this page : https://pantip.com/topic/37501302 (i did a search with P/N as liste on bikersbits page)

Reference of spring are identical to the ones posted above

spring.jpg (149.77 KiB) Viewed 4776 times

[Oyabun]

Tomtom,
Thanks for clarifying. Then it is really a generic picture on the site indeed.

[Givestrong]

I don't know why the V4 has less front travel. In theory if it still uses the same 33mm stanchion diameter - swapping in a set of older damping rods could get you to 100mm travel.
My assumption is that the front suspension travel was limited because the rear link was moved, thus the rear of the bike rides lower and in order to balance the turn in- they have lowered the front too - but it is just speculation.

Regarding the kit.
If it is indeed the one shown on the picture then the spring is a much less radical than the YSS above. On the other hand I'd definitely check the new PCX's fork stanchions. Unfortunately I have no access to the new parts fisches yet to do so. At least the stanchions of older models I've seen so far had a circlip type of cap, not a thread-on cap - so either the picture is not correct, or part of the kit is not usable. 121EUR is definitely good price for springs, emulators and a cap if it is really usable.

In case you have the possibility to do some measurements on your new bike's components I would be very happy to see them here.

I think the stanchion diameter is 31mm on the PCX, i need to check.
I've seen the reduction of travel in the specs of the model, not tested yet.
On the V4, i confirm you it's still a circlip on the top of the stanchion.

I've seen on a document of YSS than they make top caps with or without threads depending of the model.
There is a cut drawing where that top cap is mounted using the circlip.

Here is the link (it's a pdf) : https://www.yss.co.th/downloads/SPEC_TA ... DE_KIT.pdf

[Oyabun]

I think the stanchion diameter is 31mm on the PCX, i need to check.
I've seen the reduction of travel in the specs of the model, not tested yet.
On the V4, i confirm you it's still a circlip on the top of the stanchion.

I've seen on a document of YSS than they make top caps with or without threads depending of the model.
There is a cut drawing where that top cap is mounted using the circlip.

Here is the link (it's a pdf) : https://www.yss.co.th/downloads/SPEC_TA ... DE_KIT.pdf

Apparently my mistake. The PCX indeed has 31mm stanchions. I mixed it up with the Forza125, which is 33.

Thanks for the link to the PDF. Indeed it seems that there is a PCX specific circlip type preload cap. And just supports the fact that the picture on the site is not of the actual product.

[tomtomclub2005]

FYI 4 years ago i had gotten some harder springs from the german PCX forum. They were sent in from Thailand. Unfortunately at the time i just measured length (which was -5mm from stock LED springs) and now i can't access them anymore since my pcx was stolen. They came in an Honda slip Packaging but P/N was removed. So I'm pretty sure there are harder Honda springs compatible parts but god knows what P/N, only a dealer might know!

In the image below top springs are LED stock, bottom ones the harder new one.

ressortspcx-482af89.jpg (311.06 KiB) Viewed 4768 times

[ScottDR]

OK, wow. Sagging is not the word. OE front suspension on my '13 PCX150 with 8,900km on the clock.

Full height lifted from yoke to metal of the lower part of the front damper is 132MM
Static sag with no rider is 113MM. With me on (no bounce, eased down) is 97MM.

That's approximately 1/2 of total travel. I'm shocked!!! Yes, pun intended.

So Oyabun, any changes to your original PD settings or oil weight/filling height?

This thread is bloody brilliant!

[Oyabun]

Hi Scott,
That's not even that bad. 132-97 = 35mm (just a sidenote, on my bike I measure 135mm from yoke to the wiper seal when I pull down the fork legs. its is due the top out spring, so in fact we cannot use the total travel, the last few mms are taken by the top out spring which helps to avoid banging the forks on total extension)
Mine had 44mm rider sag out of ~92 usable travel on the stock springs when I measured. I might be a bit heavier, Like to sit more tho the front and push the front fork more than usual as a bad residual habit from my racing times.

I would use the following setup.
-No preload, just as you have from the installation. If you're installing the preload caps, you can dial it in later, but even not, the new springs should be fine with that amount of sag you have.
-1,5 turns from touching on the emulators It's not ease to exactly set up preload on the emulators, but don't use more than 2 turns.
-Set oil level to 80mm from the top. - Normal level of fluid in forks is 75mm measured from the top of the collapsed stanchion. With such a hard secondary spring rate, I'd risk to go down to 80mm. Make sure that you bleed the forks from air before you set the final level.
- use 15w oil read below

This latest needs a bit longer explanation. 5w-10w-15w-and 20w designation is just the ballpark. Different brands have different characteristics. Real viscosity is measured in sct, or mm2/sec. I normally use AGIP/eni fork oils, as I have access to them, but you feel free to use anything you have access to in Canada.
Here's an example http://www.oliehandel.nl/files/7/manual ... %207.5.pdf
Typical information you have to look for:
- Viscosity @40degC and @100degC - between these the fork oils are more or less linear.
- Viscosity index explains how consistent their viscosity is between these two temperature points- the higher the better.
- Given your location you might be interested in pour point what is the last temperature when they can be still poured.

A few things to consider. Heavier oils warm up more during use (higher pumping losses converted to heat) and tend to degrade faster. Also the heavier the fork oil is, the bigger the difference between cold and hot fluid temperatures - so it will provide less consistent damping. This is why super high class damping parts (eg. Ohlins and works pro racer stuff from Showa and Kayaba) use very thin oils and move a lot of fluid. Our bike is no racebike, so we're less concerned, but it needs to be mentioned - bigger is not always better. Moreover I don't know what is the lowest temperature you're planning to ride, but higher viscosity oils become fairly thick at lower temperatures.
Therefore I suggest to you to use 15w oil with a @40 viscosity above 60 sct - I'd say ideally around 70-75. The PCX needs so minimal amount of fork oil that I'd buy the best quality available and save the remaining amount for the next fork oil change. Also many riders never touch their forks, but these fluids deteriorate with use. It worths to refresh them every now and then like any operating fluid in the system.

Hope it helps.

[Oyabun]

FYI 4 years ago i had gotten some harder springs from the german PCX forum. They were sent in from Thailand. Unfortunately at the time i just measured length (which was -5mm from stock LED springs) and now i can't access them anymore since my pcx was stolen. They came in an Honda slip Packaging but P/N was removed. So I'm pretty sure there are harder Honda springs compatible parts but god knows what P/N, only a dealer might know!

In the image below top springs are LED stock, bottom ones the harder new one.

I was also looking for the specs of that spring in our email conversation from a few years ago as I did remember that picture.
No luck. You've just sent me the overal length, but no further details.

[ScottDR]

Hi Scott,
That's not even that bad. 132-97 = 35mm (just a sidenote, on my bike I measure 135mm from yoke to the wiper seal when I pull down the fork legs. its is due the top out spring, so in fact we cannot use the total travel, the last few mms are taken by the top out spring which helps to avoid banging the forks on total extension)
Mine had 44mm rider sag out of ~92 usable travel on the stock springs when I measured. I might be a bit heavier, Like to sit more tho the front and push the front fork more than usual as a bad residual habit from my racing times.

I would use the following setup.
-No preload, just as you have from the installation. If you're installing the preload caps, you can dial it in later, but even not, the new springs should be fine with that amount of sag you have.
-1,5 turns from touching on the emulators It's not ease to exactly set up preload on the emulators, but don't use more than 2 turns.
-Set oil level to 80mm from the top. - Normal level of fluid in forks is 75mm measured from the top of the collapsed stanchion. With such a hard secondary spring rate, I'd risk to go down to 80mm. Make sure that you bleed the forks from air before you set the final level.
- use 15w oil read below

This latest needs a bit longer explanation. 5w-10w-15w-and 20w designation is just the ballpark. Different brands have different characteristics. Real viscosity is measured in sct, or mm2/sec. I normally use AGIP/eni fork oils, as I have access to them, but you feel free to use anything you have access to in Canada.
Here's an example http://www.oliehandel.nl/files/7/manual ... %207.5.pdf
Typical information you have to look for:
- Viscosity @40degC and @100degC - between these the fork oils are more or less linear.
- Viscosity index explains how consistent their viscosity is between these two temperature points- the higher the better.
- Given your location you might be interested in pour point what is the last temperature when they can be still poured.

A few things to consider. Heavier oils warm up more during use (higher pumping losses converted to heat) and tend to degrade faster. Also the heavier the fork oil is, the bigger the difference between cold and hot fluid temperatures - so it will provide less consistent damping. This is why super high class damping parts (eg. Ohlins and works pro racer stuff from Showa and Kayaba) use very thin oils and move a lot of fluid. Our bike is no racebike, so we're less concerned, but it needs to be mentioned - bigger is not always better. Moreover I don't know what is the lowest temperature you're planning to ride, but higher viscosity oils become fairly thick at lower temperatures.
Therefore I suggest to you to use 15w oil with a @40 viscosity above 60 sct - I'd say ideally around 70-75. The PCX needs so minimal amount of fork oil that I'd buy the best quality available and save the remaining amount for the next fork oil change. Also many riders never touch their forks, but these fluids deteriorate with use. It worths to refresh them every now and then like any operating fluid in the system.

Hope it helps.

Absolutely helps! The 15W Ipone I purchased is 60.2 at 40C so it's going back for another brand. No preload caps will be installed.

Am I still opening up the larger holes in the damper rod to 8MM on the valving?

Thank you!!!