Finally Lowered my Dual Purpose 250, now I need stiffer springs

[Julio]

After reading several posts on this site I decided to lower my bike.
It's a Veloci Steeler 250 (made by YinXiang) almost identical to the CSC TT250.

For the rear shock, I opted for the DNM MK-AR 295mm 1000 lbs shock ... it was available thorugh Amazon. The original shock was 310mm (the new one is 15mm shorter).
After installation and measuring from the axle to a fixed point on the bike I got 30mm less... a 2 to 1 ratio, not bad.

For the Front suspension, I only slid the forks 2.5cm.

The bike feels better, seat height about 30mm lower, not much but it does help.

Now, the problem: the front suspension is too soft - specially for off-road. The bike is heavy and so am I... so I guess I'll have to change the springs, but how do I remove them? any tutorials? pictures? also how do I calculate the new spring rates?

I'll really appreciate any guidance on this topic.


Warning: Rear wheel can hit he fender on jumps and big bumps.... Changed wheel to lower profile (120/80-18)

-------------------------------
For reference, some pictures:

Rear shocks comparison


Front Fork Lowered


Measurements Before -After

[Tashka]

I would probably add a preload to the front forks, that should stiffen the front end a decent bit without having to replace springs.

[ikeus685]

y tube is full of how to's for front suspension spring replacement. Their is also some preload mods that you may also do before taking on a total spring swap."i.e. $15.00 front fork mod"
I had done an abbreviated preload mod by draining and replacing the fork oil to 20 wt and install a couple rubber washers that I hope have given a little preload.
Gluck

[Deryl]

Yeah, I would definitely change out the oil and go with 15 or 20 weight oil and add some spacers to stiffen it up before thinking of changing out springs. There have been many people who did both and said it made a big difference. A lot cheaper also and I have not heard of anyone getting different springs. You can use brass or pvc for the preload spacers. Pvc being the cheaper and easier option.

[Julio]

Tashka, Ike & Deryl,
Thanks for your comments, and yes you're right - I should try preload and oil before changing springs.

Please help... I don't know where or how to add preload on USD forks... From the Ike's picture the suspension is identical to mine...but where/how do I add the spacers?

I would really appreciate any guidance/pictures/links or link to a service manual.

[kingofqueenz]

On my TBR ( if it applies ), the pre-load spacers are right at the very top of the fork when you open the top bolt, you will see the spacer right there.

Check Dan's Youtube video of his Hawk - start at about 10:07 into the video

[NoBs]

Originally Posted by Julio

Tashka, Ike & Deryl,
Thanks for your comments, and yes you're right - I should try preload and oil before changing springs.

Please help... I don't know where or how to add preload on USD forks... From the Ike's picture the suspension is identical to mine...but where/how do I add the spacers?

I would really appreciate any guidance/pictures/links or link to a service manual.

Probably really dating myself here but are there no more air forks with a Schroeder valve to adjust the pressure ? Only negative was keeping them w/in the tolerance you wanted. I remember doing them for hard dirt riding and M/C. You made these for the most part, drill and tap the top cap of the front tubes if I recall correctly. Very inexpensive at the time..

[JerryHawk250]

Originally Posted by NoBs

Probably really dating myself here but are there no more air forks with a Schroeder valve to adjust the pressure ? Only negative was keeping them w/in the tolerance you wanted. I remember doing them for hard dirt riding and M/C. You made these for the most part, drill and tap the top cap of the front tubes if I recall correctly. Very inexpensive at the time..

Yes you're dating yourself. Had them on my old Honda 200x. I've thought about putting them on my Hawk. After I added taller spacers I found I didn't need them.

[NoBs]

Originally Posted by JerryHawk250

Yes you're dating yourself. Had them on my old Honda 200x. I've thought about putting them on my Hawk. After I added taller spacers I found I didn't need them.

We thought it was the coolest thing back in the 70's...

[Julio]

Changed fork oil to Maxima 15WT... it's significantly thicker, it has a nice orange color (vs. the original black in picture). On small bumps it does feel stiffer, but at a any medium bump or small jump it'll bottom out. I know I could add pre-load but it's way too soft for mid-enduro.

So, I want to change springs, or the entire forks... any recommendations?
Race Tech? another less expensive place?
The bars are about 910mm long, 51mm top diameter.

Also, how do I measure the current spring strength? Perhaps I could put my weight after I remove it from the bike and measure how much it commpreses... then calculate in/lbs? any tips?

[kingofqueenz]

Curious why did you opt to lower the bike?

I lowered my TBR because I do 99% street riding and as a new rider, I didn't like one footing or tippy toe at red lights

You mention that you are off-roading....

Maybe the appropriate fix here is raising everything back up?

[Megadan]

For starters, bottoming out the forks would have happened even before raising them in the triple tree. Unless the front tire is hitting the lower triple clamp now?

As far as springs go. You would want to measure your current spring length and diameter before doing anything else. That will give you an idea if there are any off the shelf options.

Then you have to figure out the rate based on weight and a few other factors. None of which you have listed, so it would be nearly impossible for anybody here to tell you what weight spring to go with.

As far as the preload suggestion, it isn't an invalid one. If you have too much rider sag, then you are operating with a limited amount of compression travel, and even with the right spring rate, if there isn't enough travel you will still bottom out.

[Julio]

Kingofqueenz and MegaDan,
Thank you both for your comments.
And yes, the bike was easily bottoming out before I lowered it.
Also, yes, usually for Enduro one would need more height, perhaps I
should have written soft-enduro (not mid) - mainly dirt roads
and single trails so clearance is not an issue and tires are not reaching the fenders.

So, from your comments, I'll try to add pre-load - found a post on a
Storm Fork oil change... the fork seems identical to mine... I've
borrowed a picture from that post edited next my fork (attached). I guess I'll just get a longer pre-load tube... any recommendations? start with a 20mm inch longer tube?

Now, some data (sorry in metric)
-Bike Weight 135Kg (full tank)
-My Weight 90Kg (yes, I need to excercise and eat less)

-Fork travel 150mm (bike on a jack)
-Travel reduction 13mm (bike own weight)
-Travel reduction 20mm (me standing on bike)

In other words, with just me on the bike I've lost 20mm of suspension, only 130mm left.

I'll Sincerely appreciate any comments.

[mtiberio]

Increasing fork oil volume will reduce air above it and increase the air spring progression (make it stiffer). For the back, increasing preload is a bad idea and sub optimal, get a stiffer spring. Measure the dimensions of your current spring (OD, wire diameter, # of coils, plus overall length and ID). Use the first 3 numbers and plug them into this formula and calculate your current spring rate. Find a replacement that is 10% stiffer, and that has the same length and ID. spring rate calculator: http://faq.f650.com/FAQs/ShocksSprin...e%20Calculator

[Julio]

Thank you all for your help and comments.
I opted to remove the spring and take some measurements (see pictures).

The spring size:
-Diameter: 31mm
-Length: 490mm
-Wire diameter 4.4mm
-Free Turns 48.4
-Fork Travel 150mm

Motorcycle weight: 130Kg
Rider Weight w/gear: 95Kg

To calculate spring rate I used the formula suggested bymtiberio
but it came out to small (perhaps the type of steel used) so I tried to calculate the spring rate using disk weights on a single fork leg:
-Pre-load using weights until it moved: 14Kg.
-Placed 70Kg in disk weights to 1 leg: compressed 103mm

Probably wrong, but I guess the spring rate would calculate to:
70Kg weight - 14Kg pre-load = 56 Kg net --> 103mm measured compression
56kg/103mm= 0.54 Kg/mm

Please help:


Next step is to add preload, but how much to start with 25mm (1 inch)? and place it at the bottom of the spring (it doesn't seem to have any pre-load spacer) ?

Also, the fork seems sluggish (rebounds too slow) I'll try 10wt oil.

Finally, If I could get cheap springs I would like to try several options.
I got a quote from Sonic Springs for 150 US dollars... not that bad if I was sure on the rate needed... too expensive to try... any other recommendations?