Dumb suspension question

[LivinLOS]

Is there any way to tell, from looking at a shock, the 'rating' of the spring for the rider weight / load ??

Darrens YZ is set up currently for a much lighter rider, and is way under sprung for me. In his box of bits theres a second rear shock, but Darren was not sure what weight it was suitable for. I cant see any markings or indications printed or stamped on the spring or anywhere.

Any way to be any closer to understanding it without simply swapping them out ??

If I need to get the suspension revalved and adjusted.. Who if anyone is best for that around here or in Thailand ??

 

[alexuk]

put a sack of potatoes on it and see how much it moves
are there no markings at all?

 

[LivinLOS]

put a sack of potatoes on it and see how much it moves
are there no markings at all?

I might need 2 sacks

Theres a sticker with rider, rebound,compression, oil height, spring weight, but helpfully none are marked / filled in. Theres nothing on the spring.

I am assuming woods / trail riding your going to run a softer shock than an MX setup, but its the preload I need to get sorted for my 100 maybe 105kg spud size..

 

[johnnysneds]

Check your sag before changing the spring out. It might be within limits. If your not sure I'll post up an easy procedure shortly.

Don't mess about with pre-load/compression until you get the sag sorted first.

I have this book in my library if you want to borrow it. It has excellent step by step guides on setting up your sag.

 

[Brian66]

If the springs are removed from the bike, a simple way to get the rating of the spring is to measure its free length. That is with it standing on a bench with no load on it. It is impossible to be accuraate unless the spring is removed from the shock and done on a bench.

Find a known weight or weights , Say 5 or 10 kilo grams, place it on the spring and measure the compression.
Divide the kilograms by the length of the springs compression and you will have it rate in Kilograms per millimetres. Do it in pounds and inches if that suits your knowledge. This is for a linear spring.

I run 11 kG per mm compression in the rear of my road racing Blade

 

[johnnysneds]

If you check your Static and Rider Sag you won't need to know what spring rate you have. If you run out of pre-load for your specified amount you know then you need a higher spring rating and you can then refer to http://racetech.com/ChooseVehicle.aspx

Below is a simple spring rate reference:

I was told I would need a stiffer rear spring for my WR as it came from Japan!!!, however after setting up my static/rider sag I had enough pre-load to keep it within my riding recommendations. It worth checking first and it won't cost you lots of time and money.

Learning how to set-up your sag has other benefits too. You can tell the condition of your shock from the "stiction" results during the test. For instance stiction for a dirt bike should be between 10-20mm. Anything in excess of this could be the direct result of bent fork tubes, worn out bushings, seals etc.

 

[Mickey Magoo]

What YZ do you have? Mine came with two shop manuals from Yamaha. I think you may find stock spring rates in the manuals (???) IIRC, one is to help with race set up ...also look on line? Yamaha also sell heavier and lighter springs for racing and they may be listed too.

Some springs have a long number written on them. Hard to see ... or maybe not there at all on aftermarket springs ... dunno?
My Ohlins (another bike) and both Eibach springs I've used have an I.D. number, I looked up the spring rate on line.

I have a '07 Yamaha WR250F. (non street legal USA off road model) This bike is set up for rider weight of about 150 lbs.(68 kgs.) I believe the YZ is about the same?
Even though I was able to crank up the preload until race sag was more or less OK (95mm to 105mm) Thing is, I weigh 200 lbs. and the bike did not handle well, especially in deep sand. The experts told me the shock is probably running too far down in the travel. This has things getting very HARSH during the last 50% of travel and the bike does the "Stink Bug Squat" under hard acceleration. Not good.

Race Tech suggested a spring rated for 220 lb. rider. I found a guy with a blown up YZ250F race bike. He was parting out everything, so I bought his aftermarket springs front and rear along with a few other gems. They were rated for 210 lb. rider ... and he had documentation to prove this. My bike is transformed. Turns much better, more plush everywhere, front sticks better ... and I can actually ride sand and not suck at it!! (who knew?) Race Tech claims it's best to ride in the top half of travel.

Paul Thede (Race Tech founder) stresses a nice balance between front and rear. (his essays are on line, very good)

Good luck.

 

[LivinLOS]

Check your sag before changing the spring out. It might be within limits. If your not sure I'll post up an easy procedure shortly.

Don't mess about with pre-load/compression until you get the sag sorted first.

I have this book in my library if you want to borrow it. It has excellent step by step guides on setting up your sag.

Ohh I really do want to borrow that book.. In fact might even get my own copy..

I want to check and adjust the blade also.. I feel I get too much chatter or feedback from the front and it could be a but plusher... First port of call would be to check everything is stock as it may well have been messed about with by locals.

 

[LivinLOS]

@ Mickey, Jonny and Brian..

All good info guys.. Will have a tinker..

 

[LUFC]

@ Mickey, Jonny and Brian..

All good info guys.. Will have a tinker..

I wouldnt waste time with the blue spring, it would bottom with my svelte 90kg and pre-loadeded up to god knows what.

Try the grey spring.

For re-valving there MAY be guys in Thailand who can do it, but I've never met anybody who had good things to say about Thai modified suspension. It will only need doing once, so get it done professionally.

Terry Hay in Oz did great work for me and at a good price - just make sure you make it clear you dont want the gold valves.

 

[bigntall]

Years ago when racing cars we had a formula written in the toolbox for calcing spring weights. It used the wire diameter (use calipers), legnth and number of coils in the equation. sorry I don't remember but do an internet search it might pull it up for you, pretty simple formula if I remember.

That YZ should have been mine LivinLos (I came close to picking it up also), hope you're enjoying the YZ.

 

[LivinLOS]

Not been enjoying it hardly at all... Life issues and cambodia distractions combined with not yet having a trailer to shift it around, not keen on it doing too many Rd miles, doesnt feel its that kind of engine or gearing. Lots of guys who modify the YZ as a more general purpose machine use the WR426 top gearing which sounds interesting and brings it more into something that could do limited miles between trails.

Theres bags of YZ info and it seems to convert to a trail / woods machine that people love, much of which was already done, but I seem to have had so little time last few months. Even with the FWW it still feels kinda snappy to me, maybe just need more seat time.

 

[bigntall]

Livin Los - Wow!! Cambodia, next time you gotta get a more geographically desireable distraction, 3

In my YZF 250 that has a tight MX grarbox like your YZ250 I installed the wider ratio 4th and 5th gears from the Yamaha WR 250 , to aid getting to the trails on the tarmac. It made it bearable and negated the need for a trailer. A worthwhile mod in my eyes and gearsets are cheap if you pick them up cheap on Ebay. I bought new and it was only a few hundred dollars.

Some data of your intended modifications for you to compare. Your YZ250 ( with 14/48 gearing) w/ the WR426 5th gear installed will be going 65 KPH at 4250 RPM's. For comparison my YZF (with the same 14/48 gearing) with WR 5th gear was turning 61 KPH at 4360 RPM's. My YZF could cruise up to about 70 KPH and still feel the motor was not being abused. Good luck.

 

[LivinLOS]

Already been reading a multitude of threads on the wr transplant tho most of my reading was using the 426 box and was doing the thinking on all the ratios.. If the YZ becomes comfortable for me, and I think it can, this mod is high on my list. Probably along with with a rekluse clutch mod.

Like I said tho, ride time more important than anything.

 

[Loop]

My KDX hardly has the ideal gear ratios as it is a WR for street/trail use.Because of this it had a 14T engine sprocket for the extra top speed for road cruising.I found it would do around the 130k mark which is hardly needed for the trails around CM that we do and had a big gap between the gears at times when changing up.
The Enduro R models use a 13T but i sourced a 12T which has made it pull much better when changing up on the occasional steep hill we come across yet it still will do 110k`s or so on the tarmac.

I`m happy with the result which is a cheap,easy and effective fix IMO.

 

[LivinLOS]

Livin Los - Wow!! Cambodia, next time you gotta get a more geographically desireable distraction, 3

hmm desirable distractions you say !

 

[KTMphil]

Oh dear..... it was just a matter of time until we ended up here..... If any of those photo's on your phone end up here, ill be forced to move this thread to the dungeon!

 

[LivinLOS]

Even if i photo shop out any bits of 'me'

 

[bigntall]

Livin Los - Wow!! Cambodia, next time you gotta get a more geographically desireable distraction, 3

hmm desirable distractions you say !

Uhhhhh, yep. I'd drive aways for that!!! So how is it that Living Los and I have not hooked up for riding yet??

 

[LivinLOS]

Because for the last few months, since getting the YZ and the best ride season, life's been complicated by Cambodia and divorce !! I really havnt had a damn day to myself..

I am really trying to tie up lose ends by which time rainy season will of course arrive..

Such is life.