FXR150 rear shock upgrade

[gav]

A cheaper upgrade would be for the more erm, manly shaped men would be to fit a stiffer spring or shorten the existing one. Then drill & braze on a tyre valve & replace the old oil

Yeah that sounds like an idea, any ideas on the spring to use?

[FROSTY:Me]

You mean cheat but from the outside appear legal?


A cheaper upgrade would be for the more erm, manly shaped men would be to fit a stiffer spring or shorten the existing one. Then drill & braze on a tyre valve & replace the old oil

Now if it was the 250 proddy days i'd say YEP cheat.
But SS150 I dunno if you are or aren't allowed to recondition (reoil,respring) the factory shock. I know you have to use the factory suspenders

[F5 Dave]

I am not advocating cheating by any means, I was talking for buckets & all that is legal. I haven't read the SS150 rules & aren't that keen to find out.

Spring rate of the std shock would be interesting to find out & is quite easy with some bathroom scales & a steel rule. Ideally you put just the free spring on a press with the scales underneath & compress the spring as m,uch as you can without running off scale & measure the compression. 10mm makes for easy math, but more is more accurate. If spring compresses 10mm & shows 58kg then you have a 5.8kg/mm spring. But 116kg over 20mm to get the same result is more accurate if you see what I mean.

When taking spring off use care. Spring pressure is dangerous. Reduce preload to min. you have to compress spring to hook the collet out. Don't use fingers in case spring slips & catches you. If don't have spring compressor small enough 3 long hoseclamps can be fed through & positioned around & done up evenly to pull 4 or so coils together.

if you don't have a press you can use a piece of 4x2 as a lever & a adequately stuck out piece of hardware (like a staircase) so you put the spring & scales close to it, hook the lever under the stair & lever the long end down & hold still while someone measures & reads scale.

With a medium amount of preload you'd want the suspension to compress 30-40mm with you on. I'm guessing they are made for a 60kg Thai ladyboy so will compress probably 80mm when a powerful chap as yourself gets on leaving ~40mm left. (last 20mm of this is probably bumpstop rubber). Again I'm guessing.

So now you can go bother your local wrecker to measure some of his springs. If he has a bunch already separated. -Many will just tell you to sod off & rightly so. Any spacer will have to hold spring properly & not collapse or slip.

You could cut your existing spring down & make a spacer. Do a search on this site on stiffening springs, I wrote something many years ago. One has to be careful to make sure coil won't spring bind when fully compressed (measure gaps when on shock with max preload & minus shock stroke (including bump rubber compression).


Or get a spring maker to make a stiffer spring. You may have to make a guess like 20% stiffer.

[koba]

Trying to get ya post count up??
I've rephrased my reply a tadd.
What I was saying was that some SS150 riders might have figured out how to modify an RG150/KR150 shock and stay inside the SS 150 rules.

Nope, are you?

The SS150 rules don't allow for any changes to the rear suspension, front is limited to springs and oil.

[UNSTABLE]

Spring rate of the std shock would be interesting to find out....

I don't know exactly what it is but it is fairly hefty. I thing Tim did some calculations on it when he was looking to change it and it was heavier rate than most big bore bikes. Because of the pickup locations on the swingarm etc and due to the fact there is no rising rate linkage, most shocks that you think may work will be far too soft. The other problem is it is so freakin short!!
Getting a custom made one might sound excessive or expensive but in reality is probably the most cost effective solution, and should yield the best results.
Personally I don't think there is too much wrong with the stock shock. Mine seems to work O.K. I don't have any rear traction issues. I think when the wibbly wobblies do come on through some fast high grip corners it's probably more the frame and swingarm flexing and tying itself in knots than anything in the suspension...

[richban]

I don't know exactly what it is but it is fairly hefty. I thing Tim did some calculations on it when he was looking to change it and it was heavier rate than most big bore bikes. Because of the pickup locations on the swingarm etc and due to the fact there is no rising rate linkage, most shocks that you think may work will be far too soft. The other problem is it is so freakin short!!
Getting a custom made one might sound excessive or expensive but in reality is probably the most cost effective solution, and should yield the best results.
Personally I don't think there is too much wrong with the stock shock. Mine seems to work O.K. I don't have any rear traction issues. I think when the wibbly wobblies do come on through some fast high grip corners it's probably more the frame and swingarm flexing and tying itself in knots than anything in the suspension...

Yeh the stock one is good. If you have a working one the valve upgrade and an oil change might make it last longer. I had know problems with mine till the seals went and it turned into a pogo stick. The standard spring rate seams fine for me. Me being 90kg bike 103. Was able to set it up with good static and rider sag. After a test day at manfeild yesterday I love the new one even more. Now the front needs more attention. The never ending story off playing with oily stuff

[Skunk]

Now the front needs more attention. The never ending story off playing with oily stuff

I have one word for you - emulators.

[richban]

I have one word for you - emulators.

Yep rodger that. YSS do a CBR150 front kit not sure but it might work on an FXR.

I am planning to build a new bike next year. Something Ali and light. Maybe something that starts with RS. If I can find one that is for next to nothing.

[Pumba]

Oh so there will be an FXR frame floating around then when you transplant the motor, look dont worry about I will take it off your hands (shock included of course). $100 sounds like a fair price, good, done deal, let me know when I can pick it up. No rush.

[richban]

Oh so there will be an FXR frame floating around then when you transplant the motor, look dont worry about I will take it off your hands (shock included of course). $100 sounds like a fair price, good, done deal, let me know when I can pick it up. No rush.

Umm well, I might just hang on to it. See got another engine sitting on me garage floor. I am planning the engine build now. It will be mad.

[Pumba]

Umm well, I might just hang on to it. See got another engine sitting on me garage floor. I am planning the engine build now. It will be mad.

Spoil sport.