Removing the rear shock ?

[pyoungbl]

Bob, when I was swapping springs on my RX4 I tried 650 lb/in...too stiff, then went down to a lower value....maybe as low as 500 or even 450. It has been a while. Lucas is giving you good advice, you should be looking at about 1/3 suspension travel suspension sag when the bike is unladen. The correct spring will get you there. At the same time, you need to have a shock that works with the spring. The OEM shock is bargain basement, a common place to save money. The valving is dead simple, just fixed holes for the oil to pass through. That's OK for gentle bumps but will lock up when you try to force fluid through those holes at a velocity higher than minimal. Of course grease will help the suspension a bit. There is grease present on the new parts, just not a lot. The grease is more to keep rust at bay than anything else since the parts run on needle bearings.

At some point Joey sent me the specs for the rear suspension. The OEM spring is rated for 142 n/mm...that converts to 810 lb/in. You can immediately see why the ride is so stiff. Add in the fact that the spring is progressively wound, meaning that as it compresses the rate goes up! Don't forget that the shock itself has progressive resistance due to the gas being compressed. Now you have doubled down on rising resistance as the shock compresses. All this is great if you are using the bike as a pack animal at low speed, not so good for the way we use the bikes.

We bought bikes that offered affordable fun. If you want the suspension to work to your satisfaction you'll have to decide how badly you want that result. Earlier I mentioned Cogent Suspension's custom shock/spring. You balked at the price. That's understandable if you think of a $5K bike needing a $700 upgrade...a might big % of the cost of the whole bike. Think of it another way. If you buy a well used BMW, KTM, Ducati and get it for a bargain price (even free) the consumables still cost the same as a brand new machine (assuming the sizes are the same)...I'm talking about tires, brake pads, stuff like that. The parts are not discounted because of the age of the bike. Suspension is the same thing, high quality is going to cost. Cogent's price is competitive, even inexpensive compared to some stuff from Ohlins. Oh, Ohlins would not even consider building a shock for my RX4...I tried. Not enough market for their effort.

All of the above is not to bash your efforts. I went down the same path. Health issues have given me lots of time to think about your suspension problem. My thoughts are offered for free. Feel free to ignore, no problem here. I'd just like to see you happy with the bike.

Peter Y.

[Bob Kelly]

Thanks Lucas ! what the heck is that last photo ?
Yah....unfortunately it looks like I need to take the rear swing arm completely off
(and I am not looking forward to that task at all)
I do have a motorcycle/ATV lift I got from HF. but the bike isn't very stable on it and finding anchor points in the shop to tie the bike down is hap-hazard at best !

SPRINGS.....
I got a spring from Race Tech and unfortunately it feels exactly like the original spring
and it is 537 lbs. it's a tad shorter but that is of no real importance for my riding.
I am thinking or ordering a 400 lb spring now because it is far too stiff there is no flex in the rear at all and there should be some sag but there isn't at all the only thing that flexes is the tire itself !
I've had over 50 motorcycles in my life time and this is the very first time I have had trouble with the rear suspension it's as if the rear suspension is locked up tight no movement at all....and that makes for a really hard ride any bumps at all and you feel them really well. a 30 minute ride and I feel like I've been beat up !
.....
So I have been trying to find out why it is so darn hard riding.... I replaced the spring with a Race tech spring of 537 lb. rate and it feels just like the original...no give at all
I've lubed the links below and noticed that they are extremely stiff ....
I am starting to wonder if it's assembled correctly too..... if anyone has a photo of their link system under the bike I'd appreciate seeing it !
....
i find it very odd that there is NO sag what so ever on this bike.... there never has been
....
.... the TT250 has some sag like it should have it's stiff to me but it's the Kids bike
and she likes it that way ...

my question to you guys is do you think a 400lb spring would be soft enough to give some sag ? .... there is no technical information on the shock or spring rate and I am going blind and I have no way to measure the original spring it's too stiff to measure !
and the one I just bought is the same way ! LOL.....
.....
thanks for the help guys ....I need all the help I can get !
....
Bob.......

[Bob Kelly]

Thanks Peter !
your post is not going on deft ears buddy I just can't afford $800.00 for a rear shock and spring..... buying the first spring from Race tech. hurt.... and that's only $190something to my door..... but it looks like even that one is too stiff why the heck would they put in a spring that is soo stiff that you could never compress it ? that doesn't make sense !
the original spring being 810 lb I think you said... that's more than the entire weight of the bike.... that is super stupid in my book.... ok I understand the travel is short on the spring for the leverage and they have to go with a stronger spring to make up for that but that much is silly !!!
to me the original shock for the rear looks like high quality and will have good durability for my type of riding.... I don't need a designer shock...i just want it softer is all.....
I am not a rich man I've been dirt poor all my life and in retirement that has gotten worse ! so I don't have alot of money to throw around
.....
can I ask you what springs you have tried and what the results were ?
what ones were too soft and what ones too hard ?
that will help me immensely ! even if you put them on a fancy custom made shock ! LOL
....
Bob.......

[Lukas]

These first pictures are the remains after I looked at the rear suspension and the parts that were left after changing the shock the original spring at my weight of 75kg works ok but the wheel was rubbing on the air box so I decided to put a longer shock I had to adjust the mounts but it was cheap and has a longer stroke and is thicker and that changes things because it works in a different amount of oil and oil is very important if you change the oil in the old shock absorber it will run better, but it is an expensive oil in the new shock absorber the spring was too hard and the bike did not bend at all I ordered a 350 pounds spring and it turned out to be too small original is at least 400 pounds so I installed the old spring in the longer shock absorber, changed the oil in it, loosened it to the maximum and it is great now only need to change the front oil, because the factory one is of low quality.https://www.aliexpress.com/item/1005...martRedirect=y https://www.aliexpress.com/item/1005...21ef1c24SLqRv5

[pyoungbl]

Bob, I do not recall what my final spring choice was for the OEM shock. The sag was OK but the actual shock was then the limiting factor. I was going with Hyperco springs. Their catalogue lists hundreds of springs so you just find the size close to what you want, then get the resistance within that series. My notes say that I used a 187AO 650 so it was a 187AO with 650 resistance. That's not to say I ended up with the 650, I think I actually ordered two different resistant levels, tried the stiffer one, switched to the softer, and wished i had one step softer still. Here's their catalogue. Look at page 11 or 12. I was using a 7" spring and had to make spacers for it to fit.file:///Users/peteryoungblood/Downloads/hyperco_catalog%20(1).pdf. The retirement issue stalks me too...retired in '03 but, damn, life is too short and the custom shock made the difference between keeping the bike and selling it. Cogent built the shock and installed their choice of spring, I do not know what spring they used. FWIW, Joey at CSC tried to help by having a local suspension expert build something from the OEM shock. That was no better than what i had already built using the Hyperco spring. I sent the test rig back to CSC with a 'thanks but no thanks'.

[pyoungbl]

this link might work better: https://www.hypercoils.com/hyperco-catalog/

[Bob Kelly]

ok I emailed them we'll see what happens...
Bob....

[Bob Kelly]

Well, after getting the 3 springs from Peter Youngblood I had to make a spacer for under the spring in order to use them... I did so... and used the weakest one he sent which I think he said was a RX3 rear coil....not sure on that, but it has on it 400/450lb.
and I put that one on and it is alot better riding than it was ...still a bit stiff though
but so much better than it was it's not even funny....
so then I set about lowering the RX4 by making a new lower link. The first rendition of the unit would not fit at all ... so I had to move the bolt holes in toward the pivot point 3/4" and drill the holes again.... and that worked great ! My original design had the bolt hole spacing at 6-3/8" and I reduced that by 3/4". Then it went right in there, bolted up and I put the seat on it and measured the seat height and it came out to 29.5"
and this time I have suspension too !
so from 31.9"(say 32") to 29.5" I lowered my bike by 2.5" which is exactly what this heavy tall bike needs to be useable ! ....( and no i don't even look at bikes that are 34" seat height !....it's like what's the point ? )
.... so I haven't ridden it today as I planned to but perhaps I will tomorrow as it will be in the 70's tomorrow so the weatherman says ! today it was a bit nippy for that !
....
so if the spring is found to be too stiff I will get a 10~11" long spring 2" I.D. x 300~350 lbs. and that should be all it takes for a cushy ride !
if that winds up being too soft I can increase the preload some so I do have some give. (the pre load is setting at the top of the spring right now not compressing it. )
.....
Bob.......

[Lukas]

It would be nice if you took some pictures because it's hard to imagine your work from the description, as far as I know shortening the dog bone on the RX3 causes the shock to be closer to the engine and the spring rubs against the engine I don't know if such a problem occurs on the RX4 again I urge you to change the oil in that shock for smooth operation without that it won't work softly and as far as I remember for the RX3S there is a lowered seat I'm going to have a look before it solves the problem of the bike being too high.

[Bob Kelly]

Lucas ! You're not shortening the distance between the pivots, your lengthening them !
and posting a video here is a P.I.T.A because I have to resize every one .
i suppose if I could find the settings in my fancy phone I could just change the settings and make them 1024x768 pixels which would give me more space in the phone...
but that is why I bought a large memory card for the Phone ! ....oh well.
....
it's conceivable that a person could make a adjustable one fairly easy or buy one that is close and use it... but finding one that is CLOSE is the key when nobody gives dimensions of the parts they sell anymore !
a turn buckle on each side would do the trick... I have a store bought one like that on my 2012 Kawasaki Ninja 250R a already short bike that needs to be shorter for me !
....
the dog bones on the RX4 ase not 2 seperate flat bars , its 2 bars welded to a seperator in the front behind the engine it's job is just to hold those bars and pivot...
it's the distance to the pivot that is attached to the bottom of the shock that makes it lower or higher for the seat height.
so if you want a lower seat height you need to make the distance between the pivot holes LONGER. I've seen several lowering kits that have holes every 1/2" on those bars
so you could choose the one you want and just cut off the excess ! ....
I'm not real happy that I didn't put in the needle bearings but I didn't have a piece of steel big enough in diameter to do that or I would have... all I had on hand was 1" so that meant no bearings.... but in my youth every bike I owned didn't have bearings down there and they lasted till the engines gave up ! so in my way of thinking it doesn't absolutely have to have bearings !
....
Bob....

edit... your only moving the pivot point back a short distance and there is plenty of room for the shock and it's spring to go that far with ease ( moving it back would be getting closer to the air box) and there is clearance there and it's not touching at all ( who knows what a bump does though LOL) i seriously doubt there will be anything touching anywhere under there !
....

[Bob Kelly]

I went out and measured the old stock unit and the new one and the old one was 4-7/8"
center to center... the new lowering link is 5-1/2"(CTC) so a mere 3/8" longer is all it is and it dropped the rear 2.5" that is surprising ! and I don't think you could go to 1/2"
longer as the bracket in the rear swing arm won't allow the center pivot on the shock to pivot that far.... it has to be 5/8" not more than that.
and I am certain that is maximum drop without grinding stuff on the frame for clearance and all that....
....so now you have something concrete to go by.... at least for the 2021 RX4 for the RX3 who knows what they have in there !!!!! this is only for the RX4 you'll have to pull the front link off and put a block on top of the rear tire and let the bike down to the desired height that you want and then measure the distance between the 2 bolt holes very accurately and then go by that for your final product ! I believe the RX3 and RX4 have the same set up as far as the links go so that's not a problem but the distances may well be different...who knows ! this lower link that I replaced is the one that connects to the frame directly behind the engine and it's far end connects to the center pivot hole in the center link that the shock connects to....just so you have no doubts !
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Please note ! at this stage being this low, the rear tire is very close to the inner fender well ....there are protrusions on the inner fender well that stick down about 3/4" I would imagine that these will be ground off by the tire over time.... I did increase the pre-load a little , to clear these more and now I have about 1" clearance....THAT IS NOT MUCH ! I measured the seat height again and it is right at 30"
so I don't think I'm going to get a 28" seat height no matter how hard I try , the tire and fender well are preventing any lower settings.




Bob....