2018 RTL OEM Rear Spring Rate Question

[h0gr1der]

I can't afford all those outstanding aftermarket shocks, and being somewhat satisfied with the ride of the RTL, I only want to upgrade the spring rate on the rear.

Does anyone have the OEM spring Specs? I've read some really technical suspension posts on here, but haven't found what I'm looking for. Ultimately, I'd like to set up my OEM rear shock so that with me aboard, there is zero pressure in the automatic leveling air bag while maintaining the original ride height. I'm 230 lbs with about 10 lbs of permanent accessories in the rear bag. Any ideas? Dumb idea?

I did add the Baja Ron front pre-load adjusters, and those work great, looking to match up the rear to the front. May also help with the air compressor reliability issue as an added benefit.

[JayBros]

I looked through the service manual for my Spyder; yes, it's four years older than yours but I couldn't find anything about the rear spring rate in it. You might try a message to brp.care@brp.com and ask them. You could tell them you understand the spring rate does not appear in the service manual but expect them to tell you to ask your Can-Am dealer.

[h0gr1der]

I looked through the service manual for my Spyder; yes, it's four years older than yours but I couldn't find anything about the rear spring rate in it. You might try a message to brp.care@brp.com and ask them. You could tell them you understand the spring rate does not appear in the service manual but expect them to tell you to ask your Can-Am dealer.

Mr. JayBros,
Thanks for taking the time to look, I'm in purgatory right now dealing with BRP Cares and the Dealer about my bike. Hostage situation day 23, no end in sight! I'm trying to get my warranty extended for the amount of time it's taking to repair the bike (water pump and left switch pack), and even asked about a loaner to sooth my nerves. I'll give you two guesses, the first one is discounted...

I did get with M2 and Elka, of course they want to sell those expensive whole units, which don't have the air bag option. I can't afford that. Ultimately, I'd like to match the spring weight to my actual weight, so the air bag runs at zero or near zero most of the time. I think that would greatly extend the life of the compressor. I also think if we could set the averaging time frame on the ride height to a longer period, so the compressor wasn't constantly bleeding off when the rear end raises on stops, then pumping back up on the next acceleration as the rear squats, that would also help.

The OEM spring is only $48, I may just buy one to test it. Gotta learn how that's done though. Never been a suspension guru.

[PMK]

There are various ways to test a spring for rate. Ultimately they will all give a weight per distance.

What you propose is valid to some extent, however I caution you that you may find that there will be an imbalance in rate front to rear.

The preload adjuster do not alter spring rate, merely change actual force.

The rear setup, via the airspring is not linear as would be changing to a firmer straight rate spring.

Without adjustable preload on the rear, altering spring rate is a bit of a shot in the dark.

Essentially, more than just testing the oem springs rate, you must plot the force graph and apply your new springs rate and force expectations.

In simple terms, a firmer rear spring, with inadequate preload will still excessively load the compressor.

[h0gr1der]

There are various ways to test a spring for rate. Ultimately they will all give a weight per distance.

What you propose is valid to some extent, however I caution you that you may find that there will be an imbalance in rate front to rear.

The preload adjuster do not alter spring rate, merely change actual force.

The rear setup, via the airspring is not linear as would be changing to a firmer straight rate spring.

Without adjustable preload on the rear, altering spring rate is a bit of a shot in the dark.

Essentially, more than just testing the oem springs rate, you must plot the force graph and apply your new springs rate and force expectations.

In simple terms, a firmer rear spring, with inadequate preload will still excessively load the compressor.

A lot of fine words there.

I was thinking in much more simplistic terms, as I am not a suspension expert. Something along the lines of 1. Determine OEM rate. 2. Find a spring manufacturer to make a progressive rate spring with an arbitrary higher force, install it and see what the resultant air bag pressure is with me and my cargo aboard. 3. Repeat until I get a result I can live with.

Probably costs less than the fancy rear shocks. I think Elka replied that they are working with Lamonster on one that retains the bag, but not finalized yet.

[BLUEKNIGHT911]

A lot of fine words there.

I was thinking in much more simplistic terms, as I am not a suspension expert. Something along the lines of 1. Determine OEM rate. 2. Find a spring manufacturer to make a progressive rate spring with an arbitrary higher force, install it and see what the resultant air bag pressure is with me and my cargo aboard. 3. Repeat until I get a result I can live with.

Probably costs less than the fancy rear shocks. I think Elka replied that they are working with Lamonster on one that retains the bag, but not finalized yet.

A few years back another member here (?) ..... did some experimenting with the rear shock .... As I recall , He ended up with two rear springs used together .... to get a progressive rate .... I'm sorry but I can't remember anymore than that ..... " Peteoz " ha s" Wilburs " maybe He can help you .... Mike

[h0gr1der]

A few years back another member here (?) ..... did some experimenting with the rear shock .... As I recall , He ended up with two rear springs used together .... to get a progressive rate .... I'm sorry but I can't remember anymore than that ..... " Peteoz " ha s" Wilburs " maybe He can help you .... Mike

Mr Blueknight911,

I appreciate your taking time to read my post and consider an answer.

I've reached out to this guy, he seems to be knowledgable but hasn't posted in about a year.

https://www.spyderlovers.com/forums/...ension-(shock)

I've read some folks actually talking tech about suspension, but I can't seem to find just the right tidbit of info that will kick me in the right direction. Mr. Spacetiger referenced a Eibach 800 lb/in spring, but it was for a 2012 RTS, so I don't know if it's the same.

I might give Eibach a call.

[PMK]

Spacetiger and I discussed suspension many times. I believe he even went so far as to purchase a spring tester.

As you can see, he focused a lot on base force at a certain ride height. Once established, he concentrated on actual spring rate. His method of preload setting, involved adapting preload adjusters and other tidbits.

Just recently, I accomplished similar changes on my Scorpa trials bike. Establishing preload was easy, but not correct. The excess preload created other issues. The obvious answer was a spring rate change.

I had two oem Scorpa springs, one straight rate and one progressive. I tested both as needed in a spring rate testing machine. With data in hand, I took a best guess at the increased spring rate to purchase. I fabricated spring perch adapters and assembled everything. With reduced preload and increased spring rate, on the Scorpa the change was noticeably better.

Rather than call Eibach, why not ask those that bought M2 shocks to tell you what rate is printed on the spring from Hyperco. Hopefully M2 did not wipe the markings away with solvent.

[PMK]

Handmade parts to fit the new spring onto the Scorpa.

[spyderyderjim]

I sent you a PM.
Jim

[PMK]

Read post number 9, 700 lb/in spring.

No mention of adding any preload.

https://www.spyderlovers.com/forums/...98#post1437398

[PMK]

Some front spring info.

https://www.spyderlovers.com/forums/...16#post1351816

[Mikey]

Forgive me if I am wrong but you don't want to spend the money to get a aftermarket shock on your bike, but you want to work on the spring to get a better ride! That coil over shock you have on your bike serve's two purposes, load caring and rebound, and damping. So you don't go down the road like a pogo stick! You can take your cheap factory shock and play with the spring all you want but the most important part of the shock is still going to be junk! It will wear out and you will be on a pogo stick. Where if you spend your money on a good rebuildable shock when your ride starts to go you have it rebuilt for cheap money and regain that ride you like!! JMO Good luck hope you find your way!!

[PMK]

Ok, you guys got me revisiting this spring swap.

I found and linked the posts.

No plans to alter our front setup with Fox Shox.

2014 RTS, crawled under and took some measurements. The oem spring is not 8”. If 8” were to be used, some type of adapter spacer / collar or similar needs to be installed.

I would beleive the 8” spring is in reference to aftermarket shocks, not the oem shock.

But wait, theres more. Our oem rear shock spring is progressively wound. Very obvious finer pitched coils at one end. Not sure if the 2013 and 2014 plus later years use the same spring. Spacetigers photos do show a spring change for the 2013 vs earlier RT series.

Can Am has stuck with a progressive spring though.

At this point, until I can get the shock out, spring removed and go test it myself, I am hesitant to spend money on a spring that dimensionally differs from what the linked posts states. I would say more details are needed to go further.

[h0gr1der]

Handmade parts to fit the new spring onto the Scorpa.

Mr. PMK,

This is kind of what I'm looking at, I appreciate your time to post the pics. I'm thinking or an 800-900 lb/in spring with a coilover adjuster sleeve setup to tune preload. I'm thinking 800 lb/in will be very close to optimum with little preload.

[PMK]

Mr. PMK,

This is kind of what I'm looking at, I appreciate your time to post the pics. I'm thinking or an 800-900 lb/in spring with a coilover adjuster sleeve setup to tune preload. I'm thinking 800 lb/in will be very close to optimum with little preload.

Essentially what Spacetiger did.

I am rethinking this a bit. My thought is leaning towards stuffing a spring rubber in the tender coils. This will bring the spring rate onto the main coils sooner, with a greater net end force. The progressive spring allowed Can Am to fit a wider range of riders without harshness. When using straight rate springs, there is a window to ensure preload amount and rate are well matched. To soft a spring and excess preload is bad, as is too firm a spring and no preload.

As for little preload, I would need to revisit Spacetigers posts. Seem to believe he was running upwards of .500".

Springs typically are available in 50 lb/in increments, sometimes less in softer ranges.

I need to find time to work on all the stuff I want to get done on the Spyder. While in the air, I will measure the shock and see if I have a better shock kicking around to install. I may install a $5 spring rubber at that time also.

My suspension tuning experience often finds that on non linkage suspensions, except old twin shock stuff, a straight rate may not be ideal. Granted it can be better than oem, but tuning the progressive spring often gets better results. However, it takes time and some testing.

BTW, I have the hose clamps and will report in a PM my opinion on changing them all to the reusable style.

[h0gr1der]

Mr. PMK,

After that rant about Oitiker clamps, it turned out to be the water pump. I think the Spyder gods are mad at me. The KISS principal was definitely absent on my coolant leak. Still don't like those clamps, and will replace them when I can.

[h0gr1der]

So, I've been pondering this a couple of days while my bike is being held hostage for repairs, and have come up with another technical question about changing the spring rate on the stock RTL rear shock.

I've had some very knowledgeable guidance, and I appreciate everyone who has done this for me. I've learned that apparently I'm going to end up with a 700-900 lb/in spring with some kind of coilover sleeve used as a preload adjuster. My goal is to basically set the ride height with me aboard with the cargo I most commonly carry to a ride height that causes the air bag to run near zero pressure.

My bike is a 2018 RTL with the ACS auto leveling system.

So, here's the next question; Using a linear spring will necessarily raise the unladen ride height to more than stock, to achieve a laden ride height in the normal range. If I start the Spyder before boarding with the air bag at zero pressure and the ride height being measured by the ride height sensor as being higher than normal, will the computer recognize this as some kind of problem and throw a code?

For any of you guys that installed an aftermarket shock with a single spring, that removes the air system from the equation, do you know what spring rate your shock has?

[trikermutha]

I believe mine maybe 500 IB spring? But cannot see it from under the bike. So I could be off a bit??

I know my compressor has not turned on yet since installing the M2 Shock.

[h0gr1der]

I believe mine maybe 500 IB spring? But cannot see it from under the bike. So I could be off a bit??

I know my compressor has not turned on yet since installing the M2 Shock.

Mr. trikermutha,

Thanks, that's the kind of info I'm looking for. From the posts with actual hands on experience, I've read from 700-900 Lb/In, but am not sure of anything else. Talked with a bunch of very helpful folks. got some insights on preload and ride quality.

[trikermutha]

I am not absolutely positive but thought Marcus said 500LB spring

Like I said compressor has not turned on yet..

I know I have to get under and do some tuning but will try and look at the spring for any specs.

[PMK]

Since the system for air ride is not an active setup. The sensor will be holding the dump valve open, possibly continuously.

Not sure, but unlikely a code will trigger. Your bike does not have selectable ride height, I believe.

Another reason I have been hesitant to install a firmer spring is that without looking hard, you can read posts about failing and bending lower shock bolts. The lower shock mount is a reasonable diameter bolt, that passes through a steel sleeve. Apparently, the bolts and sleeve are prone to bending. Knowing airsprings are inherently progressive in rate. And the airsping is secured on a structural portion of the swingarm, the issue of stress via the air ride is nonexistent.

Counting on the spring to carry the entire load may create constant stress vs intermittent stress from bottoming.

Considering the ease to disable the air ride, and plumb direct, plus the minimal cost of a small bicycle tire presents another alternate. Even easier, if concerned about dealing with this on a road trip, carry the small handpump, and priorto any issues, replumb the compressor and valves in such a way to isolate the system to simply the Shrader valve under the seat, and the bladder.

[PMK]

Wanted to add, this is a bit technical, but the Spyder I believe, but could be wrong, is utilizing a pretty typical 3:1 leverage ratio. With no linkage, and a shock near vertical, there is no rising rate built into the design. No rising rate for the spring or damper.

The airspring is inherently rising rate. Add to this, the oem rear spring is progressive. Combined, the oem coil and the airspring provide selected ride height and on earlier models a form of adjustable preload.

Asking a straight rate spring to accomplish progressive spring duties can result in compromises elsewhere in the travel.

Consider, the rear end of the Spyder is controlled by 1 1/2” of shock shaft movement. With that, any error in choosing a spring rate or control by the spring is a factor of 3 at the axle.

On dirtbikes, with linage setups, I have tested straight rate springs, and multiple variations of crossover points of progressive springs, plus each in various rates. I found the straight rate spring was best at holding the rear end up during the initial part of the stroke. This made for holding a steeper head angle and lively steering. The downside though was the straight rate spring tended to blow through the stroke and bottom easier. The progressive spring settled a bit more when cornering, but had better feels on small bumps and did not bottom violently. Each has merits and each has drawbacks.

[trikermutha]

The airbag is compensating for the extra weight that a driver and passenger is creating when sitting on the Spyder. Now if the shock spring is rated at 500 lbs in most cases that should be more than enough to keep the rear end from dragging on the ground and not needing a air bag to compensate the ride height. I have not heard of the newer Spyders having issues with bent shock bolts.

[PMK]

The airbag is compensating for the extra weight that a driver and passenger is creating when sitting on the Spyder. Now if the shock spring is rated at 500 lbs in most cases that should be more than enough to keep the rear end from dragging on the ground and not needing a air bag to compensate the ride height. I have not heard of the newer Spyders having issues with bent shock bolts.

Fully understand your comment about the spring. With over 40 years experience working on and tuning race bike suspension and more, the grasp is acceptable on the topic.

Regarding the newer bikes not bending bolts, simple thought is why not. My guess, the engineers went with a firmer progressive spring to partially assist the air ride further, thereby bottoming less, even less harshly,