RT Weight distribution

[dangme55]

Most excellent info - thanks

Jim
If you know someone with a set of race car scales the guy might have a
spring rater If so check the rate on your springs then decide what you need
from there. On the shocks your friend may know someone at Pro Shocks in
Lawrenceville Ga that will dyno them for valving so as to make a better choice
on that even as they will have adj. compression & rebound. Just make sure
the new springs are a matched set on height & rate. Heck he might have some
springs in the 10"length you can test with.I know two guys that have the RTs that
use the Ron's bar with the elka 1+r one has the 250 springs & this setup works real
good,the other has the 300 springs & he complaines they are about to beat him to
death on anything on the rough side. I need one of these guys to pull a shock & lets
have it checked for valve rate as that is a well kept secret.

spyder strider
Dan

Dan -

Thanks for the insight.

I agree about spring rate and ride comfort. A lot of people on the forums do not understand that stiffer springs make bumps bumpier!

From the suspension gurus in the books(s) softer springs make for better handling/wheel to road compliance. There are always trade-offs and softer means big chance of bottoming to the jounce stops. Ouch!

Right now I have 250# springs on order. (Again I am relying on Elka's 207# empirical data.) They are 14" versus 9.3 for the oem shocks. Can't reuse stock springs as they are too short and QA1 and other shocks are not threaded high enough on the shock body to get the perch high enough take up the slack on short spring.

My main concern now is the spring diameter. OEM shocks are pretty skinny as are the springs. The O.D. on oem shocks is about 2.5" which is the I.D. of standard coilovers. QA1 told me that the O.D is 3.25 - 3.5" - oh I hope not. There is not that much room in the 'hole' in the wing/upper arm. After doing some spring calculations I get that the O.D. should be around 3 " which will fit. I am waiting for everything to come in so I can see if it will fit. Summit should take it all back ($490) if I did not mount it I am 'purdy sure.'

If it doesn't work out I still have the 2014 oems on order and I may have to break the piggy bank for some Elkas.

Still it is going to be good experience in suspension tuning :banghead: (Experience is what you get when you don't get what you want!)

 

[spacetiger]

Dan -

Thanks for the insight.

I agree about spring rate and ride comfort. A lot of people on the forums do not understand that stiffer springs make bumps bumpier!

From the suspension gurus in the books(s) softer springs make for better handling/wheel to road compliance. There are always trade-offs and softer means big chance of bottoming to the jounce stops. Ouch!

Right now I have 250# springs on order. (Again I am relying on Elka's 207# empirical data.) They are 14" versus 9.3 for the oem shocks. Can't reuse stock springs as they are too short and QA1 and other shocks are not threaded high enough on the shock body to get the perch high enough take up the slack on short spring.

My main concern now is the spring diameter. OEM shocks are pretty skinny as are the springs. The O.D. on oem shocks is about 2.5" which is the I.D. of standard coilovers. QA1 told me that the O.D is 3.25 - 3.5" - oh I hope not. There is not that much room in the 'hole' in the wing/upper arm. After doing some spring calculations I get that the O.D. should be around 3 " which will fit. I am waiting for everything to come in so I can see if it will fit. Summit should take it all back ($490) if I did not mount it I am 'purdy sure.'

If it doesn't work out I still have the 2014 oems on order and I may have to break the piggy bank for some Elkas.

Still it is going to be good experience in suspension tuning :banghead: (Experience is what you get when you don't get what you want!)

Well you posted some interesting info. What caught my eye was the OD of the shock, ~2.5" That's the diameter of the springs I got for a set of shocks I got for my scooter... They were meant for a mid size motorcycle, so I was experimenting. I will take some measurements of the RT-S this weekend and post up the results.

You say the springs you ordered were 250 lb springs. I was not sure what you were saying, was that the max load for the spring (for the working range)? The springs I mounted on the scooter (they are a bit stiff) bottom out (2.5") at 305 lbs. I will have measure the stock RT-S shock to see what the spring can hold up than compare them to the aftermarket springs... They only cost ~100 for a pair.

Here is the link to the scooter mods: http://www.apriliaforum.com/forums/showthread.php?241311-SC250-Suspension

Here is the link to the Nighthawk mod (go to page 5): http://nighthawk-forums.com/project-logs/1984-cb700sc-retro-bike-project/


Jerry

 

[dangme55]

The beat goes on - LOL

Well you posted some interesting info. What caught my eye was the OD of the shock, ~2.5" That's the diameter of the springs I got for a set of shocks I got for my scooter... They were meant for a mid size motorcycle, so I was experimenting. I will take some measurements of the RT-S this weekend and post up the results.

You say the springs you ordered were 250 lb springs. I was not sure what you were saying, was that the max load for the spring (for the working range)? The springs I mounted on the scooter (they are a bit stiff) bottom out (2.5") at 305 lbs. I will have measure the stock RT-S shock to see what the spring can hold up than compare them to the aftermarket springs... They only cost ~100 for a pair.

Here is the link to the scooter mods: http://www.apriliaforum.com/forums/showthread.php?241311-SC250-Suspension

Here is the link to the Nighthawk mod (go to page 5): http://nighthawk-forums.com/project-logs/1984-cb700sc-retro-bike-project/


Jerry

I will check out the links. Thanks for the info.

Here is where I am at and a bit at a loss.

The shocks and springs on the Spyder are thin - might say they are 'Spyder legs' LOL

I don't have the exact measurements in front of me but the OD of the oem springs is about 2.9 inches and the wire diameter is about .359, and 9.3 in free length the shocks are about 1.6 inches in diameter - I have not found anything that comes close to those measurements.

The shocks I chose were QA1 DS901 which measure 15" collapsed and 23 3/4 extended. I did not take off a :spyder:shock to measure but the body of the shock on the machine measures 14, add an inch or so for eyelet and 7" for throw (6.85" of suspension travel) and you get about 22" extended so these will 'work.' Problem is standard ID for off the shelf springs is 2.5 in. And in order to reach the preload rings and jam nut etc and ride height I need a 14 inch spring. BRP has the bottom perch way high on the shock so they get away with a 9 inch spring. So what you get off the shelf is relatively massive. 11 active coils means .5 wire diameter and an overall OD of 3.5 inches. If you look at the upper wing opening that is a very tight fit. I am going to take a set of dividers and make measurements this afternoon. The clearance is going to be critical. nojoke If they fit this is going to look 'killer' stout.

My next option is to go to 2.25 in ID springs to get more clearance. Eibach makes a 250# spring in 2.25 " but they are hard to find. If I go that route then I will need to buy 2.5 to 2.25 adapters to resize the top hat and perch. Either that or take the hats and perches down to my trusty Craftsman lathe and turn them down from 2.5 to 2.25 - not a very difficult project.

Other than the Eibach option there are precious few 2.25 springs available here. The UK sellers have tons of 2.25's I guess it is a Europe thing. I can get them but will take a couple of weeks.

Other options I am considering:
Going to a off-road / 4 wheel shop they seem to have more spring options.
Stacking coil springs - still researching how to do that. I know the off road guys do it. That would kill 'two stones with one bird.' LOL shorter springs should mean narrower coils and I could mix/match to get progression.

Then there is the take'em back to Summit and buy oem shocks. i am not that aggravated yet. I am learning a lot of stuff I can use later.

Again, I will look at the links.

Standby for 'the rest of the story.'

 

[spacetiger]

Got a chance to pull the shock and test the spring.  Wow, it is stiff!  I put 430 lbs on it and only compressed it about an inch.  There is a little more than 1.5" travel left, so the shock can really hold up a lot.  I'll work up the analysis and graphics this coming weekend.<br><br>Jerry

 

[dangme55]

Hmmm - amazing

Got a chance to pull the shock and test the spring.  Wow, it is stiff!  I put 430 lbs on it and only compressed it about an inch.  There is a little more than 1.5" travel left, so the shock can really hold up a lot.  I'll work up the analysis and graphics this coming weekend.<br><br>Jerry


View attachment 79999

Jerry

wow that spring can bench press more than I can LOL

How do you keep that spring in line and not 'spronging' out of the rig?

Moreover that is really quite an interesting result. :shocked: I can't tell from the picture but is the weight stack directly on the spring or is there a pulley system giving mechanical advantage in the setup?

When I ran the 'theoretical' spring rate I came up with around 370# and Elka measured and came up with 207# per inch. Quite a bit of variance there among the three results. However that is not the whole story. I have yet to calculate the wheel rate which is what counts. The number(s) above only count if the spring/shock is vertical as our rear suspension is mounted. The front suspension is mounted at an angle so I have to figure out what the rate at the wheel is:gaah:
For those who are following this thread - that is why they tried to shove all that trigonometry down your throat in high school. Don't fret - there are loads of suspension calculators on the web so manual calculations are not required.

Also I am curious as to how you figured there was only 1.5" of travel left. Was that at the shock or the spring length? I figure that the stock spring should block/coil bind around 5" so it should have about 4" of travel total before it blocks. Not a knock just curious.

I am now at this point in the adventure. The new 2014 OEM spring / shocks came in this week and if I get the chance I am going to get them installed tomorrow. The Atlanta area weather forecast is rain/snow and my dealer is about 80 miles away so it might postponed until next week.

That muddied up the waters for me as I thought I had until end of December and was going to try the 'custom' solution and if I liked it i was going to cancel the new oem shock order.

I am going to send the original single adjustable QA1's and 3.5" springs back.

I got a couple of used AFCO dual adjustable shocks on EBay for $200. Even if they need rebuild I will only have about $400 invested there. So my alternative solution will be on hold for a while.

Here is what I came up with:
Dual adjustable shocks 15" collapsed 9" stroke
250# tender springs over 350# mainsprings. This should give 7" of travel, 146# initial rate.

That will now get put on back burner while I test the new oem shocks.

Cheers!

 

[spacetiger]

Jim,

When you look at the shock you will see a black rubber bumper around the chrome shaft. It's loose enough that it slides back and forth along the shaft. This is the bump stop and prevents a hard compression impact. You can slide up the rubber bumper up till it touches, then, you can measure the distance from the back of the rubber stopper to the shock body. That distance is the working range of the shock. You can get a bit more as the rubber piece will compress a tiny bit. When you look at factory specs they count the full stroke distance and ignore the rubber bumper. Every shock I have tested on the gym equipment always comes out less than the factory advertised distance = to the rubber bumper length.

I compressed the shock very close to an inch and measured the remaining gap at 1.5", so then works out to be 1" + 1.5" = 2.5" That is a nominal working range for a rear shock. When you look at the RT-S shock, it looks like a rear shock. For many bikes, the rear shock works through a compound linkage. The shock may only have a working range of 2.5", but the wheel works through a wider range. That is the case for us. You are correct on the angle of the shock accounting for the compound affect. The ratio of the working range of the shock divided by the wheel travel range is the angle of the shock. I will have to measure the rubber bumper length into the equation so I'll have to wait till Sat to post the final numbers.

When I tested the shock I left 4 indents in the preload setting. It is hard to change it once the shock is removed, so I left the preload dialed in. When you test the shock, all it does is shift the spring rate plot to the right, once it starts compressing, the data collected will allow you to calculate the K (spring rate) of the spring. That is, lbs/distance moved to covert to Lbs force to compress 1 inch. Since I had a lot of preload in, it took 430 lbs to compress it one inch. Each indent compresses the spring about 1/8" (0.125"), so 4 indents = 4 x 0.125 = 0.5" Weight to compress 1" + preload = 430 lbs. Preload = spring rate x 0.5". Since I only compressed the spring 1"; the math works out to be X + (X x 0.5) = 430 lbs or 1.5 X = 430. So solving for X = 430/1.5 = 286.667 lbs. Before I go final, I will retest the shock with no preload in. The graph of the data will reveal the spring rate.

Before changing the spring, you should have a feel for how much of the shock travel you are using. For my 2 wheeled bikes, I use zip ties on the stanchions. As the fork compresses it, pushes up the zip tie and you can measure the amount of the fork you use. You never want to bottom out, so you need to evaluate your riding envelope vs. fork length use. If you find you are always at 80% of fork travel, you should put in a stiffer spring. If you use only 60%, then you are good. I have found a good panic stop can compress the front almost 90%. So I have to find a way to do the same for the RT-S; measure the used range of the shock. To do this, I will get some plastic washers (thin) and drill the center out so they match the diameter of the shock shaft. After cutting the washer, I think I can slip it past the spring and pop it on the shaft. It will be in between the shock body and rubber bumper. As the shock compresses, it will push up the washer and thus the rubber bumper. When the shock decompresses, the washer will hold the rubber bumper up away from the shock body. I think after ring a few hundred miles under a variety of stops and turns, I can measure how much of the shock working range I need. Since I will have measured the shock on the mount and will know the the spring rate, so if I find I use 2", then I put 287 lbs/in x 2 in = 474 lbs of compressive force through the shock. With 2 shocks, I know I will have 474 lbs x 2 shocks = 948 lbs. Then through trigonometry, I can back out the vertical loading on each wheel (assuming they are equal).

On the test rig, I use a large 3/4" socket on each end. That gives me a flat surface. On the top, there is a bolt that fits into the socket and keeps it from sliding out.

Anyways, much work to do this weekend to advance our understanding of the Spyder suspension. If you can, hold off from buying items until you have done some analysis. That way, you actually know what you need. I will try to get this done this weekend, if you can wait that long..

Jerry

 

[dangme55]

Ah okay I feel better now

Jerry

Hope you had a great Thanksgiving!

Cool - nice to have someone to banter with who understands (not sure if even engineers do really) the black art of suspension tuning.

I hadn't really worked through whether to reuse the jounce bumper or not. I had run the numbers on motion ratio although off hand I don't remember what the number was.

That explains it. You were just testing to see if I was awake right. The preload adjusted numbers are more inline with what I expected. I understand preload can be a bear to adjust. I ordered a set of thrust bearings on the qa1's and if I decide to go with the AFCO's that will surely be on the list.

I did not get to the dealer so I am still not in the new 2014 shock mode as yet - next week for sure. When I get the take offs I may be able to get someone to test / dyno them.

Don't think I will be able to test the new ones before they go on. I should be able calculate the ratio of the new 2014 springs to the 2013 springs with some degree of accuracy based on relative spring heights and ride heights on each of the sets.

This would be a lot easier if BRP was a bit more forthcoming with some real specifications.

Guess I have been in Corvette world too long and I am spoiled. Chevy and the engineers, as well as aftermarket vendors put everything in the open.

Stay tuned LOL

 

[dangme55]

2014 RT Shocks on the 2013 RT - Qualitative Report

Okay - thanks again to Jerry for all his insight and sanity checking on this thread.

Yesterday my dealer -Extreme Propulsion in Cartersville - installed new oem 2014 RT shocks on my 2013 RTS-SE5.

This thread about 'duplicating adjustable shocks' and calculations was something I was going to try while i waited for the oem shocks which I did not expect until late December. I figured spares would be in short supply until production runs were finished. I guess those people anxiously awaiting their 2014's will get them soon as they shipped my spares last week.

Yesterday as I said - they were installed. Total damages $377 installed. Shocks are about $80 each - springs about $50 and install about 1 1/2 hours. If you want to try this you need shocks and springs only. The top perch and collar from the 2013 can be re-used.

I have not done all the quantitative 'stuff' yet. Haven't measured everything and compared across my notes - but the new springs are slightly stiffer as are the shocks. Apparently BRP has 'responded' and built the springs / shocks they should have done in the beginning. That is probably a cheap shot as no one can tell in advance what 'ride' characteristics the consumer wants in advance.

So this is a 'my seat of the pants' report. I will follow on with another quantitative post that Jerry and I can noodle on. LOL
From a quantitative perspective I can tell you that the tech measured ride height and it was about 3/4" higher after the new springs so they are definitely a higher rate spring.

Ride and handling are very subjective so here it is.
I wanted to maintain 'cruising' suspension characterstics - with this new set up I can say the ride is a bit firmer but not uncomfortable. So far I have only ridden solo so i still have to put the better half on the bike and see how that goes.

My 80 mile ride home has a lot of different road segments two lane, four lane, twisty and super slab. So I got a lot of different perspectives.

My main problem with the original set up was that even though I had the Bajaron installed and it helped a great deal in controlling body lean ( a very good investment) it did not solve weight transfer rate issues. My problem was that I felt that 'turn in' took too long. It was almost a two step process. I would turn the bars and the bike would start to turn, then the weight would transfer and the tires would 'bite' on the outside and I would have to take out some input. I did not like that at all.

With the new setup the weight transfer is a bit faster and smoother and the turn in is more responsive and predictable. No more hunting for the right steering input. The suspension 'sets' earlier in the turn and stays put. And that is a LOVELY thing in a corner.

Straight line is also very much improved as the bike is not upset by small irregularities in the road surface as it was before.

All in all $377 very well spent. Since I finished most of my mod's list (see below) over the last weekend I am pretty much done. One last mod to put led's on the mirrors but that will be simple.

Then I am just going to ride like crazy. Well at least until I get the mind to tinker again. That dual spring setup is still on my mind and I still have the AFCO shocks I stole for $205 on EBay.

Thanks everyone for your comments and have fun riding.:thumbup:

 

[spacetiger]

Jim,

Get some nylon washers on the shocks to help you set up the suspension. I think it is the only quantifiable way to set up the suspension on this bike.

For me, I think I have a way to make the stock shocks work out; I'm going to add a small preload spacer to each side. It will be either 0.625" or 0.75". THat should be enough to set up the bike for a rider from as low as 150 to 275 lbs. I;ll post the information after I source out what I'm going to make the spacer out of.

Are you going to look at the rear shock?

Jerry

 

[dangme55]

Think I am done tinkering for a while

Jim,

Get some nylon washers on the shocks to help you set up the suspension. I think it is the only quantifiable way to set up the suspension on this bike.

For me, I think I have a way to make the stock shocks work out; I'm going to add a small preload spacer to each side. It will be either 0.625" or 0.75". THat should be enough to set up the bike for a rider from as low as 150 to 275 lbs. I;ll post the information after I source out what I'm going to make the spacer out of.

Are you going to look at the rear shock?

Jerry

Jerry -

Great idea - I like the way you think out of the box!

I weigh #260 and my spousal unit is not shall we say 'petite.' Did I say that? oh oh!

Together with gear in storage we are definitely at max allowable if not a tad over.

I could machine a custom perch spacer as you are describing and I think that would be very useful to someone who is in the proper weight range.

Right now when I get on the bathroom scale it says 'one of you get off!' so I think I will forego the preload.

This weekend I will measure everything and post up the difference in the dimensions along with the rough calculations on the spring.

No way to test the shocks without a dyno. There is no one around me that can do that as far as I know. When I spoke to AFCO the other day they said that they had acquired Pro Shocks in Atlanta a couple of years ago and moved the operation to their home base in Indiana.

So I guess I will run around on these for a while. If I decide to go true custom with the AFCO's and long springs or dual coil set up I will start another thread and PM you.

If I had a straight RT or other model I might look at the rear shock but I think it is adequate and because of the pneumatics and adjustable preload on the rear of the RTS I am not sure I want to tackle that.

Thanks for all the help! Ryde on - Ryde on.

 

[spacetiger]

Jim,

Can you really make the spacers (out of steel or aluminum)? If I spec them out, would you make me a set? I can pay for material and shipping. I can also work up the spacer you'd need for modify your current 2012 shocks. You have to PM me the weights so I can work out the thickness you need.

Jerry