Replaced the Front Springs

My bike has a bit over 28K miles on it and a while back I ordered some new suspension parts. I went with Hyperpro for the whole setup. Today I installed the front springs and steering damper. The springs are a direct replacement for the factory springs so it was a simple matter of:

• Disassemble
• Empty
• Fill with new fluid (160 mm)
• Reassemble

The fluid was 7.5 weight. As you can see in the photos the Hyperpro springs are slightly longer at about 10 1/8" vs 9 3/4". The wire was slightly thicker as well.

I took it out for a short 60 mile shakedown ride. No major surprises. Although I didn't measure it I think its sitting up a little bit more than it used to. The ride was good, seemed a little smoother. Although I hit a bit of traffic in the canyon it was cornering no worse than before and maybe a little better.

The steering damper was a little more of a pain to install than the front forks. It might have been easier if I did it while the forks were off but I waited till the front end was back together. I also had to remove my radiator grill because I didn't think it would clear the damper.

I'm still waiting for a bracket for the rear shock assembly before I can finish things up. I'll check the sag when all the pieces are on.

I'll report more once I have a few more miles on it.

Hey Byron,
so it sounds like you decided to replace the originals due to normal wear? I'm in the process (waiting for parts) of installing sonic springs. I have the 1.1 kg but they also have an 1.2kg. Do you know what your's are rated at?

I can tell you, after checking sag on mine with 13k and oem front, it's at 2.25 inches. Total travel of the front is only 4.5, or so some specs I just read indicated that. I'm hoping that when I get mine done it improves the handling alot. It seems in your case it's only negligible if any?

Good Luck,

HankSTer,

I was going to measure the sag and that before taking things apart but like I mentioned since they are a direct replacement I'd do it once the rear is changed also. It does seem to feel a little different. This could be because there is less front sag so the head angle is slightly different. I don't have that many miles but it does seem to have a smoother ride. My run up the canyon is a road I am very familiar with. It was handling the turns about the same. I may have been coming out the some of the corners a little late which makes sense if I need a little more preload in the rear now.

As I said, at this point handling didn't get any worse, ride seems to have smoothed out (which is one of the things I was looking for) and it's going to take more miles to tell. Darn, I have to go put some more miles on the bike.

Well after a couple of days of riding with the new front springs I made my first adjustment. As I mentioned it seemed to be a little taller up front. It seemed to be a little twitchy when just starting or just before stopping. Although I could overcome its' wanting to leave a corner a little wide it wasn't quite right. I added in about 2 turns on the rear preload and it seems to have done the trick. It was back on rails again when going through turns, no more exiting wide. Also, no more twitchiness at slow speed starting or stopping.

Darn I wish the missing bracket would arrive so I could install the rear shock.

Well I got the word today that the bracket I've been waiting for is in and will be shipped to me ASAP.

Hank,

Sorry I didn't answer this sooner but sometimes it's hard for me to stay on topic or remember. Anyway, I'm upgrading more than replacing worn items. I'm looking for a smoother ride but still handle the twisties. Basically remove some of the harsh feeling out of the handlebars.

I don't know what the springs are rated at as they don't offer up or publicise the spec's on the springs. You tell them what weight the bike needs to carry and they size the spring to handle it. I don't know why the need to keep the information secret but that is the way they are.

The front springs are progressive and have more air space than the factory setup. When I'm hitting surface irregularities now it is much smoother. There is no bouncing of the front end. The tire hits the object, you can feel a gentle nudge at the hands, the front tire rebounds and you still moving flat straight ahead.

When you hit irregularities in turns it is the same. The suspension does what it needs to do and you don't change lines or anything, just keep trucking throught the turn.

With the factory setup it was always a jarring feeling when the tire hit something, even with the softer feeling Avon's on the bike.

Once the bracket for the rear shock is here and I get it mounted I will report on the setup as a whole.

Byron said:

I don't know what the springs are rated at as they don't offer up or publicise the spec's on the springs. You tell them what weight the bike needs to carry and they size the spring to handle it. I don't know why the need to keep the information secret but that is the way they are.

Click to expand...

To all:

We were directed here by a member to see if we could add some input to the question posed.

The reason we do not tell you the spring rate is that these are constant rising rate springs, so there is no "single" spring rate. They are an almost infinite numbers of rates, constantly changing as the suspension needs demand.

We are not "hiding" anything, but our springs are not the simple version of 1.1 or 1.2, they are designed to work within the exact bike we make them for (which is why we do not use PVC spacers or such), but with the added benefits of a smoother initial movement, firm handling thru the mid-stroke, and a much better resistance to bottoming.

Best of all, with constant rising rate springs, all of these attributes are there whether you are riding solo, two up, heavy, light, or anything in-between. The springs are always adjusting to the load...

Just wanted to see if we could clear up any questions, let us know if we can be of any further assistance.

Steve Larson

Nice response on the springs, makes sense. Nice that a vendor is willing to respond about their product.

This whole spring thing is getting interesting, for me anyway. I had read up on the Sonics previously as they were heavily mentioned in other threads by STers who are using them. The Sonics are a straight rate spring and their argument for that approach seems pretty solid. :|

Now Byron introduces me to the HyperPro and off I go looking at their site. Now they're a progressive rate spring and reading their arguments for this approach is pretty convincing too.

I had p(P)rogressive (both the brand & and the spring type) springs on my Vulcan and they were a vast improvement over the stock front springs.

All that said, I'll be interested to hear further reports from Byron on how the HyperPros do. I'd also like to hear anything else anybody might like to add about the progressive VS straight rate spring differences.

I hope this isn't opening up a big can o' worms that dwarfs gun control and oil all-in-one.

Pat Thompson said:

I had p(P)rogressive (both the brand & and the spring type) springs on my Vulcan and they were a vast improvement over the stock front springs.

Click to expand...

Just as a note, and not to start any sort of "pissing" match, but "Progressive" is the name of a company, which should not be confused with the design of the product in all cases.

We only ask that you as consumers check the actual designs of the springs to determine if the product is actually "constant rising rate" (which is how we would define the word "progressive"), or something else.

Progressive is a fine company, nothing bad to say about them at all. But the products we have seen (and we admit we HAVE NOT seen them all) are not constant rising rate springs, but two springs of different rates combined together. Not saying this is bad or good, better or worse, or anything else. Just trying to make sure that everyone discusses the products based on their actual design and function, not based on the name of the company.

Honestly do not know what they offer for the ST, but maybe somebody out there can research this to see if they are a true rising rate spring, or something else?

This way everyone will know what the differences between products actually are.

Steve Larson

Well I have a little more feedback on how the front springs are working. This last weekend I rode through Death Valley from the North end. We covered about 60 or so miles of dirt roads to get to Scotty's Castle. I can only say that I'm glad that I had the Hyper Pro springs installed because these were not the smoothest of dirt roads. The new springs absorbed a lot of the washboards without feeling like I was driving over square bricks which the front springs felt like on similar roads.

I hope to have the rear shock installed shortly.

stevelarson said:

Honestly do not know what they offer for the ST, but maybe somebody out there can research this to see if they are a true rising rate spring, or something else?

Steve Larson

Click to expand...

Thanks for your response, Steve. Last time I looked at the Progressive site I don't think they had an offering for the ST.

We would agree, to an extent.

Please, my comments are all pleasant, and only in the spirit of conversation.

The springs we create are constantly changing, it is not a "linear" progression of 10, 20, 30, etc.

We are capable of changing the coils, thickness of the wire, all the options to actually make the spring do what we wish, where we wish it to be done. What we mean is that the spring can "progress" at 2:1 for the first section, change to 4:1, then back to 2.5:1, etc., all the way to the end of the coil.

So the END result when placed in the fork creates the curve you would see on a shock dyno.

As for a "stiffer" spring, we in no way disagree that "your" experience was one which our spring did not satisfy.

But that does not mean that ALL the other customers who are happy with the results are wrong. What you "want", and what I "want", compared to what he, she and they "want" is NOT the same when discussing suspension. Look at every performance machine ever created, suspension for each rider is different no matter what sport you are in. It is just the nature of suspension.

So no anger here, your comments are well noted by us and we will pass them to R&D. But we do not feel that your "blanket" statement of product inadequacy is correct or warranted, as it is only your particular weight, riding style, use, set up, etc., that our springs did not fill the need for.

There are thousands of others out there that we are making more then happy already...

Steve Larson

Mr. Larson:

Thank you for your clarification with regard to your company's experience. I asked this same question prior to making my springs purchase.

I would like to suggest that if a customer decided to not disclose the amount of his/her payment to you, you might not ship product. By the same token, I was not prepared to hope that your product met my needs when riding with a passenger, so I purchased another brand of springs instead. This may be my loss if your products work to meet better my needs, but I tend to rely upon quantitative data when making buying decisions.

It seems to me that your company's disclosure of your springs' beginning and final rate of resistance to compression would have better served me, and by association, your company.

What do you say? How about disclosing the rates? The "great debate" would thus end.

Marshal Mercer

Understood...

Easy to do in this case...

103 -183 Newton/mm.

But please keep in mind, there are many numbers in-between, almost none of them "equal" space to the next, and there is the setup of the fork which plays heavily into the "curve", so be careful with how much you can actually know from these two numbers

For example, we can make the end of the curve flat or even negative, depending on how we are using the air chamber in the overall result.

For a simple example, we can have springs that go 110 - 115 - 117.5 - 120 - 117.5 - 115 - 110. So you would see a start and finish of 110 (thus believe it is a straight rate spring), yet of course it is far from it.

Just trying to help explain our world...

Steve Larson

stevelarson said:

Understood...

Easy to do in this case...

103 -183 Newton/mm.

But please keep in mind, there are many numbers in-between, almost none of them "equal" space to the next, and there is the setup of the fork which plays heavily into the "curve", so be careful with how much you can actually know from these two numbers

For example, we can make the end of the curve flat or even negative, depending on how we are using the air chamber in the overall result.

For a simple example, we can have springs that go 110 - 115 - 117.5 - 120 - 117.5 - 115 - 110. So you would see a start and finish of 110 (thus believe it is a straight rate spring), yet of course it is far from it.

Just trying to help explain our world...

Steve Larson

Click to expand...

Thanks, Steve. That is the information I needed. A measurement in kg/mm may have been more helpful to some readers, though, as they do not have an accelerometer handy; I certainly do not. I'll approximate acceleration based upon the influence of gravity alone.

As you suggest, calculating the appropriate spring rate is much more complex than it first seems.

For those of you not familiar with the "newton", it is a measurement of the amount of force required to accelerate a one kilogram mass by one meter per second, per second. In this case, the force is supplied by the movement of the combined masses of the bike, rider(s), and gear. The time it takes to do this is the fraction of a second that it takes to compress the spring(s). The spring's resistance to acceleration is what we need to know in order to mount the correct device. That, and the amount of force required just to hold up the whole mass at rest.

Marshal

Just remember that Earth gravity is about 2.6385 times that of Mars.
gonzo

Gonzo said:

Just remember that Earth gravity is about 2.6385 times that of Mars.
gonzo

Click to expand...

....AND THAT'S ON A GOOD DAY!

Marshal

Please enplane how a spring starting at 110, we'll call them pounds/inch for ease, then rising to as high as 120lbs can then soften back up to 110.
I understand coil distance and their affect on spring rate but if I have the spring in the example and add 110 pounds the spring will compress 1 inch. As I add another 110 pounds it will compress 1 more inch, the ending 110. Is this second 1 inch in compression not going to be the ending 1 inch? How can I add an additional 10 pounds to this spring and not compress the final inch before the 115 or 117.5 sections begin to compress?

Click to expand...

Sorry, I was trying to make a point, but did not do it very well.

Let's take the case of a spring with 80-140 as the start and end.

The point I was trying (very poorly) to make is that the start and end numbers do not mean much.

We can have the rate go 80-81-82-83-110-140-180, or we can go 80-120-120-120-130-135-140-180, or we can go 80-140-140-140-140-140, even 80-85-90-95-100-140-140-140.

What I am trying to say is that the start and end numbers do not, in the case of rising rate springs, tell you much of the story...

Sorry for the really bad example, the fingers were moving faster then the brain...

Steve Larson