Suspension Modification Suggestions

[abhijitz]

great advise here !!

while am not that worried about my rear, am more concerned about the front. I had a professional fix my earlier ZR7 front forks, changing the springs + adding spacer + lighter oil and it made a HUGE difference. Am more concerend about the front than the rear atm.

I sent out a mail to RaceTech requesting a quote, opening the front forks is not a hassle, but rear makes me think I can open it, but can i fit it back properly not compromising geometry? [will follow Mellow's thread on this & give it a try]

DsrtRngr : can you please pm me the price you paid for your complete suspension setup by RaceTech ? Am yet to await a quote from them, have sent out all my details.

FLSTRDR AND STEVEST1300 : what is your front fork spring rated at ? On the hyperpro website i do not see a reference of the 07 ST1300A model. [Mine is not a PAN European model]



If the price difference is huge, i might just settle in for the Hyperpro sets (front & rear) and have them changed by a professional. OR might beg for assistance here

 

[FLSTRDR]

abhijitz,
The HyperPro springs are progressive, like stock Honda. The wire diameter is slightly larger and the spring length is slightly longer. They do not have several different fork spring sizes for the ST; only one. It replaces the Honda spring without any other modification except for fork oil. The Pan European an ST are the same basic deal.
Sonny

 

[Rob Hephner]

I'll regret making this short later, but let me try to give you the Reader's Digest version of progressive versus straight.

Straight is the same rate beginning to end of travel, so the feel is more consistant. If you ride aggresively it is typically the way to go as you get more range if travel. You pick the spring rate for how you want to feel and that is it.

Progressive is a lesser rate to start and then moves to a higher rate, thus it feels softer to begin. If you cruise around and then occasionally want to be aggressive you can split the difference. But you have less usable range of motion between the two types if riding.

Let's face it, a spring is a spring and most are made on the exact same machine and packed in the box of the company that will be selling them. If you have the proper spring rate for your weight and riding style that is a great start.

Then, after that to make sure you have traction you'll want proper damping. That us where valves and oil weight come into play.


Sent from my iPhone using Tapatalk

 

[dduelin]

But you have less usable range of motion between the two types if riding.

This is interesting. Care to elaborate?

 

[Rob Hephner]

This is interesting. Care to elaborate?

That was meant to say of, not if....but if that didn't throw you then....

Typically there are 2 or 3 rates within the windings.

Just for the sake of discussion lets say you would normally run a 200 lbs straight rate spring.

You would then use a 150 lbs to 200 lbs rate spring, which would compress more quickly for the first half and then slow for the second half.

Since the range that the fork can move is fixed, let's say 8-inches, you get half of the rate for the first 2 to 4 inches and the rest will be the 200 lbs rate, whereas with a straight rate, the increase is even all the way through the range.

As I said I tried to make this short. If you don't understand that a spring rate means how much pressure is needed to move it as it is compressed, you may not understand what I am saying. (ie with a 200 lbs straight rate the first inch requires 200 lbs, the second inch 400 lbs and so on and so forth.)

Much easier for me to show a person in person.

 

[dduelin]

I caught your misspelling as "of". No problem.

I am comfortable with spring rates and have a good understanding of them in this context. I just didn't follow the assertion that progressive springs have a less usable range of travel compared to straight rate.

Let's say one spring has a rising rate compared to the other. The rising rate progressive one is 150 lb/in initially and both are 200 lb/inch at the high end of the rate, then the progressive spring will move earlier and further for the same force applied to them. Say we apply 200 lbs of force. One spring moves 1.333" and the other 1". In this example the progressive spring has a longer range of travel for the same force, no?

OK, if the suspension travel is limited by fork design and not but completely compressing the spring, as in the ST1300, then the rising rate spring has a longer range of travel for the same force. If you choose a spring that has an adequate rate and correctly preload it you won't be routinely bottoming it so I see this point as moot. Both forks will operate in the designed suspension travel of 4.25" but the one with the lower initial rate will move further in the same conditions. If the goal is to limit or lower movement then a straight rate spring would have less travel for the same force. Maybe that is what you meant to say?

 

[Rob Hephner]

I just didn't follow the assertion that progressive springs have a less usable range of travel compared to straight rate.

That's because that isn't exactly what I said, or meant to convey. (I warned that I was making it short...)

Let's say one spring has a rising rate compared to the other. The rising rate progressive one is 150 lb/in initially and both are 200 lb/inch at the high end of the rate, then the progressive spring will move earlier and further for the same force applied to them. Say we apply 200 lbs of force. One spring moves 1.333" and the other 1". In this example the progressive spring has a longer range of travel for the same force, no?

Yes, and it also means the rising rate spring has less distance for the rest of its travel.

OK, if the suspension travel is limited by fork design and not but completely compressing the spring, as in the ST1300, then the rising rate spring has a longer range of travel for the same force.

Yes, and again, since it travels more, it now has less useable range for the other type of travel...or riding style.

If you choose a spring that has an adequate rate and correctly preload it you won't be routinely bottoming it so I see this point as moot.

When you adequately preload it, it 98% of the cases, you'll eat up more of the usable range because you are using at spring rate that is less than what is needed for weight...

OR

If the lesser rate is proper and you go to a higher rate, you'll never end up using the last inch or so of travel as the weight simply will not move it.

Thus, in both cases, less usable range of motion compared to the straight rate.

Both forks will operate in the designed suspension travel of 4.25"

No, they will not because as stated before, you'll either eat up space with preload or you'll eat it up with an immovable rate.

but the one with the lower initial rate will move further in the same conditions.

Yes, it will move more and leave less.

If the goal is to limit or lower movement then a straight rate spring would have less travel for the same force. Maybe that is what you meant to say?

The goal is to suspend the bike and the rider(s) above the wheels.

If the bike is riding aggressively occasionally than a progressive rate can make more sense, if the bike is ridden aggressively I'd suggest a straight rate.

All the spring does is suspend weight, it does not by design maintain traction, that is the job of damping. Therefore if you look at how weight acts as it moves around you'll understand how a progressive spring feels the best on a showroom.

Another "best use" of a progressive spring is how it helps to auto set preload because it rises as you add more weight, thus giving the manufacturer the ability to give proper SAG to a multitude of riders. If the ST1300 came factory with a straight rate spring it would only have proper SAG in about a 20-50 lbs range, whereas with the progressive it has a 75-125 lbs range for adequate preload. Make sense?

What I was trying to say was that fretting over spring brand isn't that big of a deal. The only choice is straight versus progressive.

If you ride your bike alone all of the time, do not add passengers or luggage and ride aggressively get a straight rate for your weight.

If you ride non- aggressively and vary the weight on your bike because of passenger and luggage, get a progressive rate.

If you fit somewhere in-between, weight the options and choose.

Since you can't change the preload on the forks knowing what your spring does and how it aids you is the benefit here.

OK, no what did I confuse.

 

[dduelin]

Well, I did say that there is room for experts to disagree on the merits of straight rate vs. progressive springs on street bikes and I think I'll leave it at that. I'm quite happy with the ride and handling I have on the roads I ride at the speeds I ride.

Thanks Rob for the lucidation. Is that a word?

What sag numbers do you have on your ST?

 

[Rob Hephner]

Well, I did say that there is room for experts to disagree on the merits of straight rate vs. progressive springs on street bikes and I think I'll leave it at that. I'm quite happy with the ride and handling I have on the roads I ride at the speeds I ride.

Exactly, it is totally a preference thing and all based upon the rider and how they ride and sometimes with who they ride. LOL

I believe to make the choice it is better to understand what you're choosing, yes?

Thanks Rob for the lucidation. Is that a word?

elucidation?

What sag numbers do you have on your ST?

37mm front

38mm rear

 

[Rich R]

So.....how about those new preload adjusting fork caps.........
I am assuming you have "something" to do with this Rob
Might make all this rising rate vs straight rate conversation inconsiquential....
Rich

 

[dduelin]

Exactly, it is totally a preference thing and all based upon the rider and how they ride and sometimes with who they ride. LOL

I believe to make the choice it is better to understand what you're choosing, yes?




elucidation?



37mm front

38mm rear

What about free sag? I also have my fork tubes raised 5 mm in the clamps. It help sharpen the steering geometry lost when I reduced the sag.

 

[Chase the Lion]

On the Hyper Pro set up...they sell two different rear shocks, one with an external resevoir and one without. Anyone know if other than potentially cooler oil, if there is increased adjustabilty that justifies $300 more? Anyone pleased with their $599 rear shock for the St? Thanks

 

[Rob Hephner]

What about free sag? I also have my fork tubes raised 5 mm in the clamps. It help sharpen the steering geometry lost when I reduced the sag.

5 mm on the front. By reduced, do you mean more SAG or less?

 

[dduelin]

5 mm on the front. By reduced, do you mean more SAG or less?

Reduced as in original measurement with OEM springs and spacers was 48 mm sag or 44% of travel. I was shooting for 30-33% of travel or 32 to 36 mm sag with OEM springs. The first spacer I made gave 36 mm rider sag and I have stayed with that.

5 mm free sag, recommendations are all over the place for fork free sag but I have never seen or heard of 5 mm up front. Sure that is not for the rear? 5 would seem to indicate the springs are too soft for you and that doesn't seem right with your RT upgrade.

 

[Rob Hephner]

Reduced as in original measurement with OEM springs and spacers was 48 mm sag or 44% of travel. I was shooting for 30-33% of travel or 32 to 36 mm sag with OEM springs. The first spacer I made gave 36 mm rider sag and I have stayed with that.

5 mm free sag, recommendations are all over the place for fork free sag but I have never seen or heard of 5 mm up front. Sure that is not for the rear? 5 would seem to indicate the springs are too soft for you and that doesn't seem right with your RT upgrade.

I think I forgot a 1 in front of the 5 as in 15?? I need to check with Lenny. (I think the system was compressed 5 mm in the tube, before the weight of the bike was added?) Not real certain on that number. You are correct, the rear is 5mm.

OK, yeah less SAG in that situation is what I would shoot for as well.

 

[dduelin]

Paul Thede has been quoted 15-20 mm free sag (forks) is a good range for street bikes but aside from general recommendations to start with whatever the rider likes for his bike and his style is what is "best".

 

[Rob Hephner]

Confirmed, it is 15mm.

 

[CJewell]

Okay, so a lot of talking, but no one saying weather or not they like the suspension upgrades. I have an 04 with 54K and will either get the race tech on both ends or I will be looking at the BMW RT1200. I commute and the highways are terrible out here in CT. I am constantly adjusting the rear shock due to the weather in which I ride in and would like to have something that will not beat me up getting there. How about some straight talk from those that have purchased/installed front and rear systems, please!!

 

[Marshal_Mercer]

Okay, so a lot of talking, but no one saying weather or not they like the suspension upgrades. I have an 04 with 54K and will either get the race tech on both ends or I will be looking at the BMW RT1200. I commute and the highways are terrible out here in CT. I am constantly adjusting the rear shock due to the weather in which I ride in and would like to have something that will not beat me up getting there. How about some straight talk from those that have purchased/installed front and rear systems, please!!

CJewell:

I have an '04 as well. To answer your questions, in order:

1) I LOVE my after-market suspension, front and rear.

2) RT1200 is a great bike. Go for it if that's what you want. The new double overhead cam set up is supposed to be really nice. I've been looking at the K1300GT.

3) I adjust my rear shock only when I change from the street/highway to canyons/mountains. Two clicks, by hand, does the job. I can get everything from a pillow-soft to a rock-hard ride with very little effort.

4) Go here and here to read more.

Cheers,

Marshal

 

[CJewell]

I see that you mixed your components and I am glad that worked out for you.
I am only looking at the BMW because I have never ridden one and do not know if that suspension set up is all that it is cracked up to be. Yes, only a little bit of adjustment here and there depending on the weather and all is well, just wanted the straight scoop from the one's that have installed a suspension system. Thanks