Spring rates for Racetech ugrade front and rear?

Hi!

This has been discussed a million times before but I will ask the question again. I have done my first season on a -2015 ST1300 and this is a wonderful bike. But as most other users I find the suspension to weak when riding two up and with luggage. For solo riding I like the suspension as it is. I am now going to send the rear shock to racetech for re-spring and gold-valve modification. I will at the same time order parts to re-spring and gold-valve modify the fork.

What is the best compromise for spring rate for me? I am riding 50% solo and 50% with passenger and luggage? We are about 100kg+gear each.

Regards
/Anders

Sweden

Use the RaceTech spring rate calculator.

Go here - http://racetech.com/ProductSearch/2/Honda/ST1300/2004-15

Once there Click on the "Calculate Spring Rate and Display Available Springs" link in Yellow at the top of the page. Spring rates will be a compromise between solo and 2 up.

I'll just mention that I followed the spring rate calculator for my rear shock rebuild/respring and, as with all things, it's a performance trade off. While the STeed can now comfortably handle my wife and I for fully loaded touring with the preload cranked up, it's a bit harsh riding solo with the preload cranked all the way down. For our safety and comfort we had to increase the spring rate, but there's a trade-off.

I'll just mention that I followed the spring rate calculator for my rear shock rebuild/respring

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Did you also re-springed the front? Which spring/springs did you choose?

it's a bit harsh riding solo with the preload cranked all the way down

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This is what I want to avoid as far as possible

For our safety and comfort we had to increase the spring rate, but there's a trade-off

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This is what I feel also. The bike don't feel safe with the stock suspension and the actual overload we put on it

No I didn't do the front as I've never felt there was a big problem with running out of suspension travel or diving under heavy braking. Maybe the previous owner(s) already did something there?

As I mentioned, it's a trade off. The bike is great now when riding two up and my wife, and I are in the same weight range you quoted, but the ride is a bit harsh when it's just me aboard. However, it also tracks like it's on rails and I never feel the rear tire is anything but solidly planted, even when going over uneven pavement when heeled over, so I'm not complaining about the less than plush ride. Now that the shock has been rebuilt it can be worked on again and I may get the damping oil changed to a lower weight and see if that relieves some of the harshness. I'm not set up to remove the spring in my garage so I'll need to save up to get someone else to do this. Until then I'm okay with how it handles and feel perfectly safe with my most valuable cargo on the back.

I'm not sure there's a (cheap) solution that can give you both, but there are other options than Racetech that others have recommended here for rear suspension upgrades. Maybe check some of the other threads.

Most of the harshness on the ST1300 is due to excessive compression damping and in the fork, a very high oil level that leads to a very steep progression. To make matters worse, Honda fits too-soft springs, making the bike ride at more than 50% sag for most folks. That keeps the fork action in the highly progressive region created by the high oil level. I fitted Sonic 1200 Kg/mm straight rate fork springs and dropped the oil level according to Sonic's instructions. Though counter-intuitive, this actually gave an plusher ride, while getting the sag into the correct 25-33% of total travel range. Later I added Race Tech gold valves and 5 wt red-line oil. Front action is great now. Very plush while still very controlled.

For the rear I fitted a 1200 lb/in spring (OEM is around 900 I believe) and had Race Tech rebuild the shock, changing all the guts out with a Gold valve. Not sure what oil they used, but I think 5 wt.. Results were similar to the front, better sag numbers with the pre-load cranked only about 1/3 of the way in, where as I had it 80-90% cranked in before. For solo riding unloaded, the spring rates are just a little on the stiff side, but the bike is massively better when loaded now. There is no more wallowing and scraping hard bits in the twisties. The stiffer rate rear spring means I get more change for the same number of turns on the adjuster. The damping improvement, in spite of the stiffer spring, still provides a more compliant, less harsh ride.

Just a final note on the pre-load adjuster. These units have a nasty habit of loosing their hydraulic oil, and in a severe case can prevent you from increasing the pre-load at all. Fortunately these can be serviced at home. I have recharged the pre-load adjuster on two shocks using ATF, which seems to outlast whatever the volatile stuff that Honda uses to fill them.

For reference I weight about 230 lbs in street clothes.

wjbertrand said:

Most of the harshness on the ST1300 is due to excessive compression damping and in the fork, a very high oil level that leads to a very steep progression. To make matters worse, Honda fits too-soft springs, making the bike ride at more than 50% sag for most folks. That keeps the fork action in the highly progressive region created by the high oil level. I fitted Sonic 1200 Kg/mm straight rate fork springs and dropped the oil level according to Sonic's instructions. Though counter-intuitive, this actually gave an plusher ride, while getting the sag into the correct 25-33% of total travel range. Later I added Race Tech gold valves and 5 wt red-line oil. Front action is great now. Very plush while still very controlled.

For the rear I fitted a 1200 lb/in spring (OEM is around 900 I believe) and had Race Tech rebuild the shock, changing all the guts out with a Gold valve. Not sure what oil they used, but I think 5 wt.. Results were similar to the front, better sag numbers with the pre-load cranked only about 1/3 of the way in, where as I had it 80-90% cranked in before. For solo riding unloaded, the spring rates are just a little on the stiff side, but the bike is massively better when loaded now. There is no more wallowing and scraping hard bits in the twisties. The stiffer rate rear spring means I get more change for the same number of turns on the adjuster. The damping improvement, in spite of the stiffer spring, still provides a more compliant, less harsh ride.

Just a final note on the pre-load adjuster. These units have a nasty habit of loosing their hydraulic oil, and in a severe case can prevent you from increasing the pre-load at all. Fortunately these can be serviced at home. I have recharged the pre-load adjuster on two shocks using ATF, which seems to outlast whatever the volatile stuff that Honda uses to fill them.

For reference I weight about 230 lbs in street clothes.

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Jeff, what is your free sag with the 1200 lb spring?

dduelin said:

Jeff, what is your free sag with the 1200 lb spring?

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About 1.25" with the pre-load adjuster turned in about 1/3 from full out and recently re-filled with oil. Bags were mounted but mostly empty and no top box fitted. That's about 25% of the total 4.8" travel. Anywhere between 25 -33% is good.

Not rider sag. Free sag (loaded bike but no rider). From the previous comments it sounded like a 1200 lb spring was a lot for your riding weight. Free sag of 5 to 10mm ought to be about right if the rate is good for your riding weight.

dduelin said:

Not rider sag. Free sag (loaded bike but no rider). From the previous comments it sounded like a 1200 lb spring was a lot for your riding weight. Free sag of 5 to 10mm ought to be about right if the rate is good for your riding weight.

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Hmmm, dunno actually, I never measured it. There is at least some free sag as I can see the suspension compress slightly raising the bike up off the side stand. I'll have to check.


-Jeff

Racetech is recommending me 1,0kg/mm at the front and 23,2kg/mm on the rear as the best compromise between solo and two up riding. Does this sounds correct to you?

I've been watching this discussion from my mobile phone and haven't had a chance to add my $.02 til now. DDeulin was probably wondering when I would chime in since I've done a couple of these upgrades to members bikes, and he and I have had many discussions about the ST suspension. I'm no expert or paid professional, but I am Very mechanical and have a engineering mindset. I tried many of these springs rates on my bike before settling on what I have now. I say settling because it is a matter of give and take when trying to set the bike up for single and two up riding at the same time.

Here are my Stats,
05 ST1300
My weight = 175#/80K
Wife's weight = 140#/63K (Don't tell her I posted that)
Combined = 315#/143K
No top case, but do use a rear rack with a dry bag

Frt. = .90kg/mm
Rear = 21.4kg/mm - 1200#

I tried the .95kg/mm front springs and the 23.2kg/mm rear spring initially. This set up was perfect for 2 up, but a littler harsh for single riding. At the time I installed this my wife was only riding with me about 20% of the time. This summer she was with me about 50% of the time. If this trend continues I will move up to the 23.2kg/mm spring on the rear. When we are 2 up I crank the rear preload to the max. When one up about 1/8 of the travel. I did cheat though and used a diff case shim from a Jeep axle has a additional spacer on the rear spring so that i no longer have to add any prelod when one up. I tried following many of the forum suggestions on what spring rates I should use, and went through many trials and errors before I decided to stop trying to reinvent the wheel. I followed the recommendations given by Racetech and have been happy ever since.

I would say from my experiences that the rates they gave you are good. If you tend to carry allot of luggage when you ride 2 up then you might want to move up to the 25kg/mm rear spring. The one great thing about the gold valve upgrade is that even if the spring rate is a little low, the shock does a much better job of controlling the movement of the bike. I've chased several of the members here through SE Ohio and the Smokey Mountains while riding 2 up and surprised many of them by my ability to keep up. The new suspension is the biggest contributor to this.

If you any more questions, ask and I will try to help you. My kids are home for the holidays and we are taking a one week rode trip to Austin, TX to move the rest of my daughters stuff to her, so replies may be slow.

Now is the rear shock posted to RaceTech I am ordering a 23,2 kg/mm spring and a goldvalve modification for the shock. And a pair of 1,0kg/mm springs and the goldvalve/forkcaps kit for the fork You will most likely hear more from me with questions about fork modification and oil viscosity/level etc.

Happy new year!

I look forward to hearing how those work for you, especially the fork springs and whether you find the forkcaps worth the extra money. Good luck with your installation and configuration.

Wether the extra money for the caps is worth it really depends on what kind of person you are. I have the caps and usaully run them very close to the neutral position, which is what you would get with just the valves. If you are the type of person that doesn't constantly mess with the bike looking for a little better set up, then the caps are a waste of money. If you are a bit anal and looking for just the right set up under different conditions, then the caps are a steal.

I right 2 up about 30% of the time and ride both straight nortern roads and twisty southern roads during the year. The ability to tweak the front suspension based on these variables is priceless to me, but then I'm extremely anal.

When I first spoked to Race tech thy wanted to put a 23,2kg/mm spring on the shock. Now they say that a 25kg/mm is what I need. Although I am a quite heavy driver (110kg with gear) I am afraid of loosing all the solo riding comfort with that stiff spring. Is there anyone here with experience of a similar setup?

I ended up with a Penske spring, 1300#. No loss of comfort. But that equates to the 23.2 kg spring. I'm also a 110kg (but down to 100 ) rider and told them I occasionally have a pillion rider and wanted touring with some sport.

Did you do any two up riding with the 1300# spring? How was that compared to the stock spring?

Much better two up, never felt the spring bottom. Rode almost like I was 1-up... when she couldn't see the speedometer. But before I could occasionaly feel the rear bottom out when 2-up, no more. We put a few thousand miles on it at RockStoc 1 last year through Colorado. I've probably put 20k total on it since the upgrade. It is a definite must-do if you are in the 200+ pound category.

PS After listening to a Race-Tech sales presentation and speaking to a representative I went a different route. But no matter who you choose it is better then stock for a full size male rider.

This is the hard part. Trying to decide which way to go on spring sizes. Either one will be way better than stock. Which spring to use really depends on how much you plan to ride 2 up. Each spring will be a comprise in ride quality. It just depends on where you want to make the compromise. I do believe that if you go with Racetechs suggestion and don't like it, they will swap springs for no restocking fee. You will have to pay to have them switched. With that being said if you took the shock off yourself you can most likely change out the spring yourself. I have a spring compression tool that I modified to fit the ST shock that I can loan to you for the cost of shipping.