Suspension Modification Suggestions

[abhijitz]

I have been reading various threads and several riders have chosen the following :

Front :: springs : GP / RaceTech / Progressive / Sonic AND thinner oil combination.
Rear :: Penske Shocks, aftermarket heavier springs (?) on the stock shock

Coming from track riding with stiffer suspension on R6, i prefer stiff side. On the ST1300, the front sags in too much on bumps. At the same time, i have the rebound on rear to the max & preload 2 marks out.

I can use spacers for the front (interim) but would like to rebuild both the front & rear at the same time which will give me a pleasant ride

My weight : 180 lb with gear + wife's : 120 lb with gear [till today i have been riding solo]

I do not have the tools or mechanical expertise to rebuild the front shock myself neither have the money to buy an expensive penske so looking for a decent solution pricewise. I intend to open my forks & rear shock myself and take it to locals like Catalyst Reaction (Dave Moss) OR Evolution Suspension (Rob).

fyi - for those of you who reside around Bay Area very well know Dave's work. He fine tuned my track bike & it handles like a charm.

1. What springs & oil for the front should i be using ?
2. Should i be replacing the rear with more adjustables (pre-load/compression dampening/rebound) OR just replace the spring OR buy a brand one. If brand, what other alternates than Penske should i be using.

Appreciate your advise.

 

[mercedesman]

I too have been looking at doing something like this to my 2003A, but am also considering selling this bike and going for a new version, in which case I will be doing this anyway.

So what I have come up with is this: the guys at Race Tech, according to many of the others on this forum, like what they have done. Race Tech came up with their own valving for the ST (gold valve kit) and can either make your rear shock rebuild-able and recondition it to work with a higher rear spring rate or replace it with an aftermarket shock that is also rebuild-able. A lot of people seem to like Sonic springs for the front and will go with a higher spring rate than what Race Tech recommends. I don't know tho if the Gold Valve kit and the recommended front springs from Race Tech is equal to the standard valves and a higher rate Sonic spring.

For me, when the time comes I'll just send the forks down to Race Tech, maybe the rear shock too, have the higher rate springs installed and the shock modified to dampen the higher spring rate. I would like to keep it all stock as far as the shock adjuster is concerned, makes the install easier to deal with.

Rob Hephner had Race Tech tune his suspension and was one of the first. He is on this site and can fill you in on a lot more detail.

Mike

 

[Marshal_Mercer]

<snip> A lot of people seem to like Sonic springs for the front and will go with a higher spring rate than what Race Tech recommends.<snip>

Good choice.

The highest spring-rate that I am aware of that Race Tech offers for the ST1300 is 0.95 kg/mm.

When Race Tech installed my Gold Valves, I provided them with two sets of SonicSprings front springs, to install at their discretion. One set was 1.1 kg/mm. the other 1.2 kg/mm. Both were straight-rate. After compressing the forks and generally fiddling with the suspension, RT chose my 1.2 kg/mm over their own straight-rate 0.95 kg/mm set. They said that the 0.95s were too light for my application. I weigh 200 pounds plus gear, ride mostly solo in the mountains and canyons, and take at least one 2-3K mile long trip annually.

Marshal

 

[abhijitz]

^^ So, should i just talk to RaceTech and ask their suggestion on my riding needs? Do i need to ship the forks & shock to them?

I will pm Rob for his suggestion.

 

[Marshal_Mercer]

^^ So, should i just talk to RaceTech and ask their suggestion on my riding needs? Do i need to ship the forks & shock to them?

I will pm Rob for his suggestion.

I suggest that you call Race Tech to find where is a Service Center in your area. Ask Race Tech what parts you'll need to buy, including SonicSprings or HyperPro fork springs. Book an appointment, then ride to the Service Center for installation. The work will be completed in a few hours. You can go for a ride to see if changes need to be made, which can be done there, then you're on your way back home.

Marshal

 

[SteveST1300]

I went with Hyper Pro front springs and a rear shock specd out to my weight. A huge improvement in ride and handling well worth the money wichever brand you choose.

 

[abhijitz]

Marshal - Thanks much. RaceTech office is not far from me (6 hours). If the work can be done in few hours, i might make a trip I will call them as well.

Steve - Thanks for your suggestion.

 

[diverdown]

I have not changed my suspension yet but like you I have heard or suggestions to change it especially when riding 2 up. I called Hyper-pro and was told to email www.Annitori.com with all my information bike and me with all weights etc which I did. They recommended a setup for the bike(which I am now awaiting in the mail). I am looking forward to trying the new mods out when they come. Hope you find a solution which works for you. Jim

 

[abhijitz]

Thanks Jim. If you do not mind, please pm me the suggestions you are provided with. I will call RaceTech now & if i get a suggested setup, will post here

I have not changed my suspension yet but like you I have heard or suggestions to change it especially when riding 2 up. I called Hyper-pro and was told to email www.Annitori.com with all my information bike and me with all weights etc which I did. They recommended a setup for the bike(which I am now awaiting in the mail). I am looking forward to trying the new mods out when they come. Hope you find a solution which works for you. Jim

 

[indypup]

I'm interested in this thread too. I'd like to beef up my suspension too. I have 60K on my '07 ST13.
I hope Rob chimes in...

 

[jdpfms]

Marshal - Thanks much. RaceTech office is not far from me (6 hours). If the work can be done in few hours, i might make a trip I will call them as well.

Steve - Thanks for your suggestion.

I'm not a suspension guru, but I do have a friend who really knows his stuff. He said the best and cheapest fix for most people would be to buy the spring combo that Hyperpro has. It has progressive front springs with provided fork oil (suppose with weight for you) and a new rear spring. It cost about $260 for this, and if you do your own mechanical work you save labor on this. I may go this direction later in the year, but I'm not unhappy with my stock set up right now. But for a relatively cheap mod. if it produces major suspension improvement, it could save $1000 or more on more major setups.

JDP

 

[SteveST1300]

I went with what you mentioned except I replaced my shock as well as my stock shock had 70+ K miles on it. Gene went with just the spring on a new stock shock and was somewhat satisfied. Replacing the fork springs is a huge improvement. It took me a while to get the setings right on my shock but once I got it right the change to the bike is amazing.

 

[FLSTRDR]

Thought I would chime in my 2 cents worth at this point. I am 210lbs and my wife is 135lbs. We ride 2 up 80% of the time. The stock set up is way under sprung for us. The least expensive mod I did was to put the HyperPro front and rear springs and change fork oil to HyperPro specs. This worked well for over 20,000 miles, however riding solo the rear spring is too strong. With the mileage now at 40,000 I thought a total RaceTech set up would be in order, hearing so much positive about them. So far this has not proved to be so. I really don't feel that much improvement with their Gold Valves. There springs,1.2, were too stiff and at their recommendation changed one(1) fork leg back to a HyperPro. This helped but not a total improvement. There rear Shock sure looks impressive and well made. It did not come with any instructions about how to change the dampning or anything else. It also feels too stiff. After a phone call to them I made some changes and not happy yet. I emailed their Rep, Lenny, in November and still no reply. I emailed them for help this morning and hope to have some news soon. Maybe when they are here in Daytona next month I will be able to have them figure out what needs to be done.

 

[Marshal_Mercer]

Thought I would chime in my 2 cents worth at this point. I am 210lbs and my wife is 135lbs. We ride 2 up 80% of the time. The stock set up is way under sprung for us. The least expensive mod I did was to put the HyperPro front and rear springs and change fork oil to HyperPro specs. This worked well for over 20,000 miles, however riding solo the rear spring is too strong. With the mileage now at 40,000 I thought a total RaceTech set up would be in order, hearing so much positive about them. So far this has not proved to be so. I really don't feel that much improvement with their Gold Valves. There springs,1.2, were too stiff and at their recommendation changed one(1) fork leg back to a HyperPro. This helped but not a total improvement. There rear Shock sure looks impressive and well made. It did not come with any instructions about how to change the dampning or anything else. It also feels too stiff. After a phone call to them I made some changes and not happy yet. I emailed their Rep, Lenny, in November and still no reply. I emailed them for help this morning and hope to have some news soon. Maybe when they are here in Daytona next month I will be able to have them figure out what needs to be done.

If you have measured your front and rear sag, do you recall the numbers? That could help us understand why your bike feels stiff. Also, do you have a fork brace installed? At one point, I did, and it was binding, making the front-end stiff feeling.

I have 1.2 kg/mm front springs, as do you, along with a 1300 pound/inch rear spring on an adjustable shock. The suspension feels like a pillow when damped correctly. It feels like riding a board when set under-damped on compression though. That might be your whole problem. The stock rear shock has no provision for compression damping. Too much rebound damping will make for a rough ride also; stock shocks do have this adjustment.

Marshal

 

[FLSTRDR]

No fork brace. If I remember the front sag it is around 30-35mm and rear I don't remember. I would have to look that up at home. Made sure the front axle was not binding by the forks being out of allignment. Waiting on reply as to the adjustment on the rear shock damping.

 

[Marshal_Mercer]

No fork brace. If I remember the front sag it is around 30-35mm and rear I don't remember. I would have to look that up at home. Made sure the front axle was not binding by the forks being out of allignment. Waiting on reply as to the adjustment on the rear shock damping.

You might want to try about 38mm sag on both ends. That will soften things over smaller bumps and dips. To make that change on the front end will require new spacers (usually PVC pipe) or just cutting a bit from your existing spacers' length. I'd go with new ones, just in case I cut off too much. The rear shock is set with the pre-load adjuster.

Marshal

 

[FLSTRDR]

Thanks for your input. I just got a email from Lenny at Race Tech and he will be here the 25th so I'll get in tune with him.
Sonny

 

[dduelin]

If you are a light solo-only rider like me one might try just adding some preload spacers to the stock springs and changing to a lighter fork oil. I did this and have been quite happy with the ride and handling improvement. Race Tech recommends a .884 kg/mm fork spring for my +/- 160 lb. weight. This is only .024 kg/mm increase in spring rate over the stock spring .86 kg/mm rate. The closest aftermarket spring rate to the RT recommendation for my weight is .90 kg/mm.

There is room for experts to disagree on the merits of straight rate vs. progressive rate springs on street bikes and I was overall happy with the ride quality of the stock suspension on OEM progressive springs, I just wanted to firm things up. I set out to get the sag right and reduce or eliminate the wallowing around the headstock when cornering fast to very fast and I did that by adding 16 mm preload and going to 6.7 wt Showa (Honda) fork oil. I replaced the OEM shock with nearly new OEM take-off at 64,000 miles. Bumps and dips in corners don't upset the bike and it doesn't wallow in high speed sweepers or dive under braking. Rider sag is 36 mm, free sag is 21 mm. Originally it was just under 50 mm. The stock rear preload adjuster allows a rider sag range of less than 20 mm to more than 40 mm. I like it at 30 mm. Free sag in the rear is 7 mm.

While I have no doubt an expensive upgrade delivers the goods I also know I can ride fast on bumpy technical roads and my ST is more than capable at my skill level.

 

[DsrtRngr]

I just got my forks and rear shock back from RaceTech. I took them off myself and dropped them off for revalve/respring. I got the .95 kg/mm RT springs, and the rear has an Eibach spring. If you can change a front tire, you can remove the forks, no problem. The rear is a nuisance to get out, but not difficult.

The gold valves make the forks adjustable, once you have them installed. If you can remove and disassemble the forks on your own, you can add/remove spring washers from the valves to go from "firm (c34)" to serious firm (c35), or down to "plush"(c32). The last digit is how many big washers are used. You can change the length of spacer to get the sag correct. But to adjust the rear is more difficult, since it's gas charged.

RT puts 5wt oil in the forks, unless you tell them otherwise.

Beware of the girl in the office. She gave me a printed estimate that included two removal charges. Since I did that work myself, I expected the price to be reduced $105. But when she handed me the invoice, it had magically crept back up to the same price as before. The valve kits used to be much less expensive. Now they're priced high, and they give back a 'group buy discount' - to make you feel like it's a good deal, no doubt.

Verdict is still out, as far as fine-tuning mine. I rode someone else's bike briefly (thank-you Tim S) with the Sonics. I've read elsewhere that it can take a few hundred miles to get the fork springs limbered up. I suspect to trust / compare the spring compression numbers from each brand is a mistake, unless someone actually tests them to see if the rates are accurate.

If you mostly ride the slab highways, and you're sane, safe rider, I'd almost suggest going with the C32 setting and the .95 kg springs in front. If you tell RT that you're intermediate rider, with 200+ lbs, they're going to give you the .95's and the "firm" C34 valve.

 

[Marshal_Mercer]

<snip>
I suspect to trust / compare the spring compression numbers from each brand is a mistake, unless someone actually tests them to see if the rates are accurate.

While I was at Race Tech, they tested both my 1.1 and 1.2 kg/mm springs for actual tension. According to RT, they were very nearly spot-on spec. So-- SonicSprings seems to be making accurate representations.

DsrtRngr: since we live so close by, you might want to compare my set-up with yours. Please PM me if you're interested. I'd be happy to ride over. A RTE would also be good.

Marshal