Modifications - Performance Discuss aftermarket and DIY performance modifications

Suspension Mods - On the cheap :)

Old 10-04-2015, 06:21 PM
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Suspension Mods - On the cheap :)

Let me start by saying i love this forum. Everyone here has been so helpful, and the knowledge of the owners here is truly amazing.

Rider info:
Age: 48 yrs old
Height: 5'11"
Weight: 155 not including gear
170 with gear
Type of riding: Fast street rider

I'm at a point where i don't have the money for the suspension upgrades i want to do, like my dream list... But i can probably do a few things in the late winter, after February, so i'm forming some ideas, and looking for thoughts from you guys...

Fork Spring Swap
So i've found some old threads about guys swapping VFR springs into our Superhawk fork legs, as they are a bit stiffer. Anyone have any info on what weight they would work for? I love doing swaps from other bikes because it can be quite inexpensive (I realize some people might have issue with used fork springs, but i have used springs in there now, with 39k miles on them, so i don't require brand new stuff)

Swingarm Angle
I've been reading about ideal swingarm angles. Anyone have thoughts on an ideal swingarm angle for the Superhawk? I have a Johnson angle measurement tool, and mine is currently at 10 degrees (bike without rider).

Rake and Trail (and wheel alignment)
I'll be working on measuring my rake and trail soon, and aligning the wheels to ensure everything is straight... I haven't done that yet on this bike, and am looking forward to getting a baseline.

Goal
My goal is to do a few simple "mods" to the stock suspension that are super cheap, but net some gains in performance. I'm not really the kind of guy who throws a lot of money at brand names and "recipes". Not that anything is wrong with that, I just like to gather knowledge and do the work myself. I definitely have more time available than money.

I've done valve stacks before, including redesigning shim stacks for my riding, done spring replacements, seals, oil, spacers... None of this stuff scares me, and i'll have time over the winter.

I'm really looking forward to gathering more information to help others, such as recommended oil weights, spacer lengths, air gaps, etc... Anything i can do to help others on a budget.

(I'm hoping people find this post during our forum's time of decline because of the "active topics" link being gone)

James

Last edited by thedeatons; 10-05-2015 at 07:15 AM. Reason: Updated rider weight. I was a little off :)
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Old 10-04-2015, 07:11 PM
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Interesting question, James.

I sort of started down this path after I bought my VTR this year, as I felt guilty spending money on it as I already own a VFR800 and have done quite a bit to the suspension on that. Wasn't sure how accepting my wife was about having TWO bikes!

The cheapest thing to do would be to add a shim between the top clevis and frame at the top of the shock. I have a 6mm shim that I bought on e-bay, but honestly with a bit of aluminium of the right thickness, a hacksaw, file and drill, you could make one. That will lift the back end up and steepen the rake, giving more responsive steering.

I bought some 0.85kg/mm front springs from RaceTech, but you could use the VFR springs as you mentioned as these should be 0.74 vs the 0.585 kg/mm stock. Not perfect but probably better (stiffer) than stock.

After that - shims/valves for the fork dampers. I bought ($5 ea) some compression valve bodies from a Suzuki from a local suspension tuner. These have much bigger ports than the VTR so flow oil better, more like a Gold Valve, and I have shimmed them up the same as Gold Valves. As far as I know you can mix and match Showa cartridge parts so long as you stick with 10mm shaft/20mm id size. I have re-shimmed the stock rebound pistons with 3, 0.15 x 17mm main shims to get a bit more control. I run 5W Motul oil at 120mm from the fork top, compressed with no springs. I'm pretty happy with how all this works.

It is worth reading up on suspension set-up and I have done a bit of reading of the Race Tech Suspension Bible. Stiffer damping and springing is not always better, IMO the VTR has plenty of spring at the back, and enough damping adjustment. I ran mine with the preload at it's lightest setting and rebound set 2 turns out.

No suspension modification will be worthwhile if the basic components are worn out, so you should look at replacing the fork bushings if these have wear, and also checking the steering head bearings for play/notching. The rear shock linkages could stand some love too.

My favourite (but not suspension-related) upgrade was fitting CBR954 brakes; Honda got these right, I think they mismatched the calliper/master cylinder sizes on the VTR.

I have since succumbed to temptation and added an Ohlins shock (trust me they are worth it for the plush control), and have just ordered a rebound Gold Valve set. I'm going to mirror my VFR fork set-up as that is still a ways better than the VTR as it stands. Don't tell my wife!

Last edited by Cadbury64; 10-04-2015 at 07:17 PM.
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Old 10-04-2015, 07:44 PM
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Lol... Good stuff!

Yeah i've had Ohlins before, along with Custom Axis (same as Penske, but for quads), and i fully understand money buys suspension happiness... Unfortunately i no longer have an Ohlins/Axis budget

I'll run some numbers on those VFR springs, thanks for those numbers.

I already have a 6mm shim between the frame and top of the rear shock, and rear shock is at its lightest preload setting.

Front forks are showing 6mm above the clip-ons, with unknown oil weight (until now i haven't messed with them, as they don't leak, and i was focusing on other things).

Current swingarm angle is 10 degrees and i just tried bunping rear preload by two notches and found the angle didn't change (not on the instrument i was using anyway).

I may add more ride height to the rear just in the name of looking for a 12.5 degree swingarm angle... More on that later.

Bike rides well, but i feel the turning characteristics could be better. Turn in feels fine. Not quick, but fine. Mid corner feels ok. Corner exit i run wide, which is why i'm first examining swingarm angle/anti squat. If i can achieve a couple more degrees of swingarm angle, then i will begin to understand how i like that number and what it does for turning on my particular bike...

James
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Old 10-04-2015, 08:34 PM
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If you increase the spring preload at the shock, the ride height/swingarm angle should increase as the shock will sit higher in its stroke for any given load. If you were measuring this with the bike unladen on a stand you won't measure any change because the shock is already topped out.

If the preload is already appropriate for your weight, then you could look to adding more shim height to lengthen the shock, but that may start to get the lower chain run a bit close to the exhaust.

One other thing that may be affecting cornering feel is the tyre profile. Are they a bit worn, pressures OK etc?

If it was me, I'd be flushing and refilling the forks with some fresh oil before going too much further. No need to dismantle the seals to do this.

Last edited by Cadbury64; 10-04-2015 at 08:36 PM.
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Old 10-04-2015, 08:48 PM
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I agree about the forks, but i'd like to go in once and do it all, in the winter

Tires are near new Bridgestones and feel awesome. Love the tires in fact (023 rear/016 frt) with 42 rear/36 frt pressures.

I too was worried about the chain vs exhaust equation.

The chain is about as short as i can get it with my already short gearing, so i can't get any swingarm angle out of that...

May try a couple shims tomorrow if i have time. Will let ya know how that changes things.

James
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Old 10-05-2015, 12:26 AM
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Your bike is running wide due to a lack (or rather to much) of damping control of the fork and lack of spring.

Google "Rogering" your forks and do it. Its a free mod. Then buy the correct spring weight for your weight. This is a must.

Dont worry about swingarm angle. Its a non-issue. I have a good setup and 3mm spacer. This weekend I will be riding it all day at the track, no angle change. Bike turns perfectly. I only run a Ohlins for comfort.
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Old 10-05-2015, 02:12 PM
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Ok... it's been almost 24 hours, so time for an update

In the past 18 or so hours I've found some great information...


Race Tech forkspring rate recommendations:
Stock VTR: .585
Race tech recommends.822kg/mm FRSP S3534 series


Race Tech SpringRate Calculator settings I inputted:
-Street
-lbs
-155 my weight
-415 bike weight(semi wet) (Original Race Tech weight of bike was 435, I subtracted 20 lbs because of slips-ons, PAIR removal, lightened flywheel, stick coils, no toolkit, Sargent seat (with less foam))



Information from Manufacturers

Race Tech recommends .86

Ohlins only has an.86 spring available and doesn't have any reference as to preferred spring ratefor my weight because bike is pre 2005

Traxxion recommends(Hyperco springs) .95

GMD Computrackrecommends (K-Tech springs) .95



OEM Fork SpringRates (in kg/mm) of bikes that use FRSP S35 series springs:
Honda Superhawk OEM.585
95-99 Duc Monster900 .686
98-01 Honda Vfr800.74
04-05 Honda Hornetcb600f .75
95 Yamaha yzf600r.77
96 Yamaha yzf600r.80
01-05 Yamaha fz1 .80
99-07 Yamaha yzf600r.81
97-98 Yamaha yzf600r.81
00-01 Duc 996 sps.95



Today I ordered 1996 YamahaYZF600R fork springs (.77) for $15 shipped on Ebay!

Here are current percentages of what Race Tech recommends vs what I am going to have:

Front
.822 recommended
.77 have
93% of what RaceTech recommends I have

Rear
17.5 recommended
16.4 have
93% of what RaceTech recommends I have


So, this fork spring install of .77 will balance the front and rear to exactly 93% of what Race Tech recommends. No it's not exactly what they recommend, but it is far more balanced than what I have now, for very little money.

Furthermore, right now, with full gear on, I have exactly 23mm of sag in the rear. That is with the front OEM springs, the really soft ones. I'm planning to re-measure the sag after installing the stiffer fork springs... I'm betting it will be different

So, that being said, the stock rear spring, even though it is only 93% the value of what Race Tech recommends, seems appropriate for my weight. With this logic applied to the front forks, I should be fine with the 95 YZF600R fork springs I just picked up, as they are 93% of the value Race Tech recommends, just like the rear shock in stock form...

This winter I'll be taking the forks apart, changing out the fork oil, facing the stock valve bodies, and probably re-shimming the valve stack... Shouldn't cost too much... In fact I'm thinking I'll be into this for the $15 fork springs, cost of fork oil, and cost of a few shims... I may as well do the seals while I'm in there....

Anyway, feel free to use the information above to find some springs from another bike that work for your weight. I'm certain there are quite a few 996 SPS riders on the Ducati forums with stock springs laying around, if someone needs a .95 spring

James

Last edited by thedeatons; 10-05-2015 at 02:26 PM.
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Old 10-08-2015, 06:38 PM
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Got a surprise today! My 95 Yamaha YZF600R fork springs came in!!!

Here are some pictures of them alongside the standard bits. Initial observations are:

1) Straight rate springs!

2) Thicker coils, definitely a heavier duty coil spring.

3) Longer so a smaller preload spacer will be used.

I'll be working on making up the preload spacer out of 1" PVC, then doing the taper grind on the rebound rod, setting the fork oil level, then buttoning it all up.

I'm doing this all with the forks on the bike, as it is just a simple swap for now. This winter i will change out the fluid, swap in 3 port Suzuki Showa pistons, and change the shim stack...

James
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Old 10-08-2015, 06:40 PM
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Old 10-08-2015, 06:40 PM
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Old 10-08-2015, 06:43 PM
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Old 10-08-2015, 06:44 PM
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Last one i think...
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Old 10-08-2015, 08:24 PM
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Called it quits for the night... Used Roger's method. Took the length of the old spring, and old spacer (410mm), subtracted the new spring length, and ended up with 32mm, the length of the new spacer.

Set the oil level to 140mm from the top, once again according to Roger.

All this done with the forks on the bike. I lowered the jack enough until the forks were at the bottom to set the oil level, then installed the new springs and spacers.

Gonna taper grind the rebound rod tomorrow and set the sag front and rear.

James
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Old 10-08-2015, 08:25 PM
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Old 10-09-2015, 07:07 PM
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Tonight I got the new springs installed and did the taper grind on the rebound rod (I left the forks on the bike so I could get this done quick, but will completely disassemble the forks this winter and install new fluids, pistons, and shim stacks.



I used a 32mm spacer above the fork springs to equal 410mm total length. With the rebound adjusters all the way out I get 29mm of sag (bike only, without me on it),using Roger's method (measure extended forks, pull forks up, let go and measure,then push forks down, let go and measure, average those two, subtract from extended fork measurement). So 29mm of free sag in the front.



I checked the rear end also (stock rear shock and spring), and got 7mm of free sag in the rear. After sitting on the bike in full gear and measuring again, I got 14mm of static sag in the rear.


Still working on dialing things in...
James
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Old 10-10-2015, 08:54 AM
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Retightened the fork caps and set the rebound rods according to Roger. See below:

1) Wind the pre-load adjuster fully out.
2) Screw the Rebound fully in (flush with the cap) and then out 2 turns
3) Screw the cap onto the damper rod until it touches the lock nut
4) Screw the Rebound adjuster IN. If it will not turn in wind the lock screw and the cap UP the damper rod and try again until the Rebound screw touches after 1 turn in.
5) If the Rebound screw does not connect after 2 turns in, wind the lock screw DOWN the damper rod and try again until the Rebound screw touches after 1 turn in.
6) When you have achieved the correct position lock the cap and lock screw together using 14mm spanners

James
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Old 10-10-2015, 10:06 AM
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Initial around town impressions:

Stock setup was mushy (under rated fork springs) and harsh (too much high speed compression).

Now the front end feels firm. Can definitely tell there is a higher rated spring in there. I also notice less harshness over bumps. I think the stiffer spring rate is not allowing the fork to blow through its travel and only rely on the shim stack. Also could have something to do with the modified rebound rod... This is an unexpected, welcome blessing!

Will hit some curvy roads in about an hour and report back.

James
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Old 10-10-2015, 12:29 PM
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Just got home and i have to say this is probably the best $15 i've spent. The bikes now tracks well, doesn't dive on the brakes, allows mid-corner line changes even when leaned over pretty far, and is more comfortable/less fatiguing because the front end is riding higher now.

Definitely way less harsh in every sense. I don't notice the square edge bumps near as much. I hit my driveway curb the same as usual and it didn't feel harsh at all...

Good stuff!

James
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Old 10-10-2015, 01:27 PM
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Originally Posted by thedeatons View Post
Initial around town impressions:

Stock setup was mushy (under rated fork springs) and harsh (too much high speed compression).

Now the front end feels firm. Can definitely tell there is a higher rated spring in there. I also notice less harshness over bumps. I think the stiffer spring rate is not allowing the fork to blow through its travel and only rely on the shim stack. Also could have something to do with the modified rebound rod... This is an unexpected, welcome blessing!

Will hit some curvy roads in about an hour and report back.

James
it will feel better but still not be right. In these HMAS carts you do get some crossover between comp and rebound but a needle mod wont change that.
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Old 10-10-2015, 02:35 PM
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You are correct it's not perfect, but i'm convinced the vast majority of street riders would be totally satisfied with it...

It's easy to get in the ballpark, to get to the 95% good level. It's getting the last 5% out of it that takes the most time, and knowledge.

James
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Old 10-11-2015, 01:27 AM
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Hey James, great to hear of your success! And cheap! Well done.
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Old 10-11-2015, 05:58 AM
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Thank you!!! I'll continue to update this thread over the winter when i get into valving.

James
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Old 10-11-2015, 01:56 PM
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Originally Posted by Cadbury64 View Post
Hey James, great to hear of your success! And cheap! Well done.
+1
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Old 12-08-2015, 09:08 AM
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What are you going to do for a shock?
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Old 12-08-2015, 11:57 AM
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Nothing at this point. I want a Penske but cannot afford it right now. The stock rear spring is so close for my weight I'm not gonna bother with changing it, so I'll just wait until I have some money for an upgrade.


James
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Old 12-08-2015, 12:16 PM
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I have a rear Ohlins, and will probably be planning to do this by spring. 52,000 miles + on the bike and I haven't even looked at the front end really yet since I got it from the previous owner (which is now the glaring problem on the bike) and have starting researching what I want to do

Seeing your results and costs seems stupid not to

I'm a similar weight and height as you (within 10ish pounds), I'll need to check what exact spring is on the Ohlins and try to match the front springs to that I'm guessing

Last edited by ren; 12-08-2015 at 12:48 PM.
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Old 12-08-2015, 12:59 PM
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Yah, you have all winter to look for used springs from another bike that will work for your weight. Use the chart above to pick some out. $15 shipped was an amazing deal for the improvements I have so far, and I haven't even done the bleed hole or new fluid yet!!!

James
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Old 12-09-2015, 10:41 PM
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My low-budget mods:
GSX-R forks, wheel, brakes, triple clamp: $180
Riser clip-ons: $30
Custom size bearings and races from Allballs: $30 for upper and lower

$240 for better braking, better handling, and better looks. It's so nice to ditch the stock forks.
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Old 12-10-2015, 06:39 AM
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What year gsxr forks did you go with?

James
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Old 12-10-2015, 11:26 AM
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2006-2007.
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