suspension modification

[RADU]

Hello,

 

I have a 2002 VTEC VFR model and for quite a while now, i am not very satisfied with its stock suspensions. Although i have adjusted the rear suspension to make it more hard, i still have the feeling the moto feels "like a boat" if you know what i mean. The suspensions (both front and back) leave the impression that may be very soft. The feeling gets even more real when i load the motorcycle with luggages and passanger. A mechanic adviced me to install progressive springs on both front and rear suspension.

My questions:

1-would progressive springs make a difference; will the suspensions get more stiff and ferm?

2-if yes, what brand to choose?

3-are there available progressive springs for rear shock as well, because i haven't seen any ?

4-my model does not have an adjustment knob for rear shock absorber (soft-hard). Is it possible to mount one of these on it, or should i get a totally new shock absorber which has this feature (very expensive)? If yes, what brand/model suggestions do you have?

My purpose is to ride the motorcycle in a sport touring fashion; touring with some confort, but also in certain situations (like accelerating, braking, entering curves), i want to feel the suspensions a bit more sport, stiffer, with less "boat" effect.

 

Thanks

[Rogue_Biker]

RADU, I looked into replacing my rear shock with an all new Race Tech unit here in the USA and that route would have cost me $700 for the shock alone.  That shock only had the same factory adjustments (spring preload and rebound damping).  It sure looked very nice though.  LOL!  I believe an Ohlins unit cost $1,400.  One of our riding friends here has an Ohlins unit on his 6th Gen and loves it.  But yes, it cost MORE than my complete front and rear suspension rebuild.

 

Yes the best cost/performance ratio is to have your existing shock/front forks rebuilt to YOUR liking and your intended use.

 

My VFR handles almost like a super sport bike, which is what I asked for.  Really the best modification I've ever done, and I think many on here will echo that sentiment after they upgraded their VFR suspension.  This may not apply to the 8th Generation VFR but it certainly applies to all the others.     

 

 

[MaxSwell]

I recall DMr has sent the parts for installation of the fork upgrade through the mail to at least a couple or VFRDers. Perhaps you could contact him to see just what he could do for you and how much it'd cost.

[RADU]

14 minutes ago, Rogue_Biker said:

Really the best modification I've ever done, and I think many on here will echo that sentiment after they upgraded their VFR suspension.  This may not apply to the 8th Generation VFR but it certainly applies to all the others.     
 

 

Although not the topic of this discussion, why it does not apply to 8th gen?

 

4 hours ago, Duc2V4 said:

I put an ABS model shock on my 6 Gen and helped fellow forum member Duccmann do the same. In my case, the mounting holes for the remote adjuster mounting bracket needed to be threaded but on Duccmann's bike the bolt holes were already threaded. Other than that potential issue, the shock is a direct bolt in. I also sent it to DMr before I installed it.

Besides the preload knob mounting bracket, the shock absorber itself fitted without any modifications, right?

Can you post the thread?

 

13 minutes ago, MaxSwell said:

I recall DMr has sent the parts for installation of the fork upgrade through the mail to at least a couple or VFRDers. Perhaps you could contact him to see just what he could do for you and how much it'd cost.

You mean, he can provide the schematics and the parts needed for tuning the shock and forks? After that, do it by my own?

 

[Duc2V4]

18 minutes ago, RADU said:

Besides the preload knob mounting bracket, the shock absorber itself fitted without any modifications, right?

Can you post the thread?

 

Yes, the shock is a drop in item. Unfortunately I did not do a how-to thread nor did I take pics when I performed the installation. I can say that there is a few threads on the forum in regards to 6 Gen shock installations, I might have chimed in on one or two actually. The only caveat to the ABS model shock installation is that you have to remove the knob and mounting bracket in order to get the adjuster located in the proper position. This is not hard but caution needs to be taken, as there is a ball bearing that fits in between the knob and the adjuster body. This is what gives the knob a "click" if you will. It's spring loaded so if you're not careful..phew! off the bearing goes up in the sky!

[CandyRedRC46]

 
Unlike the shock, I've been in the forks myself so I know what's in there and, no, they don't have too little low speed compression. At least not for the road.
 
The low speed bleed is 1 mm and the stock oil viscosity is 37 cSt.
 
Race Tech who have a firmly established reputation for hard setups recommend a 1 mm bleed for racing and 1.3 mm for road use and that's in conjunction with their 16 cSt viscosity oil!
 
To save you the calculation, 1.3 mm means 69 % more flow area than 1 mm and the effect of the viscosity difference between 37 and 16 is massive.
 
The closest I could find locally was 19 cSt oil and that change alone turned my stock forks into a mushy pogo stick instantly. Not recommended. 
 
The wimpy stock springs need all the help they can get and that help comes in the shape of very strong compression damping and a high oil level. 
 
The result is forks that perform reasonably well on smooth tarmac but react harshly on the smallest bump while still feeling a bit mushy on the brakes or gentle undulations (very low speed movement so very little damping force).
 
I firmly believe that the shock is setup in pretty much the same way. 

I am just going off of the description of harsh on big bumps and mushy on small bumps....

Sent from my Nexus 6 using Tapatalk

[Rogue_Biker]

The 8th Gens are so new.  I assume they are an improvement over the 6th Gen.  Due to their newness they haven't had a chance to wear enough for their suspension performance to deteriorate.  But they will eventually wear out and they will eventually benefit from a complete suspension rebuild custom made to their owners.  All bikes eventually reach that stage.  Some bikes need it right from the factory because they are built to a lower price.  That's just reality.

 

[Duc2V4]

5 minutes ago, Rogue_Biker said:

The 8th Gens are so new.  I assume they are an improvement over the 6th Gen.  Due to their newness they haven't had a chance to wear enough for their suspension performance to deteriorate.  But they will eventually wear out and they will eventually benefit from a complete suspension rebuild custom made to their owners.  All bikes eventually reach that stage.  Some bikes need it right from the factory because they are built to a lower price.  That's just reality.

 

The standard 8 Gen could use better forks to begin with, they don't even have preload adjusters!

[BusyLittleShop]

Japanese fork springs may still employ piano wire or music wire which
is not fatigue resistant as Chrome silicon spring steel found in after
market springs such as Progressive... this is way stock springs sag with

mileage whereas after market silicon springs don't...

 

[Duc2V4]

29 minutes ago, BusyLittleShop said:

Japanese fork springs may still employ piano wire or music wire which
is not fatigue resistant as Chrome silicon spring steel found in after
market springs such as Progressive... this is way stock springs sag with

mileage whereas after market silicon springs don't...

 

Makes sense for a Yamaha, considering their a musical instrument company! 

[Terry]

8 hours ago, RC36Rider said:

 

Unlike the shock, I've been in the forks myself so I know what's in there and, no, they don't have too little low speed compression. At least not for the road.

 

The low speed bleed is 1 mm and the stock oil viscosity is 37 cSt.

 

Race Tech who have a firmly established reputation for hard setups recommend a 1 mm bleed for racing and 1.3 mm for road use and that's in conjunction with their 16 cSt viscosity oil!

 

To save you the calculation, 1.3 mm means 69 % more flow area than 1 mm and the effect of the viscosity difference between 37 and 16 is massive.

 

The closest I could find locally was 19 cSt oil and that change alone turned my stock forks into a mushy pogo stick instantly. Not recommended. 

 

The wimpy stock springs need all the help they can get and that help comes in the shape of very strong compression damping and a high oil level. 

 

The result is forks that perform reasonably well on smooth tarmac but react harshly on the smallest bump while still feeling a bit mushy on the brakes or gentle undulations (very low speed movement so very little damping force).

 

I firmly believe that the shock is setup in pretty much the same way. 

 

We might be at cross purposes here. The low speed damping is controlled by the orifice, and the high speed by the shims. However the shims are very feeble, and the ports that feed the shims are restrictive. My take on this is that the shims blow off at relatively low flow, but the maximum flow on a big hit is ultimately restricted by the port size. So you can reduce the oil viscosity and you lose even more compression control on small bumps but still get harshness on a big bump. Adding firmer shims would restore some control, but the harshness would remain. The shims that Daugherty or RaceTech would supply are 5 times stiffer than stock, but larger ports avoid harshness.

[Cogswell]

To the OP - if you want to go with an ABS shock with the remote preload adjuster, the tough part is threading the hose through so the adjuster can be bolted in to place.  You may have an easier time of it as you do not have the rear ABS pump taking up space where it passes through the sub frame.  When I removed mine to send to JD, I took a number of photos which might be helpful.  In any event, the toughest part might be finding an ABS shock to have re-built.  There aren't a lot of them around. 

 

http://www.vfrdiscussion.com/index.php?/forums/topic/79986-6th-gen-abs-shock-removal-in-pictures/

 

[RC36Rider]

17 hours ago, RADU said:

 

You mean, he can provide the schematics and the parts needed for tuning the shock and forks? After that, do it by my own?

 

 

Short answer: Yes for the forks, no for the shock.

 

Fitting the DMr parts to the forks is well within the reach of a motivated DYI enthusiast and does not require any exotic tools. There is a very detailed write up on this board by Hispanic Slammer (who runs this forum). 

 

The shock is more difficult. To do the job safely, you require a spring compressor, you need to drill the shock body in the right place to let the nitrogen charge out, drill out that hole and tap it to accept a Schräder valve (one rated for medium or even high pressure, not one from a tyre tube)... remove and refit some delicate seals... and finally recharge the nitrogen. To name only the operations that require more than a vice, a file and a set of spanners.

 

Race Tech's book (see link in an earlier post) shows how, BTW.

 

Not impossible to do but quite a bit more involved than the forks.

[Duc2V4]

2 hours ago, Cogswell said:

To the OP - if you want to go with an ABS shock with the remote preload adjuster, the tough part is threading the hose through so the adjuster can be bolted in to place.  You may have an easier time of it as you do not have the rear ABS pump taking up space where it passes through the sub frame.  When I removed mine to send to JD, I took a number of photos which might be helpful.  In any event, the toughest part might be finding an ABS shock to have re-built.  There aren't a lot of them around. 

 

http://www.vfrdiscussion.com/index.php?/forums/topic/79986-6th-gen-abs-shock-removal-in-pictures/

 

I was watching an ABS shock on eBay just last week. It might still be available.

 

I'll see if I can grab a link.

 

 

[Duc2V4]

The ABS shock appears to still be available...

 

eBay 2003 ABS Shock

[RC36Rider]

15 hours ago, BusyLittleShop said:

Japanese fork springs may still employ piano wire or music wire which
is not fatigue resistant as Chrome silicon spring steel found in after
market springs such as Progressive... 

 

 

I measured my 6Gen stock fork springs when I ripped them out and  near as I could tell using a simple ruler, they were exactly as per the service manual (334.3 mm if memory serves) but I admittedly only put 40 tkm on them.

 

I think they are fine quality but they are a downright soggy 0.74 kg/mm (softer part) from the factory.

 

I might try to cut off a few coils just for the fun of it. 

[RC36Rider]

10 hours ago, Terry said:

 

My take on this is that the shims blow off at relatively low flow, but the maximum flow on a big hit is ultimately restricted by the port size. 

 

I would agree with that. 

 

The forks are unresponsive on very small bumps (such as a lousy road surface), then rather soft, then bloody hard corresponding IMO to too small a low speed bleed, then wimpy shim stack then insufficient max flow through the tiny HMAS ports.

 

End result, they wallow, bottom, rattle or hydraulic lock depending on bump size and shape and road speed. 

 

I'm about 210 lbs and ride mostly lousy roads (twisty roads are mostly crap over here). I really should ride a BMW GS but I can't stand the ugly beast and I love my V4. 

[RC36Rider]

11 hours ago, Terry said:

 

The shims that Daugherty or RaceTech would supply are 5 times stiffer than stock, but larger ports avoid harshness.

 

 

Note that shim stack stiffness on its own does not mean much when comparing such radically different piston designs.

 

The number, size, shape and position of the ports all matter but I am definitely under the impression that the stock shim stack is decidedly wimpy. 

 

Although not identical, DMr and RT are a lot closer to each other (both are 3 port high flow) than to those "wonderful" HMAS pistons with their 4 tiny round holes (they don't deserve to be called "ports").

 

If I was a bit braver, I'd just open up the low speed bleed, drill bigger holes in the stock pistons and put in a stiffer shim stack (and fit stiffer linear springs of course).

[Terry]

Drilling bigger holes in the HMAS bodies is fraught with peril; the valves are a sintered material, and it shatters very easily if you try and drill out much more meat. I tried this on some of my surplus valves after I fitted some Gold Valves. Cheapest option is to speak nicely to Mr Daugherty; his valve bodies are reasonably priced, and as you say not dissimilar to the gold ones (although RaceTech's latest valves are looking more radically free-flowing, see below)

 

.

 

 

[Terry]

1 hour ago, RC36Rider said:

 

I measured my 6Gen stock fork springs when I ripped them out and  near as I could tell using a simple ruler, they were exactly as per the service manual (334.3 mm if memory serves) but I admittedly only put 40 tkm on them.

 

I think they are fine quality but they are a downright soggy 0.74 kg/mm (softer part) from the factory.

 

I might try to cut off a few coils just for the fun of it. 

Seems like a reasonable idea, you'd be best cutting off the tightly wound coils at the bottom, rather than the more widely spaced coils. 

[Terry]

23 hours ago, Rogue_Biker said:

If I were in Europe I would find someone within the EU to do the thorough re-springing/re-valving of the OEM suspension.  There has to be a DMr-equivalent within the EU! 

The UK guys on the VTR1000 forum all speak highly of a guy called Roger Ditchfield at Revolution Racing for suspension modifications. 

 

http://www.revolutionuk.co.uk/

 

The VTR fork uses the same pistons and shims as the 5th and 6th gen VFR, so what works on one will work on all.

[RC36Rider]

11 minutes ago, Terry said:

Drilling bigger holes in the HMAS bodies is fraught with peril; the valves are a sintered material, and it shatters very easily if you try and drill out much more meat. I tried this on some of my surplus valves after I fitted some Gold Valves.

 

Ah ! I did not know that. 

 

Good thing I'm a devout and practicing coward then. 

[RC36Rider]

4 minutes ago, Terry said:

 

http://www.revolutionuk.co.uk/

 

The VTR fork uses the same pistons and shims as the 5th and 6th gen VFR, so what works on one will work on all.

 

Do they work on OEM shocks, though ?

 

Getting the forks reworked is not so much of a problem. Even ordering valve bodies from DMr is something I'd take my chances on. EU customs just might not even bother with the small, light package. 

 

Anyway, I already have Type 1 Gold Valves in there (but I'm still a couple of iterations away from a really good setup. Too soft ATM).

[Terry]

I know what you mean about the search for the perfect shim set-up. I think when you leave things stock, they are what they are. Once you start modifying, some part of your brain keeps saying, "nearly there, but could be better if I just...".

 

I started with Daugherty compression valves and shim stacks he supplied, very similar (really very similar) to a Gold Valve design and RT C33 stack, but found these a bit jarring on big bumps, softened the shims to C32 which was better, tried C31 which was great for bump absorption and poor for control, so back to C32. I added VTR1000 rebound adjusters with stock, re-valved pistons, and with the rebound adjuster wound out to 2  1/2 turns (so basically wide open) this was better and more supple suggesting the stock low speed rebound orifice damping is on the firmer side. Replacing the stock rebound pistons with Gold Valves was still better in terms of a more fluid action.

 

Strangely the fork action on the VFR is still not quite as good as my VTR; the only difference in the mechanical parts is the VTR uses a Showa 3-port compression valve (maybe from a GSX-R?) and has three small bleeds machined into the shim sealing face, all other parts are the same as the VFR. The VTR just deals with bumps better.

[RC36Rider]

1 hour ago, Terry said:

 

Once you start modifying, some part of your brain keeps saying, "nearly there, but could be better if I just...".

 

 

Stop reading my mind, will you ! 

[VFROZ]

I tried many shim stack variations on the high flow compression pistons and original rebound pistons, but couldn't get it right.

I weigh 74kg and use 0.95 springs.

I found slow speed compression was always bad, too stiff. The bike was never compliant over small stuff.

If I went for a softer slow speed set up, the high speed compression would be too soft and bottom too easy.

This went round and round without satisfaction.

So I decided to swap out the rebound pistons with very high flow ones, this by far had the biggest impact on compression damping and slow speed comfort.

To give you an idea, I had RT17 and C32 set up with the high flow compression and stock rebound pistons, when I swapped them I ended with RT19.5 and C33 after lots of testing, both with 18mm shims instead of the racetech 17mm ones.

I have 110mm oil height equivalent (using VTR lowers) and setteled on cSt24@40c oil weight, which is a bit heavier than most recommend.

The forks now are great on the small stuff, don't dive much, and rarely bottom out.

There are lots of combinations to play with, and everyone feels the bike differently, it just depends on what you feel comfortable with and works for you.