How to make the 40mm (pre '93) front end handle (101)

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gleno

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In recent weeks I have been putting the final touches on some handling mods to my ’88 model. That process started with researching and planning a year ago, asking lots of questions along the way.

This post mostly deals with bringing a standard 40mm front end up to spec. I’ll do a separate post dealing with the rear end in the near future.

In another thread on this forum I was trying to determine what fork spring pre-load I should be using because I could not get the front end to absorb the shock loads of smaller surface irregularities but anything else the forks would soak up effortlessly. It was like riding a bicycle.

That last problem is now solved.

I have learned of few things that could help other forum members fast track their mods and avoid unnecessary confusion, errors and reading time, although this is a long post.

My sole objective was to get the V-max to handle like a Moto Guzzi or an old style Ducati with a pure emphasis on handling, handling, handling and stopping.

That’s all this project was ever about.

Handling mods installed and finished to date are:-

Front End

1)Progressive fork springs in the standard 40mm forks.
2)Progressive lowering springs in the front forks to lower the front end 2”.
3)Race Tech cartridge emulators.
4)New Steering head bearings.
5)Solid billet fork brace from Pegasus Engineering U.K.
6)17” Billet front wheel.
7)Metzeler Roadtec Z6 120 / 70 17 front tyre
8)Brembo 65mm mount quad piston calipers
9)R1 rotors
10)EBC ‘HH’ C formula pads
11)Galfer braided brake lines.
12)Tommaselli adjustable ‘clubman’ style handle bars

Rear End

1)Progressive 11.5 inch shocks
2)17” billet wheel
3)Metzeler Roadtec Z6 190 / 50 17 rear tyre
4)OTEC 770 billet swingarm
5)New swingarm bearings
6)Custom tie rod end brake arm
7)Galfer braided brake line
8)Galfer solid wave rotor
9)EBC ‘HH’C formula pads

Frame

1)Solid engine mounts
2)NO FRAME BRACES – more on this at the end of this post.

Now all these mods are easy to do. No engineering skill is required to modify a bike by bolting on parts someone else has engineered.

You do need to acquire knowledge, exercise judgment, RTFM (read the f***ing manual), know how to use tools and possess a grain of common sense.

So, if you bolt all the same bits on your V-max you should get the same results I did right?

Not unless you set it up properly.

Setup and testing is what has taken me the most time, road miles and fuel during this process.

YOU NEED TO KNOW these things….

1)When fitting Progressive Springs to your front end you are fitting a progressive spring rate, NOT just a brand of spring. This means that, unlike the standard spring or the Race Tech replacement springs which have a linear spring rate, your progressive springs work differently.

Linear springs work on the principle that a set weight load will compress a spring a set length. i.e. 100lbs may = 1”of compression. Double the load to 100lbs + 100lbs and the linear spring will compress 1”+ 1”. A progressive spring rate requires a progressively greater load to achieve the same compressed length. i.e. 100lbs may = 1” of compression but it will take 100lbs + 120lbs to achieve 1”+ 1”of compression.

The progressive is a better solution for lowered forks which don’t have the luxury of long travel to effect spring damping.

2)When fitting Race Tech Cartridge Emulators you are fitting a (almost) Linear rate damping system NOT a progressive damping system.

Unlike your fork spring, liquid fork oil is not compressible. This means that the damping effect of the fork oil under pressure is regulated by how quickly the pressure can be reduced. The standard damper rod forks in the V-max do this by allowing pressurized fork oil to escape from the lower fork to the upper fork via fixed size holes in the damper rods. This means that damping rods have progressive, rising rate damping. You have to more than double the pressure on the fork fluid to double the flow rate because the exit hole is a set size. Too much pressure will exceed the release rate and cause a hydraulic lock that transforms your damper into a rock hard strut.

Race Tech Cartridge Emulators are able to allow pressurized fork oil to escape from the lower fork to the upper fork via a variable size ‘hole’ in the emulator body controlled by a spring loaded valve. This spring has a linear compression rate. Remember, springs are compressible and if more pressure is applied to the fork oil, the emulator valve spring compresses more and allows more oil to flow to the upper fork tube. This effectively gives the emulator a linear damping rate because the valve springs controls the damping rate of the valve. Clever huh.

Cartridge emulators have a great advantage over damper rods because they are also tunable. By increasing the load on the valve spring you can increase the damping force but it will still remain Linear throughout the operational pressure range.

So why have I taken the time to outline this information?

Because some of you may be wondering why I elected to use a (P)progressive, rising rate spring with a Linear, constant rate cartridge emulator?

Well, it’s because I lowered the bike. The compressible travel length of my fork tubes is 50mm (2”) shorter than stock 140mm (5.5”) so the loads have to be absorbed over a shorter length of travel. It therefore makes sense to use a (P)Progressive, rising rate fork spring to absorb compression loads over a shorter compression length.

Cartridge emulators are more effective at controlling REBOUND damping. Being able to ‘tune’ damping adds a control feature to the bikes handling that the standard damper rod forks don’t have and the linear quality of the rebound damping removes harsh damping forces from the high pressure compression and subsequent rebound events (big bumps) at the extreme operating range of the rising rate fork springs.

The effect is to make shortened forks a less jarring experience with greater rider comfort and improve handling by keeping the tyre on the road.

The combination works really well but you have to remember a few things during setup that are not covered by the Progressive or Race Tech installation instructions or the popular Yamaha service manuals.

REMEMBER

1)Yamaha recommend 451 cc of fork oil per tube for a standard 40mm fork tube and spring combination. They do not mention how far up the fork tube this volume of fork oil will come when you fill the tube. So what is the correct oil level?
2)Progressive installation instructions suggest that you measure the height of the oil in the fork tube and adjust it to 140mm. This is with the fork tube collapsed and the spring removed. But does that level correspond to Yamaha’s recommendation of 451cc?
3)Which way should the Progressively wound spring be installed? Will it matter?
4)Race Tech suggest you add the correct amount of oil, whatever that might be, after the emulator is fitted.
5)If you are already using custom pre-load spacers, what effect do they have on fork tube volume? Do they affect oil levels? Do I need to alter the length of the pre-load spacers?

How do you tune the installed components to get best performance from your new setup when you can’t determine these reference points?

ANSWERS

1)The answer is determined by measuring the oil level with the fork springs removed and the fork collapsed. Add your 451cc and measure the level from the top of the fork tube. It’s close enough to 140mm from the top of the tube.
2)But does that level correspond to Yamaha’s recommendation of 451cc? Yes it does.
3)It does not matter to the spring, whether it is installed with the tightly wound coils at the top of the fork tube or reversed so that they are at the bottom of the tube just so long as both springs are in the same way in their respective tubes. The springs will work the same way no matter which end goes in first. BUT IT DOES MATTER TO THE FORK OIL LEVELS.

If the tightly wound end of the spring sits in the bottom of the fork tube, the extra coils are occupying space that would have been occupied by oil. The oil level will rise above 140mm and the ride will become harsher.

HINT: Fitting them with the loosely coiled end in first is easier than working out how much extra oil has been displaced by fitting them tight end first. If you are worried about balance issues (the extra mass and weight moving about high up in the fork) you need to install them the other way around and adjust the oil level to compensate.

This IS important because a 20mm rise in oil level will dramatically effect the ride quality of the front end. Progressive warn against overly high fork oil levels in the install literature.

4)Race Tech suggest you add the correct amount of oil after the emulator is fitted because the emulator occupies volume in the fork tube and sits in the fork oil. This will raise the oil level in the fork tube by an amount corresponding to the volume of space occupied by the emulator. You need to add the emulator before you add the oil to the required level.

5)Pre-load spacers normally sit above the oil level of the fork tube and do not affect oil levels BUT IF YOU HAVE NON-STANDARD SPACERS they should be hollow tubes not solids.

Spacers occupy fork tube volume and displace AIR.

DON’T UNDERESTIMATE THE IMPORTANCE OF THIS AIR SPACE ON THE PERFORMANCE OF YOUR FORKS.

The air space is another spring in the fork and has a major effect on small impacts.

If your oil level is too high,
a)This ‘air bag’ is smaller and less efficient.
b)The oil volume in the lower fork that is displaced by the introduction of the fork slide during compression of the fork has less space to go if an oil level that was set too high restricts this space.

In my case I elected to remove an amount of fork oil that corresponded to the volume displaced by the addition of the emulators and the reduced internal volume of the fork tubes due to the 2” lowering.

I used a solid, cylindrical, aluminium drift that I used to drive in the new swingarm bearings (it is almost the exact internal diameter of the fork tube) and one emulator, which I added to a measuring jug partly filled with water. By measuring the rise in water level I was able to easily see how much fork oil would be displaced by these two parts i.e approx. 60cc.

I had to remove a total of 60cc of fork oil from each fork tube to drop the oil level to the recommended level. In other words it was easier to add all the mods, then add Yamaha’s 451cc of fork oil and subtract 60cc.

I now know that with the bike raised off the front forks this corresponds to the length of the blade on my favourite screwdriver when measured from the top of the uncompressed fork tube. So I now have a dip stick. The external correspondent to this level is the upper level of the bottom triple tree clamp.

While progressive recommend you use standard spacers, my pre-load spacers had to be shortened by 50mm to allow for the lowered fork plus an additional 15mm. 15mm is the height of the Race Tech cartridge emulator now sitting under the fork spring. This was to re-set the correct fork spring pre-load.

The Result

The effect of getting the oil level set correctly was to completely eliminate the jarring effect of small vibrations in the road caused by changing pavement levels and joins in the road surface.

The fork oil was initially Yamaha standard 10wt which progressive recommend you stick with. After talking to the Race Tech distributor and reading the opinions of forum members I stepped up the grade to 15wt and the damping performance was much better. Race Tech recommended setting the emulator valve springs at two turns and that’s where they are still set.

The handling is so far removed from the stock V-max that any comparison is superfluous but here goes.

Does the bike handle? You bet your life it does, but what does that mean?

It is not a canyon carver, it’s too low to really push through country twisties or you will scrape (in order of lean angle) the aftermarket sidestand, standard footpegs and standard headers long before you run out of tyre tread.
It does stick to the road like glue.
It absorbs all the bumps (major and minor) that the road can throw at it.
It has NO headshake.
There is NO evidence of any frame flexure.
It has NO wallowing behaviour in corners.
If you pick a line for a corner, that’s where is goes.
If you have to change your line during cornering it will respond forgivingly and graciously take the new line.
There is NO low speed weave.
It will stop on a dime. It is possible to lock the front wheel under extreme braking and leave a straight black line of rubber on the road. (it won’t do stoppies). All this requires a maximum of two fingers on the front brake lever.
It will brake predictably while under brakes in a corner.
It will NOT dive significantly under heavy braking. It will compress very predictably.
It will not bottom under any braking condition I can replicate.
It is as stable as anything I have ridden WOT, in a straight line, from a standing start. It stays that way at any speed on the clock (and they have all been tested).

The solid frame mounts came from John at RM-SportMax. They and are made from Delrin, not metal. You can read about Delrin here http://en.wikipedia.org/wiki/Polyoxymethylene

This single frame mod has provided all the rigidity required on a V-max. It just doesn’t flex at all but it does allow you to feel vibration through the frame and seat. This is not annoying; it’s more like positive feedback.

Any hint I have had of a frame flex has always been caused by incorrect swingarm bearing tension or steering head bearing tension, not frame movement.

I have not refitted my frame brace. I threw it in the bin.

With something the size of a V-max engine solidly braced in the frame there is no prospect of movement. I know you guys who swear by them will not agree but in my opinion V-max frame braces are as useful as most fishing lures i.e. they are very good at catching fisherman but make little difference to the fish.

Thank you to all the forum members who answered some of my many questions. Your input has helped make the mods a very rewarding experience.

If you have read all the way through this, thanks for listening and I hope you got some useful info from it.
 
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Re: Making a the 40mm (pre '93) front end handle

Excellent :thumbs up:

Probably the best written and most useful tech writeup I have run into so far on this site. Very useful information here. (now to try it and find out if you are right:biglaugh:)

Good job!
 
Re: Making a the 40mm (pre '93) front end handle

My bike is set up very similar to yours.I did not go as low with the rear shocks though.I also still believe the racetech 1.0 springs are a better choice for my riding style with 20wt. oil in them.
I have no complaints at all with my handling now that it stops when I want it too.I can hang with or beat easily any of the guys that I know around here in the twisties.I think knowing the road plays the biggest part in that though.I have nearly crashed several times in the past flying on unknown roads.
I also have to disagree with you on the frame braces.
I rode with the solid mounts for a while before putting on the braces.The solid mounts helped raise the frame flex level by 30-40 mph but it still would under heavy power in big sweeper turns.The frame braces raised this again by 30-40 mph.It just again starts to flex a little at say 130 weaving through traffic on the highway.
I think at the topend speeds most of the ill handling comes from the air hitting you.Ever sit up staight while really flying ?Bike does all kinds of goofy shit till you tuck back down.
My swingarm is braced and the bearings are fairly new and adjusted.I also gusseted the rear frame box that the driveshaft goes through.
 
Re: Making a the 40mm (pre '93) front end handle

oh, one other note - the stock springs are progressive too.

Sean
 
Re: Making a the 40mm (pre '93) front end handle

I was told by HYPERPro that Progressive springs are actually NOT progressive (rising rate spring) but a dual rate. Hyperpros are actual rising rate
 
Re: Making a the 40mm (pre '93) front end handle

I was told by HYPERPro that Progressive springs are actually NOT progressive (rising rate spring) but a dual rate. Hyperpros are actual rising rate

I vote sticky for Glennos post.

True dual rate springs are TWO separate springs stacked on top of each other with a spacer in between to keep them from tangling.

The shorter and softer of the two springs pretty much fully compresses before the harder and longer of the two begins compressing.

It is a true dual rate in that the transistion from the first rate to the second rate happens very quickly; or instantaneously depending on how close the two rates are to each other. If the soft rate is far enough away from the hard rate then the soft will FULLY compress before the hard begins compressing.

You'll find them on a lot of rear shocks Works Performance shocks pushes them pretty hard and they are what I have on the back of my Max.


A single spring wound "progressively" tighter or with "progressively" fatter coil wire diameter is in every sense "progressive" and would be almost completely impossible to make into a dual rate spring.

A one piece wound spring cannot be made to transition from one rate to another fast enough to honestly be called dual rate-it has to gradually-"progressively" transition from one to the other.


And by the way Glenno GREAT writeup! Your setup almost matches mine except I'm running Racetechs like most, am not lowered in the front and have frame braces along with solid mounts. My emulators are set on 2.5 turns and am running 15wt oil.

Like you it took a lot of time toying with the hardware to get it sorted out to my liking and if I had the time or interest I don't doubt that it could still be made even better

I have to agree that the solid mounts probably did more than anything else to eliminate the cornering wallow we've all come to know and love. They were one of the last things I did and the one that FINALLY eliminated that problem.

I am in no way making comments on the quality or appropriateness of one spring versus the other;

Rusty
 
Re: Making a the 40mm (pre '93) front end handle

I vote sticky for Glennos post.

I did just that and cleaned up the title to read clearer.

Now... If Busta doesn't want it as a sticky he can remove so keep that in mind. He is our divine shadow!:worthy:

Awesome write up!
 
Re: Making a the 40mm (pre '93) front end handle

My bike is set up very similar to yours.I did not go as low with the rear shocks though.I also still believe the racetech 1.0 springs are a better choice for my riding style with 20wt. oil in them.
I have no complaints at all with my handling now that it stops when I want it too.I can hang with or beat easily any of the guys that I know around here in the twisties.I think knowing the road plays the biggest part in that though.I have nearly crashed several times in the past flying on unknown roads.
I also have to disagree with you on the frame braces.
I rode with the solid mounts for a while before putting on the braces.The solid mounts helped raise the frame flex level by 30-40 mph but it still would under heavy power in big sweeper turns.The frame braces raised this again by 30-40 mph.It just again starts to flex a little at say 130 weaving through traffic on the highway.
I think at the topend speeds most of the ill handling comes from the air hitting you.Ever sit up staight while really flying ?Bike does all kinds of goofy shit till you tuck back down.
My swingarm is braced and the bearings are fairly new and adjusted.I also gusseted the rear frame box that the driveshaft goes through.

I have to agree with your comment about air buffeting of the rider in the upright riding position being responsible for most of the goofy high speed behaviour of the V-max.

I've never found this worrying, just very annoying. Flat bars, Drag bars or the 'Clubman' style bar go a long way to resolving this by lowering the riders position so that air flows more easily around a riders body.

These bars also transfer rider weight onto the handle bars and front forks and make the fine tuning of the front end a necessity because you feel so much more of the road in this riding position.

It was after fitting the lower bars, specifically to stop wind buffeting affecting high speed handling, that I become very aware of the shortcomings in the damper performance of my front forks.

So the bike had to keep evolving.
 
Re: Making a the 40mm (pre '93) front end handle

I have to agree with your comment about air buffeting of the rider in the upright riding position being responsible for most of the goofy high speed behaviour of the V-max.

I've never found this worrying, just very annoying. Flat bars, Drag bars or the 'Clubman' style bar go a long way to resolving this by lowering the riders position so that air flows more easily around a riders body.

These bars also transfer rider weight onto the handle bars and front forks and make the fine tuning of the front end a necessity because you feel so much more of the road in this riding position.

It was after fitting the lower bars, specifically to stop wind buffeting affecting high speed handling, that I become very aware of the shortcomings in the damper performance of my front forks.

So the bike had to keep evolving.

Biggest issue a lot of peeps having when cornering is they aren't weighting the front tire... Biasing your weight on the front tire really helps the bike! It's amazing! Try it sometime. On my SV I slide off the seat and really bias it forward unless I am running my huge tank bag.:thumbs up:
 
Hey Gleno,
I've just sat here and read your post twice over. I was just about to make a comment about 'pity you're not in Australia' when I read where you're from.
I don't suppose you're in Sydney are you? I have an 88 vmax, though I don't have an ounce of the technical knowledge you have, and would love to go over those mods with you.
Or maybe you'd like another project??? worth the question!!
 
Great thread, I have 2000 Max and have done the mods and have the frame brace, if they help a little that's great but the they look really macho and that's enough of a reason for me to have them on my Vmax:clapping:
 
Gleno this write up is great. The thread is dated but I'm trying to keep my bike on the ground when hitting those mega harsh bumps at highway speed. I've got Progressive springs with Emulators and light weight Mercon 5 ATF fluid in the forks,all new internal bushings, Delrin mounts. The ride is great over normal bumps in the rode,the emulators work great. But,I've gone air born over a few major bumps on the highway. The rebound is hard & jarring. I know there's a limit to how good we can get these old forks to perform. Have they reached their limits? Christian, my riding partner has similar issues, we believe his forks to be stock, and slid up the trees 2 ". The one thing I don't think I did was lower my fork oil level when installing the emulators. I also question the emulators sealing under big loads, with just metal butting metal. That's easy and first on the list. Fork oil weight is on my mind too. Any suggestion from the members would be greatly appreciated. I know there's a lot of knowledge on this forum.
Steve-o
 
Gleno this write up is great. The thread is dated but I'm trying to keep my bike on the ground when hitting those mega harsh bumps at highway speed. I've got Progressive springs with Emulators and light weight Mercon 5 ATF fluid in the forks,all new internal bushings, Delrin mounts. The ride is great over normal bumps in the rode,the emulators work great. But,I've gone air born over a few major bumps on the highway. The rebound is hard & jarring. I know there's a limit to how good we can get these old forks to perform. Have they reached their limits? Christian, my riding partner has similar issues, we believe his forks to be stock, and slid up the trees 2 ". The one thing I don't think I did was lower my fork oil level when installing the emulators. I also question the emulators sealing under big loads, with just metal butting metal. That's easy and first on the list. Fork oil weight is on my mind too. Any suggestion from the members would be greatly appreciated. I know there's a lot of knowledge on this forum.
Steve-o

I think Rusty hit on what may be needed for these forks, which is a true dual rate spring. Although I'm happy enough with my everyday riding performance with Progressive springs, Ricor Intiminators, 10wt (or maybe 15wt) fork oil they are a bit slow reacting when I get around the Hooligans. The Ricor's call for 5 wt oil so that's a major part of my issue with a front end that I really have to manhandle when riding on bumpy pavement. I could probably also use a few more lbs. of spring rate to keep the front wheel a bit more in tune with the rest of the bike. Even having the wide 200 rear tire it sticks and turns pretty good, surely it can handle more turning/ lean angle than I can give it.
 
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Thanks Brian. I've been reading plenty since I posted and really feel that the rebound is worse than stock on harsh bumps at highway speeds. Having drilled the bottom damper holes, I've turned the dampening over to the Ricor's. So, what I'm thinking is happening is when I hit the mega bumps, the Ricor's bypass the fork oil out the sides. I saw in previous post when adapters between the damper rod top and Ricor valve were used to get a better fit. I'm wondering if an o-ring that fits the inside of the fork tube will seal better. Also, the smaller holes in the top of the damper rod might be closed off or brazed and re drilled smaller. I'm regretting not putting the money in a sport bike fork instead. I've got the yellow springs on my Ricor's and adjusted fairly stiff. Like I said, they work well on average road bumps, but on a major hit? They don't do it for me. I'm wondering if steady rate springs might handle sever conditions better than progressive wound springs? That soft first stage night be too quick to compress on harsh bumps, though Ricor claims OEM springs work well with their valving, and that's what stock springs are.
 
Thanks Brian. I've been reading plenty since I posted and really feel that the rebound is worse than stock on harsh bumps at highway speeds. Having drilled the bottom damper holes, I've turned the dampening over to the Ricor's. So, what I'm thinking is happening is when I hit the mega bumps, the Ricor's bypass the fork oil out the sides. I saw in previous post when adapters between the damper rod top and Ricor valve were used to get a better fit. I'm wondering if an o-ring that fits the inside of the fork tube will seal better. Also, the smaller holes in the top of the damper rod might be closed off or brazed and re drilled smaller. I'm regretting not putting the money in a sport bike fork instead. I've got the yellow springs on my Ricor's and adjusted fairly stiff. Like I said, they work well on average road bumps, but on a major hit? They don't do it for me. I'm wondering if steady rate springs might handle sever conditions better than progressive wound springs? That soft first stage night be too quick to compress on harsh bumps, though Ricor claims OEM springs work well with their valving, and that's what stock springs are.

Steve Ive got a question, have you set the sag on the front end? Mine was pretty harsh, with just the progressives, and ricors. I measured the sag, and it was only 15 mm, so I took 15 mm off the PVC spacer. That put me at 30 mm, and then swapped back to the stock caps, which gave me another 5 mm. 35 mm sag feels pretty good on my 07.

Online they say 30 mm for the street, but I can always add in some shim if I need to.
 
Steve Ive got a question, have you set the sag on the front end? Mine was pretty harsh, with just the progressives, and ricors. I measured the sag, and it was only 15 mm, so I took 15 mm off the PVC spacer. That put me at 30 mm, and then swapped back to the stock caps, which gave me another 5 mm. 35 mm sag feels pretty good on my 07.

Online they say 30 mm for the street, but I can always add in some shim if I need to.

Mine is tighter than that Eric, thanks. I'll always try simle and cost effective first. Much appreciated.
 

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