rear suspension sag?

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graham heise
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rear suspension sag?

#1 Post by graham heise » Thu Jan 10, 2013 9:18 am

G'day race fans. Today i had some help and measured the distance between the ground and lowest part of rear side fairing above the axle ( below helmet holder key hole) with me in the saddle. Came up with 630mm. Without me, bike only, it measured 675mm. Front measurements aside i want to know what rear ride hight is the average amongst my fellow forum rz owners. My dilemma is i have been scraping chambers and boots without using all of the side grip of the tyre. I'm wondering if an r6 rear shock conversion with it's 15mm extra lenght will keep my pipes and pegs of the ground. I weigh 95kg so i'm no pedrosa but i want to solve a ground clearance issue before i start to modify.
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graham heise
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Re: rear suspension sag?

#2 Post by graham heise » Thu Jan 10, 2013 9:54 am

Just to add. my chambers are 115mm at ther widest below the brake peddle, hugging the frame. Estimate of 140-150mm chamber ground clearance without rider.
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GPJeremy
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Re: rear suspension sag?

#3 Post by GPJeremy » Fri Jan 11, 2013 1:25 pm

Raising the rear ride height will give you some added ground clearance, but it will also sharpen the steering, noticeably. Changing ride height also places more weight on the front of the bike and ( I'm assuming, 90-section, bias-ply) front tire. Additionally, sag, is a function of spring pre-load, not ride height.
As far as I know, the stock RZ shock is not rebuildable and therefore imo, not even worth re-springing. So, if you're out of pre-load adjustment on the stock shock, an R6 shock, or any other aftermartket alternative is your best bet. There's a wealth of info here and all over the web about the R6 conversion, old FOX shocks come up on eBay from time to time and Hagon ( I believe) makes a new shock. Someone out there also makes or converts Penske shocks, there are a couple forum members that have direct-fit Penske shocks. In any case, you'd still need to have the bike sprung for your weight (and potentially valved to your needs) to make the most from your money.
However, there could be an easier solution: can you get more weight off the bike? You don't have to be Ricky-racer and drag a knee through the bends, but getting more weight off the motorcycle will solve some ground clearance issues. Just shooting your butt off the inside of the seat and weighting the outside foot peg might do the trick. It still won't help you use up all of the tire, but I'm not sure it's possible to run all the way to the edge of the stock tires without grinding through the pipes. Something to think about.
'85 RZ 350, Toomey pipes, Boyeson reeds, FZ 600 swingarm with FJ 600 Forks and wheels.

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Re: rear suspension sag?

#4 Post by cookie » Mon Jan 14, 2013 7:04 pm

115mm is a pretty fat pipe to retain ground clearance with. With my race bike (with 106mm dia belly section) we did a 17" wheel conversion and lost what little clearance we had. I ended up cutting and re-welding the dog bones shorter to regain clearance.
45mm is a lot of static sag from what I recall, sounds like you need a new rear shock regardless, assuming you're out of adjustment.
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This old RZ
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Re: rear suspension sag?

#5 Post by This old RZ » Mon Jan 14, 2013 7:51 pm

@ 210lb your really pushing the design limits of the RZ :smt002 Im 195 now so Not saying :smt005
If you are using the orig shock.......NEWS FLASH its long...long....gone.

Sounds like your roadracing the bike by your description, so I think you understand a little of what is needed. Im not sure what chambers you are using either,I havent measured mine in depth..but alot of the "fat bellied pipes" just will not work for clearance. Something to consider.

As far as your boots...do you have rearsets...probably all you need to do there. move your feet up a little.

As for the R-6 shock,As stated it pushes the rear of your bike up one full 1" ,and its non adjustable,in so doing affects everything on the front,It can enhance or detract the turn in,ability to hold a line,front end dive is increased,grip and lean angle. All are affected so if your having issues now it could multiply the issue. or you might like it? who knows I have my opinion on that :smt005

What you need is a new non 30 year old shock,if your track riding,properly set up for your weight and riding style. ...your shock ,suspension is far more important than your chambers,carbs,reeds...even tires. Look around ,barter,swap ,beg or steal for a decent r RZ shock you will not regret it.
There are options all vary on price rebuilability and age. here are a few, search your neck of the woods and youll most likley discover more. GOOD lUCK!
FoX Twin Clicker
Penske
Hagon
Maxton
Works
HAPPY 30th YAMAHA YVPS 350 1983-2013. DONT OVER THINK IT , JUST BUILD IT AND BE JUST AS FAST AND RELIABLE

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JonW
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Re: rear suspension sag?

#6 Post by JonW » Mon Jan 14, 2013 7:57 pm

This old RZ wrote: As for the R-6 shock,As stated it pushes the rear of your bike up one full 1" ,and its non adjustable,in so doing affects everything on the front,It can enhance or detract the turn in,ability to hold a line,front end dive is increased,grip and lean angle. All are affected so if your having issues now it could multiply the issue. or you might like it? who knows I have my opinion on that :smt005
Im confused, how is this shock not adjustable?

Image

It also DID NOT push the back of my bike up by 1inch.

So are you thinking about a different shock Old RZ?
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JonW
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Re: rear suspension sag?

#7 Post by JonW » Mon Jan 14, 2013 8:01 pm

This bit we do agree on... I would also add Nitron to the list. As has been said elsewhere, if you want the best suspension ever you will need to not just buy a fancy shock, tho it may help. You need a professional to set the bike up for your weight and riding style. That costs money and time, but will work well. Fitting a better shock and playing with the adjustments will get you a better handling bike but nothing beats a professional and that is what you need for racing.
This old RZ wrote: What you need is a new non 30 year old shock,if your track riding,properly set up for your weight and riding style. ...your shock ,suspension is far more important than your chambers,carbs,reeds...even tires. Look around ,barter,swap ,beg or steal for a decent r RZ shock you will not regret it.
There are options all vary on price rebuilability and age. here are a few, search your neck of the woods and youll most likley discover more. GOOD lUCK!
FoX Twin Clicker
Penske
Hagon
Maxton
Works
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

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This old RZ
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Re: rear suspension sag?

#8 Post by This old RZ » Mon Jan 14, 2013 11:10 pm

Its the factory shocks inability to have a seperate ride height adjustment :smt002 , not the preload and comp/rebound adjustments the shock does have that covered. when the shocks have a seperate ride height adjuster,its a sign of higer spec components geared for track days and racing. Do you need it on the street...NO, not at all unless your a very skilled fast road riding maniac.
The aftermarket r-6 shocks mainly Ohlins Im reffering to have adjustments ,shim stacks on the early models? and later models utilize threaded collars if im not mistaken? Its been awile since Ive looked at a R-6 with aftermarket goodies,the R-6 type bikes just totally dont intrest me..at all. So im pretty much out of touch with them on a detailed in depth scale.
NOTE**If the author decides to buy a good shock from virtually any company,there is no need whatsoever to have "professional setup" almost all of the shock companies will ask you your weight for the spring..thats the most important field,then the rest is purely up to the rider testing until he feels its where he wants it. general preload/compression/rebound adjustment that the higher end shocks provide will give a baseline ,feedback from other riders and tech records will help get one into the ballpark range then the rest is up to the rider. For hard core serious racing and track days high end revalving could provide even better results,but for a RZ being a 30 year old machine the replacement shock,set up for riders weight and gear..is all thats needed ,no need to start changing valving beyond what is provided..for most folks there are always exceptions.
The RZ is undersprung from the factory originally designed for people probably weighing around 150 -160 lbsrange ,being 200+ lbs just crushes the poor old thing and with zero adjustments avail,beyond a preload system thats sure to be totally useless since 1988 :smt005 ..No wonder hes having issues,a new rear shock with the correct spring provided,all by itself may just cure his issue.
Good note on the Nitron to add to the list,i forgot about them :smt023
HAPPY 30th YAMAHA YVPS 350 1983-2013. DONT OVER THINK IT , JUST BUILD IT AND BE JUST AS FAST AND RELIABLE

graham heise
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Re: rear suspension sag?

#9 Post by graham heise » Tue Jan 15, 2013 8:41 am

Hello race fans. Thank you for your imput. I'm glad the topic has at least sparked debate. Although i did ask a question that still isn't answered. "Ride height to bottom of gaurd with and without rider?"
Yes this is a race bike. My first. I'm 45 and 95kilo's, hoping to pedal an rz350 around in local competition of period bikes for my first year of racing. Mick doohan raced his first season on an rz350 at surfers paradise raceway (my town) when he started.
That said my limited budget and interest at knowing how things work has lead me to do most of the work myself on the bike. I have a 2001 r6 shock, I'm contemplating using it. I believe it's capable of giving me a firm, responsive rear on the bike. If i need to modify the dog bones to a better ride height i will. The forks i'm thinking a firmer linear spring set for a ride height to match the back, hoping to balance the bike into it's neutral steering position. I figure the lower the centre of gravity = Faster the bike . I have to trade in ?my weight, limited budget and chamber size and ride the best with what i've got.
Down the track I'd love to spend coin on all things better and faster but that goes against the whole idea of budget racing on a bike i really like. If i can't beat em in the corner, i'll have to smash them on the gas.
Piece by piece this bike is coming together. I'll be dropping what weight i can from the bike and could run 86 model progressive forks that i have.
Does anyone run an R6 shock set up on a track bike? Graham
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Re: rear suspension sag?

#10 Post by Evans Ward » Tue Jan 15, 2013 9:15 am

Graham,

I'm 6'2" and 210 lbs so your size weight wise. I've run both progressive and single rate linear springs on my stock RZ forks. If you have the $ and time, please consider new linear fork springs matched to your weight as they are a noticable upgrade over the progressive springs IMHO. I also went with the gold valve emulators (Mikes XS China knock offs). These look very close to the Race Tech gold valve units. Really love the way the front end feels now with this set up. There is some work/ modification involved in going the emulator route but was worth it I feel. For new linear springs, Mikes XS emulators, new bushings, seals, oil, etc- you will have approximately $250 (US dollars) invested. Again, budget is always a contributing factor as to what options you seek and implement. My goal is to steadily and continously improve my RZ. If I had to start over, I would probably upgrade the brakes, suspension, and cooling system in that particular order even before performance mods.
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Re: rear suspension sag?

#11 Post by Gazzah » Thu Jan 31, 2013 4:52 am

Hi Graham,
just thought I'd throw in my 2 cents worth. I put a 99 R6 shock into my 83 rz250, and have found it has raised the arse of the bike by about the 1 inch or so, therefore it did increase the ground clearance. Suprisingly the spring is a bit too soft to be perfect as Ive had to wind the preload right up to get approx 35mm of sag (Im 85kg). It steers a lot quicker now as its thrown more weight forward and yes probably highlights the soft front end a lot more.
Still its a 1000% better than the original so I'd say give it a crack.

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Re: rear suspension sag?

#12 Post by kampinguru » Tue Mar 01, 2016 12:50 pm

To put my experience into the mix, they are all right about good suspension making you faster than a good motor. When I was racing, I crashed my RZ in one heat race and borrowed a competitors bike for my next heat race(he was not running in that class). His bike was ungodly fast in a straight line (not stock in a production class). He had crap brakes and the front suspension bottomed out when braking for a corner. My lap times suffered in that heat race. Fast is only good in a straight line. Suspension helps you go fast in the corners. Spend the money there. I just had my old racing shock rebuilt by John Sharrard at Accelerated Technologies. It is an old White Power shock with nitrogen. I had him set it up for my weight and riding style when he rebuilt it. I really should get a heavier spring for the rear but since it will be for the street only, I can just adjust the preload to do what I want out of it.

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JonW
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Re: rear suspension sag?

#13 Post by JonW » Tue Mar 01, 2016 7:11 pm

holy thread resurrection! :D
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

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Re: rear suspension sag?

#14 Post by mike YPVS » Tue Mar 01, 2016 7:14 pm

Jeez! don't get me started on this one

oh yes! tis three years ago lol

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Re: rear suspension sag?

#15 Post by seahorse » Sun Mar 27, 2016 1:20 am

On the shock thing, I just finished a bog stock RZ rebuild and alas the rear was very soft on the first ride.
So I did a lot of net searching on the best replacement for my budget. I could not find any thing to fit my wallet, and after reading a lot of to and fro-ing on the R6 shock replacements, I decided to try and fix the spongy issue first, failing that I would save up for a LSL shock or Penski or equivelant.
So what I did was select the best of two old shocks I had, I removed both springs using a spring compressor ( threaded rods with hooks).
The shock I used was the one that compressed smoothly with some resistance and even returned a bit. The other shock just compressed under less resistance and Just stayed put.
I the cut the full circle starting coil from the spare spring and welded it to the full circle starting point of the spring I had selected to use. This gave me about 10-12 mm preload on the old spring. I then rebuilt the shock ( put the spring back on the shock) very carefully.
I was bloody amazed at how perfect it turned out. I started with unweighted to bike weighted was about 10mm sag, then me on top it dropped another 35 mm.
After the Seahorse Shock Mod "SSM", I ended up with 5 mm unweighted to weighted sag then another 20mm with me on top.
Fuck knows how long its gunna last but I took it for a ride and its Night and day, perfect.
As bare would say it'l do for shopping, and chasing granny's for now.

You could make your own spacer with a bit of 10mm flat or round bar bent to represent a bangle and use that as a spacer to preload the spring. All I can say is be bloody careful when compressing the spring its a bloody dangerous job.
Kind regards Seahorse
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