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Old 05-05-18, 07:59 PM   #1
Frank_drebbin
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Default Rear preload for a lighter rider?

Hi,
I have a 2016 SV650 (6000 miles) and I'm a small rider, 5ft5 and Just under 10 stone (138 lbs).

I was wondering if I should reduce the preload on the rear shock, it does feel quite clunky over bumps. When I sit on the bike it only compresses about an inch. I think reducing the preload may help. Does anyone have any advice as well as what size hook wrench would fit?

Thanks again.

Edit: I am stupid, I didn't realise there was a wrench in the toolkit, I have adjusted for testing.

Last edited by Frank_drebbin; 05-05-18 at 08:08 PM.
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Old 05-05-18, 08:43 PM   #2
Bibio
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Default Re: Rear preload for a lighter rider?

the standard suspension on the SV is shizz.. no it really is. good news is it can be vastly improved but at a cost.

lets set a few misconceptions about suspension right:
the spring of a shock or inside forks is for preload, its to set the ride height so the suspension is sitting at the correct height to do its job properly. this is called sag settings.

when setting up your sag you set the static sag e.g. the weight of the bike upright. its when you check the rider sag that you then find out if you need to change the spring rate for the rider.

preload is not to make suspension stiffer or softer, it cant its a spring it has a rate and that rate never changes yes even on "dual rate" springs, with these there are two rates that never change. only when you wind the preload up that much the damper is topping out does it "stiffen" suspension. problem is that you no longer have suspension with the proper sag to take care of chassis movement while braking/accelerating and going over bumps.

you dont adjust preload to "lower" the seat height of a bike. you need to use either a modified shock or lowering links. adjusting the sag via the spring to lower it sets the damper higher so gives less travel before it bottoms out which will lead to a harsher ride.

believe this or not but at 10st your overweight for the bikes standard front suspension but pretty much bang on for the rear.

go and google "bike sag settings" this usually returns settings for race setups so add 3-5mm rear and 7-10mm front e.g. increase.
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Old 06-05-18, 12:03 AM   #3
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Default Re: Rear preload for a lighter rider?

I believe Frank's bike is an AL7.
The fork springs are not used in any other Suzuki, the rear shock and linkage is the same as the SFV.
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Old 06-05-18, 07:27 AM   #4
Frank_drebbin
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Default Re: Rear preload for a lighter rider?

Thanks all for the replies. I think I understand the nature of preload now. Essentially the spring rate is linear, so changing preload doesn't make it harder or softer, simply changes the ride height to counteract rider weight and therefore determine sag. A heavier rider needs more preload, as without it they will compress the shock "lower" more when sitting on the bike so they have too much sag. A lighter rider needs less preload, so the bike rides lower, and their lower weight presses the bike down less.

The only way to make it "stiffer" or "softer" is with a different spring, and the only way to improve the quality of the ride is with a more expensive shock and/or with better/adjustable damping (or a softer seat?!).

Is all that right? If so my only last question is what setting of preload should I run it at at a guess (I will try measuring it, but at ballpark what do you think?). Currently it is on minimum preload, and stock it was two clicks of pre-load.

Thanks for all the helpful info and advice
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Old 06-05-18, 08:40 AM   #5
Frank_drebbin
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Default Re: Rear preload for a lighter rider?

Interesting on the seat. The suzuki one looks lovely, although I don't find the stock one too bad. I did 150 miles on it the day of purchase and while I was still at the end, I didn't get any particular chafing or sore thighs, very odd.

I'll let you know how the different preload feels if I notice. The "luimoto" seat covers on ebay look very smart. Looks wise anyway
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Old 06-05-18, 02:19 PM   #6
Bibio
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Default Re: Rear preload for a lighter rider?

preload is not to set the rider sag. its to set the bike (static) sag.

once you set the static sag you then CHECK the rider sag measurements.
once you have the measurements you can determine if the bike needs new springs.

if you cant change the springs then set the bike static sag and leave it there, do not adjust for rider sag. only time you would adjust rider sag is when you rarely carry a pillion but you must set it back after carrying a pillion.

when you set the bike static sag and change it to match rider sag you also change the static sag so you no longer have the correct static sag.

the spring (unless its completely wrong) has nothing to do with comfort its the actual dampening system inside the suspension that is responsible.

dampening controls the rate at which the spring is allowed to move in an up/down motion. if the dampening is wrong then you will either get too much movement of the spring or too little. but the tricky part is that the spring has to match the dampening and visa versa. this is why you cant just stick another shock from another bike onto your sv as the shock is set up for that donor bike. now having said that it can work as long as the linkage and weight of the donor bike matches the sv and the rider.

step up an aftermarket shock such as nitron. these are built for the rider weight and the style of riding the rider does. the valving shims inside the shock are setup for the purpose and spring weight. this is why when ordering a shock you must tell them what type of riding you do. the worst thing you can do is put a shock that is setup for racing/track use on a bike that is used for the road as its too "stiff" a setup.

i could go on and on about this subject but the upshot is that with the OP being 10st then all he needs to do is set the static sag for road use and leave it there.

one last thing which a lot of people dont like to hear is that you must service suspension and its not as long an interval as you might expect. suspension oil gets a hammering and to keep your suspension in top condition it need a service just like the rest of the bike. at most i would say every 5th engine oil change you should be looking at servicing the suspension and brakes.
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Old 06-05-18, 02:46 PM   #7
Frank_drebbin
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Default Re: Rear preload for a lighter rider?

It slowly seems to be making sense. Here is a very clear video on what to do:

https://www.youtube.com/watch?v=TMDCEU98_9w

I will try setting this up. Thanks.
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Old 06-05-18, 03:16 PM   #8
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Default Re: Rear preload for a lighter rider?

Do what Bib suggests and upgrade the shock, best money I spent on the curvy

I bought a seat which had been improved, the standard was painful after 30 miles, I can do 300 on my seat with a couple of stops
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Old 06-05-18, 03:47 PM   #9
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Default Re: Rear preload for a lighter rider?

Quote:
Originally Posted by Frank_drebbin View Post
It slowly seems to be making sense. Here is a very clear video on what to do:

https://www.youtube.com/watch?v=TMDCEU98_9w

I will try setting this up. Thanks.
pretty much except that you dont adjust for rider sag. this is the biggest common mistake that people make because they dont want to face the fact that the spring rate is wrong.

you check and then set static sag to 10mm for road use.

you then put the rider on and check the rider sag 30-40mm.

lets say:
bike off ground (free sag) 500mm

your static sag (bike on ground and upright) should be as near to 510mm as possible for road use.

your rider sag (bike on ground and upright with rider) should be 530-540 with nearer the higher number better for road use.

if the rider sag does not fall in between the 530-540mm range then you need to change the springs. do not wind the preload up or down to match the rider.

always SET static sag and leave it there. changing the rider sag with using the preload will also change the static sag.

however, lets say if you have a rider sag of 545mm and a static sag of 10mm you can wind the preload down by 5mm to achieve the correct numbers. the only problem with this is that you are now going into race setup settings which are no good for road use.

the above is also true in the opposite direction. lets say your static sag is 10mm and the rider sag is 525mm you cant add 5mm to the static sag to increase the rider sag as the static sag would then be 15mm.

a few mm here or there is not going to make that much odds in the grand scheme of things so dont fret too much about numbers as long as your not getting wildly large increases/decreases.

why do you need static sag?
simple, during braking in particular if you dont have a negative number then your suspension "tops out" too soon so more inclined to lift the rear wheel off the ground during braking. this then upsets the chassis for corner entry and or emergency stops. with race settings things are a lot more precise and the front setup is matched to the rear using stiffer spring rates.
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Old 06-05-18, 03:59 PM   #10
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Default Re: Rear preload for a lighter rider?

IMHO just ride and enjoy the bike, don't get too technical as majority of riders will reach their limit long before the bike does ,- maybe when you have ridden bike for a while think about improving suspension. Every standard bike setup is a compromise but if you start worrying about things it will undoubtedly spoil your enjoyment. I would be more inclined to spend any spare money on front fenda extenda and radiator guard, a hugger if you like the look, and good set of tyres also maybe an ABBA stand.
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