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Author Topic: Suspension setup for rider weight??  (Read 778 times)

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Offline Sir Rat

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Suspension setup for rider weight??
« on: October 04, 2011, 10:52:07 pm »
I have just bought a CRF450R and its suspension is set up almost perfect for me. The previous owner had it set by MP suspension for a rider 90kg.  I have a track that I ride very often and I could feel/see the difference from this bike to another bike where the suspension is not set for the same weight rider.
Not once did it feel like it is going to bottoming out or taking any strain.

Maybe the more knowledgeable riders can tell me if a bikes suspension is set for a rider of 75kg, would a rider of 90kg cause damage to bike suspension (spring, inner-parts) if he rides it hard on rough terrain?

A XR400's suspension took some serious knocks off just me riding it in terrain that was a little rough. To date I have only had to have seals and rubbers replaced.

Could the Xr400 springs have been damage as well?

I also had a DR250 that lost the back shock wish had to be completely rebuild. I also suspect heavy rider damage here. I think it was more suited for a 75-80kg rider.

Is rider weight only important if you ride a bike hard or should it be taken serious under all circumstances?   :-\



« Last Edit: October 26, 2011, 03:09:34 pm by R-O-V-Rat »
 

Offline superfoxi

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Re: Suspension setup for ride weight??
« Reply #1 on: October 04, 2011, 11:44:02 pm »
You are not going to damage your suspension unless you bottom out all the time. There is a hydraulic stop build into the forks that prevents real metal-to-metal bottoming out. The shock has a rubber stop that prevents the same thing.
But you are not making use of the full performance the suspension has to offer. You will immediately feel that you can go much faster and safer for longer if the suspension is set up properly and the spring rate is right for your weight.
It's easy to check:
1. adjust static sag to 20 to 30mm (35mm for KTM's with PDS)

2. sit on the bike in a normal riding position and measure the sag again (get somebody to help you holding the bike steady)
The "rider sag" or "race sag" should be 100mm (105mm for KTM's with PDS).

If the rider sag is more than 100mm the spring is too "soft" - you need a higher spring rate. If the rider sag is less than 100mm then your spring rate is too high.

You are welcome to bring your bike to me to measure sag and get  basic set up. It's free of charge.
I might even have the right springs for you... ;)

« Last Edit: October 05, 2011, 09:09:01 am by superfoxi »
 

Offline Sir Rat

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Re: Suspension setup for ride weight??
« Reply #2 on: October 05, 2011, 07:50:18 am »
Thanks Mr Superfoxi.

Are you saying that if the bike spring ratio is set-up for a rider of 70kg and correct sag for 70kg rider, it would most likely sag way more for a 90kg rider and this heavier ride would then cause it to bottom more often and result in damage?
 

Offline superfoxi

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Re: Suspension setup for ride weight??
« Reply #3 on: October 05, 2011, 08:49:39 am »
You will not damage your suspension if you are 20kg's more than the optimal weight for the bikes spring rate but setting up the suspension properly is the most important thing on any (dirt)-bike. You are riding a high end of piece of Japanese technology that you can only use to half of it's potential  ;) .
« Last Edit: October 05, 2011, 08:50:49 am by superfoxi »
 

Offline Rough Rider

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Re: Suspension setup for ride weight??
« Reply #4 on: October 05, 2011, 09:04:14 am »
You are not going to damage your suspension unless you bottom out all the time. There is a hydraulic stop build into the forks that prevents real metal-to-metal bottoming out. The shock has a rubber stop that prevents the same thing.
But you are not making use of the full performance the suspension has to offer. You will immediately feel that you can go much faster and safer for longer if the suspension is set up properly and the spring rate is right for your weight.
It's easy to check:
1. adjust static sag to 20 to 30mm (35mm for KTM's with PDS)

2. sit on the bike in a normal riding position and measure the sag again (get somebody to help you holding the bike steady)
The "rider sag" or "race sag" should be 300mm (305mm for KTM's with PDS).

If the rider sag is more than 300mm the spring is too "soft" - you need a higher spring rate. If the rider sag is less than 300mm then your spring rate is too high.

You are welcome to bring your bike to me to measure sag and get  basic set up. It's free of charge.
I might even have the right springs for you... ;)



Superfoxi are you sure about that, all my bikes have the rider sag set at 95 - 105mm?
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Offline superfoxi

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Re: Suspension setup for ride weight??
« Reply #5 on: October 05, 2011, 09:11:36 am »
 :imaposer: sorry about that...was a bit too late at night when I posted...
It was supposed to be 100mm (+/-300mm is the total suspension travel and your rider sag is +/- 33% of that).
Thanx for waking me up!
« Last Edit: October 05, 2011, 09:13:08 am by superfoxi »
 

Offline Beserker

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Re: Suspension setup for ride weight??
« Reply #6 on: October 24, 2011, 11:32:46 pm »
@Superfoxi

I agree with your sentiments 100%...rear suspension race sag is definitely the most important single adjustment affecting your bikes handling traits. You should check this crucial adjustment before each ride or at minimum, monthly to insure it remains at your determined setting.

I do differ from you regarding the procedure though, but stand to be corrected,

For this adjustment procedure, the bike should be brought to normal racing weight - correct fuel, transmission oil and coolant levels. The shock should be cool to the touch, as heat build up will directly affect your sag.

Using a tape measure, measure the unloaded dimension when your bike is supported by a bike center stand and the rear wheel is off the ground. Measure the distance from the rear axle up to the fixed point in line with the arc of the axle. Usually the fender and side panel junction or some conven-ient point near the fender like a seat bolt. You can put a mark on the fender, which lines up with an even number to make it a little simpler. Write down as Dimension A

Now, place the motorcycle on level ground. Next measure the loaded dimension with the rider aboard, wearing all normal riding gear. Bounce your weight on the seat a couple of times to help the suspension overcome any stiction and settle to a good reference point straight up from the pegs. Make sure to keep your hands on the bars, stay in a normal riding position, and make sure all of your weight is on the seat with your feet barely touching the ground with enough to just keep your balance. Using a helper, measure the distance between the same two points determining Dimension B

The race sag dimension is the difference between the unloaded (Dimension A) and the loaded (Dimension B) measurements. Adjust spring preload as necessary to obtain the correct handling results....it should be approx 100mm - 125 mm.

Next you must compare the rear suspension sag under the weight of the sprung portion of the bike alone (without riderís weight) to the unloaded dimension. Having the prop-er spring rates in the front and rear is critical for proper handling. The spring rates must be selected to match the size of the bike and weight of the rider. Heavier riders require stiffer spring rates. A good approximation of your rear spring requirements can be found by measuring the rear suspensionís static sag. This universally accepted measurement will quickly determine if your rear spring is approximately correct for your weight. Static sag is a measurement of how much the bike sags under its own weight.
Important note: You must first set the race sag to determine this measurement.

The first measurement is taken, as earlier, with the bike on a bike center stand, and the rear wheel hang-ing freely. Measure the distance between the rear axle and some convenient point near the fender like a seat bolt, determining dimension A

The second measurement is taken with the bike on the ground. Push up and down to allow the bike to find its natural resting position. Again, measure the distance between the same two points used above. This determines dimension C.
Note: The static sag is the difference between dimension A&C....should be about 30 - 40mm

Many times there is much confusion about the specifications above. Remember it this way, before check-ing your static sag, you must first set your race sag. If after setting the race sag the static sag is more than your range in the rear, the spring may be too stiff for your weight. In this case, the spring is not compressed enough to allow the suspension to extend far enough on its own. A spring thatís too firm does not allow the rear tire to hook up under acceleration and passes more of the bumps on to the rider. If the static sag is less than your range in the rear, the spring maybe too soft for your weight. In this case, the spring required so much preload to achieve the proper race sag that it makes the rear end too high or even top-out when the rider dismounts. As a result, the weight transfer is incorrect and the rear end tops-out under even light brak-ing and on downhillís.
Also, remember you may adjust your race sag within your specified range depending on track conditions and riding style. Less sag can improve turning ability at the cost of slightly reduced overall stability. More sag can improve overall stability but may reduce turning performance slightly. After adjusting the spring preload to obtain the proper race sag, the suspension should sag, within the specified range, from the weight of the bike alone.
« Last Edit: October 24, 2011, 11:37:12 pm by Beserker »
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Offline superfoxi

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Re: Suspension setup for ride weight??
« Reply #7 on: October 25, 2011, 08:45:26 am »
The reason why I would adjust the static sag first is that the static sag is more important than the rider sag. If the rider sag is out by lets say 25mm the bike will still be ridable. But if the static sag is out by the same amount you will have major handling problems as the static sag could be zero or something like 50mm. If you set the static sag first, then you know that at least your most important measurement is right...
 

Offline Beserker

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Re: Suspension setup for ride weight??
« Reply #8 on: October 25, 2011, 09:11:19 am »
Cool...I work from the premise that you would be aiming for optimum,  if it ain't right...replace, regardless.

These are race bikes that we are talking about, not commuters.

In the case of a commuter your procedure is correct for an interim, till you get the springs sorted.

Thanks for your feedback, I never thought of it that way.

Cheers
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Offline Rough Rider

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Re: Suspension setup for ride weight??
« Reply #9 on: October 25, 2011, 10:54:43 am »
The way I understand it is you set the static sag correctly and then you check the rider sag. If the rider sag is out but the static sag is correct your spring weight is incorrect and the spring has to be changed. It is pointless having the rider sag correct and the static sag out. It stands to reason that if the spring is the incorrect weight for you it is not possible to have both rider and static correct.
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Offline superfoxi

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Re: Suspension setup for ride weight??
« Reply #10 on: October 25, 2011, 11:14:39 am »
Both ways of measuring are correct in the end. I just think it is easier to set the static sag first. And I totally agree that you should get the correct spring rate for your weight...
 

Offline Beserker

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Re: Suspension setup for ride weight??
« Reply #11 on: October 25, 2011, 11:45:18 am »
The way I understand it is you set the static sag correctly and then you check the rider sag. If the rider sag is out but the static sag is correct your spring weight is incorrect and the spring has to be changed. It is pointless having the rider sag correct and the static sag out. It stands to reason that if the spring is the incorrect weight for you it is not possible to have both rider and static correct.

If your Race Sag (or what you call Rider Sag) is correct, and Static Sag not, your spring weight is incorrect.

Race Sag caters for a lot wider spectrum of factors, i.e. type of terrain, fuel requirements, rider weight incl. equipment, and can be anything between 100 to 150mm, and as such, to a large extend be the determining factor.
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Offline Rough Rider

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Re: Suspension setup for ride weight??
« Reply #12 on: October 25, 2011, 11:47:02 am »
The easiest thing to do is go into the Race Tech calculator and it will show you what weight your spring should be; saves a lot of time.

http://racetech.com/ChooseVehicle.aspx
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Offline Beserker

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Re: Suspension setup for ride weight??
« Reply #13 on: October 25, 2011, 12:02:48 pm »
The easiest thing to do is go into the Race Tech calculator and it will show you what weight your spring should be; saves a lot of time.

http://racetech.com/ChooseVehicle.aspx

Nice..

Not to vaak for a Husky rider, are you?   ;D

But they are discriminatory regarding my age ....oops!
« Last Edit: October 25, 2011, 12:03:51 pm by Beserker »
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Offline Rough Rider

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Re: Suspension setup for ride weight??
« Reply #14 on: October 25, 2011, 12:07:51 pm »
The easiest thing to do is go into the Race Tech calculator and it will show you what weight your spring should be; saves a lot of time.

http://racetech.com/ChooseVehicle.aspx

Nice..

Not to vaak for a Husky rider, are you?   ;D

But they are discriminatory regarding my age ....oops!

Only problem is they don't have the 610TE 2009 in their data base.

I'm You not much older than me you  :biggrin:
« Last Edit: October 25, 2011, 12:11:50 pm by Rough Rider »
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Offline Rough Rider

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Re: Suspension setup for ride weight??
« Reply #15 on: October 25, 2011, 12:13:01 pm »
The easiest thing to do is go into the Race Tech calculator and it will show you what weight your spring should be; saves a lot of time.

http://racetech.com/ChooseVehicle.aspx

Nice..

Not to vaak for a Husky rider, are you?   ;D

But they are discriminatory regarding my age ....oops!

Besides I also own a Honda
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Offline Beserker

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Re: Suspension setup for ride weight??
« Reply #16 on: October 25, 2011, 12:15:21 pm »
Besides I also own a Honda

Redemption  :deal:
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