Trying to decide between Racetech 1200 or 1300 spring

I found that I had to dial in more rebound damping than the intial 2 turns out to get a controlled ride from the rebuilt shock. I was getting a poko ride at 2 turns.
 
Right now I am using 1 turn out and it seems to work. I will fine tuning this as I ride. I am still out about 7 clicks on the pre-load. I thought with the stiffer spring I would not have to do this.
 
That's about where I am with the rebound. Maybe closer to 7/8. I too was surprised how much preload I had to crank in to get the proper sag. I work for a axle manufactor and was able to find a case bearing that was the same diameter as the spring. It was .125" thick and made about for all but 1 click. I placed this spacer at the button of the spring and placed their spacer on top of the spring. I think the spacer they use needs to be a little thicker.




Sent from my Droid X2 using tapatalk 2
 
For general knowledge purposes what are the free sag and rider sag numbers you guys are seeing with the new springs?
 
roadriderg said:
On the rear I am about 38 mm with 7 turns out on the pre-load. On the new 9.6 front spring I am at about 36mm.
Click to expand...
What is the free sag on the rear? Sag with just weight of bike, no rider or cargo.
 
On the front bike only it is approx 29mm with rider is about 41.5 gives me about 35.5. Rear bike only is about 25.5 mm ,45 mm with me on the bike. Just measured this give me about 35.25 on the rear. I tightened one click on the last ride. This is without help holding the bike to get measurments.after approx 300 miles since replacement.
 
Don't compare the difference, just measure the sag numbers with rider on - then rider off.

Rider or static sag is sag with a rider and usual cargo load. Free sag is sag of just bike alone with no rider or cargo.

So, are you saying 41.5 mm rider sag and 29 mm free sag (front) and 45 mm rider sag and 25.5 mm free sag (rear)?

Thanks
 
dduelin said:
Don't compare the difference, just measure the sag numbers with rider on - then rider off.

Rider or static sag is sag with a rider and usual cargo load. Free sag is sag of just bike alone with no rider or cargo.

So, are you saying 41.5 mm rider sag and 29 mm free sag (front) and 45 mm rider sag and 25.5 mm free sag (rear)?

Thanks
Click to expand...

Yes that is true! The difference is m1-(m2+m3)/2= static sag.. M1= distance with bike on center, m2 is bike unloaded, m3 is bike with rider on..
 
roadriderg said:
Yes that is true! The difference is m1-(m2+m3)/2= static sag.. M1= distance with bike on center, m2 is bike unloaded, m3 is bike with rider on..
Click to expand...
I can't make sense of your calculation. As stated (m2+m3)/2 is the average of free sag and static sag which doesn't make sense. These should be separate numbers because of the relationship between them. The average of the figures in parentheses is the average of measurements made after taking stiction into account.

Free sag is an important indicator of individualized spring rate because it is measured after preload is adjusted for the weight of rider. Because we have few if any free sag numbers after springs are changed from stock I thought this would be a good opportunity to see what difference it made. The founder of RaceTech says rear free sag should be 5 - 10 mm so 25.5 mm doesn't seem right.

I hope this makes sense.
 
I don't have the number with me right now, but I can tell you the the free sag is no where close to the 5-10mm that Racetech calls for. If I remember correctly it is in the 25mm range. I haven't been able to find out why the difference. The instructions say that if rider sag is set correctly and free sake is more than recommended than you need a lighter spring with more preload. I didn't take measurements with the stock spring. I'll post the numbers I have when I get home tonight.

Sent from my Droid X2 using tapatalk 2
 
Maybe we are talking the relationship between static sag and free sag which would be in those numbers. Then I would be about 6+ front and 9.5+ rear at this point.

I would need help to get a true static sag allowing for stiction.

It indeed would be interesting to get a stock measurement, a st1300p which uses a heaver spring, and a hyperpro measurement. My spring is the 1200 lb racetec spring, maybe also a 1300 lb racetech spring measurement.

If free sag needs to be 5 to 10 mm then something is wrong with the spring setup. With that in mind there is approx 350 lbs on the rear of the bike without rider and that will compress the spring only 10 mm? So how is an addition 190 lb rider going to compress the bike a further 25mm to get in the range of desired sag?
 
roadriderg said:
........... If free sag needs to be 5 to 10 mm then something is wrong with the spring setup. With that in mind there is approx 350 lbs on the rear of the bike without rider and that will compress the spring only 10 mm? So how is an addition 190 lb rider going to compress the bike a further 25mm to get in the range of desired sag?
Click to expand...
There are many suspension tuning resources available to us and most of them will explain it better than I will.

The spring starts out under compression before the shock is installed on the bike. The spring has to press against the spring retaining collar and there is the spacer RT places under the spring. So the spring is "preloaded" before weight of bike and rider are placed on it. Therefore a certain amount of weight has to be loaded on it before the spring begins to compress. This weight is of course the bike itself then rider.

A geared up 190 lb rider approaches 30% of the total weight of the bike/ rider system which is not insignificant. If the spring is close to the right strength the shock's adjustable preload device can easily set the target sag setting. Lets use 30 mm for the target. So weight of bike and rider compress the shock to the target of 30 mm from fully extended. If sag initially is 45 mm we add preload to reduce sag to 30 mm. If we remove the weight of rider and measure sag again we get free sag. The relationship of free sag to rider sag is a reliable indicator of whether not the spring's strength is good for this bike and rider. If the spring is too soft we had to use a lot of preload to hit the target of 30 mm, therefore when we remove rider weight the shock extends a long way. Free sag is zero (topped out) to 5 mm. If the spring is too strong initial rider sag might be 30 mm or less. In this case we would have to remove preload to hit the target of 30 mm. When the rider is removed free sag would be in excess of 10 mm. Too much free sag indicates a too stiff spring. It needed little to no preload adjustment.

These are suggestions of course and individuall bike/rider systems may vary in the amount of sag they like, both overall and front to rear.
 
I may be a little dense but here is what I understand.
Rear shock.
1. I can get the desired overall sag with me on the bike using the preload. that is approx 35 to 36 mm from fully extended fork (on centerstand) to weighted with bike and rider.
2. The distance between the 35 to 36 mm overall sag to free sag is 9 to 10 mm. (free sag being the distance from fully extend fork on centerstand to weighted with bike alone.)

In your discription I believe you are stating free sag is the distance from overall sag to bike alone sag. My understanding is free sag is the overall length from shock fully extended to sag with bike weight alone.

The spring does have some preload on it(I do not know how much) and the collar this was rebuilt by racetech.
 
It's straight forward. Use the formula and method in post #34 to measure sag with rider on the bike. Use preload as required to hit target sag number. This is static or rider sag.

Repeat, leaving preload where it was. This time the rider is not on the bike. This sag number is free sag. Some suspension tuning books, guides, or websites suggest rear shock rider sag of 5 to 10 mm indicates the spring rate of the spring is in the ball park for bike and rider. Too little sag - the spring may be too soft. Too much sag - the spring may be too stiff.

If it is more or less than the prescribed and the owner/rider is happy............ then no harm no foul.
 
OK, here are my number with the 1200# spring and a 175# rider. Rider Sag = 36.5mm, Free Sag = 19.11mm. I would be interested to see what the stock spring measurements are.
 
I consulted my notes from past measurements. With this 155 lb rider the stock spring has 7 mm free sag with 28 mm rider sag. I like a higher rear ride height. I think I set the sag at 30 or 32 mm another time and the free sag increased to 8 mm. (I had 7 and 8 both written down but not cross referenced with rider sag)
 
After several months of dealing with this it just came to me that the RaceTech numbers of 5 - 10mm. of free sag are with 30mm. of rider sag. When set at 30mm. I get 11mm. of free sag. This puts me much closer to the recommended free sag number. RaceTech and Sonic both suggested that 36mm of sag front and rear was the sweet spot for the ST1300.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom