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are fork springs marked?

  • Thread starter Thread starter loud et
  • Start date Start date
L

loud et

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Well dumb as I am......I drained, cleaned and refilled my front forks last year when I wrapped up my 1100 E rebuild. The dumb part is that I should have done the spring mod and added some PVC to stiffen them up. My sag is 2" and forks still dive when braking.
So.....I was in the garage mulling things over....looking for the pvc and whatnot.
I happen to have another front end from a 80-81 1100e. For some reason I took a better look at them and they are actually Forks By Frank. Now I just HAVE to pop a top cap and pull a spring out to see what's in there. I know the guy I got the parts from has a few well built 1100E's that are turbo'dand upgraded in various ways. I may find some good aftermarket fork springs in there.
Will find out soon.

SO, do fork springs, either OEM or aftermarket have identifying marks or numbers?
 
Not to forget that I installed SS front brake lines today and my diving front end is way more noticeable now.
Wow...ss lines are awesome.:)
 
There are no identifying numbers on forks. I 'think' there's a way to calculate the spring rating or something to determine what they are. You can also measure the overall length to determine if they are progressive. I've emailed Progressive directly for that info in the past.
 
The only fork springs I've seen with markings are Race Tech.

It's easy enough to see if a spring is wound progressively, but Progressive brand springs are not marked. As noted above, you may be able to narrow things down by comparing the appearance of the spring and overall length with Progressive's specs.

There are web-based spring calculators out there, but tiny differences in wire diameter measurements can make a big difference in the calculated rate. Might be worth a try -- you can at least ballpark it like this. Bear in mind that you will have to do several calculations if it's a progressively wound spring.

If you're really convinced you need to know the rate of a certain spring, it would be far more accurate to measure -- you could build a simple jig that holds the spring or a fork leg (preferably with the seal removed) and allows you to stack on a known amount of weight and take measurements.

Do a bit of math and you're there. Most fork spring measurements you see are expressed in kg/mm. (Although sometimes you'll see pounds/inch.) So if you stack on, say, 50kg and it moves 50mm, that's 1.0 kg/mm (a pretty heavy aftermarket fork spring). If it moves 83mm with the same amount of weight, that's .60 kg/mm. Very soft, but common in the dangerously squishy OEM fork springs Japanese manufacturers have inexplicably insisted on using for the last 40+ years.

If it's a progressively wound spring, then you'd need to measure (probably using smaller amounts of weight than the example) at several different points in the spring's travel to get a picture of the spring's range of rates.

Sonic Springs and Race Tech have calculators on their sites to help you calculate the correct spring rate (for a straight rate spring) for your bike, your weight, and your riding style.

If you don't like math and you're an average weight rider riding in an average way, then a set of Progressive fork springs is a decent "one size fits most" solution.
 
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Well Brian, thanks for the info....but I went ahead and added PVC to my stock forks.
Noticible difference on the road and in sag. I'm happy for now.

Second note, the Forks by Frank tubes are custom shorties....they are 1-3/4" shorter than stock tubes. It figures, a guy from the hood with old turbo Gs's would lower his bikes. Lol "City extended swingarm syndrome" and lowered "SLAMMED" ha ha The po just cut the stock springs down to fit.
I will just sell these forks to a short person. Lol
 
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