Hello I have a 1998 fatboy and installing progressive springs heavy duty ones . I weigh 240 LBS and am wanting what weight of oil should I use with these new springs 5 , 10 or 15 ? thank you for ay input . I got sick and tired of bottoming out the suspension while enjoying the ride thank you for any input ....

 

For what it's worth, I put Progressives on my '03 FLSTFI and used HD 'Heavy' oil with them. I have less 'diving' and better handling than the original setup...but then I only weigh 140lbs.

 

Along with fork oil weight which will control how fast the forks compress and rebound, fork oil quantity will help control the forks bottoming. I'm pretty sure that bikes come with what amounts to as 5wt. I recently changed my oil and I went with 10wt and, I just put the amount in Oz's that my manual called out. I didn't measure the levels where because I didn't have the time to do the method I'm going to describe next. The best way (IMHO) to measure fork oil is to measure from the top of the fork tube but, for most people just adding a few cc's of fork oil is probably easier. If you want to use the measuring option you have to remove the springs and collapse the forks. First put in the amount of oil in Oz's(refer to owners manual for amount) Then collapse the fork and determine how far from the top of the tube the oil height is ( I don't remember but I think the owners manual gives this measurement) using a large syringe with marks on it. I prefer this method because it's the most accurate. Then, if the forks bottom to easy, RAISE the level slightly, maybe 1/8" and then ride the bike. If it still bottoms too easy, raise the level another 1/8". Bear in mend that each time you check it, you have to pull the springs. I prefer this method as I said because it's the most accurate. Now, for most people the easiest way is to just add a few cc's of oil because all you have to do is pull the fork cap. It can take time to get it how you want it, but if you want the forks to perform well, it's worth it, at least to me it is. I hope I haven't got you confused! Take care and, have fun! BTW, I weigh 245#

 

I replaced the front springs on the Sporty with Progressives, but I chose to put in the Progressive Monotubes in the Fatboy. They're cartridges so I don't have to worry about what type of oil or how much to use. Supposed to be maintenance free as well.

 

Some great advise thank for all the input cheers

 

thank for the help

 

they are a great idea unfortunate i already have the springs

 

I put 15 in my Fatboy last change due to excessive brake dive. I only weigh 160 so had no problems with bottoming except for really big bumps!

 

Start with 10wt. I have Progressive standard springs (215lbs} and I found 15wt too stiff. I ended up mixing 10 and 15 to give me 12.5wt. Over 15 years, changed every 20K. I like it.

 

I would call progressive and ask them. When I put in the monotubes, I called them with some questions and they were very helpful.