What Shock Spring Do I Need?

A couple of years ago, I bought a Penske 2 way adjustable shock from Traxxion Dynamics. At the time I weighed about 285. I have lost down to 245 and thought it might be time for a lighter/softer shock spring as the rear of the bike is rather bouncy.

I dug out my invoice from Traxxion to see what was on the shock. They had installed a 1400#/in spring on it originally. I did the math and that works out to a 25.06 kg/m spring.

I see other posts on this forum about people running 18-19 kg/mm springs. I went to the Traxxion website and a 1300# spring is what they recommend. I've tried calling Phil Douglas at AfterShocks and all I get is an answering machine. My e-mail to him has also gone unanswered.

I punched my data into the RaceTech website and they come back and say a 16 kg/mm spring.

Needless to say, I am thoroughly confused. There's a big difference in a 25 kg/mm spring and a 16 kg/mm spring. The stock spring on the bike is supposedly a 15.3 kg/mm spring.

Any help and advice would be appreciated. I'm calling Lindemann and After Shocks both and the people you need to talk to are always out and plain and simple, I don't trust Traxxion's numbers.

A 1400 lbs spring?! That sounds like overkill, even at 285 lbs. :rolleyes:

I'd say you'd probably want a 1200 lbs spring. That's about 21.4 kg spring. If you plan on losing more weight, maybe even go down to a 1100 lbs spring (19.7 kg).

pete, i am 250 and have an f4i shock on my 6th gen. i put a 950lb spring on it and love it.

I want to post a semi-apology here. I kept trying AfterShocks this evening and I finally got through to Sarah. Seems that Phil Douglas was in a motorcycle accident himself a few weeks back and has not been able to put the hours into his business he normally does.

I apologize if I implied that Phil was neglecting his customers. Sarah promised she would make sure Phil personally saw my e-mail and she would respond to it.

She did say according to her calcs, I should be running about an 1100# spring. She's helping Phil run a business, so of course she offered to have me send the shock out to them to have it valved properly and the correct spring installed. No beef with Phil, Sarah, or AfterShocks, but I have a little bit of a bitter taste in my mouth that I paid Traxxion $700 for the shock & spring to get it like it was suppose to be in the first place and now I've got to pay somebody else another $300 to get the shock setup properly.

If you go on Traxxion's website, they recommend a 1300# spring for a rider of normal weight for the 6th generation VFR's.

It amazes me that there is such a spread in suggested spring rates between RaceTech, AfterShocks, and Traxxion. Traxxion recommends a 1300# spring regardless of the brand of shock.

I wish there was some way to calculate what should be the correct spring rate given my particular bike, weight, etc. I know it's fairly complicated due to linkage lengths/ratios, etc.

One thing I did learn today though, you can purchase springs directly from Hyperco and the range of selection they have is incredible. They're a lot more reasonable too, $75-85 for a spring.

I welcome any and all input.