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spring rate calulator


Guest Wistrick

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Here is a table that I've made using the calculations I've come up with:

Rider Weight Range vs. Shock Spring Rate (lb/in)

110-145lb = 1100lb/in

145-180lb = 1150lb/in

180-210lb = 1200lb/in

210-245lb = 1250lb/in

245-280lb = 1300lb/in

To be specific, a 250lb rider calculates to 1270lb/in. Since you can't buy a spring with that rate, you have to select the closest one available. I typically go up, in this case to 1300lb/in. There are other factors that play into it as well. Hopefully this gives you an idea!

JD if I take your 1270# and divide that by 250 I get 5.08. If I take that 5.08 and x by my 220# I get a 1117.6 spring which is very very close to being right. I think 1250# would be right for me for about 30mm rider sag. Also if I take the average Honda designed rider of 170# and x 5.08 I get 863# spring which is very close to what Honda seems to have calculated. 5.08 kinda seems like a magic number but it doesn't follow the rest of the numbers on your table.

Curious, what rider sag number is your target?

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Guest Pete McCrary

To all:

I will climb up on my soap box one more time.

You're spending $900-1300 for a Penske rear shock. You're spending $300-500 for a RaceTech/Sonic front end.

Spend $19.95 with Amazon.com and buy a copy of Andrew Trevitt's Sportbike Suspension Tuning and read it.

Pete

I have the book and have read it!!! I will call GP suspension and ask what size rear spring I am getting???

BTW I spent $480 on a GP suspension front end and $890 on the penske tongue.gif But you do make a good point.

Dan

Dang, I'm even better at guessing what kind of money is being spent than the correct shock spring rates. :ph34r:

Pete

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Guest Pete McCrary

Here is a table that I've made using the calculations I've come up with:

Rider Weight Range vs. Shock Spring Rate (lb/in)

110-145lb = 1100lb/in

145-180lb = 1150lb/in

180-210lb = 1200lb/in

210-245lb = 1250lb/in

245-280lb = 1300lb/in

To be specific, a 250lb rider calculates to 1270lb/in. Since you can't buy a spring with that rate, you have to select the closest one available. I typically go up, in this case to 1300lb/in. There are other factors that play into it as well. Hopefully this gives you an idea!

Jamie:

Are you using a calculator, slide rule, or abacus? Those numbers look pretty good.

Pete

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  • 8 months later...

already have a WP 3-way with 180 (1028) spring I could use with some .95 fork springs...

if I have the correct spring fitted to the shock won't I have to get it valved to match the new spring?

218lbs. w/o gear

Edited by 04asphalt
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already have a WP 3-way with 180 (1028) spring I could use with some .95 fork springs...

if I have the correct spring fitted to the shock won't I have to get it valved to match the new spring?

218lbs. w/o gear

I'm not familiar with WP, but Ohlins says that their shock adjustments can cover the entire range of possible springs you can install.

IMO as long as your Not Maxed out on either side of adjustments and have the desired compliance than revalving isn't necessary.

No if you were racing the bike you would rather have the valving in the middle of it's range for said shock spring, but most street riders set and forget. :blush:

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  • 1 year later...

already have a WP 3-way with 180 (1028) spring I could use with some .95 fork springs...

if I have the correct spring fitted to the shock won't I have to get it valved to match the new spring?

218lbs. w/o gear

been awhile, did I screw up getting 1.0 fork springs to balance the the rear 1028 (180) rear at my new 210lbs. birthday suit?

Edited by 04asphalt
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Not really, how does the bike feel to you now???

.95's might have been enough, the 1.0 is Not that different, but I do think the the 1028 rear is soft for your weight and the 1.0 is too much for the 1028 rear.

I run .95's w/a 20kg(1122lb) rear and weight 190lbs.

Your set-up is very close, but maybe a little harsh on teh front and over working the rear slightly.

BR

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Not really, how does the bike feel to you now???

.95's might have been enough, the 1.0 is Not that different, but I do think the the 1028 rear is soft for your weight and the 1.0 is too much for the 1028 rear.

I run .95's w/a 20kg(1122lb) rear and weight 190lbs.

Your set-up is very close, but maybe a little harsh on teh front and over working the rear slightly.

BR

just finished re-reading "transformed wow" and was thinking the same. thanks once again BR

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  • 3 years later...
  • Member Contributer

Race Tech have updated their 'calculator' for the 6th Gen.

It now yields the following results for a 90 kg Street rider:

F: 0.987 kg/mm

R: 20.337 kg/mm

I ran the same scenario not so long ago (I forgot when exactly) and I got 17.837 kg/mm. :wacko:

PS: Yes, I know the last comment on this thread is going for 4 years old but it's still pinned so ...

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While shopping for RT stuff for my VF500F2 I already pointed out that the weights used in their calculator are wrong or funky at least.

I spoke with one of their tech guys, asking what "semi-wet" was supposed to mean for their weight for the was way off.

RT say semi-wet is 180.5kilo

But the DRY weight is 185-189kg depending on year, kerb (so with ALL liquids) 202-206kg..

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While shopping for RT stuff for my VF500F2 I already pointed out that the weights used in their calculator are wrong or funky at least.

Actually ... the weight displayed by the RT calculator could be a fairly accurate sprung weight which is what spring rate calculations should be based on.

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Semi-wet = all fluids but empty tank.

Sprung weight = basically the weight actually bearing on the springs i.e. not counting the wheels, brakes, fork sliders, some part of the swingarm...

Seen like this, the 218 odd kg used for the 6th Gen makes more sense.

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  • 2 weeks later...
  • 8 months later...
  • Member Contributer

Here's Jamie's recommemdation with his fork spring ranges [from 'tranformed wow' thread]

 

"Here are the tables for a VFR800

Forks:

110-145lb 0.85kg/mm

145-175lb 0.90kg/mm

175-210lb 0.95kg/mm

210-245lb 1.00kg/mm

245-280lb 1.05kg/mm

Shock

110-145lb 1050lb/in

145-175lb 1100lb/in

175-210lb 1150lb/in

210-245lb 1200lb/in

245-280lb 1250lb/in

I would certainly suggest a set of 0.95kg/mm springs up front and a 1150lb/in (20.54kg/mm) spring out back. This would apploy to all street riders, the only time you would need to change is if you were an expert track rider on slicks. I hope this helps!"

 

 

Jamie, thanks for reposting this table. I was reading through this thread to see if anyone had quoted these spring recommendations from the 'transformed wow' thread. You provide a solid starting point for spring rate.

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Jamie, one question to help refine the approach to your spring recommendations.

 

Question- are your rider weights for full rider with gear weight or do they reference dripping naked rider only weight?

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6 hours ago, sfdownhill said:

Jamie, one question to help refine the approach to your spring recommendations.

 

Question- are your rider weights for full rider with gear weight or do they reference dripping naked rider only weight?

You'll get a quicker response if you email Jamie directly. Jamie@daughertymotorsports.com

He is very friendly and is usually ready with answers...of course if he's not buried with work. I have had him do all three of my bikes BTW.

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  • 1 year later...

Hello. Please tell what front/rear spring rates would be ok for 60-65kg rider fro VTEC? Riding style - sport touring, aggressive cornering, hard braking, frequently 2up.

0.85/17.8 kg/mm or 0.9/17.8(Racetech site) or maybe 0.9/19.6 (JD's table) ? Thanks!

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braga2, I went with Jamie's recommendations for springs and valving. I told him my weight and that I put 85% emphasis on track/hard sport riding and 15% emphasis on loaded touring. He used his extensive experience to rebuild my Penske shock and CBR600F4i forks to these specifications. Couldn't be happier - 18 days on the track last year and just finished a 4257 mile trip w full luggage on the same bike, same DMr suspension. [DMr = Daugherty Motorsports]

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