how do you calculate rake and trail - SV650.org

15-04-06, 08:18 PM

as the tittle says is it possible to work out rake & trail and how would you do this for a given bike

Sid Squid · 16-04-06, 12:51 PM

Easiest to use makers quoted figures, failing that get the bike on a perfectly level surface, using a spirit level and a protractor measure the rake, unless you've got a Harley forks and steering axis will be parallel, if they're not it's complicated. Trail - measure from point directly below front spindle to extended steering axis point - keeping sttering perfectly square. For ease I'd probably make some measurements and produce a diagram.

16-04-06, 03:54 PM

thanks squid

21QUEST · 16-04-06, 07:22 PM

Are you trying to work out how different changes affect the rake and trail?

Cheers
Ben

16-04-06, 11:03 PM

This site explains what to measure:

http://www.sportrider.com/tech/146_0310_art/

17-04-06, 10:13 PM

thats a handy site. no just want to see the difference between the gsxr forks conversion and the stock sv forks and to try and counter act any problems that may arise with it i know a steering damper helps but im not too pleased to have a 120/50 front tyre on

21QUEST · 17-04-06, 10:36 PM

Quote:

Originally Posted by mart

.......but im not too pleased to have a 120/50 front tyre on

You mean a 120/70 ?

Nice link extreme3d. Helped confirm a few bits for me.

Inch difference in fork length is equivalent about 1 degree reduction in rake. Personally I work with 0.03714 dgrees for every mm.

My calculations are these

Depending on how much shorter you make the GSXR forks(some say 20 mm but I make it about 25mm) , these are my figures

Forks 20mm Shorter
120/60/17( Dunlop 220) with rolling radius 288mm measured TRAIL=93.53
120/70/17(Pilot Road) with Rolling radius 299mm measured TRAIL=98.44

Forks 25mm Shorter
120/60/17(Tyre as above) TRAIL= 92.46
120/70/17(Tyre as above) TRAIL=97.33

Those figure are for the curvy with standard rake taken as 24.8 degrees/GSXR forks flush with top yoke. Yoke offset for the GSXR600/750/1000 up to K3 is 32mm.

The yoke offset for the SV650 Curvy is 29mm by the way. Don't know the offset for the Pointy.

Cheers
Ben

22-04-06, 03:10 PM

Im racing a curvy with gixxer front end and some JHS internals
its effectively steepened the rake about 1 degree.
a lil advise dude --if youre thinking of doing it get the forks rebuilt using .95 springs --the difference is un believable

21QUEST · 22-04-06, 03:19 PM

xj/frosty , if you don't mind me asking how much do you weigh (With gear or without).

Also did you have the forks lengthened? Personally don't think really required with a 120/70 but just curious.

Cheers
Ben

22-04-06, 03:41 PM

I' 176cm and currently weigh in at 68 kg nekkid--scales are right by the shower
And nope diddnt have the forks changed externally--Ive actually got em pushed through the yokes 12mm (1/2 inch) to quicken up the steering.
Mind you -My setup isnt soposed to work -Im running an ohlins shock setup for a k3 gixxer 600 with 97mm doggies. Looks like is bums hanging down compared to other sv's. I've always used a lot of body english so it seems to suit my riding style .

15-04-06, 08:18 PM	#1
mart Guest Posts: n/a	how do you calculate rake and trail as the tittle says is it possible to work out rake & trail and how would you do this for a given bike

16-04-06, 12:51 PM	#2
Sid Squid No, I don't lend tools. Mega Poster Join Date: Jul 2003 Location: Skunk Works, Nth London Posts: 8,680	Easiest to use makers quoted figures, failing that get the bike on a perfectly level surface, using a spirit level and a protractor measure the rake, unless you've got a Harley forks and steering axis will be parallel, if they're not it's complicated. Trail - measure from point directly below front spindle to extended steering axis point - keeping sttering perfectly square. For ease I'd probably make some measurements and produce a diagram. __________________ If an SV650 has a flat tyre in the forest and no-one is there to blow it up, how long will it be 'til someone posts that the reg/rec is duff and the world will end unless a CBR unit is fitted? A little bit of knowledge = a dangerous thing. "a deathless anthem of nuclear-strength romantic angst"

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16-04-06, 11:03 PM	#5
extreme3d Guest Posts: n/a	This site explains what to measure: http://www.sportrider.com/tech/146_0310_art/

17-04-06, 10:13 PM	#6
mart Guest Posts: n/a	thats a handy site. no just want to see the difference between the gsxr forks conversion and the stock sv forks and to try and counter act any problems that may arise with it i know a steering damper helps but im not too pleased to have a 120/50 front tyre on

22-04-06, 03:10 PM	#8
xj/frosty Guest Posts: n/a	Im racing a curvy with gixxer front end and some JHS internals its effectively steepened the rake about 1 degree. a lil advise dude --if youre thinking of doing it get the forks rebuilt using .95 springs --the difference is un believable

22-04-06, 03:41 PM	#10
xj/frosty Guest Posts: n/a	I' 176cm and currently weigh in at 68 kg nekkid--scales are right by the shower And nope diddnt have the forks changed externally--Ive actually got em pushed through the yokes 12mm (1/2 inch) to quicken up the steering. Mind you -My setup isnt soposed to work -Im running an ohlins shock setup for a k3 gixxer 600 with 97mm doggies. Looks like is bums hanging down compared to other sv's. I've always used a lot of body english so it seems to suit my riding style .